Changes

0.48.1.0
========

Features
--------

- CollectTransforms : Added a node for collecting transforms from different
  contexts and storing them as attributes (#2708).
- CollectPrimitiveVariables Added a node for collecting primitive variables
  from different contexts (#2708).
- PrimitiveVariableExists : Added utility node for querying the existence
  of a primitive variable (#2708).

Improvements
------------

- ArnoldLight : Improved performance (#2718).
- SceneInspector : Added tooltips with the unabbreviated name of the item
  being inspected (#2722).

Fixes
-----

- Expression : Fixed threading bug in UI error handling (#2652, #2723).
- ColorProcessor/Shuffle : Fixed bugs caused by attempted computation of non-existent
 upstream channels (#2701, #2731).
- Light : Fixed bounds computation (#2725).
- AnimationGadget : Fixes crash caused by dragging keys on adjacent frames (#2720).

0.48.0.0
========

Features
--------

- Viewer : The 3D viewer now updates asynchronously, keeping the UI responsive while the scene
  is computed in the background (#2649).
- AnimationEditor : Added a new editor to allow the graphical editing of animation
  curves. This can be found on the tab next to the GraphEditor in the standard layouts (#2632).
- DeleteObject node (#2694).
- CopyAttributes node (#2710).

Improvements
------------

- TranslateTool : Added handles for movement in the XY,XZ,YZ and camera planes (#2709).
- Layouts menu (#51, #2698) :
  - Added "Default/..." menu items to allow the default startup layout to be chosen.
  - Added new "Save As/..." menu items to allow previously saved layouts to be replaced.
- SceneInspector (#2607) :
  - Added filter to sets sections.
  - Moved set computations to background process, so they don't block the UI.
- Shader : Improved performance (#2644).
- ArnoldLightUI : Added support for "userDefault" parameter metadata. This matches
  the format already in use for ArnoldShaderUI (#2646).
- Viewer :
  - Added selection mask, to choose which types of objects can be selected (#2696).
  - Added more Arnold diagnostic shading modes (#2645)
    - Matte
    - Opaque
    - Receive shadows
    - Self shadows
- ArnoldAttributes :
  - Added `volumeStepScale`, `shapeStepSize` and `shapeStepScale` attributes (#2634).
  - Clarified intended usage of subdividePolygons attribute (#2680).
- FormatPlug : Made "Custom" mode persistent, so it is remembered across save and reload (#2660).
- InteractiveRender : Removed unnecessary deletion and recreation of objects when `childNames`
  changes (#2690, #2649).

Fixes
-----

- GraphEditor :
  - Fixed arrowheads on axis-aligned auxiliary connections (#2647, #2648).
  - Fixed potential auto-scroll bug when dragging a node (#2705).
- LocalDispatcher/TractorDispatcher : Fixed problems using `imath` context variables (#2653, #2654).
- OSLObject : Fixed crashes caused by indexed primitive variables (#2655).
- Viewer : Fixed visibility of children of look-through camera (#2694).
- ObjectSource : Fixed transform.* -> out.bound dirty propagation (#2649).

API
---

- SceneGadget :
  - Added `setPaused()/getPaused()` and `state()` methods (#2649).
  - Replaced `baseState()` with `set/getOpenGLOptions() methods (#2649).
  - Added `waitForCompletion()` method (#2649).
  - Added `set/getBlockingPaths()` methods (#2649).
  - Added `set/getSelectionMask()` methods (#2696).
- RenderController : Added new utility class for controlling interactive renders (#2649).
- AnimationGadget : Added new Gadget for editing animation curves (#2632).
- Animation (#2632) :
  - Keys are now reference counted, so ownership can be shared between CurvePlugs and the
    AnimationEditor.
  - Keys may be edited in place with `key->setTime()` etc, and the CurvePlug automatically updates.
  - `CurvePlug::keys()` has been replaced with `CurvePlug::begin()` and `CurvePlug::end()`.
    This hides the internal choice of container while still providing iteration.
  - Added optional `threshold` argument to `closestKey()`.
- IECoreScenePreview::Renderer (#2649) :
  - Added `command()` virtual method.
  - Added `name()` virtual method.
- IECoreGLPreview::OpenGLRenderer (#2649) :
  - Made it possible to call `render()` concurrently with edits.
  - Added support for highlighting selected objects.
  - Added "gl:queryBound" command.
  - Added "gl:querySelection" command.
  - Added support for custom object and attribute visualisers.
  - Added options for controlling base attributes.
- PresetsPlugValueWidget : Added support for an optional "Custom" menu item, which allows the
  user to enter an arbitary value. This is controlled by "presetsPlugValueWidget:allowCustom"
  plug metadata (#2660).
- BusyWidget : Added `busy` constructor argument (#2607).
- LightTweaks (#2660) :
  - Moved TweakPlug to the GafferScene namespace, so it can be reused by other
    nodes.
  - Added "Remove" mode.
- Layouts (#2698) :
  - Added `persistent` argument to `add()` method, mirroring the `Bookmarks.add()` API.
    This automatically takes care of saving persistent layouts into the startup location.
  - Added `setDefault()/getDefault()` and `createDefault()` methods to allow the management
    of a default layout.
- Handle (#2709) :
  - Added `set/getVisibleOnHover()` methods.
  - Added `PlanarDrag` axis accessors.
- TranslateHandle (#2709) :
  - Added `axisMask()` method.
- FilteredSceneProcessor : Added constructor to allow array `inPlug()`.
- Style :
  - Added methods for rendering animation curves (#2632).
  - Added `width` and `userColor` arguments to `renderLine()` (#2632).
  - Added `userColor` argument to `renderText()` (#2632).
  - Added XY/XZ/YZ Axes enum values (#2709).
- ViewportGadget : Added `set/getVariableAspectZoom()` method (#2632).

Build
-----

- ViewportGadget : Fixed compilation on Windows (#2705).
- OpenImageIOReader : Fixed compilation with XCode 9.4 (#2712).
- Updated Cortex to version 10.0.0-a28
- Updated FreeType version 2.9.1
- Updated Python to version 2.7.15
- Updated Alembic to version 1.7.8

Breaking Changes
----------------

- GafferSceneUI : Moved visualiser base classes to IECoreGLPreview (#2649).
- ArnoldAttributes : Changed volume step attributes (#2634).
- GafferImage : Removed FormatPlug compatibility for files saved in Gaffer 0.16 or older.
  To migrate, resave the file in Gaffer 0.47 (#2682).
- GafferOSL::ShadingEngine : Removed `scope` parameter from `needsAttribute()` (#2655).
- Layouts (#2698) :
  - Removed `save()` method. Use the `persistent` argument to `add()` and `setDefault()` instead.
  - Added `applicationRoot` argument to constructor. You should use `acquire()` instead anyway.
- LayoutMenu : Removed `delete()` method (#2698).
- GUI config : Renamed standard layout from "Default" to "Standard" (#2698).
- TranslateHandle : translation()` method now returns a V3f rather than a float (#2709).
- TransformTool : Made `orientedTransform()` method const (#2709).
- Style : Changed method signatures, enum values, and added virtual functions (#2632).
- Animation : Refactored API. See API section for more details (#2632).
- IECoreScenePreview::Renderer : Added virtual methods (#2649).
- InteractiveRender : Added and removed private member data (ABI break) (#2649).
- SceneGadget (#2649) :
  - Added/removed private members (ABI break).
  - Remove `baseState()`.
- SceneView : Reorganised/simplified drawingMode plugs (#2649).

0.47.0.0
========

Features
---------

- ImageView : Introduced asynchronous processing, so that the UI remains responsive while
  the viewer updates progressively (#2578).
- Apps : Added a new `dispatch` application. This dispatches task nodes such as ImageWriters,
  SystemCommands and Render nodes, either from within an existing .gfr file or by
  creating nodes on the fly. This differs from the execute app in that it performs a
  full dispatch via a dispatcher, rather than executing a single task node (#2588).
- Revamped OSL shaders (#2539).
  - Added MultiplyVector, DotProduct, CrossProduct, RemapFloat, RemapColor, RemapVector,
    FloatToColor, ColorToFloat, FloatToVector, VectorToFloat, ColorToVector,
    Luminance, MixColor, MixVector, MixFloat, AddColor, AddFloat, AddVector,
    DivideColor, DivideFloat, DivideVector, MultiplyColor, MultiplyFloat, MultiplyVector,
    SubtractColor, SubtractFloat, SubtractVector, InvertMatrix, Length, Normalize,
    PowFloat, RoundFloat, SinFloat, MatrixTransform, CompareColor, CompareFloat,
    CompareVector, SwitchColor, SwitchFloat, SwitchVector, CoordinateSystemTransform,
    CoordinateSystemMatrix.
  - Removed some old shaders, keeping compatibility by converting them to new shaders
    during loading.
- Appleseed : Updated to [version 1.9](https://github.com/appleseedhq/appleseed/releases/tag/1.9.0-beta)
  (#2570).

Improvements
------------

- Instancer : Replaced original proof-of-concept Instancer with a new version intended
  to be suitable for production use (#2642) :
  - Added support for orientation and scale primitive variables.
  - Added support for index and id primitive variables.
  - Added support for creating per-instance attributes.
  - Added support for sets.
  - Improved performance by removing `${instancer:id}` context variable.
- Documentation : Improved structure and presentation (#2612, #2613, #2616, #2619, #2625, #2628, #2631).
- Appleseed (#2570) :
  - Added support for pixel_time AOV.
  - Added denoiser options to AppleseedOptions node.
- OSLImage/OSLObject (#2586) :
  - Added support for `time` global variable.
  - Added support for reading context variables.
- OSLImage : Improved performance by only reading the upstream channels needed by the
  shader (#2586).
- Arnold renderer : Improved shader conversion performance (#2594).
- ArnoldOptions : Changed default value for `parallel_node_init` to on. This matches the default
  in Arnold 5.1 (#2594).
- OSLImage/OSLObject/RankFilter/Resample : Added cancellation support. This improves
  responsiveness in the new asynchronous ImageView (#2586, #2590).
- Isolate/Prune : Improved set processing performance (#2587).
- BranchCreator : Improved set processing performance (#2594).
- Application : Moved startup file execution before argument evaluation. This makes it
  possible for a startup file to manipulate application arguments if necessary (#2588).
- Stats app : Added `-canceller` argument (#2586).
- UI : Renamed Scene Hierarchy to Hierarchy View and Node Graph to Graph Editor.
- AttributeVisualiser : Added support for visualising Color3f attributes #2641).

Fixes
-----

- Viewer :
  - Fixed display of nested lights in look-through menu (#2615).
  - Fixed selection after expanding the selected locations (#2617).
- Metadata :
  - Fixed GIL management bug (#2582).
  - Fixed crash if `None` is passed to `registerValue()` (#2582).
  - Fixed bindings for change signals (#2610).
- UI : Fixed initial size and position of Preferences, Settings and Node Editor
  windows (#2643).
- ContextAlgo : Fixed GIL management (#2618).
- SubGraph : Fixed crash in `correspondingInput()`. This manifested itself as crashes in
  the NodeGraph when dragging a Box with an unconnected BoxOut node over a connection (#2583).
- TractorDispatcher : Fixed bug handling nodes like TaskList and FrameMask nodes, that don't
  have any work of their own to do (#2584).
- ImageAlgo : Fixed GIL management bug (#2585).
- Arnold/OSL : Fixed problems caused by Arnold trying to recompile Gaffer's OSL shaders
  unnecessarily. We no longer install the shader source files (#2539).
- ScriptNode : Fixed GIL management bug (#2578).
- BackgroundTask : Fixed interactions with ScriptNode lifetime (#2578).
- Threading : Fixed bugs caused by TBB cancellation propagation (#2589).
- LocalDispatcher : Fixed exception handling during foreground dispatch. Exceptions from
  Tasks are now propagated back to the caller instead of being suppressed (#2588).
- Appleseed : Disabled SPPM for interactive renders (#2570).
- Catalogue : Fixed bug where orphaned Catalogue tried to save an image (#2621).
- ViewportGadget : Fixed `setCameraTransform()` to trigger a rerender (#2639).
- Arnold : Worked around clashes between Mesa drivers and libai.so (#2638).

API
---

- DispatchUI : Added `DispatchDialogue` class (#2588).
- Dispatcher :
  - Added `dispatchSignal()` (#2574).
  - Improved signal exception handling (#2574).
  - Added `deregisterDispatcher()` static method (#2588).
  - Removed "frame" variable from TaskBatch contexts. This means it is no longer
    available to PythonCommand code in sequence mode (#2608).
- Outputs : Added `deregisterOutput()` method (#2581).
- GafferUI : Added new BackgroundMethod decorator to assist in performing processing in
  background threads (#2578).
- ShadingEngine : Added `hash()` method (#2586).
- PlugLayout :
  - Added `embedded` constructor argument (#2599).
  - Added "<layoutName>:width" metadata support (#2604).
- Editor : Added `instanceCreatedSignal()` method. This can be used to customise the
  standard editors immediately after they've been created (#2605).
- BusyWidget : Added `setBusy()` and `getBusy()` methods (#2604).
- ImageGadget : Added `setPaused()/getPaused()` and `state()` methods (#2604).
- ScriptEditor : Added `outputWidget()` accessor (#2622).

Build
-----

- Updated Appleseed version to 1.9.
- Updated OpenImageIO version to 1.8.12.
- Updated OpenShadingLanguage version to 1.9.9.
- Updated GLEW version to 2.1.0.
- Updated Cortex version to 10.0.0-a25.
- Improved documentation build process (#2622).

Breaking Changes
----------------

- Instancer : Added and removed plugs, changed behaviour and structure of output scene (#2642).
- Metadata : Changed function signatures for `GafferBindings::metadataModuleDependencies`
  and `GafferBindings::metadataModuleDependencies`. Source compatibility is retained (#2579).
- Action (#2578) :
  - Added new arguments to constructor and `enact()`.
  - Added new data member.
  - Source compatibility is retained.
- EditorWidget : Renamed to Editor (#2605).
- BackgroundTask : Replaced `done()` method with `status()`.
- SceneHierarchy : Renamed to HierarchyView (#2640).
- NodeGraph : Renamed to GraphEditor (#2640).

0.46.1.0
========

Features
--------

- ReverseWinding : Added new node that reverses the winding order of meshes (#2568).
- MeshDistortion : Added new node that calculates the distortion of a mesh from a
  reference shape (#2568).

Improvements
------------

- Stats app : Added `-sets` command line argument, to allow scene sets to be computed (#2572).
- OSLObject : Added support for reading and writing UVs via new InUV and OutUV shaders (#2569).
- SceneViewUI : Defer camera and light set computation until required (#2567).

Fixes
-----

- Arnold : Fixed NodeEditor layout of new standard_surface shader parameters (#2573).
- Catalogue : Fixed crash caused by non-writable directory (#2571).
- Stats app : Fixed bugs in `-preCache` argument. It was using the wrong context and
  not respecting the `-frames` flag (#2572).
- WidgetAlgo : Fixed bug when `grab()` with the event loop running (#2575).
- MapOffset : Fixed bug when offsetting an indexed uv set (#2576).

0.46.0.0
========

Features
--------

- FrameMask : Added new node to mask out upstream tasks on particular frames (#2558).

Improvements
------------

- Layouts (#2522) :
  - Simplified space-bar panel expansion, and removed the annoying auto-expand
    behaviour for collapsed panels.
  - Removed tabs from the Scene layout's Timeline panel.
- DeleteFaces/DeletePoints/DeleteCurves : Added invert plug (#2546).
- Spline widgets (#2551) :
  - Added axis lines at y=0 and y=1.
  - Improved framing behaviour.
  - Made float splines display as curves by default.
- Dispatcher : Reduced overhead of job directory creation (#2557).
- OSLObject : Added support for double primitive variables (#2547).

Fixes
-----

- Layouts : Fixed circular references created by layout menus. These could cause crashes
  during shutdown (#2522).
- BoolPlugValueWidget : Fixed displayMode metadata handling. This restores the little
  switches on the Attributes nodes (#2553).

API
---

- Metadata : Improved wildcard matching (#2536) :
  - Stopped '*' matching '.' in a plug path. This mimics how '*' doesn't match '/' in a
    glob match or in the PathMatcher.
  - Added '...' wildcard that matches any number of plug path elements, in the same way a
    PathMatcher does.
- ImageAlgo (#2561) :
  - Added support for lambdas in `parallelGatherTiles()`.
  - Added a `tileOrder` parameter to `parallelProcessTiles()`.
  - Added python bindings for `parallelGatherTiles()`.
- Context : Added optional `IECore::Canceller` that can be used to cancel long
  running background processes (#2559).
- BackgroundTask : Added new class to assist in the running of processes on background
  threads (#2559).
- ParallelAlgo (#2559) :
  - Added `callOnUIThread()` method.
  - Added `callOnBackgroundThread()` method.

Breaking Changes
----------------

- SplitContainer (#2522) :
  - Removed `animationDuration` argument from `setSizes()` method.
  - Removed `targetSizes()` method.
- Metadata : `*` no longer matches `.` in a plug path (#2536).
- PlugValueWidget : Removed `registerCreator()` method. Use metadata instead (#2536).
- ImageAlgo : Changed signatures for `parallelProcessTiles()` and `parallelGatherTiles()`
  (#2561).
- StringAlgo : Removed. Use `IECore::StringAlgo` instead (#2534).
- Display : Removed `executeOnUIThread()` method. Use ParallelAlgo instead (#2559).
- Gadget : Removed `executeOnUIThread()` method. Use ParallelAlgo instead (#2559).

Build
-----

- Requires Cortex 10.0.0-a20.
- Improved experimental CMake build setup (#2560).

0.45.3.0
========

Features
--------

- GafferSceneUI : Added CameraTool to the Viewer (#2531).
  - This enables the movement of the camera in the viewport to be pushed back upstream
    into the node for the camera or light that is currently being looked through. Note
    that once activated, the CameraTool will remain active even after another tool has
    been chosen.

Improvements
------------

- ShaderUI : Added support for userDefault metadata for shader parameters (#2544).

Fixes
-----

- SceneGadget : Fixed dirty propogation (#2541).
- Metadata (#2544) :
  - Added `deregisterValue()` overload for string targets.
  - Fixed overwriting of values for string targets.
- FormatPlug::acquireDefaultFormatPlug() : Fixed crashes if None is passed via
  python bindings (#2549).

Build
-----

- Added experimental CMake build in contrib (#2543).

API
---

- ViewportGadget (#2531) :
  - Added accessors for center of interest.
  - Added `orthographic3D` camera mode.
- BoolPlugValueWidget (#2531) :
  - Added support for `BoolWidget.DisplayMode.Tool`
  - Added `boolWidget()` accessor, matching `StringPlugValueWidget.textWidget()`.
- GafferUI : Add ToolUI (#2531) :
  - This sets up the "active" plug to use a BoolPlugValueWidget in tool mode,
    with an appropriate icon.
- Viewer : Added support for "tool:exclusive" metadata (#2531) :
  - This allows certain tools to be marked as non-exclusive, allowing them to
    remain active even when another tool has been chosen.
- TransformTool : Exposed constructor for Selection class (#2531).

0.45.2.0
========

Improvements
------------

- ArnoldAttributes : Added support for "subdiv_uv_smoothing" Arnold parameter (#2538).
- OSLObject : Improved performance by removing unnecessary primitive variable resampling (#2523).
- BoxUI : Removed "Promote as Box.enabled" menu item. The regular "Promote to Box" menu
  item should be used instead (#2528).

Fixes
-----

- SceneHierarchy : Fixed bug which caused the scene selection to be cleared
  unnecessarily (#2525).
- SceneInspector (#2532) :
  - Fixed selection bug in Globals->Sets section.
  - Fixed graphical glitch in Globals->Sets section.
- Transform Tools : Fixed context management bug (#2524).
- FileMenu : Fixed premature exit when opening backup containing error (#2526, #2527).
- OpenGLShader : Fixed serialisation (#2529).
- Box : Fixed creation of Boxes around existing SceneNode graphs (#2530).
- SceneGadget : Fixed Python binding for `getScene()` (#2532).

API
---

- ShaderUI : Added `hideShaders()` function (#2533).

0.45.1.0
========

Improvements
------------

- NodeGraph (#2495) :
  - Added automatic layout for auxiliary nodes.
  - Improved aesthetics of auxiliary nodes and connections.
- Viewer :
  - PointsPrimitives now default to drawing as GL points. The Drawing dropdown menu can
    be used to display them as disks instead (#2512).
  - Enabled anti-aliasing in the 3d view (#2521).
- Application : Gaffer processes are now named `gaffer ...` rather than
  `python gaffer.py ...` (#2511).
- Expression : Added support for `"x" in context` Python syntax (#2513).
- NodeEditor : Added Lock/Unlock menu items to the tool menu (#2517).
- Shader : Added support for showing/hiding output parameters in the NodeGraph (#2515).
- Arnold : Enabled procedural instancing during interactive renders. This requires a
  minimum Arnold version of 5.0.1.4 (#2519).

Fixes
-----

- Viewer : Fixed inaccurate picking of points and curves (#2512).
- Transform tools (#2137, #2516) :
  - Fixed bug where pivot was ignored.
  - Fixed bug affecting Transform node when space was set to World.
  - Fixed drawing order so handles are always on top.
- NodeGraph :
  - Fixed kink in connection drawing (#2500).
  - Fixed inaccurate picking in the corners of rounded nodes (#2500).
- NodeEditor (#2517) :
  - Fixed update bug which allowed plugs to be edited after an
    ancestor node was made read only.
  - Fixed bugs which allowed plugs to be added to read only nodes.
- Encapsulate : Fixed double transformation bug (#2518).

API
---

- Set : Added iterators (#2495).
- MetadataAlgo (#2517) :
  - Added `ancestorAffectedByChange()` function.
  - Added `readOnlyAffectedByChange()` functions.

0.45.0.0
========

Features
--------

- Added Ramp image node (#2470).
- Added SplinefColor4fPlug type (#2470).
- Added system to backup all open scripts at frequent intervals.
  This is controlled via the Preferences dialogue (#2469, #2499, #2503).

Improvements
------------

- Viewer :
  - Improved performance significantly when selecting large numbers of
    objects (#2450, #2486).
  - Improved reporting of errors involving look-through cameras (#2490).
  - Improved camera selection UI (#2490).
  - Added default camera settings dialogue (#2490).
  - Added Ctrl+K shortcut to fit clipping planes to selection (#2490).
  - Added Ctrl+F shortcut to frame selection and fit clipping planes to
    match (#2490).
  - Added context menu (#2490).
- SceneHierarchy (#2450, #2486) :
  - Improved performance significantly when selecting or expanding large numbers
    of objects.
  - Multiple selections made in the Viewer are now highlighted properly in the
    SceneHierarchy (#76).
- Significantly reduced file sizes and load times for scripts
  containing many shader and/or light nodes (#2455).
- NodeGraph
  - Added ability to Shift+Drag a connection to duplicate it (#2480).
  - Improved representation of Expression, Animation and Random nodes (#2458, #2497).
  - Improved highlighting behaviour for connections to selected nodes (#2473).
- ScriptNode :
  - The current frame is now saved with the script and restored on
    loading (#2468).
  - Read-only files are now read-only in the UI (#2503).
- ArnoldAttributes : Added attributes to control volume motion blur (#2433).
- Arnold : Added support for OSL shaders with multiple outputs (#2494).
- Stats/Execute apps : By default the current frame stored in the script is
  executed, rather than frame 1 as before. Use the `-frames` commandline argument
  to specify a specific range of frames to execute (#2468).
- CompoundDataPlugValueWidget : Added array types to plug creation menu (#2433).
- Startup : Startup files are now executed in isolated scopes, so they cannot
  accidentally rely on other startup files (#2462).
- Expression : Python expressions can now read from CompoundDataPlugs (#2484).

Fixes
-----

- Appleseed : Fixed crashes when editing cameras during interactive renders (#2489).
- Browser : Fixed bug caused by missing import (#2449).
- OpenColorIO : Added workaround for OpenColorIO bug whereby config parsing would
  fail for non-English locales (#1654, #2460).
- Python wrappers : Fixed exception translation (#2459).
- BoxIn : Plug values are now preserved when promoting an input plug (#2461).
- Tractor Dispatcher : Fixed accumulation of tractor plugs on TaskNodes (#2463).
- GraphComponent : Fixed bug which could prevent multiple scripts from being
  loaded in parallel (#2464).
- GraphComponentPath : Fixed bug whereby children did not inherit the filter
  from their parent (#2465).
- OSLLight : Fixed metadata for child plugs of parameters (#2474).
- Shader : Fixed serialisation bugs introduced in version 0.43 (#2454, #2455).
- Spline UI : Prevented creation of multiple editing dialogues for the same
  plug (#2472).
- Added backwards compatibility for scripts referencing the old
  `GafferScene.PathMatcher`, `GafferScene.PathMatcherData` and
  `GafferScene.PathMatcherDataPlug` types (#2457).
- Layouts :
  - Fixed incorrect vertical sizing of Timelines in custom
    layouts (#2502).
  - Fixed bug serialising custom layouts containing special characters (#2492).
- ScriptNode :
  - Hid "frame" plug from the UI, and clarified in the documentation
    that is not intended for widespread use (#2504).
  - Fixed a bug loading old scripts which referenced `IECore::Data` types
    wrapping `imath` types (#2487).
- Viewer (#2490) : Fixed bug where centre of interest was lost when switching between
  the default and look-through cameras.
- PlugValueWidget : Fixed bug that allowed drags to be received for read-only
  plugs (#2503).
- GUI App : Errors are now reported correctly when loading files from the command
  line (#2499).
- Serialiser : Fixed handling of exceptions in Python serialisers (#2475).
- Expression : Fixed initial UI state so that the expression is not editable until
  a language has been chosen. This avoids problems where an expression was entered
  and then lost when the language was set (#2482).
- PlugAlgo : Fixed problems with metadata promotion when using non-Box parents (#2488).
- NodeAlgo : Fixed attempts to apply user defaults to plugs that are not settable (#2507).

API
---

- PathListingWidget : Added faster expansion and selection methods using
  `IECore.PathMatcher()` to store sets of paths (#2450).
- AuxiliaryNodeGadget : Added new class to represent nodes like Expression and
  Animation in the NodeGraph (#2458).
- Style : Added `state` argument to `renderAuxiliaryConnection()` (#2473).
- Added GafferUI.Backups class (#2469).
- ImageGadget : Added `loadTexture()` method (#2490).
- ViewportGadget : Added `fitClippingPlanes()` method (#2490).
- Viewer : Added `viewContextMenuSignal()`. This allows context menus for views to be
  customised using the same basic mechanism we use in the NodeGraph and elsewhere.
  (#2490).
- FileMenu : Added `addScript()` function (#2499).
- Serialisation : Improved support for Python serialisers (#2475).
- ConnectionCreator : Added new class to improve drag & drop functionality in
  the NodeGraph (#2480).
- ContextAlgo : Added `affects*Paths()` methods (#2486).

Breaking Changes
----------------

- Stats app : Replaced `-frame` parameter with `-frames` (#2468).
- Style : Changed signature for `renderAuxiliaryConnection()` method (#2473).
- View : Removed `framingBound()` method (#2490).
- RendererAlgo : Renamed `createDisplayDirectories()` to `createOutputDirectories()`
  (#2452).
- PlugAdder (#2480) :
  - Removed `edge` constructor argument.
  - Changed base class.
- Nodule : Changed base class (#2480).
- ConnectionGadget : Changed base class (#2480).
- NodeGadget : Renamed `noduleTangent()` to `connectionTangent()` (#2480).
- ContextAlgo : The scene selection is now stored as a PathMatcher and not
  StringVectorData (#2486).
- SceneGadget : Changed signatures for methods for accessing selection and
  expansion (#2486).
- Style : Added new `renderAuxiliaryConnection()` virtual method (#2497).

0.44.0.0
========

Features
--------

- Added Checkerboard image node (#2403).
- Added ArnoldAtmosphere and ArnoldBackground nodes (#2444).

Improvements
------------

- NodeGraph : Added rendering of auxiliary connections, for instance between Expressions
  and the nodes they are connected to (#2436).
- Build : Hid symbols that do not need to be exported (#2431).
- OSLObject : Added support for creating string primitive variables (#2425).
- ArnoldShader : Added support for shader outputs of type string and boolean (#2439).

Fixes
-----

- MessageWidget : Fixed crash when clicking on message buttons (#2438).
- BoxIO : Fix promotion of ArrayPlugs (#2446).

API
---

- Style : Added `renderAuxiliaryConnection()` method (#2436).
- Scene : Added GlobalShader base class (#2444).
- GafferVDB : Using IECoreVDB (#2440).

Breaking Changes
----------------

- Plug : Removed deprecated PerformsSubstitutions flag. Use the `substitutions`
  argument to the StringPlug constructor instead (#2432).
- Style : Added a virtual method (#2436).
- ArnoldAOVShader : Changed base class (#2444).

Build
-----

- Added WARNINGS_AS_ERRORS build argument. This defaults to being on,
  which is the same behaviour as before (#2431).
- Added ASAN build argument for use with Clang (#2434).

0.43.0.0
========

Features
--------

- GafferVDB : Added PointsGridToPoints node and visualisation
  of VDB point grids (#2386).

Improvements
------------

- Appleseed : Added support for Capsules generated by the Encapsulate
  node (#2402).
- ImageReader (#2380) :
  - Reimplemented to use Gaffer's native cache instead of
    OpenImageIO's cache, giving speedups of 20-30% in some cases. This
    also paves the way for introducing deep images to Gaffer.
  - Added initial support for multi-part OpenEXR files.

Fixes
-----

- ValuePlug : Fixed problems when serialising compound plugs (#1500, #2395).
  - BoxPlugs were being serialised with `setValue()` calls for the leaf plugs
    _and_ the top level plug itself.
  - FormatPlugs were incorrectly attempting to serialise a `getValue()` call
    at the top level even when input connections existed at the leaf level.
    This prevented a common pattern for the dispatch of image networks from
    working.
- Camera node : Fixed "Copy From Viewer" tool menu item (#2396).
- SceneInspector : Fixed transform component display (#2396).
- Expression : Fixed bug caused by non-serialisable input plugs (#2395).
- CollectImages/Merge/Offset : Fix out of bounds input tile accesses
  (#2380).
- TabbedContainer : Fixed an incompatibility with Qt5 (#2426).
- PythonCommand : Exposed imath module to the execution command (#2428).
- CompoundPlug : Added compatibility config for legacy gfr files (#2429).

API
---

- Serialisation : Added support for nested classes in `classPath()` method (#2400).
- Plug : Remove deprecated ReadOnly flag (#2401).
- Moved PathMatcher/PathMatcherData/PathMatcherDataPlug from GafferScene to Gaffer (#2404).
- Filter : Removed Result enum. Use IECore::PathMatcher::Result instead (#2404).

Breaking Changes
----------------

- GafferScene :
  - Removed AlembicSource node. Use a SceneReader instead (#2397).
  - Removed AlembicPath and AlembicPathPreview.
- GafferCortex : Removed TimeCodeParameter support. This parameter type
  has been removed from Cortex (#2427).
- GafferTest : Removed SphereNode (#2399).
- ValuePlugSerialiser : Removed `valueNeedsSerialisation()` virtual
  method (#2395).
- OpenImageIOReader : Removed cache related methods (#2380).
- Removed Plug::ReadOnly flag. Use MetadataAlgo instead (#2401).
- ValuePlugSerialiser : Removed flagsMask argument from `repr()` method (#2401).
- Filter : Removed Result enum. Use IECore::PathMatcher::Result instead (#2404).

0.42.0.0
========

This major release brings significant version upgrades to all supported
renderers : Arnold 5, 3Delight 13 (NSI), and Appleseed 1.8. It also
introduces native support for OpenVDB, and initial support for reading
and writing USD files. This is of course in addition to the usual
assortment of improvements and bug fixes.

> Note :
>
> As of this release we no longer support Arnold 4 or 3Delight 12.
> Additionally, some Cortex functionality has been moved to the
> IECoreScene python module, and we now use the imath python module
> to access types like V3f, Color3f etc. Custom scripts and/or
> expressions may need to be updated accordingly. See the Breaking
> Changes section for more details.

Features
--------

- Arnold 5 support (#2308) :
  - Added support for rendering arbitrary meshes as volumes. Previously
    they were converted to box volumes.
  - Added support for light path expressions.
  - Added support for transform_type.
  - Added ArnoldAOVShader node to support AOV shaders.
  - Added support for volume_padding (#2356).
- 3Delight 13 support via the NSI API (#2311).
  - All shading/lighting is now performed via OSL shaders.
  - Includes full support for adding/removing/moving objects during
    interactive rendering.
- Appleseed 1.8 support (#2371) :
  - Updated version to 1.8.1.
  - Added AOV presets to the Outputs node.
- USD (#2393)
  - The SceneReader node can now read USD files.
  - The SceneWriter node can now write USD files.
- VDB (#2373) :
  - Added native support for representing VDB volume data in Gaffer
    scenes.
  - The standard SceneReader node can now load .vdb files.
  - VDB objects can be rendered directly to Arnold.
  - The Viewer now provides basic visualisation of VDB grids.
  - The SceneInspector provides inspection of grid metadata etc
    in the Object section.
  - Several new nodes demonstrate the feasibility of manipulating
    VDB grids directly in Gaffer's node graph :
      - LevelSetToMesh
      - MeshToLevelSet
      - LevelSetOffset
- Catalogue : Added a new CatalogueSelect node. This can be placed
  downstream of a Catalogue to override the image to view (#2370).
- UI Editor : Added the ability to add custom buttons to a plug (#2348).
- Gadget : Introduced layer-based rendering for Gadget-based UI
  elements (#2304).

Improvements
------------

- OpenColorIO nodes : Added role presets to all colorspace plugs (#2379)
- NodeGraph : Added icons to signify that a node has been bookmarked (#2369)
- PlugLayout : Improved layout of successive accessory widgets. They
  are now all placed in the same row (#2348).
- Simplified 3delight configuration based on $DELIGHT environment
  variable (#2311).
- TaskPlug/FilterPlug/ShaderPlug : Tightened `acceptsInput()` constraints (#2321).
- OSLObject : Added support for reading and writing matrix primitive variables (#2327).
- GafferImage : Moved default format plug creation to gui config (#2333).

Fixes
-----

- Catalogue :
  - Fixed bug that prevented images with a '.' in the filename from
    being loaded (#2370).
  - Fixed crashes caused by removing several images in quick
    succession (#2337).
- File Menu : Fixed "Import..." bugs (#1077, #2339).
- Edit Menu : Fixed automatic layout of pasted nodes (#2383)
- ShaderPlug : Fixed bug when deserialising inputs from BoxIO nodes (#2374)
- Crop : Fixed bug whereby changing the format plug value did not trigger
  recomputation (#2368).
- ImageWriter (#2364) :
  - Fixed a crash when writing a data window with a single pixel .
  - Fixed writing of empty data windows to write a single pixel data
    window instead of a full image. OpenEXR does not support empty data
    windows, so we must write at least one pixel.
- NodeGraph :
  - Fixed confusing Box navigation behaviour (#2343, #2347).
  - Fixed overlay text to always be on top (#674, #2304).
  - Fixed layering so dragged connections are always drawn behind
    nodes, and highlighted plugs are drawn above all others (#2304).
- SubGraph : Accounted for BoxIO nodes in `correspondingInput() (#2360).
  This fixed a node reconnection bug when deleting a Box or Reference, and
  allows Box and Reference nodes to be drag-inserted onto existing connections.
- ScriptNode :
  - Fixed node deletion problems caused by errors in `correspondingInput()`
    implementations. This was preventing nodes representing missing Arnold
    shaders from being deleted (#2355).
  - Fixed crashes caused by syntax errors in code passed to `execute()` method.
    This could cause a crash when pasting invalid text into the NodeGraph.
    (#2319, #2320)
- Shader/ShaderPlug : Fixed GIL management bug which could cause a deadlock
  in the `attributes()` and `attributesHash()` methods (#2354).
- GraphComponent : Fixed crashes caused by passing `None` to the Python
  bindings (#2338).
- VectorWarp : Fixed handling of nan/inf (#2341).
- Expression : Fixed copy/paste bug (#2336).
- BoxIO : Fixed undo/redo of `insert()` method (#2314).
- RendererAlgo : Fixed crash when renderer returns a null ObjectInterface (#2302).
- SetUI : Fixed set name context menus to account for intermediate nodes between
  destination and filter (#2312).
- StandardLightVisualiser : Fixed for Cortex 10 UV conventions (#2311).
- PlugAlgo : Fixed promotion of non-serialisable output plugs (#2314).
- Serialiser : Fixed syntax error created by `moduleDependencies()` (#2320).
- Plug : Fixed `setInput( nullptr )` so it removes inputs from all descendant
  plugs (#2323).

API
---

- OpenColorIOTransform : Added method to query available role names (#2379)
- Added default template arguments to simplify usage of several methods (#2361)
  - `PlugGadget::getPlug()`
  - `IndividualContainer::getChild()`
  - `Dot::inPlug()` and `Dot::outPlug()`
  - `View::inPlug()`, `View::getPreprocessor()` and `View::preprocessedInPlug()`
  - `Metadata::value()`
  - `BoxIO::plug()` and `BoxIO::promotedPlug()`
- Added GafferUI.ButtonPlugValueWidget (#2348).
- ScriptNode : Added `importFile()` method (#2339).
- Added new OpenGL renderer backend (#2302).
- Gadget : Introduced layer-based rendering (#2304).
- GafferOSL :
  - Added ClosurePlug type (#2308).
  - Added OSLLight node (#2311).

Breaking Changes
----------------

- Removed GafferRenderMan, and with it support for 3Delight versions
  prior to 13 (#2311).
- Removed support for Arnold 4 (#2308).
- Gaffer and Cortex now use the official `imath` python module rather
  than custom bindings in IECore (#2378).
- Cortex scene classes have moved to a new IECoreScene module, as we
  continue to simplify and modularize Cortex (#2362).
- Removed SplineEditor/SplinePlugGadget since they have never been
  used (#2375).
- Removed ProceduralHolder node. This was not exposed via the UI,
  had never been used, and is no longer supported by any of the
  renderer backends (#2366).
- Shader : Removed deprecated state methods (#2354).
- Removed RenderableGadget. If similar functionality is required,
  use an ObjectToSceneNode and a SceneGadget (#2334).
- SceneAlgo : Removed camera/transform utilities. These relied on conventions
  and functionality that will be removed in Cortex 10 (#2332).
- RendererAlgo : Removed obsolete functions used only with the legacy
  renderer backends (#2318).
- Removed code for handling `IECore::Light`. Lights are now
  always represented as shaders assigned to a location (#2331).
- Removed SceneProcedural and ScriptProcedural. These were only useful
  in legacy renderer backends, which have now all been removed (#2318).
- Removed ExecutableRender node. This used the legacy renderer backends
  which have all been removed (#2318).
- Gadget : Modified rendering API (#2304).
- Removed IncrementingPlugValueWidget. Use RefreshPlugValueWidget
  instead (#2322).
- Removed EnumPlugValueWidget. Use PresetsPlugValueWidget and
  metadata presets instead (#2322).
- ViewportGadget : Refactored camera transform handling. The camera
  transform is now accessed via new `setCameraTransform()`/`getCameraTransform()`
  methods, rather than via the camera itself (#2351).
- ScriptNode : Modified signature of `ScriptExecutedSignal` to use raw pointers
  (#2336).

0.41.0.0
========

Breaking Changes
----------------

- Adopted Cortex 10 UV representation (#2281) :
  - UVs are now represented as V2f primitive variables,
    not separate s/t float primitive variables.
  - Primary UV set is called "uv".
  - UV origin is in the bottom left, with increasing values of
    V going _up_ (flipped vertically compared to previous orientation).
  - Indices are now stored on the same primitive variable as the
    UVs themselves.
  - This has affected the plugs and default values for a number of
    nodes.
- SplinePlug : Changed value representation from IECore::Spline to new
  SplineDefinition class (#2148).
- Algo headers : Removed compatibility namespacing (#2299).
- Removed CompoundPlug. Use Plug or ValuePlug instead (#2298, #1323).
- Removed CompoundPlugValueWidget. Use PlugLayout instead (#2298).
- FilteredSceneProcessor : Removed deprecated `filterContext` method.
  Use FilterPlug::FilterScope instead (#2260).
- Stopped installing Cortex image ops. Use GafferImage nodes instead (#2258).
- Removed OpenImageIOAlgo. Use IECoreImage::OpenImageIOAlgo instead (#2258).
- Removed GafferCortexUI::ImageReaderPathPreview. Use
  GafferImageUI::ImageReaderPathPreview instead (#2258).
- GafferBindings : Hid internal details in GafferModule (#2289).
- GafferUIBindings : Hid internal details in GafferUIModule (#2256).
- GafferCortexBindings : Hid internal details in GafferCortexModule (#2248).

Features
--------

- Added Viewer visualisation of Arnold light filters (#2275).
- Added Encapsulate node. This encapsulates portions of a scene by
  collapsing the hierarchy and replacing it with a procedural which
  will be evaluated at render time (#2283).
- Added FloatSpline OSL shader ((#2292).
- Added VTuneMonitor to annotate VTune profiles with node processes (#2247).

Improvements
------------

- LightTweaks : Added "Delete" menu item to context menu (#2285).
- OSLShader : Improved node graph labels (#2296).
- Parent : Defaulted "root" plug to value of "/" (#2242).
- ArnoldOptions : Added abortOnError and maxSubdivison settings (#2290).
- SplinePlug :
  - Added MonotoneCubic interpolation option (#2148).
  - Added option to preview splines as curves rather than a colour ramp (#2292).
- CollectScenes : Added "root" plug, to allow subtrees to be collected
  from the input scene (#2238).
- OSLObject/ShadingEngine : Added multithreaded evaluation for improved
  performance (#2251).
- CompoundDataPlug : Added menu items for adding box plugs (#2263).
- Browser/View apps : Improved image preview (#2258).
- Filter plug UI : Decluttered embedded filter UIs (#2276).
- Group/BranchCreator : Optimised context management (#2270).

Fixes
-----

- ArnoldRender : Fixed error handling for aborted renders (#2279).
- SplineWidget :
  - Fixed incorrect colours in rightmost column (#2295).
  - Fixed editing of float splines (#2292).
  - Fixed curve width (#2293).
  - Fixed drawing of curves with minimum Y values other than 0 (#2292).
- ImageWriter : Fixed bug when writing JPEG with blank scanlines (#2268).
- ImageReader : Fixed "enabled" plug, so that turning it off outputs a default
  blank image (#2254).
- Documentation :
  - Fixed formatting of supported file extensions (#2244).
  - Clarified that the SceneReader node does support Alembic (#2244).
  - Fixed URL (#2273).
- BoxIO : Fixed bug that could cause promoted plugs to initially be
  invisible in the NodeGraph (#2284).
- GraphGadget : Fixed GIL handling in `setRoot()` and `setFilter()`
  methods (#2287).
- PlugLayout : Collapsible layouts are now used if a `rootSection`
  is specified (#2276).
- PlugAlgo : Fixed bug where promoted plugs had the wrong value (#2298).
- Prune : Fixed hashing of sets (#2243).
- Text : Fixed problems with vertical alignment when there was too much
  text to fit in the text area (#2291).

API
---

- ValuePlug : The `Node::plugSetSignal()` is now emitted for all ancestors, not
  just for ValuePlugs (#2298).
- GafferCortex::ParameterHandler : Added `hash()` method (#2298).
- RendererAlgo : Added optional `root` argument to `outputObjects()` (#2283).
- SceneAlgo : Added `parallelProcessLocations()` overload taking `root` (#2283).
- Wrapper classes : Added templated variadic constructors (#2250).
- PlugAlgo : Added `promoteWithName()` function (#2284).
- Added Capsule class to represent encapsulated scene hierarchy (#2283).
- StandardLightVisualiser : Added method for querying spotlight parameters (#2275).
- WidgetAlgo : Fixed `grab()` to work around Qt bugs on OSX (#2307).

Build
-----

- Added compatibility with OIIO 1.8 (#2261).
- Requires Cortex 10.0.0-a4.
- Made SConstruct compatible with Python 3 (#2280).
- Fixed problems building the documentation (#2307).

0.40.0.0
========

This release brings improved Alembic support, support for Arnold light filters and Appleseed area lights,
and the usual medley of miscellaneous improvements and bug fixes.

The astute observer may note that the version number leaves a gap from the previous major version
of 0.34. This is because 0.40 is the first version to require the use of a C++11 compiler,
but some current users are stuck on older toolchains for a little while longer. We intend to use the
intervening versions to provide backported feature releases for the older toolchains where needed.

Breaking Changes
----------------

- Simplified GafferScene/GafferSceneUI/GafferImage/GafferImageUI bindings by hiding code which
  is only used internally (#2142, #2152).
- TaskNode : Rederived from DependencyNode (#2163)
- Removed OrphanRemover/Behaviour classes. Use StandardSet's built-in orphan removal instead (#2212).
- CompoundNodule : Removed deprecated constructor arguments. Use metadata instead (#2216).
- ContextProcessor : Changed signature of `processContext()` and added `affectsContext()` pure
  virtual method (#2220).
- SceneInspector (#2222) :
  - Renamed `SceneInspector.inspectsAttributes()` to SceneInspector.supportsInheritance()`.
  - Removed `SceneInspector.SideBySideDiff.frame()` method. Client code should use the new
    setValueWidget/getValueWidget accessors to get access to the frame contents instead.
- Replaced use of boost::function with std::function (#2224)
- Display :
  - Removed server management. Use the Catalogue or manage a display server directly instead (#2228).
  - Display : Removed `dataReceivedSignal()`
- Removed GafferBindings::ExceptionAlgo. Use IECorePython::ExceptionAlgo instead (#2241).

Features
--------

- Alembic (#2234) :
  - SceneReader and SceneWriter nodes can now read and write Alembic files directly.
    The old AlembicSource node is now deprecated.
  - Improved performance.
  - Added support for points and curves geometry.
  - Fixed mesh winding order.
- Light Filters. Added initial support for Arnold light filters. These can be loaded using the
  regular ArnoldShader node and assigned to lights using the ShaderAssignment node (#2135).
- Appleseed : Added rectangular area lights (#2237).

Improvements
------------

- SceneWriter (#2161) :
  - Added support for serialising sets to .scc files.
  - Improved performance by multithreading scene generation.
- TaskNode : Errors are now reported in the NodeGraph (#2163)
- Execute app : Improved error reporting (#2163)
- OSL expressions : Added support for M44f plugs (#2187)
- Shader node : Added attributeSuffix plug. This is primarily of
  use with light filters (#2135).
- StandardNodeGadget : Added support for "iconScale" metadata (#2211)
- OSLShader : Added support for "icon" and "iconScale" shader metadata (#2211)
- ArnoldRender : Improved render shutdown performance (#2203)
- OSL ShadingEngine : Added support for converting aggregate data to arrays in `getattribute()` (#2219).
- SceneInspector (#2222) :
  - Improved discoverability of diff, inheritance and history views
  - Removed history traceback from fields where it was irrelevant
  - Fixed click-to-select in Set history tracebacks
- NodeGraph : Node double click and Edit.. menu items now always open a floating
  NodeEditor (#2222)
- Merge (#2223) :
  - Improved labelling of node inputs (#260)
  - Changed default operation to "Over"
- Stats app : Added -preCache argument (#2236)
- Appleseed (#2237) :
  - Updated to version 1.7.1-beta
  - Added double sided material assignment attribute
  - Added per ray type bounce limits
  - Improved default texture cache size

Fixes
-----

- NodeGraph : Fixed graphical glitches when drawing connections (#2156, #2170, #2230)
- Dot :
  - Fixed bug where Dots created with Control+Click were not always immediately draggable (#2139)
  - Fixed bug where any click (not just left click) would create a Dot (#2147)
  - Fixed bug with Control+Click creation of Dots in Boxes (#2197)
- Qt :
  - Fixed crashes when reparenting child windows (#2168)
  - Fixed bug with VectorDataWidget and Qt4 (#2162)
  - Fixed bug with GLWidget host resource sharing for Qt4 hosts (#2173)
  - Suppressed GLWidget warning messages on OSX (#2195)
- Catalogue :
  - Fixed crashes when saving renders to disk (#2174)
  - Fixed shuffling of switch plugs during image delete (#2193)
- Fixed loading of old files which referred to OIIO's "catrom" filter, which is now
  named "catmull-rom" (#2177).
- OpenGLShader : Fixed problems caused by attempting to reload shaders when no GL
  implementation is available (#2176)
- OSLImage (#2198) :
  - Fixed bug which meant that tiles with origin -64 were passed through unchanged
  - Fixed UVs for images with negative display window origins
  - Fixed global `P` values to reflect pixel centres, not corners
- Menu : Fixed handling of special regex characters in search field (#2221)
- Color editors : Fixed bug that allowed the creation of multiple editors for the
  same plug (#2209, #2222)
- ScriptNode : Fixed bug where `isExecuting()` returned the wrong result when
  loading a script containing references (#2227).
- Reference : Fixed "Duplicate as Box" menu item to create the Box with the
  right parent when the Reference node is not at the root of the script (#2229).
- MonitorAlgo : Fixed use of unitialised value (#2233)
- CompoundDataPlug : Fixed bug which prevented non-alphanumeric names being used
  in `addMembers()` (#2228)

API
---

- Added default template arguments for Plug and GraphComponent methods. This simplifies
  the use of methods like `GraphComponent::getChild()` and `Plug::getInput()` (#2167).
- Added `SceneAlgo::parallelProcessLocations`. Over time this will replace `parallelTraverse()` (#2161).
- ImageAlgo : Fixed tile range for `parallelProcessTiles` (#2164)
- TaskNode : Rederived from DependencyNode (#2163)
- Arnold ParameterHandler : Allowed plug type to be overriden using a `gaffer.plugType` metadata
  entry (#2135).
- StandardSet : Added automatic orphan removal feature (#2212)
- Context : Added `EditableScope::removeMatching()` method (#2220)
- Menu : Added support for `partial( WeakMethod( ... ) )` in commands (#2222)
- NodeSetEditor : Added `floating` argument to `acquire()` method (#2222)

Build
-----

- Fixed invalid debug assertions in Shape node (#2186)
- C++11 is now required as a minimum (#2167)
- Improved speed of Travis tests (#2145)
- Requires Cortex 10.0.0-a1

0.34.0.0
========

Breaking Changes
----------------

- ImageReader/ImageWriter : Replaced hardcoded colourspace management with configurable
  system. The default colourspace for several file formats has changed. (#2121)
- ImagePlug : Changed type of `metadataPlug()` (#2087)
- ImageWriter : Changed default exr compression to "zips" (#2092)
- Shader : Added `loadShader()` and `reloadShader()` virtual methods (#2098, #2088)
- ScriptNode : Added argument to `ScriptNode::paste()`. Default behaviour is unchanged. (#2117)
- ConnectionGadget : Added virtual method (#2102)

Features
--------

- Added configurable colourspace management to ImageReader and ImageWriter nodes (#2121)
- Added ResamplePrimitiveVariables node (#2105)
- Added DeleteFaces node (#2118)
- Added DeletePoints node (#2120
- Added DeleteCurves node (#2120)
- Added CollectImages node (#2116)
- Added CollectScenes node (#2127)
- Added DeleteSceneContextVariables node (#2111)
- Added DeleteImageContextVariables node (#2111)
- Added Erode and Dilate filters (#2134)
- Added support for Qt5 (#2132)

Improvements
------------

- Image : Improved performance for complex graphs (#2111)
- OSLShader : Improved shader reloading (#2088)
- OSLObject : Added interpolation plug. This allows shading to be
  performed per-face or per-face-vertex in addition to the previous
  vertex shading. (#2113)
- DirtyPropagationScope : Added python bindings (#2104)
- NodeGraph :
  - Improved drawing of connections (#2102)
  - Added Control+Click to insert Dots into connections (#2072)
- ImageReader : Added fileFormat and dataType items to metadata (#2121)
- Catalogue : (#2106)
  - Improved performance
  - Moved saving/snapshotting to the background, so the UI remains responsive while
    they occur
- ContextVariables : Added extraVariables plug to facilitate use
  with expressions (#2131).

Fixes
-----

- Catalogue : Fixed bug where shader view images leaked into the catalogue (#2106)
- EditMenu : Fixed error handling for paste action (#2117)
- Wrapper :
  - Fixed SIP-related problems with Arnold setup on OSX (#2107)
  - Defaulted to using lldb for debugging on OSX (#2110)
- MessageWidget : Fixed widget parenting bug (#2117)
- BoxIO : Disabled removal of promoted plugs when a BoxIO is deleted from a parent
 with childNodesAreReadOnly metadata (#2122)
- ImagePlug : Fixed GIL management bugs in `imageHash()` and `channelDataHash()` bindings (#2106)
- Shape/Text : Fixed bug where disabling the node still modified the image (#2106)
- ImageProcessor : Fixed bug which prevented some nodes from using expressions based on
  channel name. The bug was introduced in version 0.30.0.0 (#2124).
- Box : Fixed bug which could prevent the boxing of nodes containing internal
  connections (#2126).
- TransformTool : Fixed interaction with Transform node (#2136).

API
---

- Added AtomicCompoundDataPlug (#2087)
- ImagePlug/ImageNode : Changed metadataPlug() to AtomicCompoundDataPlug (#2087)
- ScriptNode : Added `continueOnError` argument to `paste()` method. (#2117)
- ShadingEngine : Added `needsAttribute()` method (#2114)
- Shader : Added `reloadShader()` method (#2088)
- ConnectionGadget : Added `closestPoint() method (#2102)
- Display : Added `copy` argument to `setDriver()` method (#2106)
- Catalogue : Added `Image::copyFrom()` method (#2106)
- Context : Added `removeMatching()` method (#2111)
- DependencyNodeClass : Added constructor taking no_init, for when a
  DependencyNode has no public constructor (#2134)

Build
-----

- Fixed compilation with GCC 4.1.2 (#2103)
- Updated dependencies : (#2109)
  - OIIO 1.7.15
  - OSL 1.8.9
  - Cortex 9.21.1
  - Qt 5

0.33.3.0
========

Improvements
------------

- ImageWriter : Added plug for jpeg chroma subsampling (#2101)
- Layer selector :
  - Sorted layer names (#2089)
  - Simplified menu for standard *.RGBA layers (#2100)
- Seeds : Added densityPrimitiveVariable plug to allow point density to be varied
  across the surface of a mesh (#2095)
- Added InInt and OutInt OSL shaders, to support integer primitive variables in
  the OSLObject node (#2093)
- Stats app : Added -task argument to allow collection of stats from TaskNodes (#2090)
- Arnold :
  - Added standard AOVs to Outputs node config (#2089)
  - Cleaned up UI for alHair (#2086)
- GraphGadget : (#2078)
  - Added Ctrl+click to select a Backdrop without selecting the nodes it contains
  - Fixed keyboard modifiers for node selection
- SplineWidget (#2079) :
  - Added dropdown menu for selecting interpolation (BSpline/Linear/CatmullRom)
  - Fixed banding when drawing at large sizes

Fixes
-----

- Metadata : Fixed bug which could cause crashes at shutdown if a python slot
  was connected to a metadata signal (#2097)
- Image view : Fixed error handling bug (#2091)
- Catalogue :
  - Fixed hangs caused by GIL management bug (#2085)
  - Fixed bug whereby selection was lost when renaming an image (#2082)
- Backdrop : Fixed problems caused by driving title/description with an expression
  which contains an error (#2083)

API
---

- SceneView : Added `frame()` method for framing objects (#2084)
- GafferSceneUI : Added ContextAlgo namespace containing functions for managing
  scene expansion and selection (#2084)
- PlugWidget/PlugValueWidget : Added `acquire()` methods (#2084)
- WidgetAlgo : Added `grab()` method for taking screengrabs (#2084)

0.33.2.0
========

Features
--------

- Added Image Catalogue node (#2077)
  - Key features include:
      - Loading, exporting, removing, and renaming images on disk.
      - Receiving renders from an InteractiveRender node, automatically combining
        multiple AOVs into a single image stream.
      - Snapshot (copying) images, including in-progress renders.
      - Adding notes to images.
      - Drag 'n' drop of any other image node into the image list to snapshot it
        and add it to the catalogue.

Improvements
------------

- OSL ShadingEngine : Added 'shading:index' special attr to getattribute (#2067)
  - This can be used to fetch the index of the current shading point.

Fixes
-----

- BoxIO : Fixed `setup()` to deal with non-serialisable plugs (#2081)
- DebugDispatcher : Fixed naming bug when creating nodes inside other nodes (#2073)
- Plug : Fixed bug whereby non-serialisable children were serialised (#2077)

API
---

- Display : Added setDriver/getDriver mechanism (#2077)
- PathBinding : Added bindings for pathChangedSignalCreated and havePathChangedSignal (#2077)

0.33.1.0
========

Improvements
------------

- ArnoldOptions : Added "ai:parallel_node_init" (#2062).
  - This defaults off to match Arnold's default, but it may be beneficial to turn on
    in many cases. Note that it is not safe to use with Cryptomatte currently.
- Stats App (#2059) :
  - Added parameter to allow storing stats in a file.
  - Added parameter to optionally supress the node summary.
  - Sorted args alphabetically for consistency of output.
- CompoundDataPlug : Added support for InternedStringVectorData (#2065)
- Dispatcher : Improve batching of no-ops such as TaskList (#2064)
- GafferDispatchTest : Added DebugDispatcher (#2064)
- Documentation : Added metadata reference (#2063)

Fixes
-----

- SetExpressions : Support ':' in names of sets and objects (#2070)
- EventLoop : Specify application name as "Gaffer" (#2071)
- FilterPlugValueWidget : Remove unnecessary node placement code (#2074)

Build
-----

- Using C++03 ABI with GCC 5.1 and greater (#2069)
- Fixed gcc 4.1 compilation issues (#2057)

0.33.0.0
========

Breaking Changes
----------------

- Image :
  - ImageWriter : Defaults to writing all channels instead of just RGB (#2021).
  - DeleteChannels : Changed channels plug default to "" (#2021).
  - ImageStats : (#2018)
    - Defaulted to sampling A in addition to RGB.
    - Changed interpretation of ImageStats channels to simply be a list of 4
      channels that correspond directly to the output RGBA plugs. Behaviour is
      unchanged apart from situations where an incomplete or ambiguous channel
      mask was in use.
  - Warp : New API (#1980).
    - Engine no longer depends on channelName.
    - Derived classes no longer responsible for computing inputWindow.
- API :
  - Renamed UndoContext to UndoScope (#2049).
  - Removed `Nodule::registerNodule()` overload which took a plug name regex.
    Use "plugValueWidget:type" metadata instead (#2045).
  - Added private data member to PerformanceMonitor (#2016).
  - Added `createUStrings` argument to OpenImageIOAlgo::DataView
    constructor (#2040).
  - Removed ChannelMaskPlug.  Use a StringPlug and `StringAlgo::matchMultiple()`
    instead (#2021).
  - Renamed renderer backends to "Arnold" and "Appleseed" (#1994).
  - Added virtual method to Style class (#2051).

Features
--------

- Scene :
  - Added light linking (#1985)
    - Light links are specified as set expressions using the StandardAttributes
      node.
    - Currently only supported in the Arnold renderer backend.
  - Added "scene:renderer" context variable which  can be used to query which
    renderer a scene is being generated for (#1994).
  - SetFilter : Added support for using arbitrary set expressions instead of
    just a single set (#2052).
  - Added RotateTool for interactively rotating objects in the viewport (#2051).
  - Added MeshTangents node to compute Tangent & Binormal primitive variables on a mesh (#2028).
- Image
  - Added Median node (#2022)
  - Added Mix node (#2026)
  - Added CopyChannels node (#2006)
  - Improved support for images with multiple layers : (#2018, #2021)
    - Added layer selector to image viewer
    - Added improved layer/channel selection to many nodes
    - Added ability to use wildcards to select channels to process
  - Added colorSpace plugs to ImageReader and ImageWriter (#2004).
- Box : Added BoxIn and BoxOut nodes to improve the visualisation of promoted
  plugs within the NodeGraph (#2011).

Improvements
------------

- TaskList : Added "sequence plug" (#2044).
- Improved GafferImage performance (#2016, #2031).
- OSLShader : Added support for vector->color connections (#2042).
- Expression : Added context menu for inserting common functions and node
  bookmarks (#2039).
- Stats app : Added performance monitor summary (#2016).
- Merge : Added min and max modes (#2027).
- Grade : Added support for grading alpha channel (#2023).
- Warp : Improved filtering (#1980).
- Added more string matching features #2015 :
  - `[A-Z]` style character classes
  - `?` to match any character
  - '\' to escape a subsequent wildcard
- Added mode and units settings to the UVWarp node, and renamed it to
  VectorWarp (#2014).
- StandardNodeGadget : Added more metadata support (#2011)
  - "icon" to add an icon.
  - "nodeGadget:shape" to choose a rectangular or oval shape

Fixes
-----

- Shader : Fixed bug when assigning a disabled shader
  with pass-through defined (#2025).
- OSLCode : Fixed string length menu item (#2039).
- Expression :
  - Fixed string context variable comparison bug (#2040).
  - Protected context from modification (#2010).
- ErrorDialogue : Fixed bug in message handling code (#2030).
- StringAlgo : Fixed bug in `matchMultiple()` (#2015).
- Switch/Dot : Fixed plug colours in NodeGraph (#2008).
- Transform/Resize : Fixed sinc filter (#1980).
- Fixed export of color/vector plugs from Boxes (#2012).
- Resize : Stopped resampling when only pixel aspect
  ratio is changed (#2007).
- Fixed crash in viewport mouse handling (#2005).
- Fixed Node Reference link in help menu (#2002).
- Fixed framing of lights in the Viewer, by giving them a default bounding
  box (#2054).

API
---

- MetadataAlgo :
  - Added "childNodesAreReadOnly" metadata. This makes it possible to make the
    internal nodes of a node read-only, while still allowing the external
    plugs of the node to be edited (#2048).
  - Added functions for bookmarking nodes (#2039).
  - Added `childAffectedByChange()` overload for Node changes (#2029).
  - Added `copy()` function (#2003).
  - Added `copyColors()` function (#2008).
- NoduleLayout : Added support for custom Gadgets to be specified via metadata
  (#2043).
- ImagePlug :
- Context management (#2041, #2016) :
  - Added Context::EditableScope utility class. Use this instead of the
    now-deprecated Context::Borrowed copy contructor.
  - Added PathScope/SetScope/GlobalScope utility classes to ScenePlug
  - Added GlobalScope/ChannelDataScope utility classes to ImagePlug.
  - Added FilterPlug::SceneScope utility class.
- Added V2iVectorDataPlug (#2031).
- NodeGadget :
  - Added support for "nodeGadget:type" metadata to control the type of gadget
    created by a node (#2029).
- GraphGadget : Added support for dynamically changing "nodeGadget:type"
  metadata (#2029).
- Added ChannelPlugValueWidget (#2026).
- Added RGBAPlugValueWidget (#2018).
- ImageGadget : Added methods for selecting which channels to view (#2021).
- ImageAlgo : Added `channelNames()` and `layerNames()` functions (#2019).
- Added SetAlgo namespace with methods for evaluating set expressions (#1985).
- PathMatcher : Added `intersection()` method (#1985).
- Added FilterAlgo namespace with methods for doing filtered image sampling
  (#1980).
- SceneAlgo : Added render adaptor API. This provides a simple registry
  of SceneProcessors which will be used internally within Render nodes
  to perform just-in-time adaptations of the scene for rendering (#1994).
- PlugAlgo : Added plug promotion methods (#2003).
- Added RotateHandle class (#2051).

Build
-----

- DEBUG build option now also disables optimisations (#2009).
- Enabled coloured compiler output (#2000).
- Updated to use Cortex 9.18.0
- Added QtUiTools module to build package.

0.32.0.0
========

Breaking Changes
----------------

- GLWidget : Replaced setOverlay/getOverlay with addOverlay/removeOverlay (#1979).
- Gadget (#1979) :
  - Added member variable.
  - Made `Gadget::visible()` method const.

Improvements
------------

- ArnoldOptions : Added texture system settings (#1958).
- CustomOptions, CustomAttributes, PrimitiveVariables, OSLCode : Added option to add point and normal values in addition to vectors (#1977).
- OSLShader : Added support for specifying nodule visibility via metadata (#1975).
- Appleseed :
  - Added automatic instancing support (#1978).
  - Added support for multiple cameras (#1978).
- GUI : User defaults are now applied to new ScriptNodes (#1960).
- OpenColorIO : Added support for specifying OCIO context variables per node (#1988).
- UIEditor / UserPlugs :
  - Added menu items for adding array plugs (#1989).
  - Added control for setting the documentation:url metadata (#1995).
- Main menu (#1987) :
  - Added options for flushing Arnold render caches.
  - Added issue tracker link
  - Renamed "mailing list" to "forum"
- GLWidget (#1979) :
  - Added support for multiple overlays.
  - Fixed overlay drawing problems.
- Viewer (#1979) :
  - Added support for tool toolbars.
  - Added support for tool shortcuts.
  - Added sidebar showing all available tools.
  - Added translate and scale manipulators.
- Arnold : Added support for subdiv_smooth_derivs attribute on polymeshes (#1996).

Fixes
-----

- Isolate : Fixed bug when using keepLights or keepCameras (#1965).
- InteractiveArnoldRender : Fixed occasional hangs (#1983).
- Browser app : Fixed shutdown errors (#1981).
- Light visualisers : Fixed errors triggered by specific intensity values (#1982).
- OSLShader : Fixed ambiguities between point, vector and normal types (#1977).
- Display : Fixed to support retries after failing to launch the server (#1972).
- UIEditor : Fixed preset naming bugs (#1966).
- Wrapper : Fixed bugs when Gaffer was installed in a location with spaces in the file path (#1961, #1962).
- ErrorDialogue : Fixed parentWindow lifetime issues (#1986).
- CDL : Fixed dirty propagation (#1988).
- Crop : Fixed hang when using a crop with no input image (#1993).
- DispatcherUI : Removed emulated "PlaybackRange" option which was clashing with CustomRange (#1991).
- NodeUI : Fixed documentation:url metadata (#1995).

API
---

- GafferUI::PlugAdder : Added support for subclassing in Python ()
- CompoundNumericPlug : Added `IECore::GeometricData::Interpretation` setting (#1977).
- Added `GafferImage::OpenImageIOAlgo` namespace with various utility functions (#1977).
- Added `Gaffer::PlugAlgo` namespace with a `replacePlug()` utility function (#1977).
- Fixed binding of `Serialiser::childNeedsSerialisation` (#1973).
- Added `WidgetAlgo.joinEdges()` (#1979).
- Gadget : Added setEnabled/getEnabled/enabled methods (#1979).
- Style : Using enum to define axes for translate/scale handles (#1979).
- StandardStyle : Added `disabledState()` (#1979).

Build
-----

- Fixed build on macOS Sierra (#1978, #1992).
  - Using clang on OSX.
  - Removed troublesome XCode 8.2 build for now.
- Updated standard dependency versions :
  - Appleseed 1.6.0-beta
  - Boost 1.61
  - OSL 1.7.5
  - Alembic 1.6.1
  - FreeType 2.7.1
  - Qt 4.8.7
  - Cortex 9.16.2

0.31.0.0
========

Breaking Changes
----------------

- ScriptNode (#1935)
  - Removed evaluate() method.
  - Removed scriptEvaluatedSignal() method.
  - Reordered virtual methods.
- Options (#1929)
  - Moved "prefix" plug to CustomOptions node.
  - Added virtual method.
- Shader : Removed NetworkBuilder from the API (#1936).
- OSL ShadingEngine : Added argument to `shade()` method (#1944).
- Moved all Algo to nested namespaces (#1953).

Improvements
------------

- ShaderSwitch (#1938)
  - Added support for all parameter types.
  - Added support for expressions and other inputs to the index plug.
- Added a generic Switch node to the NodeGraph menu (#1938).
- ArnoldShader
  - Added support for pass-through of an input parameter when disabled (#1936).
  - Added simplified NodeGraph view for shaders like AlSurface and Standard. They
    are now shown with most parameters hidden by default, and additional parameters
    can be added on demand (#1951).
- OSLShader : Added support for pass-through of input parameters (#1936).
- ArnoldOptions : Added sample clamp options (#1943).
- Camera : Added "Copy From Viewer" item to NodeEditor tool menu (#1950).
- Stats app (#1949)
  - Added command line arguments to output
  - Added current version to output
  - Added -contextMonitor argument (#1952)
- OSLObject : Added support for "world" and "object" coordinate systems (#1944).
- Arnold renderer : Added automatic creation of directories for log files (#1954).
- Rewrote NodeGraph nodule layout code for improved consistency between plugs on nodes
  and nested plugs. StandardNodeGadget and CompoundNodule now support the same set of
  metadata (#1952).

Fixes
-----

- Fixed error when importing GafferScene or GafferImage before GafferDispatch.
- ScriptNode : Fixed node deletion code to automatically reconnect nested child plugs (#1936).
- Set : Fixed update bug (#1941).
- ObjectSource : Fixed update bug (#1941).
- Reference : Fix reload bug where connections to nested plugs were lost (#1940).
- Dot : Fixed bug where output plug was lost during save (#1946).
- OSLImage : Fix `affects()` so input image affects shading.
- ChannelDataProcess : Fix `affects()`.

API
---

- ScriptNode (#1935)
  - Made serialisation and execution useable from C++.
  - Added `isExecuting()` method.
- Switch
  - Added `setup()` method to simplify creation of custom switches.
  - Added `activeInPlug()` method.
- ImageGadget
  - Added `textureLoader()` method.
- Added PlugAdder gadget to simplify the process of adding dynamic
  plugs within the NodeGraph.
- OSL Shading Engine : Added support for named transform spaces (#1944).
- Added ContextMonitor class.
- Menu : Added `modal` argument to `popup()` method.
- MetadataAlgo : Added `affectedByChange()` overload for nodes.

0.30.2.0
========

Improvements
------------

- Graph Layout : Don't apply positions if the layout algorithm fails.
- StandardOptions : Added "render:sampleMotion" parameter.
  - Currently with Arnold support ( RenderMan support requires Cortex update ).
- Arnold backend : Options prefixed with "header:" are written into the header of image outputs.

Fixes
-----

- ArnoldDisplacement :
  - Accepts OSLShader inputs to map plug.
  - Fixed dirty propagation.
- ArnoldOptions : Removed errorColorBadMesh option.
- Arnold backend : Leave instancing of ASS archives to Arnold itself.
  - Fixed a crash bug when Arnold's procedural cache is in use (tested in Arnold 4.2.15.1)
- Build :
  - Fixed failing Travis tests by removing `ImageWriterTest.testMultipleWrite()`.
  - IE options supply DCC specific LINKFLAGS if specified.

0.30.1.0
========

Improvements
------------

- Arnold backend : Added support for adding arbitrary parameters to the Arnold options by using
a CustomOptions node to create options prefixed with "ai:declare:" (#1911).
- ArnoldOptions : Added AA_seed. If not specified, this defaults to the current frame (#1913).
- Expression : Added support for PathMatcherDataPlugs in python expressions. In particular this allows the FilterResults node to be used as an input to an expression (#1915).
- Documentation : Added Expression reference (#1918).

Fixes
-----

- Dispatcher
  - Fixed GIL management bug which could cause deadlock if pre/post dispatch slots launched threads that attempt to use Python (#1916).
  - Fixed UI bug in frame range field (#1917).
- Reference : Reconnect outputs from any plugs.

API
---

- Menu : Added support for `functools.partial` in "active" and "checkBox" fields (#1914).
- NodeGraph : Added support for "nodeGraph:childrenViewable" metadata. This controls whether the subgraph of a node is accessible via the "Show Contents..." menu item and the cursor down keypress (#1914).
- PathMatcher/PathMatcherData : Added Python __repr__ support (#1915).

0.30.0.0
========

Breaking Changes
----------------

- Resample : Replaced `dataWindow` plug with `matrix` plug (#1896).
- OpenImageIOReader : Changed units of cache memory limit methods to bytes (#1895).
- Serialiser : Added `serialisation` argument to all methods (#1882).
- Metadata : Removed `inherit` argument from the `plugsWithMetadata()` and `nodesWithMetadata()`
  methods (#1882).
- ExecutableRender : Removed `command()` method (#1885).
- Changed return type of `Filter::outPlug()`, `FilteredSceneProcessor::filterPlug() and
  `FilterProcessor::inPlug()`. Source code compatibility is maintained.

Features
--------

- Added Mirror node for flipping and flopping images (#1896).
- Added FilterResults node for searching an input scene for
  all locations matched by a filter (#1908).

Improvements
------------

- Reference : Added "Duplicate as Box" menu item in NodeGraph (#1898, #1899).
- Box : Added "Import Reference" menu item in NodeEditor (#1898, #1899).
- OSLObject/OSLImage : Added support for vector shader parameters (#1901).
- OSLShader : Added support for array parameters (#1892).
- Render nodes : Added cache clearing after scene generation (#1900).
- Stats app : Added OIIO memory usage reporting (#1895).
- GUI app : Increased default cache size to 1 gigabyte (#1895).
- Image view : Added solo channel plug and button (#1881).
- Node Graph :
  - The internal network of Reference nodes may now
     be viewed by pressing the cursor down key (#1882).
- ArnoldShader : Added support for "gaffer.plugType" "" metadata.
  This can be used to disable the loading of a plug (#1884).
- Documentation
  - Added release notes section (#1886).
  - Fixed broken links (#1894).
- Improved loading times for scripts with many ArnoldShaders.
- Added support for alternate shiboken install location (#1891).
- Isolate : Added `keepLights` and `keepCameras` plugs (#1893).
- Light Visualisers :
  - Added basic area light visualisations to StandardLightVisualiser.
  - Added visualisation metadata for Arnold quad, disk, cylinder, and skydome lights.

Fixes
-----

- ImageTransform : Fixed negative scaling (#1896, #1613).
- Set : Fixed filter update bug (#1878, #1908).
- Cache preferences : Stopped serialising metadata unnecessarily (#1895).
- OSX (#1879, #1566, #1880, #1885)
  - Fixed numerous build errors
  - Fixed problems caused by System Integrity Protection
- Reference (#561, #1882)
  - Fixed copy/paste of nodes from inside a Reference
  - Prevented editing of internal nodes. They may now be viewed
    but in a read-only state.
- Arnold
  - Fixed ai:shape:step_size attribute (#1883).
- Fixed crashes when using as_color_texture shader (#1905).

API
---

- OpenImageIOReader (#1895)
  - Added `cacheMemoryUsage()` static method
  - Changed units of cache memory limit methods to bytes.
- Serialiser : Added `serialisation` argument to all methods (#1882)
- Metadata (#1882)
  - Added simplified API and deprecated previous API
  - Added MetadataAlgo.h with methods for controlling read-onliness and
    querying if a metadata change affects a particular plug.
  - Removed `inherit` argument from the `plugsWithMetadata()` and `nodesWithMetadata()`
    methods.
- Plug : Deprecated ReadOnly flag - use MetadataAlgo instead (#1882).
- ExecutableRender : Removed `command()` method (#OSX).
- StandardNodule : Added support for "label" metadata (#1889).
- Added M44fVectorDataPlug (#1892).
- ValuePlug : Added `clearCache()` method (#1900).
- ErrorDialogue
  - Added ErrorHandler context manager.
  - Added `messages` constructor parameter.

0.29.0.0
========

Highlights of this release include an entirely rewritten Appleseed backend with support
for editing geometry and environment lights during interactive renders, an OSLCode node
for the writing of OSL shaders within Gaffer, and much improved OSL support in GafferArnold.

Apps
----

- Screengrab
  - Added delay command line argument (#1861).

Core
----

- StringPlug
  - Fixed substitutions when plug has an input (#1860).

Appleseed
---------

- InteractiveAppleseedRender (#1833)
  - Reimplemented completely to using new Gaffer scene description
    APIs.
  - Added support for adding/removing/deforming/transforming objects during rendering.
  - Added support for changing environment lights during rendering.
  - Improved performance and responsiveness.
- AppleseedRender (#1833)
  - Reimplemented completely to using new Gaffer scene description APIs.
- AppleseedShaderBall
  - Added threads and max samples settings (#1833).
  - Increased sphere tesselation #1869.

Arnold
------

- InteractiveArnoldRender
  - Added support for editing subdivision attributes while rendering (#1855).
- ArnoldOptions
  - Added log verbosity settings (#1866).
- OSL
  - Improved OSL shader support using Arnold's new osl_shader node (#1873).
- Improved warning messages for unsupported parameters (#1872).

OSL
---

- Added OSLCode node, to allow editing of OSL shader snippets on the fly (#1861).

UI
--

- ArnoldShader
  - Added support for specifying UI layout via Arnold metadata.
    In particular, this greatly improves the NodeEditor UI for the
    AlShaders (#757, #1864).
- ArnoldAttributes
  - Fixed formatting of Subdivision section summary (#1855).
- NodeMenu
  - Sorted Arnold shaders into submenus (#1870).
- ScriptEditor/Expression/PythonCommand
  - Made code font monospaced (#1861).
- ShaderView
  - Fixed initial framing  (#1861).
  - Fixed bug triggered by shaders changing type  (#1861).
- Expression
  - Fixed broken popup menus on non-ValuePlugs (#1861).
- OSLShader
  - Fixed support for "null" widget type (#1865).
- ImageReader/SceneReader/AlembicSource
  - Improved layout of reload button (#1867).
- ArnoldOptions
  - Moved threads setting to Rendering section.
- Added indentation to nested collapsible widgets (#1866).
- SceneInspector
  - Fixed errors when selected path doesn't exist (#1874).
- Display
  - Don't attempt to start server unless UI is connected (#222).
- Added home shortcut for image view.
- Selection/Crop Tools
  - Fixed precision issues when far from origin.

Documentation
-------------

- Consolidated reference docs into a parent section (#1860).
- Added string substitutions reference (#1860).

API
---

- Renderer
  - Added bool return value to ObjectInterface::attributes(), to signify
    success/failure #1855.
- OSLShader
  - Added support for unloading with `OSLShader::loadShader( "" )` (#1859).
  - Fixed loading of surface type after loading of shader type (#1859).
- LabelPlugValueWidget
  - Added support for "labelPlugValueWidget:renameable" metadata (#1861).
- MultiLineTextWidget
  - Added "role" property (#1861).
- MultiLineStringPlugValueWidget
  - Added support for specifying role via "multiLineStringPlugValueWidget:role"
    metadata (#1861).
- OSL
  - Added GafferOSL/Spline.h header, to simplify use of splines in shaders (#1861).
- View
  - Removed `virtual void plugDirtied()`.
- CompoundDataPlug
  - Added support for BoolVectorData (#1863).
- PlugLayout
  - Added support for "layout:accessory" metadata.
- Added RefreshPlugValueWidget and deprecated IncrementingPlugValueWidget (#1867).
- ViewportGadget
  - Don't convert raster positions to V2i.

Build
-----

- Added OSLHOME build option, only necessary when building without using GafferHQ/dependencies (#1871).

Breaking changes
----------------

- View
  - Removed `virtual void plugDirtied()`.

0.28.3.0
========

OSL
---

- Metadata
  - Support OSL "page", "connectable", and "URL" metadata
  - Support metadata on spline plugs
  - Support min/max metadata

0.28.2.1
========

API
---

- ArnoldShader
  - Fix `outPlug()` loading bug introduced in 0.28.2.0.


0.28.2.0
========

UI
--

- Fixed incorrect re-use of widgets when swapping plugs with the same name.

Scene
-----

- Fixed context scoping issue during renders.

Arnold
------

- Added curve min_pixel_width and mode attributes.
- Shaders are now re-loadable, and will automatically reload during script load.

Cortex
------

- Fixed incorrect re-use of plugs when swapping parameters with the same name.

API
---

- SceneAlgo
  - Fixed context used by `sets()` function.
- RendererAlgo (preview)
  - Fixed context used by `RenderSets` class.
- ArnoldShader
  - Added keepExistingValue argument to `loadShader()`.
  - Added `loadShader()` to serialisation.
  - Reusing existing plugs wherever possible.
- CompoundParameterHandler
  - Match by parameter object instead of name.
- CompoundPlugValueWidget
  - Match by plug object instead of name.

0.28.1.0
========

UI
--

- The 3D Viewer can now look through lights (#1846).
- Prefixed NodeMenu search text for RSL and OSL shaders with ri and osl respectively (#1850).

Arnold
------

- Added support for trace sets (#1847). Any standard gaffer set with a name beginning with "render:" will be exported to Arnold as a trace set.
- Fixed ArnoldDisplacement crash (#1849).
- Added support for a `gaffer.nodeMenu.category` metadata value to customise the shader menu (#1850).

Scene
-----

- Added LightToCamera node (#1846).

API
---

- Context (#1848)
  - Added GIL release in `set()` method bindings to
    fix potential deadlocks.
  - Fixed bug which meant that `remove()` wasn't
    emitting `changedSignal()`.
- SceneAlgo
  - Added `sets()` overload to compute a subset of all sets.
- RendererAlgo (preview)
  - Added RenderSets utility class.
  - Modified output methods to take a RenderSets argument.
- ShaderPlug
  - Fixed bug involving plugs with no input (#1849).

Build
-----

- Added INSTALL_POST_COMMAND option, to allow custom commands to be run after installation (#1845).

0.28.0.1
========

UI
--

- Viewer
  - Construct as invisible to avoid unnecessary updates
  - Improved renderer management for shader swatches
  - Support reregistration of shader swatch scenes

Scene
-----

- FilterPlug
  - Fixed compatibility with legacy SubGraphs and Dots

Arnold
------

- ArnoldShaderBall
  - Added threads plug and limited cores used by the shader swatches

Appleseed
---------

- Removed unwanted shaders from Appleseed shader menu

Build
-----

- Resources now install even when not building docs

0.28.0.0
========

UI
--

- Viewer
  - Added interactive shader swatches (#1828).
  - Added visualisation of Arnold spotlight lens radius (#1835).
  - Fixed visualisation of lights aligned to camera (#1835).
- NodeGraph
  - Added "Move To" menu items for Dot nodes.
- InteractiveRender
  - Added Play/Pause/Stop buttons.

Scene
-----

- Added LightTweaks node (#1829).
- Added ShaderBall node (#1828).
- Added CopyOptions node (#1834).
- Fixed FilterSwitch serialisation bug (#1814, #1815).

Arnold
------

- Added support for shader network inputs to light parameters (#1828).
- Added support for spline shader parameters (#1813).
- Added support for OSL shaders (#1813).
- Added bucketSize and bucketScanning options to ArnoldOptions node (#1827).
- Added ArnoldShaderBall node (#1828).
- Added performance monitor support to ArnoldRender (#1831).
- Improved parameter linking support in renderer backend.
- Fixed crashes caused by trying to use two render nodes at once in the same process (#1818).

Appleseed
---------

- Added AppleseedShaderBall node (#1828).
- Fixed problems with searchpath initialisation (#1828).

RenderMan
---------

- Added RenderManShaderBall node (#1828).

Dispatch
--------

- Fixed performance problems with complex dispatch graphs (#1820).

Image
-----

- Fixed sizing of whitespace in Text node (#1822).

OSL
---

- Fixed problems with OSL_SHADER_PATHS initialisation (#1813).

Documentation
-------------

- Added missing image to "Getting Started" tutorial (#1810).

Build
-----

- Replaced appleseed build options with single APPLESEED_ROOT option (#1812).

API
---

- Scene
  - Added FilterPlug (#1815).
  - Added ShaderPlug (#1828).
  - Deprecated public attributes methods on Shader node.
  - Allowed ObjectSource derived classes to define more than one default set (#1821).
- UI
  - Added `Gadget::visibilityChangedSignal()` (#1828).
- Arnold
  - Added gaffer.plugType metadata support for shader parameters (#1817).
- Monitor
  - Added support for NULL argument to Scope class (#1831).

Breaking Changes
----------------

- Added an argument to `GafferArnold::ParameterAlgo::setupPlug()` (#1817).
- Modified ObjectSource virtual methods (#1821).

0.27.1.0
========

Core
----

- Fixed crash caused by using an invalid expression language (#1801).

Arnold
------

- Fixed motion blurred light bug (#1805).
- Fixed overscan rendering (#1803).

OSL
---

- Added support for matrix parameters (#1798, #1800)

API
---

- Replaced cropWindow with renderRegion in new IECoreScenePreview::Renderer::camera().

0.27.0.1
========

UI
--

- ViewportGadget
  - Exposed world position to shaders

0.27.0.0
========

Apps
----

- Screengrab (#1793, #1559)
  - Added arguments for Viewer and NodeGraph framing
  - Added arguments for Viewer and SceneHiearchy expansion and selection
  - Added argument for grabbing a single plug from the NodeEditor

Scene
-----

- Fixed SubTree to error when an invalid root is entered (#1786, #1790).
- Added filter input to Set, to define additional paths to add/remove.

Arnold
------

- Added ArnoldMeshLight node (#1787)
- Added ArnoldDisplacement node (#1776)
- Added subdivision attributes to ArnoldAttributes (#1776)
- ArnoldOptions (#1788)
  - Added total depth and transparency depth/threshold plugs
- Fixed warnings about unhandled light parameters
- Fixed crashes/errors caused by multiple cameras and a threading
  bug (#1785)
- Fixed bogus warning about "ai:log:filename" option.

OSL
---

- Expression (#1791, #1789)
  - Fixed string comparison bug
  - Fixed bugs when plug names share a common prefix
  - Fixed mistaken assignments
- Added support for spline parameters in shaders (#1782)
- Fixed reload button on shader UI

Documenation
------------

- Added basic lighting and rendering tutorial (#1793).

Build
-----

- Fixed debug builds (#1781)
- Added debug builds to Travis tests (#1781)
- Fixed clang compilation error in Serialisation.cpp

API
---

- Made FilteredSceneProcessor subclassable in Python.

Breaking Changes
----------------

- Rederived Set from FilteredSceneProcessor.
- Changed LightVisualiser API
  - Added attributeName argument to visualise() virtual method.
  - Added attributeName argument to registerLightVisualiser() factory method.
- Changed StandardLightVisualiser metadata prefix convention from
  "light:renderer:shaderName" to "renderer:light:shaderName", to
  match the ordering of the data as it appears in the scene module
  (attributeName:shaderName).
- Light nodes now output IECore::Shader objects rather than IECore::Lights

0.26.0.0
========

Arnold
------

- Added automatic instancing of identical objects (#1775).
- Added support for user attributes (#1775).
- Added support for filter widths in output specifications (#1773).
- Updated subdivision attributes to match Arnold versions 4.2.8.0 and
  onwards (#1775).
- Moved path setup to wrapper. This means that `gaffer env kick` can
  be used to render a pregenerated ass file (#1774).

UI
--

- NodeGraph
  - Added automatic layout of nodes generated by scripts (#1751, #1771).
  - Fixed duplicate position plug names (#762).

API
---

- Renamed ExecutableNode to TaskNode (#1767).
- Protected TaskNode internal virtual methods. Use the TaskPlug
  methods instead (#1767).
- Replaced OSLRenderer with ShadingEngine (#1770).
- GraphGadget
  - Added unpositionedNodes() method (#1751).

Build
-----

- Updated public build to use OSL 1.7.2 and OIIO 1.6.14.

Breaking Changes
-----------------

- Renamed ExecutableNode.
- Protected internal TaskNode methods.
- Replaced OSLRenderer with ShadingEngine.
- Dropped support for OSL versions prior to 1.7.

0.25.1.0
========

Apps
-----------------------------------------------------------------------

- Screengrab
  - Support for grabbing the ScriptEditor.

UI
-----------------------------------------------------------------------

- Fixed crash on mouse move over an about-to-become-visible GLWidget.

Scene
-----------------------------------------------------------------------

- Attributes
  - Avoided unnecessary dirty propagation.
  - Deactivated filter field when in global mode.
- InteractiveRender
  - Fixed object visibility bug.
  - Fixed context management bugs.
- RenderUI
  - Exposing nodules for task plugs.

Image
-----------------------------------------------------------------------

- ImageGadget
  - Taking pixel aspect into account when drawing.
  - Fixed color inspector for non-square pixels.

Arnold
-----------------------------------------------------------------------

- ArnoldRenderer
  - Reusing shaders where possible.
  - Ensuring shader nodes are named (uniquely).
  - Fixed sharing of attributes between lights.
  - Fixed time_samples.
  - Fixed default shader override on ExternalProcedurals.
- ArnoldOptions
  - Added missing sampling and depth options.
- ArnoldAttributes
  - Supporting additional shading attributes.
    - "ai:matte", "ai:opaque", "ai:receive_shadows" and "ai:self_shadows"

Documentation
-----------------------------------------------------------------------

- Added scripting tutorials and reference.
- Added bookmarks to config file tutorial.
- Added examples for the "test" app.
- Added OpenVDB license to appendices.
- Renamed "Performance Guidelines" tutorial to "Managing Complexity".

API
-----------------------------------------------------------------------

- ScriptEditor
  - Added inputWidget() and execute() methods.
- ImageGadget
  - Added pixelAt() method.
  - Added missing bindings.

0.25.0.0
========

Apps
-----------------------------------------------------------------------

- Fixed ordering of GAFFER_STARTUP_PATHS, so that custom scripts can
  override Gaffer's built in configuration files (#1752).

Scene
-----------------------------------------------------------------------

- Set
  - Added support for modifying multiple sets with a single node,
    by entering multiple names separated by spaces (#1748).

Arnold
-----------------------------------------------------------------------

- ArnoldRender node now uses the same backend as the
  InteractiveArnoldRender node. Rendering is now performed directly
  in Gaffer rather than using a procedural (#1755).
- ArnoldShader ( #1758)
  - Added support for BYTE and UINT input parameters and VECTOR
    and POINT output types.
- Added support for crop windows, overscan and resolution multipliers
  (#1744).

Build
-----------------------------------------------------------------------

- Fixed compilation of GafferAppleseed with GCC 5 (#1757).

API
-----------------------------------------------------------------------

- Made IECorePreview module private (#1731).
- Changed default orientation of environment light visualiser (#1749).
- Fixed SceneAlgo::camera() when "option:render:camera" is "".

Incompatibilities
-----------------------------------------------------------------------

- Made IECoreScenePreview private.
- ArnoldRender node no longer has a verbosity plug.
- Changed default orientation of environment light visualiser.

0.24.1.0
========

Core
-----------------------------------------------------------------------

- Fixed performance of acceptsInput() for serial Switch networks (#1722)
- Context now uses GeometricTypedData where appropriate.
- Disallow setting user defaults on nodes in nodes.
- Fixed serialization of dynamic TransformPlug

UI
-----------------------------------------------------------------------

- Improved picking of "backwards" connections.

Apps
-----------------------------------------------------------------------

- Added basic documentation.

Scene
-----------------------------------------------------------------------

- Updated several nodes to register metadata in one shot with `registerNode()`
- SceneView
  - Fixed drawing mode.
  - Added controls for curve drawing.
    - Using uninterpolated GL lines by default.
- Restored default base state in SceneGadget.
- GafferScene
  - Added preview of new Cortex Renderer API.
  - Added preview of RendererAlgo for new Renderer API.
  - Added preview of new InteractiveRender node.
- SceneAlgo
  - Added `globalAttributes()` function.
- SceneNode
  - Reduced unnecessary dirty signalling.

Image
-----------------------------------------------------------------------

- Removed unnecessary `UVWarp::Engine::hash()` method.
- ImageWriter can now be subclassed in Python.

OSL
-----------------------------------------------------------------------

- Updated OSLShaderUI to register metadata in one shot with `registerNode()`
- OSL Expressions now support V3f data from the Context.

Arnold
-----------------------------------------------------------------------

- ArnoldOptions
  - Added licensing section.
  - Added basic support for controlling render logs.
- Added preview of IECoreArnold ShaderAlgo.
- Added preview of IECoreArnold ProceduralAlgo.
- Added preview of new IECoreArnold Renderer.
- Added InteractiveArnoldRender node.
- Added support for Arnold matrix parameters as M44fPlugs

RenderMan
-----------------------------------------------------------------------

- Remove deprecated RenderManShaderUI class
- Updated RenderMan shaders to register metadata in one shot with `registerNode()`

0.24.0.0
========

UI
-----------------------------------------------------------------------

- Added node reference documentation menu item to NodeEditor tool menus.
- GafferUI.Collapsible supports Widget.reveal().
- ScriptWindow no longer stops the EventLoop if it's already stopped.
- Fixed PathWidget WeakMethod error at shutdown.

Scene
-----------------------------------------------------------------------

- Improved error messages emitted by Group node.

Image
-----------------------------------------------------------------------

- Fixed UVWarp crash triggered by negative data window origins (#1707).

OSL
-----------------------------------------------------------------------

- Fixed crash when deleting connections to an OSL expression (#1695).
- Added support for BoolPlugs in OSL expressions (#1697).

Dispatch
-----------------------------------------------------------------------

- Stopped SystemCommand swallowing the stdout of launched processes
  (#1712).
- Disabled automatic substitutions for command (#1692). This was broken
  by #1671.
- Added LocalDispatcher environmentCommand plug.

Arnold
-----------------------------------------------------------------------

- Added ArnoldVDB node (#1711).
- Added volume step size to ArnoldAttributes node (#1694).
- Fixed metadata for ArnoldLight UIs (#1696).
- Added "ai:threads" option
  - Exposed via ArnoldOptions under the Performance section.
  - ArnoldRender uses ai:threads option to drive kick -t command line arg.

Apps
-----------------------------------------------------------------------

- Removed procedural app
- Screengrab app
  - Added `-editor` argument
  - Added `-selection` argument
  - Added `-nodeEditor.reveal` argument
  - Fix crashes at shutdown

Documentation
-----------------------------------------------------------------------

- Introduced HTML documentation which is shipped with every Gaffer
  release (#1702, #1708, #1710).
- Mentioned PerformanceMonitor.

Build
-----------------------------------------------------------------------

- Simplified packaging. Use the gafferDependencies project if the
  dependencies are needed for your build.
- Convert BUILD_DIR to an absolute path.

API
-----------------------------------------------------------------------

- View (#1713)
  - Removed View3D and ObjectView derived classes.
  - Removed update() and updateRequestSignal() methods.
- Added DocumentationAlgo namespace with functions to assist in
  auto-generating documentation.
- Removed CompoundPlug usage from Shader nodes (#1701).
- Added **kw arguments to all Widget constructors.
- Removed deprecated Widget keyword arguments(#655, #1704).
- Removed all use of deprecated IECorePython::Wrapper (#1116, #1703).
- Removed deprecated `ValuePlug::inCompute()` method. Use `Process::current()`
  instead.
- Removed deprecated `Filter::matchPlug()` method. Use `Filter::outPlug()`
  instead.
- Removed deprecated SignalBinder class. Use SignalClass instead.
- Removed deprecated iterator methods. Use `Iterator::done()` instead.

0.23.2.0
========

Apps
-----------------------------------------------------------------------

- Stats
  - Fixed bug which caused errors when there were no items to print
    in a particular category (#1667).
  - Added -performanceMonitor flag, which outputs in depth statistics
    for use in analysing and optimising performance (#1668).
  - Added -image flag for outputting image statistics (#1680).

UI
-----------------------------------------------------------------------

- Added back "Remove Input" menu option for promoted plugs. This differs
  from the "Unpromote" option in that it breaks the connection but keeps
  the promoted plug on the outside of the box (#1678).
- NodeGraph (#1679)
  - Tightened rules for inserting nodes into noodles. Nodes are now only
    inserted when disabling the inserted node would create a pass-through
    equivalent to the original connection, and deleting the node will
    restore the original connection. Previously nodes could be inserted
    in such a way that one end of the connection was broken, or two new
    connections were made which had no logical in->out connection through
    the inserted node.
  - Stopped highlighting connections when hovering in their middle, where
    they cannot be dragged anyway.
  - Made it harder to accidentally drag a long connection by grabbing it
    in the middle - the sensitive section is now limited to a shorter
    segment near the end.

Scene
-----------------------------------------------------------------------

- Improved output of objects and transforms which are static, but for
  which motion blur has been requested via StandardAttributes. Motion
  blocks are now omitted when no motion is detected (#1662).
- ScriptProcedural (#1676)
  - Fixed clearing of caches after procedural expansion in Arnold.
  - Improved error reporting to include the node which caused the
    error.
  - Added support for performance monitoring.
- StandardOptions
  - Added new performanceMonitor option, which enables/disables the
    performance monitoring now supported by the ScriptProcedural
    (#1676).
- Duplicate
  - Optimised set name computation. This knocks 35% off the time
    to compute a set in a custom downstream node with certain
    suboptimal qualities (#1682).
- Fixed hangs caused by missing GIL management in SceneAlgo
  bindings (#1686, #1687).

Dispatch
-----------------------------------------------------------------------

- ExecutableNodes now support automatic substitution of variables in
  StringPlug values, in the same way as has always been supported
  by other node types (#887, #1671).
- Fixed order of dispatch when postTasks exist (#1675).

Arnold
-----------------------------------------------------------------------

- Removed use of deprecated UI APIs. Specifically,
  `PlugValueWidget.registerCreator()` has been deprecated, and all code
  should use the equivalent "plugValueWidget:type" metadata instead
  (#1673).

RenderMan
-----------------------------------------------------------------------

- Added initial support for using OSL shaders in 3delight.

Appleseed
-----------------------------------------------------------------------

- Updated to [Appleseed 1.4.0-beta](https://github.com/appleseedhq/appleseed/releases/tag/1.4.0-beta).
- Renamed volume priority attribute to medium priority.

Cortex
-----------------------------------------------------------------------

- Fixed UI error when launching a ClassVectorParameter UI with
  preexisting child parameters (#665, #1670).

Documentation
-----------------------------------------------------------------------

- Added GafferDispatch to the API docs.

API
-----------------------------------------------------------------------

- Added Process and Monitor classes. Processes expose internal
  processes such as ComputeNode::compute() and ComputeNode::hash()
  to Monitors - classes which can observe the internal workings of
  Gaffer via the exposed Processes (#1668).
- Added PerformanceMonitor class. This uses the Monitor/Process
  API to collect statistics useful in analysing and optimising
  performance (#1668).
- RendererAlgo
  - Added outputObject() method (#1662).
  - Added outputTransform() method (#1662).
- ValuePlug
  - Deprecated inCompute() method - use Process::current() instead
    (#1668).
- FormatData
  - Added workaround for unstable hash() method when compiling with
    GCC 4.4.7 (#1669).
- ExecutableNode
  - Moved public interface to TaskPlug. The ExecutableNode virtual
    interface is now considered to be protected, and will be made
    so in a future release.
- ScenePlug
  - Fixed python binding for pathToString().
  - Added helpers for accessing globals and set names. These manage
    the context such that it is friendlier to the hash cache, by
    removing variables we know to change frequently but which cannot
    affect the result #(1683).

Build
-----------------------------------------------------------------------

- Updated Cortex to version 9.8.0.
- Updated Appleseed version to 1.4.0-beta.

0.23.1.0
========

Apps
-----------------------------------------------------------------------

- Stats App
  - Added outputs for scene traversal time and memory usage.

Core
-----------------------------------------------------------------------

- Improved performance of the computation cache, particularly when under
  heavy multithreaded load (#1638).
- Fixed GIL lock issues.
  - CompoundDataPlug releases when adding child plugs.
  - GraphComponent releases when adding/removing children.
  - Reference releases in load().
- Switch
  - Add SwitchTraits<BaseType> to control context for index evaluation.

UI
-----------------------------------------------------------------------

- SceneHierarchy
  - Added search field (#1572, #1649).
  - Added set filter (#48, #1649).
- NodeEditor
  - Improved error handling for labels and multiline text fields (#1650).
- NodeGraph
  - Fix "Find..." shortcut.
- SceneInspector
  - Fixed labelling of CoordinateSystem sets (#1648).
- ExecutableNode
  - Fixed UI for individually promoted pre/post tasks (#1647).
- UIEditor
  - Add label field to plug section.
- GLWidget
  - Supports use in Maya when using PySide.

Scene
-----------------------------------------------------------------------

- ScenePlug
  - set() and setHash() are friendlier to the hash cache.
- SceneSwitch
  - Removed scene:path from context for index.
- FilterProcessor
  - Implement pass-through when disabled.
- PathFilter
  - Fixed bugs which treated empty paths as "/" rather than ignoring them (#1642)
   - Avoid unnecessary hashing of __pathMatcher plug.
- Set
  - Fixed bugs which treated empty paths as "/" rather than ignoring them (#1642)
- SetFilter
  - Remove unnecessary context manipulation..
- DeleteSets
  - Fixed bug which could pass-through a deleted set.
- Isolate/Prune
  - Fixed bugs which caused incorrect results when used with a
    particular custom filter outside of Gaffer (#1652).
- Shader
  - Fixed crashes caused by cyclic connections in shader networks (#1646).
- Fixed GIL lock issues.
  - Outputs releases in addOutput().

Image
-----------------------------------------------------------------------

- Warp
  - Added Warp base class.
  - Added UVWarp node.
- BufferAlgo
  - Added index() function.
- ImageSwitch
  - Removed tile variables from context for index.

RenderMan
-----------------------------------------------------------------------

- Fixed GIL lock issues.
  - RenderManShader releases in loadShader().

API
-----------------------------------------------------------------------

- PathMatcher
  - Fixed bugs which treated empty paths as "/" rather than as empty (#1642).
- SceneAlgo
  - Added PathMatcher overloads for `filteredParallelTraverse()` and
    `matchingPaths()` (#1649).
- MultiLineTextWidget
  - Added `setErrored()/getErrored()` methods to (#1650).
- MultiLineStringPlugValueWidget/LabelPlugValueWidget
  - Added error handling (#1650).
- ExecutableNode
  - Disabled nodule creation by default for all but TaskPlugs. Nodules
    can be explicitly reenabled using a ( "nodule:type", "GafferUI.StandardNodule" )
    metadata registration for a particular plug.
- DownstreamIterator/RecursiveChildIterators
  - Fixed API for completion of iteration.
- FilteredChildIterator
  - Added done() method.
- TypedObjectPlug bindings : Add _copy argument to defaultValue() method.

Build
-----------------------------------------------------------------------

- GafferUI now links to QtOpenGL

0.23.0.1
========

Cortex
-----------------------------------------------------------------------

- Fixed ParameterisedHolder::parameterChanged() exception handling.

0.23.0.0
========

Core
-----------------------------------------------------------------------

- Reverted cyclic connection check on plug connection
- Reduced hash cache clearing frequency to speed up instancing.

UI
-----------------------------------------------------------------------

- Fixed labelling of renamed plugs which had a custom label. The label
  is now removed by the rename operation (#1635).

Scene
-----------------------------------------------------------------------

- Improved set performance and memory usage significantly for all node
  types (#1623).
- Added a MeshToPoints node (#1640).
- Added sets support in the Duplicate node (#1623).

Arnold
-----------------------------------------------------------------------

- Added support for motion blur, courtesy of Cortex 9.7.0.

API
-----------------------------------------------------------------------

- Fixed python bindings to accept any iterable where previously only
  lists were accepted (#1634).
- ScriptWindow
  - Added createIfNecessary argument to ScriptWindow.acquire() (#1639).
- NameLabel (#1635)
  - Exposed default formatter.
  - Deprecated setText().
- PathMatcher (#1623)
  - Reimplemented using lazy-copy-on-write sharing.
  - Added addPaths() overload with prefix path.
  - Added subTree() method.
  - Added `RawIterator find( path )` method.

Build
-----------------------------------------------------------------------

- Updated release builds to Cortex 9.7.0.
- Updated OCIO build to be compatible with Maya. It should now be
  possible to run a standard Gaffer build from within Maya.

Incompatibilities
-----------------------------------------------------------------------

- PathMatcher binary compatibility changes.

0.22.0.0
========

This release brings support for dispatching via Pixar's Tractor, in
additional to the usual medley of bug fixes and optimisations.

Core
-----------------------------------------------------------------------

- Prevented the creation of cyclic connections (#1630).

UI
-----------------------------------------------------------------------

- Fixed bugs in "Set Key" plug menu item.
- Fixed Backdrop node positioning when creating a backdrop with no
  nodes selected (#1625).
- Fixed NodeEditor layout problems caused by long summaries (#1629).

Scene
-----------------------------------------------------------------------

- SceneProcedural (#1615)
  - Fixed bug which could cause motion blurred bounding
    boxes to be computed incorrectly.
  - Removed duplicate attribute computations. This shaves
    9% off the time to first pixel for a complex benchmark scene.

RenderMan
-----------------------------------------------------------------------

- Improved time to first pixel for raytraced 3delight renders (#1614).

Arnold
-----------------------------------------------------------------------

- Fixed warnings about inaccurate bounds (#1614).

Appleseed
-----------------------------------------------------------------------

- Added support for volume priority attribute (#1631).

Tractor
-----------------------------------------------------------------------

- Added a new GafferTractor module, which enables dispatching of
  Gaffer's task graphs to renderfarms running Pixar's Tractor (#1619).

Cortex
-----------------------------------------------------------------------

- Fixed UI for promoted presets parameters (#1624).
- Fixed parameter ordering in UI (#1627).

API
-----------------------------------------------------------------------

- ValuePlug
  - Prevented the addition of children which are not themselves
    ValuePlugs.
  - Allowed subclassing in Python.
- FilteredSceneProcessor
  - Removed restrictions on `Filter::sceneAffectsMatch()` (#1620).
- SceneProcedural/ScriptProcedural
  - Added support for using Renderer::Procedural::noBound (#1614).
- Fixed GIL management in DependencyNodeWrapper.
- Added DownstreamIterator.
- Improved error handling during dirty propagation.
- Batched dirty propagation during script loading, execution and
  destruction (#1632).

Tests
-----------------------------------------------------------------------

- Unexpected messages are now treated as errors.

Build
-----------------------------------------------------------------------

- Requires Cortex 9.6.0.

0.21.0.0
========

Apps
-----------------------------------------------------------------------

- Added `gaffer stats` application. This takes a script and prints out
  information about version, settings, variables and nodes (#1437).

Core
-----------------------------------------------------------------------

- Fixed serialisation of quotes and other special characters in metadata
  keys. This was most visible when using special characters in custom
  preset names (#1599).
- Simplified metadata serialisations (#1599).

UI
-----------------------------------------------------------------------

- Fixed UV orientation for area light visualisations (#1600).
- Fixed environment light visualisations on OSX (#1609).
- Viewer (#1592)
  - Improved image viewer performance.
  - Fixed several image viewer bugs (#1427, #1426, #1356, #773).
  - Added support for custom toolbars on all edges of the viewer,
    for both views and nodes.
- Fixed hang when browsing scene locations (#1618).

Image
-----------------------------------------------------------------------

- Fixed reference counting bugs in Premultiply and Unpremultiply nodes
  (#1598).
- Fixed crashes caused by Merge requesting nonexistent upstream
  channels (#1596).

Appleseed
-----------------------------------------------------------------------

- Added support for exposure parameters on Appleseed lights (#1608).
- Simplified light menus (#1608).
- Improved environment light visualisations (#1608).

API
-----------------------------------------------------------------------

- ImageAlgo
  - Added channelExists() function (#1596).
- ExceptionAlgo
  - Fixed line number extraction for syntax errors (#1599).
- Menu
  - Fixed broken shortcuts after assigning new menu definition (#1597).
  - Fixed scoping of MenuBar shortcuts. In particular this fixes
    a bug whereby an embedded Gaffer panel could prevent Maya's
    main window shortcuts from working (#1597).
- Replaced all old-style python classes with new style ones #1607.
- GafferImageUI
  - Added ImageGadget class.
- PlugLayout improvements
  - Added support for "layout:divider" metadata - this replaces
    the old "divider" metadata.
  - Added support for multiple layouts, using a different metadata
    prefix for each layout.
  - Added support for creating partial layouts, using a new rootSection
    constructor argument.
- Toolbar improvements
  - Toolbars can now be defined for all edges, not just the top of
    frame (#1592).
  - StandardNodeToolbar has a new constructor argument to choose which
    edge to create the toolbar for. A new "toolbarLayout:section" metadata
    value chooses which toolbar plugs belong in, with values of
    "Top", "Bottom", "Left" and "Right" (#1592).
- GLWidget
  - Improved overlay mechanism. Overlays may be queried and removed as
    well as set. Container overlays are transparent to mouse events in
    areas where no child widget exists (#1592).
- NumericPlugValueWidget
  - Added support for "fixedCharacterWidth" metadata.

Build
-----------------------------------------------------------------------

- Added GCC 5 build to Travis test setup.

Incompatibilities
-----------------------------------------------------------------------

- Removed ImageView::update() virtual override.
- Replaced GLWidget.addOverlay() method with setOverlay()/getOverlay() methods.

0.20.0.0
========

Apps
-----------------------------------------------------------------------

- Added support for choosing the debugger used via a new GAFFER_DEBUGGER
  environment variable.

Core
-----------------------------------------------------------------------

- Improved ContextProcessor performance. This shaved 10% off the startup
  time for a complex render (#1573).
- Added framesPerSecond plug to ScriptNode. This provides user-level
  control over the frame rate for each script (#1576).
- Fixed hang triggered by deletion of a plug during computation
  (#1576, #1580).

Dispatch
-----------------------------------------------------------------------

- Moved all dispatch functionality from Gaffer module into a new
  GafferDispatch module. Backwards compatibility is provided by
  config files, but it is recommended that code be updated to use
  GafferDispatch directly (#1577).
- Renamed "requirements" plug to "preTasks" and "requirement" plug
  to "task". Again, backwards compatibility is provided by a config
  file, but it is recommended that code be updated to use the new
  names (#1577).
- Added "postTasks". These are nodes that are executed following another
  node, even if they are not explicitly included in the list of nodes
  to dispatch (#1577).
- Added "dispatcher.immediate" plug to all executable nodes. This
  causes the node to be executed immediately in the current process
  when dispatched (#1577).
- Removed "dispatcher.local.executeInForeground" plug - use the new
  "dispatcher.immediate" plug instead (#1577).
- Added sequence support to PythonCommand node. This causes the command
  to be called once for all frames, instead of once per frame (#1578).
- Fixed bug which could cause all frames downstream of pass-through
  nodes (like TaskList and TaskContextVariables) to depend on all
  upstream frames (#1577).
- Fixed detection of direct dependency cycles (#1577).

Image
-----------------------------------------------------------------------

- Crop
  - Added option to crop to a specific format, optionally centered (#1570).
- Fixed crashes triggered by images with empty data windows (#1575).
- Improved ImageWriter to write out images progressively as the input
  image is generated (#1517). This improved speed by 65% and memory usage
  by 60% when generating a 10K image.

Scene
-----------------------------------------------------------------------

- Lights are now represented as attributes at a location rather than as
  objects. This allows lights for multiple different renderers to exist
  at the same location, allows the creation of area lights, and provides
  the necessary support for using shader networks within lights in the
  future (#1590).
- Shader nodes now support the loading of light shaders (#1590).
- Added metadata support for specifying the orientation of lights
  in the renderer (#1590).

RenderMan
-----------------------------------------------------------------------

- Fixed crash when reloading coshader arrays.

UI
-----------------------------------------------------------------------

- Improved viewport visualisation of lights (#1590, #11).
- Added workaround for PySide bug which prevented stylesheets from
  working as expected (#1574).
- Improved error reporting for failed dispatches (#1593).
- Fixed graphical glitch in OpDialogue error icon (#1593).

API
-----------------------------------------------------------------------

- ImageAlgo
  - Added parallelProcessTiles and parallelGather tiles functions
    to facilitate easy parallel processing of images (#1517).
- BufferAlgo
  - Moved image window methods from ImageAlgo (#1517).
- Format
  - Fixed space conversions for empty boxes (#1575).
- TestCase
  - Improved output for assertTypeNamesArePrefixed() failures.
- Dispatch
  - Renamed requirements -> preTasks
  - Added LoggingExecutableNode to GafferDispatchTest. This
    facilitates easier testing of dispatchers.
- SceneUI
  - Added ObjectVisualiser and AttributeVisualiser base classes
    to support custom representations of objects and attributes
    within the viewport (#1590).
- Metadata
  - Added methods for adding and querying non-node values (#1590).

Build
-----------------------------------------------------------------------

- Added CXXSTD argument to SConstruct. Pass CXXSTD=c++11 to build
  with C++11 support (#1586).
- Added testing with GCC 4.8 and C++11 to Travis test setup (#1586).
- Updated Cortex version to 9.5.0 (minimum requirement is 9.3.0).

Incompatibilities
-----------------------------------------------------------------------

- Removed "dispatcher.local.executeInForeground" plug - use the new
  "dispatcher.immediate" plug instead.
- Moved image window methods from ImageAlgo.h into BufferAlgo.h.
- Lights are now represented as attributes rather than as objects (#1590).
- The Parameters node no longer works for lights (#1590).

0.19.0.0
========

Apps
-----------------------------------------------------------------------

- Added a preference for OIIO cache memory to the gui app.

Core
-----------------------------------------------------------------------

- Added a TaskSwitch node.
- Added support for variable substitutions within SystemCommand.
- Added a PythonCommand node.
- Expression
	- Added support for assigning floats to IntPlugs in Python expressions.
	- Added detection of circular dependencies within expressions.
- Added support for metadata edits on Reference nodes (#1536).
- Fixed bug which caused internal connections to be removed when
  unparenting a Node.

UI
-----------------------------------------------------------------------

- Fixed SceneInspector context bug.
- Fixed display bug in Wedge string mode

Image
-----------------------------------------------------------------------

- Added Blur node.
- Added Text node.
- ImageReader
	- Added modes for handling missing frames.
	- Added settings for masking image sequences.
	- Added automatic conversion to linear using OIIO colorspace
	  metadata (#250).
	- Renamed old ImageReader to OpenImageIOReader - this is now
	  just a utility class which is used internally.
- Added ImagePrimitiveProcessor base class.
- Added methods for controlling the OIIO cache memory.
- Fixed bug which prevented the ImageWriter using the requested
  compression (#1538).
- Resample
	- Added expandDataWindow plug.
	- Added support for "smoothGaussian" filter.
	- Fixed bug which prevented subpixel translations.
- Fixed dirty propagation bugs in Offset node.
- Added Difference operation to Merge.
- ImageTransform
	- Improved performance up to 50%.
	- Improved quality.
	- Changed rotation direction to counter clockwise.
	- Made "cubic" the default filter./
- Removed Reformat node. Use Resize instead.
- Fixed computation of max in ImageStats.
- Fixed performance bug when ImageNodes are used inside
  a Box subclass implemented in Python.
- Fixed Merge dataWindow computation when the first input
  is unconnected.

Arnold
-----------------------------------------------------------------------

- Added ray depth setting to ArnoldOptions node.

Documentation
-----------------------------------------------------------------------

- Updated for latest changes.

API
-----------------------------------------------------------------------

- Added python bindings for ImageWriter::Mode.
- Expression::setExpression() preserves previous state in the case
  that parsing fails.
- Stopped CompoundNumericPlug::getChild() from masking the base class
  equivalents.
- Added ImageTestCase with assertImagesEqual() method.
- Removed filter from ImageSampler.
- Added Resample::filters() method.
- ImageTestCase
	- Fixed threshold comparison bug in assertImagesEqual().
	- Added assertImageHashesEqual() method.
- Added OpenColorIOTransform::availableSpaces() method
- Context::Scope may now be constructed with a NULL argument -
  this is a no-op.
- Reintroduced default format substitutions to AtomicFormatPlug.
- Added GafferImage::Shape base class.
- Removed ChannelMaskPlug::channelIndex() method. Use ImageAlgo
  colorIndex() method instead.
- Added channel name utility methods to ImageAlgo.

Build
-----------------------------------------------------------------------

- Improved reporting in Travis config.
- Updated several dependencies to match the VFX Reference Platform.
	- Boost 1.55
	- OpenEXR 2.2.0
	- OpenColorIO 1.0.9
- Updated to Appleseed 1.3.0-beta

Incompatibilities
-----------------------------------------------------------------------

- ImageTransform now uses OIIO filters rather than GafferImage filters -
  the old filter names are no longer supported.
- ImageTransform now rotates counter clockwise.
- Removed Reformat and redirected it to Resize, which supports OIIO filters
  rather than GafferImage filters.
- Removed filter plug from ImageSampler. Bilinear interpolation is used
  instead.
- Removed FilterPlug. Use StringPlug instead.
- Removed Filter. Use OIIO filters instead.
- Removed FilterPlugValueWidget. Use presets instead.
- Removed ChannelMaskPlug::channelIndex() method. Use ImageAlgo
  colorIndex() method instead.

0.18.0.0
========

This release brings a number of updates to GafferImage, including
user-editable Formats, bug fixes to Resize and Crop, and a new Offset
node. It also fixes a few bugs todo with Expressions, Switches, and UI
crashes.

Core
-----------------------------------------------------------------------

- `Node::userPlug()` is now a Plug instead of a CompoundPlug.
- Preventing unwanted child connection tracking on userPlug().
- Changed scriptNode() to return `this` when node is a ScriptNode.
- Support indirect connections to Switch index
    - Emitting Node::plugInputChangedSignal() for all downstream connections.
- Expressions don't let `__in` plug track child inputs.
- Added top level plug argument to `Expression::Engine::apply()`.
- PythonExpressionEngine drives `apply()` by plug type not data type.
- PythonExpressionEngine supports arbitrary compound plugs types.
- Improved PythonExpressionEngine::defaultExpression().
- Fixed a bug in plugs/nodesWithMetadata.
- Fixed errors when serialising parent metadata only.
- Reference/Box no longer export user plugs (#801).

UI
-----------------------------------------------------------------------

- Skipping intermediate dots in tooltips.
- Fixed crash in the GraphGadget when a non-nodule plug was removed from a node.
- Improved UI robustness for errors on enabledPlug() expressions.
- Fixed potential connection lifetime bugs in the Viewer.

Image
-----------------------------------------------------------------------

- Added AtomicFormatPlug and replaced all non-user facing FormatPlugs with this.
    - This plug does not perform default format substitutions.
    - This plug does not serialise registered Formats.
- Changed FormatPlug to be a user-editable Format specification
    - Using FormatPlug in all user facing scenarios (e.g. Constant, Resize, etc).
- Deprecated Reformat. Use Resize instead.
- Moved default Format mechanism onto FormatPlug.
- Fixed default Format issues inside boxes (#888).
- Fixed nodes which were unusable if no default format was specified in the context (#888).
    - We now fall back to a default default format in that case.
- The default format was not getting transferred to the script context after loading (#888).
- Rationalised and simplified the Format registry.
    - Fixed registerFormat() so that a second registration overrides the first.
    - Requiring name when registering a format.
    - Names should no longer include the numeric values.
    - Renamed removeFormat() to deregisterFormat().
    - Removed unused signals and not-so-useful methods.
    - Separated registered names and ostream output.
        - The ostream output just uses numeric values, keeping it in line with
          the Imath classes.
        - Querying the registered name for a format returns an
          empty string if it hasn't been registered. Previously it returned
          a generated name, making it hard to tell if it had actually been
          registered or not.
- FormatPlugValueWidget supports manual entry of custom formats.
    - This widget only supports FormatPlugs, not AtomicFormatPlugs.
- ImageStats now uses a postCreate to set plug values via the UI only.
- Renamed CropUI.postCreateCrop to CropUI.postCreate.
- Fixed Resize disabling.
- Add Offset node.
- Fixed bug in Crop::affects().
- Added Crop "resetOrigin" plug.
    - This resets the origin of the format back to [0,0], which is intuitively what is expected.

Incompatibilities
-----------------------------------------------------------------------

- Changed type of Node::userPlug()
- Moved default Format API from Format class onto FormatPlug class.
- Changed Format registry API.
- Crop now resets the display window origin to 0,0. Turn off the "resetOrigin" plug for the old behaviour.
- Renamed CropUI.postCreateCrop to CropUI.postCreate.

0.17.0.0
========

This release brings several major features in addition to the usual
enhancements and bug fixes. Of particular interest are the addition
of a basic keyframing system, support for using OSL expressions
alongside the existing Python expressions, and several new image
processing nodes exposing OpenColorIO functionality.

Core
-----------------------------------------------------------------------

- Added Animation node, providing basic support for keyframed animation.
- Added frames-per-second support to Contexts, to map between frames
  and a time in seconds.
- Expression
  - Fixed bug when identical expressions acted on different plug types.
  - Added support for calling `context.getTime()`.
  - Added support for calling `context.getFramesPerSecond()`.
  - Fixed bugs when a plug or node is renamed.
  - Fixed bugs when manually disconnecting an output or input
    of an expression.
  - Improved error reporting in the UI.
- Fixed InputGenerator backwards compatibility bug introduced in
  0.16.0.0.
- Box
  - Promoting a plug now properly copies plug metadata (#1468).
- Plug
  - Fixed rare crash during dirty propagation.
  - Fixed bug in child connection tracking behaviour.

UI
-----------------------------------------------------------------------

- NodeEditor
  - Plug context menus
    - Added keyframing menu items for numeric and bool plugs.
    - Added Lock/Unlock meu items.
    - Added menu item for creating an OSL expression.
  - Tool menu
    - Added "Revert to Defaults" menu item.
- NodeGraph
  - Added right click menu items for reordering plugs on Boxes.
  - Fixed bugs triggered by the dynamic hiding and showing of plugs
    via the UIEditor.
- Dot
  - Added optional labels. These can be derived from the
    dot node name or the upstream node name or may be
    specified directly.
- Shader loading dialogues
  - Added bookmarks.
- Viewer
  - Fixed bug which could mean the camera would move unexpectedly
    even when look-through mode is not enabled.
  - Fixed OpenColorIO configs.
- UIEditor
  - Fixed renaming of empty user sections.
  - Prevented renaming of section to invalid names like "".
  - Added default Settings section.
  - Fixed presets UI to update values when the selected preset
    changes.
  - Ignores user plugs on box nodes.
- Box
  - Added default Settings section.
  - Disabled plug addition button in User section.
- Fixed bug which could cause the display of corrupted icons.
- ShaderSwitch
  - Fixed UI to provide access to each input rather than just the
    array input as a whole (#1461).
- Numeric fields
  - Ensured that keyboard-nudged numbers have an extra 0 added as
    necessary to ensure that the same digit is always being modified.

Image
-----------------------------------------------------------------------

- New OpenColorIO nodes
  - LUT
  - CDL
  - DisplayTransform
- ImageWriter
  - Added file format options.
  - Made sure OIIO queries for nchannel and alpha support are
    respected.
- Merge
  - Fixed artifacts when the data windows differ between layers.
  - Fixed crash.
- Resize
  - Fixed artifacts when upsizing with the sinc filter (#1457).
- Changed convention for image bounding boxes to specify that the
  maximum coordinates are exclusive (outside the box).
- Fixed Crop UI for images with the default format.
- Resample
  - Fixed incorrect input sample region.

Scene
-----------------------------------------------------------------------

- Fixed loading of UnionFilters from Gaffer 0.15.0.0 (#1474).
- Fixed loading of FilterSwitches from Gaffer 0.15.0.0 (#1474).
- Attributes are now output to the renderer before shaders at the
  same location. This works around a bug in 3delight's shader
  construction.
- Fixed crash when loading sets from an empty SceneReader.
- Added support for frames-per-second to SceneReader, AlembicSource
  and SceneWriter.

OSL
-----------------------------------------------------------------------

- Added support for using OSL as a general purpose expression language.

Cortex
-----------------------------------------------------------------------

- Fixed issue where non-ValuePlugs were not syncing during setPlugValue().
- Fixed OpHolder node summaries.

API
-----------------------------------------------------------------------

- Expression
  - Redesigned API to better support multiple languages.
- Context
  - Added "framesPerSecond" variable and time accessors.
- Metadata
  - Added nodesWithMetadata() and plugsWithMetadata() methods.
- StandardNodeGadget
  - Removed orientation constructor parameter. Use metadata instead.
  - Added dynamic nodule reordering controlled by metadata.
- ScriptNode
  - Fixed undo merging for CompoundNumericPlugs (#422).
- Plug
  - Made setFlags() undoable.
- PlugLayout
  - Ignore custom widgets with type "". This allows a widget
    inherited from a base class to be removed by a derived class
    or instance metadata.
- Removed UserPlugValueWidget.
- Added UserPlug namespace.
- Deprecated use of arbitrary Widget constructor keyword arguments
  for auto-parenting. The `parenting` argument should be used instead.
- Image
  - Renamed GafferImage::OpenColorIO to ColorSpace.
  - Changed convention for image bounding boxes to specify that the
    maximum coordinates are exclusive (outside the box).
    - Added image window utility methods to assist with this change.
  - Added OpenColorIOTransform abstract base class. This makes it
    easy to implement nodes whose processing is performed via OpenColorIO.
  - Sampler
    - Remove sample window accessors.
    - Deprecated constructor taking a filter.
- Added NumericWidget.valueToString() method.

Incompatibilities
-----------------------------------------------------------------------

- Redesigned expression API to better support multiple languages.
- Changed convention for image bounding boxes to specify that the
  maximum coordinates are exclusive (outside the box).
- NodeGadget
  - Added noduleAddedSignal() and noduleRemovedSignal().
- StandardNodeGadget
  - Removed orientation constructor parameter. Use metadata instead.
- GraphComponentWrapper
  - Improved constructors to allow any type to be passed to the single
    argument constructor.
- Removed UserPlugValueWidget.
- Deprecated use of arbitrary Widget constructor keyword arguments
  for auto-parenting. The `parenting` argument should be used instead.
- Renamed GafferImage::OpenColorIO to ColorSpace.
- Sampler
  - Remove sample window accessors.
  - Deprecated constructor taking a filter.

0.16.0.4
========

Scene
-----------------------------------------------------------------------
- Output attributes to the renderer before other state to fix some inconsistent behaviour

Build
-----------------------------------------------------------------------
- Updated IE internal build options

0.16.0.3
========

UI
-----------------------------------------------------------------------

- fixed a problem whereby presets were not being transferred when
  promoting a compound plug on a RenderManAttributes node.

Core
-----------------------------------------------------------------------

- Fixed issue where non-ValuePlugs were not syncing during
  setPlugValue().

0.16.0.2
========

UI
-----------------------------------------------------------------------

- Box : Copy all metadata when promoting plugs.
- UIEditor : Never edit user plug for Box nodes.

0.16.0.1
========

UI
-----------------------------------------------------------------------

- UIEditor : Update preset value on selection change.
- ShaderSwitchUI : Fix NodeGraph representation (#1461).

0.16.0.0
========

Apps
-----------------------------------------------------------------------

- Python
  - Sets __name__ to "__main__" to conform more closely to a standard
    python interpreter (#1405).
  - Fixed to accepts -flag arguments (#1406).
- GUI
  - Removed cortex nodes from the node menu. They can be reintroduced
    with an appropriate config file, but our intention is that Cortex
    play only a "behind the scenes" role in Gaffer in the future.

Core
-----------------------------------------------------------------------

- Added version metadata to all saved files (#1436).
- Fixed dispatching of nodes inside References.
- Python expressions can now write to AtomicBoxPlugs.
- Added support for promoting ArrayPlugs to boxes.

UI
-----------------------------------------------------------------------

- Fixed image format menu to make changes undoable.
- Added sequence browsing to the relevant file choosers.
- Hid TaskContextVariables.variables plug in the NodeGraph.
- Fixed editability of promoted CompoundDataPlugs.
- Box promotion now tranfers nodule and connection colours.

Image
-----------------------------------------------------------------------

- Added a Resize node. This will replace the Reformat node over time.
- Added a Crop node.
- Added a Shuffle node (#1380).
- Added Premultiply and Unpremultiply nodes.
- ImageWriter
    - Fixed writing to image formats which don't support separate
      display and data windows - the full display window is now written,
      padded with black as necessary.
    - Added progress message.
    - Fixed tiled writing (previously scanlines were always written).

Scene
-----------------------------------------------------------------------

- Fixed bug in Isolate which meant that a filter which matched nothing
  at all had no effect. It now removes the entire scene as expected.
- Fixed bug in Prune which meant that a filter which matched the root
  was not removing the entire scene.
- Added support for arbitrary IECore::PreWorldRenderables in global
  options.
- Improved performance of bounds propagation (around 7% improvement
  for a Transform node and a complex filter).

Cortex
-----------------------------------------------------------------------

- Fixed bug which caused errors with read-only parameter plugs.

API
-----------------------------------------------------------------------

- Replaced all InputGenerators with ArrayPlugs, and removed InputGenerator
  class. ImageProcessor and SceneProcessor may now provide an array of
  inputs for any derived class to use.
- Paths
  - Added sequence support to FileSystemPath.
  - Added FileSequencePathFilter class for filtering sequences from
    FileSystemPath.
  - FileSequencePathPlugValueWidget supports metadata for sequence
    display.
  - Deprecated SequencePath.
- Added Resample node to GafferImage, for use in node internals.
- Dispatcher
  - The current job directory is added to the context for use
    by Executable nodes.
- Sampler
  - Fixed binding of sample( int, int )
- Added AtomicBox2fPlug.
- Made SceneNode and SceneProcessor subclassable in Python.
- Made ImageNode and ImageProcessor subclassable in Python.
- Made SubGraph subclassable in Python.
- Added _copy argument to ImagePlug.channelData() method.
- CompoundPlug deprecation
  - Rederived the following plugs from ValuePlug or Plug in preparation
    for removal of CompoundPlug :
      - BoxPlug
      - CompoundNumericPlug
      - Transform2DPlug
      - TransformPlug
      - CompoundDataPlug
      - ArrayPlug
  - Replaced use of CompoundPlug in the following nodes
    - Light
    - Outputs
- Added support for extra constructor arguments in node wrappers.

Incompatibilities
-----------------------------------------------------------------------

The scene and image processing nodes have been overhauled to allow any
node to use an array of inputs. While full backwards compatibility with
old scenes is expected, please let us know if you have any problems
loading an old scene. Please also update any dependent code to the new
APIs as soon as possible.

- Removed InputGenerator. Use ArrayPlug instead.
- Removed FilterMixinBase. Use FilterProcessor instead.
- SwitchComputeNode and SwitchDependencyNode now require that the "in"
  plug is an ArrayPlug.
- Changed base classes for many plugs, breaking binary compatibility
  but in most cases not source compatibility.


Build
-----------------------------------------------------------------------

- Added checks for doxygen and inkscape prior to building.
- Fixed non-reporting of graphics build errors (#1395).
- Updated to faster container-based testing on Travis.
- Added appleseed unit tests to Travis setup.

0.15.0.0
========

UI
-----------------------------------------------------------------------

- UI Editor
  - Added dropdown menu for choosing widget type (#739).
  - Added section for specifying additional widget settings (#739).
  - Added preset editor (#739).
  - Added section for editing section summaries.
  - Added NodeGraph section.
- Added drag and drop of objects onto Set nodes in the NodeGraph.
- Fixed crash which could occur when opening recent files.
- Fixed crash which could occur when using OpenGL widgets within Maya.
- Added support for summary tooltips on node UI tabs (#332).
- Fixed bugs which could cause a blank NodeEditor if an expression
  referenced a script variable.
- Fixed bugs in channel mask menus on image processing nodes.

Core
-----------------------------------------------------------------------

- Added Wedge node. This allows tasks to be dispatched multiple times
  using a range of values (#1372).
- Added TaskContextVariables node. This allows variables to be defined
  within the tree of tasks (renders etc) executed by a dispatcher.
- Added Loop node. This takes an input and loops it N times through an
  external graph before outputting it again. This provides the user with
  the ability to do things with the graph which were previously only
  achievable with code.
- Reference
  - Fixed serialisation of empty reference.
  - Fixed serialisation of user plug metadata.
  - Fixed referencing of promoted plugs
    - ExecutableNode requirements plug
    - UnionFilter filter inputs
    - OSLImage and OSLObject shader plugs.
    - RenderManShader coshader plugs (#1358).
- Expression
  - Fixed support for setting GafferImage FormatPlugs.
- ContextVariables
  - Fixed serialisation bug where additional plugs were added on
    save/load and copy/paste.
- Improved Context and ValuePlug performance.

Image
-----------------------------------------------------------------------

- Added ImageLoop node.
- Performance
  - Improved Reformat performance.
  - Improved threading peformance for small images.
- ImageWriter
  - Improved error messages.
  - Fixed bugs with empty filenames and filenames using
    substitutions.
- ImageTransform
  - Fixed copy/paste.
  - Fixed dirty propagation bug which could prevent the viewer
    updating at the right time.
- ImageReader
  - Added error reporting for missing files.

Scene
-----------------------------------------------------------------------

- Added SceneLoop node.
- Transform
  - Fixed bugs in World mode.
  - Added Parent, Local Reset and World Reset modes.
  - Renamed Object space to Local.
  - Changed default space to Local.
  - Note that these are backwards incompatible changes, necessary to
    fix an important bug and get the Transform node on a solid footing
    for the future. To get the same results as the old World mode, use
    the new Parent mode.
- FreezeTransform
  - Fixed bug which prevented the UI updating when the input object
    was changed.
- Fixed bugs which could cause incorrect bounds to be computed.

Appleseed
-----------------------------------------------------------------------

- Removed options and attributes that are not useful in Gaffer.
- Fixed default values for some options and attributes.
- Documented all nodes.
- Added support for shading overrides.

API
-----------------------------------------------------------------------

- Pass-through connections may now be made for FormatPlug (#1250).
- Added TaskContextProcessor base class. This enables the development
  of ExecutableNodes which request their input requirements in different
  contexts.
- Added support for directly setting Color3f context values from Python.
- UI Metadata additions. Many additions were made to the metadata supported
  by the Node UIs, and the existing UIs were ported to make use of it.
  - "layout:visibilityActivator"
  - "plugValueWidget:type"
  - "compoundDataPlugValueWidget:editable"
  - "boolPlugValueWidget:displayMode"
  - "vectorDataPlugValueWidget:dragPointer"
  - "pathPlugValueWidget:leaf"
  - "pathPlugValueWidget:valid"
  - "pathPlugValueWidget:bookmarks"
  - "fileSystemPathPlugValueWidget:extensions"
  - "fileSystemPathPlugValueWidget:extensionsLabel"
- ScriptProcedural
  - Added context parameter.
- BoolWidget
  - Added setDisplayMode()/getDisplayMode() accessors.
- Added AcceptsDependencyCycles Plug flag. See the Loop node for an
  example of use.
- Added FileSystemPathPlugValueWidget.
- Metadata
  - Fixed inconsistent handling of NULL values.
  - Added methods for deregistering values.
- Removed GafferUI.SectionedCompoundPlugValueWidget.
- Activator expressions are now attached to the parent of the plug, rather than always being on the node.
- Removed StringPlugValueWidget continuousUpdate constructor argument. Use metadata instead.
- Removed MultiLineStringPlugValueWidget continuousUpdate constructor argument. Use metadata instead.
- SceneNode
  - Added childNames argument to bounds union methods.
- SceneAlgo
  - Added `bound( const IECore::Object * )` function.

Build
-----------------------------------------------------------------------

- Updated to Cortex 9.0.0.
- Updated to OIIO 1.5.17.
- Updated to OSL 1.6.8.
- Updated to 1.2.0-beta.

Incompatibilies
-----------------------------------------------------------------------

- Removed `Reference::fileNamePlug()` (#801). Use `Reference::fileName()`
  instead. Use `continueOnError = True` when loading old scripts.
- Removed arguments from CompoundDataPlugValueWidget constructor. Use
  Metadata instead.
- Removed SectionedCompoundDataPlugVlueWidget. Use LayoutPlugValueWidget
  and metadata instead.
- Changed base class for ImagePlug.
- Changed base class for ScenePlug.
- Changed base class for SplinePlug.
- Removed ImageMixinBase. Use ImageProcessor instead.
- Removed SceneMixinBase. Use SceneProcessor instead.
- Removed GafferUI.SectionedCompoundPlugValueWidget. Use LayoutPlugValueWidget instead.
- Activator expressions are now attached to the parent of the plug, rather than always being on the node.
- Changed ChannelMaskPlugValueWidget constructor arguments.
- Changed Transform behaviour to fix bug in world space mode, add new modes and change the default mode to local. If you need the old world space behaviour, use the new parent space mode.

0.14.0.0
========

UI
-----------------------------------------------------------------------

- NodeGraph
  - Improved "Select Affected Objects" menu item. This is now available
    on filters as well as on scene processors.
  - Added support for dragging objects from the Viewer and SceneHierarchy
    and dropping them onto scene processors and PathFilters, to specify
    the affected objects.
      - Dragging onto a node replaces the current paths.
      - Shift+Drag adds to the current paths.
      - Control+Drag removes from the current paths.
  - Added plug context menu for moving promoted plugs on Boxes.
- NodeEditor
  - Added "Select Affected Objects" menu item in the tool menu for
    filters and scene processors.
- UIEditor
  - Added + button for adding plugs, and - button for deleting them.
  - Added the ability to create nested sections and drag+drop plugs
    between them.
- Viewer
  - Fixed grid and gnomon menus.

Core
-----------------------------------------------------------------------

- Expression
  - Added support for setting multiple plugs from one
    expression (#1315).
  - Added support for vector, color and box outputs (#1315).
  - Added support for assigning to plugs within conditional
    branches (#1349).

Scene
-----------------------------------------------------------------------

- Improved ParentConstraint so it is acts more like the equivalent
  parenting operation, and maintains the local transforms of the
  objects being constrained. Note that this is a change of behaviour,
  but one that we feel is much for the better.
- Fixed ShaderAssignment to allow referencing of promoted shader input
  plugs.

API
-----------------------------------------------------------------------

- Added `parallelTraverse()` and `filteredParallelTraverse()` methods
  to SceneAlgo. These make it trivial to traverse all locations in a
  scene using multiple threads.
- Added inputTransform argument to `Constraint::computeConstraint()`.
- Removed TransformPlugValueWidget.
- Used Plug rather than CompoundPlug in several places. CompoundPlug
  is being phased out because the Plug base class is now perfectly
  capable of having child plugs.
    - `ExecutableNode::dispatcherPlug()`
    - LocalDispatcher dispatcher plug
    - `Shader::parametersPlug()`
- Fixed support for boost python object methods as menu commands.
- Pointer
  - Fixed `registerPointer()` method.
  - Added binding for `registerPointer()`.
- Added `scoped` argument to `Signal.connect()` python bindings.
- Added `SignalClass` for binding signals, and deprecated the old
  `SignalBinder`.
- Added support for binding signals with 4 arguments.
- Added `LazyMethod.flush()` method.
- Fixed update bug in `PathListingWidget.setSelectedPaths()`.
- Added support for "nodule:type" metadata to control the type
  of nodule created for a plug. This should be used in preference
  to `Nodule::registerNodule()`, which has been deprecated.
- Added support for modifying CompoundNodule orientation, spacing
  and direction using plug metadata.
- Improved signalling of instance metadata changes.
- Added default arguments for ValuePlug constructor arguments.

 Incompatibilities
-----------------------------------------------------------------------

- Changed Constraint::computeConstraint() function signature.
- Changed ParentConstraint behaviour to include the local transform of the constrained object.
- Removed TransformPlugValueWidget.
- Changed plug type returned by ExecutableNode::dispatcherPlug().
- Changed Dispatcher::SetupPlugsFn signature.
- Changed ExecutableNode::dispatcherPlug() signature.
- Changed Shader::parametersPlug() to Plug rather than CompoundPlug.
- Removed asUserPlug arguments from Box promotion methods. Plugs are
  now always promoted directly under a box, and never as user plugs.
- Changed signature of `Nodule::registerNodule()` when registering a subclass.
- Changed signature of CompoundNodule constructor, which now accepts a Plug
  rather than CompoundPlug.
- Replaced UIEditor setSelectedPlug()/getSelectedPlug() methods with
  setSelection()/getSelection().
- Added arguments to Metadata signals.

0.13.1.0
========

Apps
-----------------------------------------------------------------------

- Test app can now run multiple named test cases, specified via the
  "testCases" command line argument.
- Fixed errors caused by special characters in .gfr filenames.

UI
-----------------------------------------------------------------------

- Fixed unwanted viewport scrolling when dragging from one NodeGraph
  into another, or from the NodeEditor across a NodeGraph (#1321).
- Hid Viewer diagnostic modes for unavailable renderers.
- Fixed SceneInspector inheritance and history windows, which were broken
  in 0.13.0.0.
- Fixed ObjectWriter UI, which was broken in 0.13.0.0.

OSL
-----------------------------------------------------------------------

- Added utility shaders for float maths and noise.

Image
-----------------------------------------------------------------------

- Fixed bug in DeleteChannels::hashChannelNames().

Houdini
-----------------------------------------------------------------------

- Added support for Houdini 14 (requires Cortex 9.0.0-b7).

API
-----------------------------------------------------------------------

- Added GafferUI._qtObject method.
- PlugLayout
  - Added layoutSections() method.
  - Added section argument to layoutOrder() method.

Build
-----------------------------------------------------------------------

- Added support for Boost >= 1.54.
- Fixed Appleseed packaging. We were omitting the directory containing
  the Cortex display driver.

0.13.0.0
========

Apps
-----------------------------------------------------------------------

- Improved error message for execute app.

Core
-----------------------------------------------------------------------

- Improved Dispatcher
  - Stopped merging of identical tasks from different nodes.
    We decided that this auto-merging caused more confusion than it
    was worth, and it may actually have prevented useful executable
    graphs which would have been intentionally running identical
    tasks at different points in the graph.
  - Added cycle detection.

UI
-----------------------------------------------------------------------

- Avoided unnecessary rebuilds of MenuBar menus. This can improve
  performance for slow-to-build custom menus.
- Added font file browser to the Text node.
- Improved NodeGraph plug tooltips - they now contain the plug description.
- Plugs may now be promoted to Box level via the right click plug
  menu in the NodeGraph.
- Fixed search box in file open dialogues.
- Improved dialogues for picking scene paths
  - Opened in tree mode rather than list mode
  - Removed unnecessary columns
  - Added filtering to display only cameras where appropriate
- CustomAttributes/DeleteAttributes
  - Added right click menu for quickly adding attributes from the
    currently selected object.
- Viewer
  - Added shading mode menu. This allows the default shading to be overridden
    with another shader. Currently configured menu entries allow visualisation
    of shader assignments and visibility for RenderMan, Arnold and Appleseed
    (#1037).
  - Improved error handling.
- SceneInspector
  - Improved shader display in attributes section. The node colour of the
    assigned shader is used as the background colour.
  - Improved performance (#1050).
- Node UIs
  - Added tool menu to NodeEditor
  - Added support for metadata-driven activators.
  - Added support for metadata-driven section summaries.
  - Added support for metadata-driven custom widgets.

Scene
-----------------------------------------------------------------------

- InteractiveRender
  - Fixed crash when deleting a running InteractiveRender.
  - Fixed coordinate system update problem.
- Fixed bug preventing filter plugs from being promoted to Boxes.
- Improved set computation
  - Separated the computation of sets from the computation of globals.
    This should prevent delays caused when calculating large unneeded
    sets along with the globals.
  - Made sets compute individually on demand. This should reduce the
    overhead of large unneeded sets.
  - Added "sets" plug to source nodes, to allow set membership to
    be defined at creation time.
  - Optimised SetFilter hashing.
  - Prevented wildcards from being used in the Set node (#1307).
- Made Parameters node compatible with subclasses of Light/Camera/ExternalProcedural,
  such as those used internally at IE.
- Shader node now adds "gaffer:nodeColor" entry into the blind data
  for the shader in the scene - this allows UI components to display
  the colour as appropriate.
- Added AttributeVisualiser node. This applies an OpenGL shader to
  visualise the values of attributes and shader assignments.

Appleseed
-----------------------------------------------------------------------

- Fixed typo in AppleseedOptions plug names.

Documentation
-----------------------------------------------------------------------

- Improved doxyen documentation configuration.
- Documented all GafferScene nodes.
- Documented all GafferOSL nodes.
- Documented all GafferRenderMan nodes.
- Documented all GafferArnold nodes.
- Added support for Arnold "desc" metadata items.

API
-----------------------------------------------------------------------

- Refactored Node UI to provide all features via the PlugLayout and
  Metadata entries.
  - Added support for a "fixedLineHeight" metadata entry in
    MultiLineStringPlugValueWidget.
  - Added support for "layout:section" metadata - this allows the
    layout to be split into sections, and will provide the basis for
    replacing the Sectioned* widgets, adding support for sections in
    the UIEditor, and replacing the section management code in the
    StandardNodeUI.
  - Added support for Metadata activators - these allow the editability
    of a plug to be driven by the values of other plugs.
  - Added support for section summaries driven by Metadata.
  - Deprecated SectionedCompoundDataPlugValueWidget.
  - Deprecated SectionedCompoundPlugValueWidget.
  - Improved layoutOrder() API. It now returns the ordered plugs
    for a specific parent, rather than accepting a possibly unrelated
    list of plugs.
  - Added support for arbitrary custom widgets to be inserted into
    layouts.
  - Reimplemented StandardNodeUI using PlugLayout.
- Fixed ExecutableNode::requirements() binding.
- Added support for fixing the height (measured in number of lines)
  of the MultiLineTextWidget.
- Fixed support for functools.partial( classMethod ) commands in
  Menus.
- ScenePath : added setScene()/getScene() accessors.
- Added SceneFilterPathFilter class. This tongue twister uses any of
  the GafferScene::Filter nodes to implement a Gaffer::PathFilter to
  filter the children of a GafferScene::ScenePath.
- Added ScenePath::createStandardFilter() method.
- Fixed crash when a Path is deleted before its PathFilter.
- Added PathChooserDialogue.pathChooserWidget() method.
- Added ScenePathPlugValueWidget.
- Gave precedence to exact plug matches over wildcard matches in Metadata
  queries.
- Added addition controls over Context substitution methods.
- Improved StringPlug with additional control over substitutions.
- Improved PlugType to support box and bool plugs.
- Added ValuePlugSerialiser::repr() method. This is intended to allow
  derived class bindings to base their own `repr()` implementation on
  the ValuePlug one.
- Made TypedObjectPlug compatible with instantiation for new types
  outside of Gaffer. This is achieved by moving the implementation into a
  .inl file which may be included as necessary. Added TypedObjectPlugClass
  to simplify binding such instantiations.
- Implemented PathMatcherData::hash().
- Added GafferScene::PathMatcherDataPlug.
- Reimplemented SceneNode sets API.
- Added GafferUI.LazyMethod for deferring widget method calls until
  visible/idle.

 Incompatibilities
-----------------------------------------------------------------------

- StringPlug
  - Reimplemented as a standalone class
  - TypedPlug<string> is no longer instantiated (binary incompatibility).
  - Must now include "Gaffer/StringPlug.h" rather than "Gaffer/TypedPlug.h"
    (source incompatibility).
- GafferCortex
  - Removed BoxParameterHandler and CompoundNumericParameterHandler. Their
    functionality is now covered by TypedParameterHandler.
- GafferScene
  - Reimplemented sets API.
  - Removed SceneReader "sets" plug.
- GafferAppleseed
  - Fixed typo in AppleseedOptions plug names.
- PlugLayout
  - Changed layoutOrder() signature.
- StandardNodeUI
  - Removed DisplayMode enum.
  - Removed displayMode constructor argument.
  - Removed _header() method.
  - Removed _tabbedContainer() method.

Build
-----------------------------------------------------------------------

- Updated default dependency versions
  - OIIO 1.5.13
  - OSL 1.6.3dev
  - LLVM 3.4
  - Alembic 1.5.8
  - Cortex 9.0.0-b6
- Added bundled Appleseed renderer

0.12.1.0
========

Core
-----------------------------------------------------------------------

- Fixed hangs introduced in 0.12.0.0. These were seen when stopping
  Appleseed renders and when ganging plugs in Caribou.
- Fixed thread-related crashes introduced in 0.12.0.0. These have not
  been observed in the wild, but caused intermittent failures in the
  unit tests.

UI
-----------------------------------------------------------------------

- Improved error messages output by OpDialogue.
- Fixed unwanted auto-expansion in SceneHierarchy panel.

Scene
-----------------------------------------------------------------------

- Added current scene location to error messages emitted by SceneProcedural.
- Reduced memory usage for sets by 10%.
- Optimised set computations. This reduces globals computation time for
  a complex production scene by 60%.
- Fixed PathFilter wildcard matching bug.

OSL
-----------------------------------------------------------------------

- Added metadata presets support for color and point parameters.

API
-----------------------------------------------------------------------

- Added iterators to GafferScene::PathMatcher.
- Added GafferUI.EditMenu.selectionAvailable() method.

0.12.0.0
========

Core
-----------------------------------------------------------------------

- Optimised CompoundDataPlug::hash() to ignore disabled members. This
  reduces globals hashing time by 20% for a complex production scene.
- Fixes Expression serialisation bugs (#1081, #1243).
- Optimised ValuePlug hash caching. It now caches more aggressively,
  keeping cache entries alive across multiple computations. This reduces
  scene traversal time for a complex production scene by 70%.
- Improved dirty propagation mechanism.
  - Batched propagation for UndoContexts, so dirtiness is signalled
    only once for operations batched within a single undo action.
  - Fixed bugs which meant dirtiness was signalled when child/parent
    plug connections were in an inconsistent state.
  - Addition and removal of dynamic plugs now triggers dirty
    propagation.
- The values of environment variables used for string plug
  substitutions are now frozen at startup.

UI
-----------------------------------------------------------------------

- Improved indicator for non-default plug values (#1216).
- Added copy/paste entries to plug menus (#601).
- SceneInspector now shows parameters for ExternalProcedural and
  Light objects.
- Added available set names to Set node "sets" plug popup menu.

Scene
-----------------------------------------------------------------------

- Fixed PathMatcher wildcard matching bug (#1252).
- Added Parameters node. This can be used for tweaking the parameters
  of lights, cameras and external procedurals (#1259).
- Added PointsType node (#476).
- Fixes Seeds node to take into account the bounding box of the generated
  points.
- Fixed dirty propagation bugs in CoordinateSystem and ClippingPlane
  nodes.
- Improved InteractiveRenderer pausing during edits.
- Added DeleteSets node.
- Fixed CustomOptions dirty propagation (#1039).
- Fixed ContextVariables dirty propagation.
- Optimised Filter mechanism, giving a 7-20% improvement in performance
  across a range of production scenes.

Appleseed
-----------------------------------------------------------------------

- Added support for interactive renderering with shader and light
  edits.

Image
-----------------------------------------------------------------------

- Added support for image metadata
  - ImagePlug has a new metadata child plug.
  - ImageReader reads metadata from file.
  - ImageWriter writes metadata to file.
  - ImagePrimitiveSource loads metadata from `ImagePrimitive::blindData()`.
  - Merge copies metadata from the first input.
  - ImageMetadata node creates/sets metadata.
  - DeleteImageMetadata node removed metadata.
  - CopyImageMetadata transfers metadata from one image to another.
- Optimised many nodes with direct internal pass-though connections.

API
-----------------------------------------------------------------------

- StringAlgo
  - Added `hasWildcards()` function.
  - Removed flawed MatchPatternLess (#1252).
- NodeAlgo
  - Added `isSetToUserDefault( plug )` function.
- RendererAlgo
  - Added `outputAttributes()` method.
- ImageNode
  - `hash*()` and `compute*()` methods are no longer pure virtual.
    This allows subclasses to make direct internal connections to
    pass through input plugs unchanged.
- PlugValueWidget
  - Replaced `_dropValue()` method with `_convertValue()`.
- Menu
  - Added support for `functools.partial( WeakMethod )`
    in menu commands.
- Simplified and improved Merge node implementation.
- Added MetadataProcessor base class to GafferImage.
- Added Plug::dirty() virtual method. This is used to inform a Plug
  that it has been dirtied by Plug::propagateDirtiness().
- Fixed DependencyNodeWrapper to translate python exceptions to C++.

Build
-----------------------------------------------------------------------

- Fixed compilation without NDEBUG=1 with gcc 4.1.2.

 Incompatibilities
-----------------------------------------------------------------------

- Removed MatchPatternLess from StringAlgo.h.
- Replaced PlugValueWidget `_dropValue()` method with `_convertValue()`.
- Removed GafferImage::FilterProcessor.
- Added/removed virtual overrides in GafferImage.
- Added virtual function to Plug.

0.11.0.0
========

Image
-----------------------------------------------------------------------

- Image nodes are now documented
- RemoveChannels renamed to DeleteChannels

Scene
-----------------------------------------------------------------------

- Fixed a bug in the InteractiveRender that was causing a crash when the scene child names changed.

0.10.1.0
========

UI
-----------------------------------------------------------------------

- Fixed FilterPlugValueWidget filter menu

Scene
-----------------------------------------------------------------------

- Fixed dirty propagation for globals in the camera node
- IPR now blocks the UI while it's starting up, and is more selective
  about sending scene edits.

Core
-----------------------------------------------------------------------

- Fixed dirty propagation bug in expressions

0.10.0.0
========

Core
-----------------------------------------------------------------------

- Reimplemented paths framework in C++ (#1190). This gives much
  improved performance - 10x or more speed improvements in the
  SceneHierarchy panel.
- Fixed subprocess hangs seen when dispatching renders inside Maya.
- Restored compatibility with references from prior to version 0.8.0.0.

UI
-----------------------------------------------------------------------

- Added bookmarks system for NodeGraph (#849).
  - Bookmark nodes using the right-click node context menu
  - Connect plugs to bookmarked nodes using the right-click plug
    context menu.
- Added NodeGraph Ctrl+Click to select all downstream nodes (#941).
- Added additional "Edit/Select Connected" menu items
- Fixed "Edit/SelectConnected" menu items to ignore invisible nodes.
- Fixed "Edit/SelectAll" menu item to ignore invisible nodes (#1207).
- Highlighted plugs at non-default values in the NodeEditor (#1216).
- SceneInspector
  - Significant performance improvements.
  - Added name based filtering for options and attributes (#1159).
  - Added query caching.
- Fixed bug whereby Widget.setVisible( notABool ) could cause problems.
- Fixed clearing of StandardNodeGadget errors for non-DependencyNodes.

Scene
-----------------------------------------------------------------------

- Added "mode" plug to Set node. This allows paths to be added to or
  removed from existing sets, in addition to the old behaviour of
  creating a new set (or replacing an existing one of the same name).
- Added ClippingPlane node.
- Added "enabled" plug to Filter nodes (#1196).
- Added FilterSwitch node (#1197).
- Added "name" plug to Duplicate node, to provide control over the
  names given to the duplicates (#1200).

Appleseed
-----------------------------------------------------------------------

- Added photon target attribute.
- Added sampler option.
- Synced default options with new Appleseed defaults.

Cortex
-----------------------------------------------------------------------

- Added UI hint to control the visibility of the header in the
  ParameterisedHolder node UI.

API
-----------------------------------------------------------------------

- GraphGadget
  - Added degreesOfSeparation argument to upstreamNodeGadgets() method.
  - Added downstreamNodeGadgets() and connectedNodeGadgets() methods.
- EditMenu
  - Added scope() method. This should be used by custom edit menu
    commands to ensure they operate on the right portion of the
    node graph.
- CompoundVectorParameterValueWidget
  - Added support for "showIndices" parameter user data.
- PathMatcher
  - Added addPaths() and removePaths() methods, each taking a second
    PathMatcher to provide the paths.
- Serialisation
  - Made classPath() and modulePath() methods compatible with passing
    a class as well as an instance.
- PathListingWidget
  - Added setSortable() and getSortable() methods.
- Added MatchPatternPathFilter
- Added bindings for SceneAlgo camera() and shutter() functions.
- Metadata
  - Added control over persistence of instance values.
- Added preprocessor macros for gaffer version numbers.

Incompatibilities
-----------------------------------------------------------------------

- Path
  - The info API has been replaced with a property API. Emulation
    for the old API exists, but it has been deprecated.
  - Properties must derive from RunTimeTyped, whereas info could
    contain any python type.
  - Subclasses now _must_ implement the copy() method.
- PathListingWidget
  - Column python class has been replaced with several specialised
    C++ subclasses. It is no longer possible to derive from Column
    in python.
- GraphGadget
  - Added argument to upstreamNodeGadgets() method.
- GafferScene::Filter
  - Renamed "match" plug to "out". Backwards compatibility is
    provided by a __getattr__ alias in Python.

Build
-----------------------------------------------------------------------

- Updated public build to use Cortex 9.0.0-b4.
- libGafferUI now links with Qt. This must be considered when building
  Gaffer to be hosted inside other applications.
- Requires subprocess32 python module.
- Added subprocess32 to dependencies build process.

0.9.0.0
=======

This is primarily a bugfix release.

Core
-----------------------------------------------------------------------

- Documented all nodes and plugs.
- Improved Reference workflow
  - Boxes exported for referencing contain new default values for all
    promoted plugs to match their current values on the Box.
  - When reloading a reference, only values the user has changed from
    their defaults will be kept. Other values will be updated from the
    new reference.
  - Box metadata is included when exporting for referencing. This
    means that colours and descriptions set via the UIEditor will
    be transferred onto any Reference nodes which load the exported
    reference (#1171).
- Added "-threads" command line argument to Gaffer.Application
- Fixed "gaffer execute" error handling

Cortex
-----------------------------------------------------------------------

- Documented all nodes and plugs.

Scene
-----------------------------------------------------------------------

- Added hack for controlling TBB concurrency from SceneProcedural
  - Using the GAFFERSCENE_SCENEPROCEDURAL_THREADS environment variable

RenderMan
-----------------------------------------------------------------------

- Fixed hangs caused by deleting or reconnecting a paused
  InteractiveRenderManRender node.

Appleseed
-----------------------------------------------------------------------

- Fixed render threads and texture memory options.

Image
-----------------------------------------------------------------------

- Fixed bug which prevented serialisation of read only FormatPlugs.

UI
-----------------------------------------------------------------------

- Fixed creation of expressions for BoolPlugs.
- Fixed context used by scene view camera chooser.

API
-----------------------------------------------------------------------

- Added Metadata::registerNode() method. This allows all the metadata
  for a node and its plugs to be registered with a single function call
  (#1160).
- Added GafferTest.TestCase.assertNodesAreDocumented().
- Serialisation
  - Added serialisation argument to `Serialiser::constructor()`.
  - Added Serialisation::parent() accessor.
- ValuePlug
  - Simplified handling of default values.
  - Added isSetToDefault() method.
- Made CompoundDataPlug::addMember() set default value for name plug
  (#935).
- Added Python bindings for tbb::task_scheduler_init

Incompatibilities
-----------------------------------------------------------------------

- Added argument to virtual method `Serialiser::constructor()`.
- Changed layout of ValuePlug classes.
- Removed virtual overrides from some ValuePlug classes.
- Added virtual method to ValuePlug.

Build
-----------------------------------------------------------------------

- Updated public build to use Cortex 9.0.0-b3.
- Included Shiboken module in release packages.

0.8.2.0
=======

Core
-----------------------------------------------------------------------

- Prevented errors in Metadata slots from stopping other slots running.

Scene
-----------------------------------------------------------------------

- Fixed BranchCreator dirty propagation.

RenderMan
-----------------------------------------------------------------------

- Add trace bias in RenderManAttributes.

Image
-----------------------------------------------------------------------

- Stopped display transforms hardcoding OCIO "linear" colour space.
- Fixed dirty propagation for Merge node.

UI
-----------------------------------------------------------------------

- Fixed evaluation time of look-through cameras in the Viewer.
- Added camera name to resolution gate overlay.
- Removed redundant render requests from CompoundNodule.
- Simplified Gadget render requests when children are added/removed
- Prevented duplicate errors on StandardNodeGadget tooltips.
- Fixed CompoundEditor lifetime bug
- Setting DispatcherUI frameRange widget text in PlaybackRange mode.
- Made NameWidget replace " " with "_" automatically.

API
-----------------------------------------------------------------------

- Removed GafferBindings::CatchingSlotCaller.
- Added Gaffer::CatchingSignalCombiner class.
- Added Gadget::requestRender() method.

Build
-----------------------------------------------------------------------

- Fixed GafferRenderMan public build.

0.8.1.0
=======

Core
-----------------------------------------------------------------------

- Fixed ComputeNodeWrapper exception handling.

UI
-----------------------------------------------------------------------

- Fixed GafferUI crashes seen at Python shutdown.
- Added support for hiding some fields of CompoundNumericPlugValueWidgets.
- Update DispatcherUI; can dispatch box with promoted requirement.
- Fixed crashes when deleting a node immediately after it errored.

Scene
-----------------------------------------------------------------------

- Fixed light visibility bug.
- Fixed coordinate system visibility bug.
- Added visible() function to SceneAlgo.h.
- Added GL FacingRatio shader

RenderMan
-----------------------------------------------------------------------

- Added "vector2" widget annotation support for RenderMan shaders.

Build
-----------------------------------------------------------------------

- Stopped installing the python module by default
- Moved installDir to /tmp for local IE builds.
- Fixed release script to ignore GAFFER_OPTIONS_FILE environment variable.
- Updated IE publicDependenciesBuild script.
- Enabled testing of UI modules on Travis CI.
- Added debug output to installDependencies.py.

0.8.0.0
=======

Apps
-----------------------------------------------------------------------

- Python
    - Added support for executing files with arbitrary extensions.
    - Properly handled `sys.exit()` usage from within a script.
    - Updated sys.argv so `gaffer python myScript.py` behaves like
      `python myScript.py`.

Core
-----------------------------------------------------------------------

- Made small optimisations to the computation engine.

UI
-----------------------------------------------------------------------

- Added "layout:widgetType" metadata entry.
- Improved image rendering quality.
- Added error display in the node graph (#1115).
- Added menu item for applying Random node to IntPlugs.
- Fixed Box UI error when connecting external BoolPlug to internal IntPlug.

Scene
-----------------------------------------------------------------------

- Removed support for attribute caches.
- Optimised SceneReader hashes.
- Improved hash computation for many node types. This should improve
  cache memory usage and speed.
- Fixed SceneReader for invalid files and paths. Previously it would
  error on the first attempt, but either silently fail or crash on
  subsequent attempts.
- Optimised PathMatcher construction.
- Multithreaded child procedural instantiation in SceneProcedural.

RenderMan
-----------------------------------------------------------------------

- Added support for a "nodeColor" annotation.

Image
-----------------------------------------------------------------------

- Optimised ImageReader. Reduced runtime of ImageReader->ImageTransform
  benchmark by nearly 40%.
- Fixed thread-safety bug in ImageReader.

OSL
-----------------------------------------------------------------------

- Added UI support for OSL "help", "label", "divider", "widget" and
  "options" metadata entries.

Appleseed
-----------------------------------------------------------------------

- Added visibility attributes to AppleseedAttributes node.

API
-----------------------------------------------------------------------

- Added outputsToIgnore argument to GafferTest.TestCase.assertHashesValid().
- Added NodeAlgo support for plug presets specified en masse via arrays.
- Added Node::errorSignal().
- Added tokenize() function to StringAlgo.h.
- Added support for array metadata in OSLShader.
- Simplified OSLShader::*Metadata() python return types.
- Added Python bindings exposing the OSL version.
- Removed Source node.
- Removed FileSource node.
- Detemplatized ObjectSource.
- Added GafferUI.LayoutPlugValueWidget. This is entirely metadata-driven,
  and will be used to slowly replace legacy CompoundPlugValueWidget UIs.
- Deprecated CompoundPlugValueWidget.
- Fixed drawing of ImageGadget children.
- Added Gadget::executeOnUIThread() method.

Build
-----------------------------------------------------------------------

- Updated README with simplified build instructions.
- Added support for OSL 1.6.
- Requires Cortex 9.0.0-b2.
- Added Qt headers to Gaffer packages.
- Fixed TBB compilation on OS X.

Incompatibilities
-----------------------------------------------------------------------

- Simplified OSLShader::*Metadata() python return types.
- Removed support for attribute caches.
- Removed Source node.
- Removed FileSource node.
- Detemplatized ObjectSource.

0.7.0.0
========

This release brings the exciting addition of support for the open source [Appleseed](http://appleseedhq.net/) renderer. It also adds the much asked for Dot node, and a tool for editing render crop windows. Plus of course the usual small improvements, optimisations and bug fixes.

## UI

- Added resolution gate and crop windows overlays to 3d viewer (#1016).
- Added tool for manipulating crop window.
- Added "User Default" item to plug popup menus.
- Added sneaky hotkey for navigating inside any node in NodeGraph.
- Fixed Reference node UI to match equivalent Box node UI (#1108).
- Improved positioning of nodes created by the NodeMenu.
- Improved table widget (#204).
	- Remove button disabled when selection empty
	- Newly added rows are selected automatically
	- Newly added row has keyboard focus for immediate editing
- Added customisable presets to plug widgets (#1113).
- Fixed bugs where image viewer was using incorrect context (#1124).
- Fixed bug where channel mask UI was using incorrect context.
- Added a refresh button to ImageReaders.
- Added support for specifying node, nodule, and connection colours via Metadata (#89).
- Added support for setting node colour in the UIEditor or from the RMB popup in the graph.
- Fixed bug in ColorChooserDialogue.waitForColor().
- Added basic colour scheme for nodes in the GUI app (#1098, #154).

## Core

- Optimised Switch node for constant indices. A benchmark with the bunny scene followed by 50 switches shows a 6x speedup overall.
- Added Dot node (#12).
- Fixed bindings for Metadata types other than simple typed data (#1136).

## Scene

- Added min/max limits to StandardOptions crop window plug.
- Fixed bugs which prevented ObjectSource nodes from working after create/undo/redo.
- Fixed UnionFilter to accept inputs from Boxes.

## Image

- ImageWriter now creates the necessary directories before writing images.

## RenderMan

- Added shader Metadata option "shaderTypeOverride" (#pragma annotation "shaderTypeOverride" "ri:shader" will force the Gaffer shader type to "ri:shader").

## Appleseed

- Added support for the Appleseed renderer, courtesy of Esteban Tovagliari.

## API

- Optimised ScenePlug::stringToPath(). This gives an 88% reduction in runtime for a synthetic test of just that function, and a 7% reduction in total runtime for a scene benchmark using the Instancer.
- Added hasUserDefault( plug ) and applyUserDefault( plug ) to NodeAlgo.
- Added Context.__contains__ binding.
- Simplified numeric plug bindings.
- Added min/max values to BoxPlug.
- Added handy CompoundDataPlug::MemberPlug child accessors.
- Added GafferBindings::NodeClass() overload for suppressing init.
- Moved shutter() and transform() from RendererAlgo.h to SceneAlgo.h.
- Added camera() methods to SceneAlgo.h.
- Removed GLWidget minimum size.
- Fixed bug where ViewportGadget::setCamera() could forget viewport size.
- Fixed ViewportGadget::RasterScope to work during selection.
- Added ViewportGadget::preRenderSignal().
- Made View::update() non-pure virtual.
- Added View::contextChangedSignal().
- Added Tool base class.
- Fixed bugs in ExceptionAlgo formatPythonException().
- Fixed StandardStyle border widths to be independent of border radius.
- Added Menu.popupPosition() method.
- Improved support for functools.partial() callables in Menu commands.
- Added metadata to control StandardNodeGadget minimum width, padding, and nodule spacing.
- Improved StandardNodeGadget drag/drop handling. Previously it would accept drags it wasn't going to use, preventing other handlers from working.
- Added Nodule::updateDragEndPoint() virtual method.
- Fixed ScriptNode::deleteNodes() for nodes without enabled plugs.
- Added customisable edge gadgets to StandardNodeGadget.
- Added support for changing nodule position on StandardNodeGadget.
- Guaranteed order of Metadata::registered*Values().
- Added plug presets methods to Gaffer.NodeAlgo.
- Added GafferUI.PresetsPlugValueWidget.
- Added PlugValueWidget.childPlugValueWidget(), so derived classes don't need to implement it if they don't have such children (#1123).
- Added Style::renderNodeFrame() to distinguish between frames drawn for nodes and those drawn as normal frames.
- Updated Style bindings.
- Added useDisplayTransform argument to ColorSwatch constructor.
- Added useDisplayTransform argument to ColorChooser and ColorChooserDialogue.
- Added DataBinding.h header with dataToPython().

## Build

- Added scripts for automating releases.
- Updated IE public build script to use MILESTONE_VERSION, and renamed it to publicDependenciesBuild, since it is no longer used for producing the public release builds.
- Requires Cortex 9.0.0-b1 for Appleseed support.

## Incompatibilities

- Moved shutter() and transform() from RendererAlgo.h to SceneAlgo.h.
- Made View::update() non-pure virtual.
- Added virtual method to Nodule.
- Added and reordered Style virtual methods.

0.6.0.0
=======

#### UI

- Fixed bug which prevented newly created nodes from being inserted inline in the Node Graph.
- Added error display to string and numeric plug widgets - typically this is useful when a bad expression has been entered. Previously bad expressions would break the UI.
- Optimised the 3d view significantly.
- Fixed UI reordering bug in UIEditor (#847).
- Added menu item for deleting CompoundDataPlugValueWidget children.

#### Apps

- Added ignoreScriptLoadErrors parameter to execute app.

#### Core

- LocalDispatcher now has an option to ignore errors when loading the script (#1084).

#### Scene

- Fixed Grid node GL shader assignment.
- Fixed bug in Instancer dirty propagation.
- Fixed SubTree set computation when root path omits the leading slash.
- Added "isolate from" capability to GafferScene.Isolate node.

#### API

- Added support for invalid variants to GafferUI._Variant.fromVariant().
- Added TextWidget setErrored()/getErrored() methods.
- Added GafferSceneUI::SceneGadget class, for optimised display of scenes in OpenGL.
- Removed bloat from SceneProcedural - this was being used previously to implement the viewer but is no longer needed.
- Added ValuePlug::getValue() arguments for when hash is known.
- Added TypedPlugClass helper to GafferBindings.
- Improved exceptions thrown from ScriptNode::execute().
- ScriptProcedural now ignores errors when loading the script.
- Added PlugLayout.layoutOrder() static method.
- Fixed deadlocks if computes spawn their own threads.
- Added GafferScene::PathMatcher::prune() and isEmpty() methods.

#### Incompatibilities

- Added argument to ValuePlug::getObjectValue(), and associated derived class getValue() calls. Source compatibility is maintained, but binary compatibility is not.
- View::setContext() is now virtual.

#### Build

- Requires Cortex 9.0.0-a10

0.5.0.1
=======

#### Scene

- Fixed signal threading bug in SceneProcedural which was causing sporadic crashes

0.5.0.0
=======

#### Core

- Fixed LocalDispatcher to quote command line arguments and ignore "ui:" prefixed context variables.
- Avoiding shell subprocess for Local Jobs stats.
- LocalDispatcher now just constructs a Job and lets it do the heavy lifting
- Fixed bug where script context changes could leak into local background dispatches.
- added python error catching to ConnectionBinding, to prevent crashes
- Fixed serialization bug with extra plugs on references
- Dispatcher::frameRange() is now public and virtual.

#### UI

- Menu widget: Added support for icons
- Disabled Kill button when no jobs are selected.
- Job details tab is scrollable and resizable.
- Fixed context errors in teh scene inspector
- Added button to remove failed jobs.
- Preventing update error for deleted display node.
- Adding support for icons in menus

#### Image

- Preventing OIIO error overflow crash

0.4.0.0
=======

#### Core

- Plugs and ValuePlugs now accept children (#1043).
- Added child matching to connected Plugs (#1043).
- Added LocalDispatcher.Job and LocalDispatcher.JobPool to track running batches (#1064).
- Failing batches not stop a LocalDispatch job.

#### UI

- Improved Object section of SceneInspector (#897).
- Added a window for tracking currently running LocalDispatcher jobs (#872).
- Fixed reparenting bug with DispatcherWindows (#1064).

#### Scene

- Fixed poor performance of Prune/Isolate in presence of SetFilter.
- Added sets support to Parent node (#1065).
- Outputting all cameras, not just the primary camera, to the renderer.
- Added support for per-camera resolution overrides, specified with a "resolutionOverride" V2iData in the camera parameters.

#### API

- Plugs and ValuePlugs now accept children. CompoundPlug will be deprecated.
- Added BranchCreator::hashBranchGlobals() and computeBranchGlobals(), and implemented them for Parent.
- Added outputCameras() and overload for outputCamera() to RendererAlgo.h.
- Added LocalDispatcher.Job and LocalDispatcher.JobPool to track running batches.

#### Incompatible changes

- Added additional virtual methods to BranchCreator
- ValuePlug::settable() is no longer virtual
- Removed methods and member variable from CompoundPlug
- InteractiveRender "updateCamera" plug renamed to "updateCameras".

0.3.0.0
=======

#### Core

- Added SubGraph base class, which Reference and Box now derive from, allowing them both to be enabled/disabled.
- Redesigned Dispatcher registration (#922) (see API section for details).

#### UI

- Nodes created via the NodeMenu apply default values to their plugs, using the "userDefault" key in the Metadata (#1038).
- Exposed the DispatcherWindow to the public API.

#### Cortex

- Moved Cortex-specific functionality into new GafferCortex library and module.
	- The Gaffer core itself remains heavily dependent on Cortex, and always will. Here we're splitting out "end user" functionality such as OpHolders and ProceduralHolders, so that GafferCortex can be thought of as the user-visible presence of Cortex within Gaffer.
	- This remains backwards compatible for now via startup files, which allows a grace period for dependent code to update to the new module layout.

#### RenderMan

- Added basic support for RenderMan volume shaders.

#### API

- Added Gaffer.NodeAlgo python scope with applyUserDefaults( node ) (#1038).
- Redesigned Dispatcher registration (#922).
	- Dispatchers are registered with Creator functions rather than instances.
	- Added get/setDefaultDispatcherType(), which can be used to create a new instance of the default type.
	- SetupPlugsFn is now a static function that can be registered along with a Creator, rather than a virtual method of Dispatcher instances.
- Added gil release to GafferScene.matchingPaths python binding.
- Fixed StringPlug string substitution bug.
- Catching error_already_set in Dispatcher bindings.

#### Incompatible changes

- Reference and Box now derive from SubGraph rather than Node or DependencyNode.
- Redesigned Dispatcher registration (#922) (see API section for details).

0.2.1.0
=======

#### Core

* Expression node optimizations

#### Scene

* Made ShaderAssignment use the shader type as an attribute name.
* Added Group::nextInPlug() method
* InteractiveRender now updates all attributes, not just shaders

#### UI

* Dispatcher FrameRange UI displays the value that will actually be dispatched.
* Removed unwanted horizontal padding from frameless Buttons.

0.2.0.0
=======

This release brings significant optimisations, further additions to the SceneInspector, and the usual collection of miscellaneous enhancements and bug fixes.

#### Core

- Optimised Context::substitute(). This gives a 73% reduction in runtime for a substitutions benchmark.
- Added '\' as an escape character in Context::substitute() (#997).
- Boxes may now be enabled/disabled and define pass-through behaviours (#1015).
- Significant optimisations to the computation engine.
- Added TaskList node for grouping the dispatch of several input requirements.

#### Image

- Fixed Display node for bucket sizes larger than the native tile size.
- Fixed problems when running embedded in Maya.

#### Scene

- Added code to clear caches after full procedural expansion in batch renders.
- Added scene pass-through to the InteractiveRender node. This allows it to be seen in the Viewer, SceneHierarchy, SceneInspector etc.
- Significant optimisations. A benchmark scene can now be generated in 3% of its previous runtime.

#### RenderMan

- Added "command" plug to RenderManRender. This allows the user to customise the command used to render the RIB (#1017).

#### UI

- SceneInspector improvements
	- Added set membership section (#930).
	- Added sets section to globals (#895).
	- Improved responsiveness.
- MenuButton improvements
	- Menus are shown on press rather than release (#742).
	- Added menu indicator (#493).
- Fixed OpDialogue bug which caused it to return to the parameters pane when it should have been displaying an error.
- Dispatcher improvements
	- Added PlaybackRange to the frames mode menu (#1007).
	- Renamed ScriptRange to FullRange.

#### API

- Added custom Diff support to SceneInspector.
- Fixed crashes when passing None to PathMatcher python methods.
- Added accessors for the buttons on VectorDataWidget (#1003).
- Fixed broken SceneInspector.Row.getAlternate() method.
- Added SceneProcedural::allRenderedSignal().
- Added Context::remove() method.

#### Incompatible changes

- SceneInspector API changes.
- Box rederived from DependencyNode.
- Dispatcher ScriptRange renamed to FullRange.

#### Build

- Improved Travis continuous integration setup
	- Added running of unit tests
	- Added GafferRenderMan support
- Fixed installation to paths starting with "./"
- Fixed RenderManShader compilation in Clang 3.4
- GafferOSL compatibility for OSL version 1.5

0.1.1.0
=======

#### Core

- Optimised computation for long chains of nodes (#963).
	- Optimised repeat calls to Context::hash().
	- Added Context::changed() method.
	- Made Context::hash() ignore "ui:" prefixed entries.
	- Refactored ValuePlug::hash() to delegate to Computation.

#### UI

- Fixed Execute->Repeat Previous menu item.
- Fixed display of '<', '>' and '&' in SceneInspector.

#### Scene

- Added an ExternalProcedural node (#722).
- Added pass-through plugs to ExecutableRender nodes and SceneWriter.
- Added pixelAspectRatio, overscan, and resolutionMultiplier options (#979).

#### Image

- Added pass-through plugs for ImageWriter.

#### Build

- Requires Cortex 9.0.0-a6
- Fixed typedef issues when building with GCC 4.8
- Added Travis config for build verification (doesn't run the tests yet)

0.1.0.0
=======

#### Apps

- The "gui" app now tolerates errors when loading scripts from the command line. Note that currently errors are only reported to the shell.
- The "execute" app can now handle nodes inside Boxes.

#### Core

- Improved version numbering (#980)
	- Versions are now MILESTONE.MAJOR.MINOR.PATCH
		- Changes to MILESTONE version denote major development landmarks
		- Changes to MAJOR version denote backwards incompatible changes
		- Changes to MINOR version denote new backwards compatible features
		- Changes to PATCH version denote bug fixes
	- Added Gaffer.About.compatibilityVersion() method
	- Added GAFFER_COMPATIBILITY_VERSION macro for conditional compilation of C++ extensions
- Fixed bug whereby GraphComponent::setName() could allow duplicate names
- Dispatcher improvements
	- `Dispatcher::postDispatchSignal()` is now always executed, even if execution is cancelled or fails. A new boolean argument is passed to specify whether or not dispatch succeeded.
	- Dispatcher now creates job directories automatically, so derived classes don't have to

#### Incompatible changes

- `Dispatcher::postDispatchSignal()` signature change.
- Dispatcher jobDirectory() semantics change.
- Dispatcher jobDirectoryPlug() -> jobsDirectoryPlug() rename.

#### Build

- Requires Cortex 9.0.0-a5

0.101.0
=======

#### Core

- ExecutableNodes now accept Boxes as requirements inputs and outputs.
- Dispatchers accept Boxes for direct dispatching (#925).
- Added SystemCommand executable node.
- Optimised plug dirty propagation.
- Added matchMultiple() function to StringAlgo.h.

#### Scene

- Renamed Displays node to Outputs. Also changed "label" plug to "name" and the old "name" plug to "fileName" (#54).
- Fixed dirty propagation bug in Outputs node.
- Added an outputOutputs() method to RendererAlgo.h, so outputOptions() need only output actual options.
- Added DeleteGlobals node.
- Added DeleteOutputs node.
- Added DeleteOptions node (#965).
- Added wildcard matching to DeleteAttributes and DeletePrimitiveVariables.
- Prefixed options in scene globals with "option:".
- Added global mode to Attributes node, which places the attributes in the globals (with "attribute:" prefixes).
- Updated render nodes to support global attributes.
- Added global attribute support to SceneProcedural (#964).
- Fixed RendererAlgo outputScene() to include coordinate systems.

#### UI

- Added Outputs section to the SceneInspector (#921).
- Updated SceneInspector to display global attributes.
- Fixed display of single empty bounding box in SceneInspector.

#### RenderMan

- Added FrameBegin/FrameEnd in RIBs generated by RenderManRender (#358). Requires Cortex 9.0.0-a5.

#### OSL

- Fixed default arguments for OSL In* and Out* shaders.

#### Build

- Set default compiler optimisation level to -O3.
- Added missing OSL, OIIO, OCIO includes to the dependency package.
- Clang compatibility fixes.

0.100.0
=======

This release features significant improvements to Dispatcher and SceneInspector functionality, along with the usual bunch of small fixes and improvements.

#### Apps

- Changed shutdown warnings to debug messages.

#### Core

- Dispatcher improvements
	- Dispatching can be cancelled via preDispatchSignal() (#929).
	- Added batching (#870, #871).
	- Optimised foreground execution in LocalDispatcher.
	- Added per-node foreground execution overrides for LocalDispatcher (#927).
- Added support for module level config files.

#### UI

- SceneInspector improvements
	- Added history tracebacks (#834).
	- Added attribute inheritance diagramming (#206).
	- Added value drag/drop (#830).
	- Improved transform section (#896).
	- Optimised by deferring updates during playback.
	- Optimised by deferring updates when not directly visible.
	- Fixed errors where the selected path doesn't exist.

#### Scene

- Fixed SceneWriter::hash() to include file path.
- Fixed SceneWriter when caching multiple time samples.
- Added support for coordinate systems.

#### API

- Fixed Fixed python bindings crash when passing None for a scene path.
- Added removeOnClose argument to Window.addChildWindow() method.
- Fixed EventLoop bug where exection was thrown if an idle callback was removed and re-added during the same idle event.
- Added hotspots to Pointer class.
- Refactored ExecutableNode API
	- Removed "execution" prefix from method names.
	- ExecutableNodes now execute() using the current Context. Multi-context execution can be accomplished using executeSequence( frames ) assuming the client only needs to vary the frame of the current Context. requiresSequenceExecution() can be defined by nodes with special needs (SceneWriter for example), to alert clients that sequence execution is more appropriate.
	- Dispatcher::doDispatch() is now passed a DAG of TaskBatch nodes, simplifying the task of implementing more complex dispatchers.
- Fixed call sequence for GraphComponent::parentChanging(). When a child is being transferred from one parent to another, it is now called at a point where the child still has the original parent.
- Added ViewportGadget raster<->world space conversion methods.
- Added Handle::dragOffset() method.

#### Build

- Best used with 3delight version 11.0.96. This has bug fixes to support moving coordinate systems during IPR.
- Requires Cortex 9.0.0-a3.

0.99.0
======

#### Apps

- Fixed potential startup error in gui viewer.py configuration file.

#### Core

- Added background execution mode to the LocalDispatcher.

#### UI

- Added a gnomon to the 3d viewer (#41).
- Improved SceneInspector
	- Reimplemented as a hierarchy with a registration mechanism for custom sections (#36, #821).
	- Improved diff formatting (#894).
	- Improved numeric formatting and alignment.
	- Added options section (#197).
- Implemented error tolerant loading for file menu operations. Errors are reported via a dialogue, and will no longer prevent loading of a script (#746).
- Fixed ScriptEditor to execute code in the right context. Prior to this, any queries performed in the script editor were always evaluated at frame 1.
- Dispatcher UI no longer forces background execution - this is now controlled by per-dispatcher settings.

#### Scene

- Improved IPR
	- Fixed hang during shutdown with active IPR render (#855).
	- Implemented camera edits for IPR rendering (#190).
	- Prevented errors in other nodes from causing incomplete edits.
	- Fixed UI errors caused by deleting camera during IPR (#898).
	- Optimised updates by pruning invisible hierarchies.
	- Fixed bug in shader edits at non-leaf locations.
- Optimised Instancer, especially the computation of the bounding box for all the instances. This particular operation is now 18x faster on a 6 core machine, 7x faster on a 2 core machine.
- Added an automatically created set for tracking all cameras in the scene.
- Improved reporting of invalid cameras (#371).
- Fixed FilteredSceneProcessor::acceptsInput() crash when inputPlug is null.

#### API

- Registered automatic from-python conversions for ScenePlug::ScenePath. This replaces the need to manually wrap any functions taking a ScenePath, making the bindings simpler.
- Added exists() method to SceneAlgo. This can be used to query whether or not a particular location exists within a scene.
- Replaced boost_intrusive_ptr with raw pointer where appropriate, to follow the convention laid out in Cortex.
- Removed deprecated Box metadata methods. The standard Metadata API should be used instead.
- Added missing wrapper for NodeGadget::nodule() overload.
- Added OpDialogue preExecuteSignal() and postExecuteSignal().
- Added OpDialogue parameterisedHolder() method.
- Added a flags argument to ParameterHandler::setupPlug(). This allows clients to choose the default flags for their plugs, rather than being forced to have (Default | Dynamic) plugs.
- Added ViewDescription constructor for 3 argument registerView.
- Added Style::renderTranslateHandle() method.
- Added GafferUI::Handle gadget.
- Moved translatePythonException() to a new ExceptionAlgo.h header.
- Added formatPythonException() function to ExceptionAlgo.h.
- Added continueOnError argument to ScriptNode execution methods.
- Added error return value to ScriptNode execution methods.
- Improved EventLoop.executeOnUIThread() to execute immediately when used on main thread.

#### Build

- Requires Cortex-9.0.0a2
- Updated default build to use PySide 1.2.2.
- Stopped using python-config for build configuration. It was unreliable on Mac, and the hardcoded paths it returns prevented us from building with prebuilt binary dependencies.

0.98.0
======

This release makes dispatchers available via the UI for the first time. Dispatchers allow many tasks (such as rib generation, rendering and compositing) to be processed for a series of frames, with dependencies between the tasks determining the execution order. It also adds support for adding and removing lights during IPR renders, and the usual  small fixes and improvements.

#### Apps

- Added context parameter to the execute app. This takes a series of key/value pairs that allow additional context variables to be specified.
- Fixed shutdown warning when running `gaffer test GafferTest`.
- Added repeat parameter to test app.

#### UI

- Integrated Dispatchers into the UI with a Dispatcher window, which can be launched in any of the following ways :
	- The /Execute/ExecuteSelected menu item (Ctrl+E)
	- The Execute button the NodeEditor
	- The right click node menu in the NodeGraph.
- Fixed several shutdown warnings.
- Fixed bug in Reference node menu item.

#### Core

- Added jobName and jobDirectory plugs to Dispatcher. These control the creation of a location for storing temporary files needed for the dispatch.
- Added Frame Range options to Dispatcher.
- Improved LocalDispatcher to dispatch tasks in a subprocess (#866).
- Fixed ExecutableOpHolder hash computation.
- Implemented variable substitutions for ExecutableOpHolder.
- Fixed ObjectWriter hash computation (#878).

#### Scene

- Implemented light add/remove/hide/show for IPR (#874).
- Stopped ExecutableRender saving the script when it executes (#310). This is now done automatically by the dispatchers, which save a copy into the job directory.
- Fixed ExecutableRender hash computation.
- Fixed SceneWriter hash computation.

#### Image

- Fixed ImageWriter hash computation.

#### API

- Added ScenePlug::pathToString() method.
- Added outputLight() method to RendererAlgo.h.
- Fixed bug in DependencyNode dirty propagation order. This ensures that dirtiness is only signalled for a plug after it has been signalled for all the plugs it depends on and all its children.
- Derived all Gaffer unit tests from GafferTest.TestCase.
- Simplified Dispatcher implementations by providing doDispatch with the unique task list.
- Made Dispatcher::uniqueTasks() private.
- Dispatchers now require that all nodes belong to the same ScriptNode.
- Fixed ExecutableNode::Task comparison functions and member access (#865).
- Improved Plug bindings with a new PlugClass helper class.
- ExecutableNode::executionHash() must now call the base class implementation first - see documentation for details.

0.97.0
======

This release is focussed mainly on optimisation and bug fixes, with significant speedups being provided by moving to a new caching implementation provided by Cortex 9. Behind the scenes it also contains progress towards exposing Dispatcher functionality at the user level.

#### Core

- Optimised FilteredChildIterator and PlugIterator. This alone gives more than a 5% speedup in a simple Instancer benchmark.
- Fixed serialisation of non-dynamic ArrayPlugs. This bug caused the appearance of duplicate requirements plugs on executable nodes (#580).

#### UI

- Added a grid to the 3D viewer.
- Added NodeGraph menu item for selecting objects affected by a node - accessed by right clicking on a filtered scene node.
- Fixed several causes of zombie widgets which could cause errors at shutdown.
- Moved the Execute button for ExecutableNodes to a prominent position in the header of the NodeEditor.
- Added SceneWriter to the node menu. Also reorganised the Scene menu to include a File submenu, and simplified the Object menu by moving generators into the Source submenu.

#### Scene

- Optimised Shader network computation - reducing runtime by 35% for typical production networks.

#### Arnold

- Fixed ArnoldRender "Generate expanded .ass" mode. It was using a "-resaveop" command line flag removed from kick in Arnold version 4.0.10.0.

#### API

- Added ability for Gadgets to have child Gadgets. Previously only ContainerGadgets could have children.
- Rederived NodeGadget from Gadget rather than IndividualContainer. This allows more flexibility in NodeGadget implementations, and also better hides the implementation details.
- Added methods for controlling Gadget visibility.
- Rederived ViewportGadget from Gadget rather than IndividualContainer. This allows viewports to have multiple child gadgets, which paves the way for more complex views and interactive manipulators.
- Made UI registration methods accept classes in place of TypeIds.
- Added public GafferScene::Filter methods for specifying input scene via Context.
- Added SceneAlgo.h with methods for querying all objects matching a filter.
- Continued refactoring the Executable framework, in preparation for exposing it to users
	- Americanized spelling.
	- Renamed ExecuteUI to DispatcherUI.
	- Renamed ExecutableNode "dispatcherParameters" plug to simply "dispatcher".
	- Rederived SceneWriter from ExecutableNode.
	- Rederived Dispatcher from Node, to allow settings to be specified via plugs.
	- Renamed Dispatcher::addAllPlugs() to Dispatcher::setupPlugs().
	- Renamed Dispatcher::addPlugs() to Dispatcher::doSetupPlugs.
- Added shutdown checks for zombie widgets and scripts.
- Fixed "base class not created yet" GafferRenderMan import error.
- Added _copy parameter to Shader::state() python binding.

#### Documentation

- Improved formatting of Doxygen documentation - a brief description of each class is now shown above the detailed member documentation.

#### Build

- Requires Cortex 9.0.0-a1.
- Recent Cortex LRUCache improvements offer significant performance gains.
- Updated default TBB version to 4.2.

0.96.0
======

#### Core

- Added support for Box data to CompoundDataPlug.
- Optimised the Context class considerably, particularly for temporary Contexts created during computation. A synthetic test which does nothing but create temporary Contexts shows a reduction in runtime of 97%, resulting in a 30% reduction in total runtime for a more real-world test using the Instancer node (#427).
- Fixed Context copy construction doubling in Python bindings.
- Fixed circular references within the undo system, which caused memory leaks where scripts were not destroyed at the appropriate time (#397).
- Optimised ComputeNode::hash(). This yields ~14% reduction in runtime for a simple Reformat benchmark.

#### UI

- Fixed PyQt circular references within GafferUI.Menu (#397).
- Fixed crash caused by File->Quit menu item.
- Improved UI for BoxPlugs.

#### Scene

- Added crop window to StandardOptions node (#688).
- Renamed gaffer:visibility attribute to scene:visible, to support the standard attribute with that name in Cortex scene caches.
- Added a SetFilter node (#92).
- Fixed deadlock removing input from running InteractiveRender node, or undoing or redoing such an operation.
- Added pausing for interactive renders (#646).

#### API

- Renamed BoxPlug min() and max() methods to minPlug() and maxPlug().
- Made Context::Scope noncopyable.
- Added GAFFERTEST_ASSERT macro. This should be used by test cases implemented in C++, and throws an exception which can be caught and reported by the Python unit test runner.
- Added _copy argument to Context::get() bindings.
- Added optimised Context copy constructor, primarily for use in constructing temporary Contexts. See class documentation for details.
- Added checks for zombie ScriptNodes and Widgets at app shutdown. This can catch many common programming errors.
- Added BoxPlugValueWidget class.

0.95.0
======

#### UI

- Improved SceneReader UI with right click menu for toggling tags on and off in the tags and sets plugs.

#### Core

- Fixed bug with references containing non-default plug values (#844).

#### Scene

- Added preliminary support for sets (#92).
	- Added a Set node. This allows users to manage sets of named locations (with optional wildcards) as part of their graph flow.
	- Replaced "gaffer:forwardDeclarations" globals entry with a private set named "__lights".
	- Updated hierarchy modifying nodes to also modify sets to keep them in sync with the hierarchy.
	- Implemented loading of tags as sets in SceneReader.
	- An upcoming release will contain a SetFilter for actually making the sets useful.
- Added a FreezeTransform node (#822).

#### RenderMan

- Fixes IPR bug where shaders could leak onto the wrong objects.

#### API

- Typedefed PathMatcherData into GafferScene namespace.
- Optimised PathMatcher (the underlying data structure for sets).
- Replaced GafferScene::Render base class with RendererAlgo.h header.
- Simplified Executable nodes and tidied up implementation, in preparation for actually integrating Despatchers properly.

0.94.0
======

#### Apps

- Increased default size of browser app (#795).
- Added bookmarks support to Op windows in the browser app (#787).
- Fixed position of quit confirmation dialogue (#751).
- Fixed parsing of command line arguments with spaces.

#### UI

- Fixed PySide incompatibility in VectorDataWidget.
- Improved VectorDataWidget numeric editing (#637).
- Simplified OpDialogue exception reporting (#806).
- Fixed "Open Recent..." crash bug in PySide builds (#548).
- Used OpDialogue to improve progress/error reports in OpPathPreview (#792).
- Enabled background mode for OpDialogue launched from BrowserEditor.
- Fixed OpPathPreview UI glitch.
- Fixed "KeyError: 'currentTab'" error when loading custom layouts.
- Added more sensible initial widget sizes to BrowserEditor. The sizes are also saved and restored when modes are switched.
- Improved Bookmarks
    - Identifies recent items by full paths, so multiple recent items with the same basename may coexist.
    - Prevents heavy usage of one bookmarks category from removing the recent items for the general (no category) bookmarks.
    - Improves bookmarks UI in PathChooserWidget to display full paths of recent items.
	- Most recent items are now displayed at the top.
	- Added creation of bookmarks by dragging on to bookmarks icon.
- Fixed cursor bug in StringPlugValueWidget continuous update mode (#796).
- Fixed bug in non-editable MultiLineStringPlugValueWidgets.
- Fixed upside down nodule labels.
- Fixed overzealous Viewport drag tracking (#550).
- Improved SceneHierarchy to view any output ScenePlug, regardless of name. This improves compatibility with Boxes, where the user can make an output plug with any name they want.
- Added right click menu for Box plugs in NodeGraph. This allows the renaming and deletion of promoted nodules.
- Added dropdown menu for Displays node quantize parameters.
- Improved Displays node UI (#15).
- Added command-line representation of Op values in the UI (#793).
- Added workaround for squash/stretch in viewport camera look-through (#826).
-  Added custom editor to PathVectorDataWidget. This enables tab completion, nice dropdown menus and a browser for PathVectorDataParameters.
- Added indexing methods to VectorDataWidget.
- Added presetsOnly dropdown menus to CompoundVectorParameterValueWidget (#470).
- Added an auto-load preset for ops (#804).
- Added filtering by image type for ImageReader and ImageWriter file dialogues.

#### Core

- Combined setValue() serialisation for CompoundNumericPlugs (#761).
- Fixed Box plug promotion to support ImagePlugs and ScenePlugs.

#### Scene

- Renamed GLSL shaders to UpperCamelCase. This matches the naming convention we use for OSL shaders.
- Added a Grid node.
- Fixed FilteredSceneProcessor to allow Box promotion of Filter plug.

#### Image

- Fixed a bug in ImageTransform that could result in corrupted output.

#### API

- Added GraphComponentClass and GadgetClass to improve bindings.
- Added NodeGadgetClass to improve bindings of NodeGadgets.
- Added immediate execution mode to OpDialogue.
- Fixed NodeGadget::noduleTangent() binding.
- Fixed potential bug in NodeGadget::create().
- Fixed LRUCache getter cost calculations.
- Fixed Metadata test hang.
- Improved Window.resizeToFitChild() behaviour. If called on an as-yet unshown window, it would move the window to the top left corner of the screen. Now the window will still be opened in a sensible place. Added additional shrink and expand arguments to further control the resize behaviour.
- Added support for fixed size CompoundVectorParameterValueWidget. The ["UI"]["sizeEditable"] user data entry can be given a BoolData value of False, which will cause the +/- buttons to be hidden in the UI, enforcing a fixed length on the data in the vector parameters.
- Added per-column editability to CompoundVectorParameterValueWidget. This uses a ["UI"]["editable"] user data entry in each child parameter, where a BoolData value of False will make the column for that parameter read-only (#766).
- Made Bookmarks.acquire() support passing Widgets and GraphComponents.
- Added support for callable dialogue keywords in PathPlugValueWidget.
- Fixed drag/drop to allow modal dialogue creation in dropSignal().
- Added public Serialisation::acquireSerialiser() method.
- Added ValuePlugSerialiser::valueNeedsSerialisation() method. This can be reimplemented by derived classes to provide more control over the serialisation of values.
- Privatised numeric and string PlugValueWidget implementations.
- Added ViewportGadget viewportChangedSignal() and cameraChangedSignal().
- Added SpacerGadget size accessors.
- Added iterator typedefs for all GafferUI::Gadget subclasses.
- Improved Box plug promotion API.
- Made BlockedConnection and UndoContext non-copyable.
- Added useNameAsPlugName argument to CompoundDataPlug::addMembers(). Also added python bindings for CompoundDataPlug::fillCompoundData() and CompoundDataPlug::fillCompoundObject().
- Gave Displays node parameter plugs more useful names.
- Added VectorDataWidget.editSignal(). This allows custom Widgets to be provided to edit the values held in the table cells.
- Added Widget.focusChangedSignal().
- Added VectorDataWidget setColumnEditable/getColumnEditable methods.
- Added right click preset menu for CompoundVectorParameterValueWidget. This also adds the ability for any custom parameter menu to operate with CompoundVectorParameters, whereas before they couldn't.

#### Build

- Now using Coverity static analysis - this resulted in a number of bugs being found and fixed in this version.

0.93.0
======

#### Core

- Added the ability to specify Metadata overrides to specify instances of Plugs and Nodes.

#### UI

- Added UI Editor. This allows the user plug layout for any node to be edited - plugs can be reordered, dividers added and help strings specified. In particular this allows the creation of custom UIs for Boxes, which can then be exported and loaded by References.
- Fixed initial unsortedness of PathListingWidgets.

#### Scene

- Added PrimitiveVariables node. This allows arbitrary primitive variables with constant interpolation to be added to objects.
- Added Duplicate node. This allows arbitrary numbers of duplicates of subhierarchies to be created, each with their own transform.

#### OSL

- Specifying lockgeom=1 by default for all OSL shading engines. This means that primitive variables (user data in OSL parlance) are not automatically mapped to shader inputs unless those inputs have explicitly set lockgeom=0 in the source (which is rare). This almost doubles the speed of a simple image noising operation.
- Fixed OSLShader::acceptsInput( NULL ) crash.

#### API

- Added PlugLayout class, which creates node editor UIs driven by Metadata. This will replace all existing plug layouts over time.
- Added StringAlgo.h, containing various string utilities, including wildcard matching (#707).
- Added metadata accessors to OSLShader.
- Fixed module import order and namespace pollution issues.
- Replaced Metadata regexes with new string matching code.
- Added Metadata signals emitted on registration of values.
- Made NameWidget accept None for the the GraphComponent.
- Added borderWidth argument to SplitContainer constructor.
- Added PathListingWidget setHeaderVisible()/getHeaderVisible() methods.
- Added PathListingWidget.pathAt() method.
- Fixed bug in GafferUI::Pointer::setFromFile( "" )
- Added a DictPath.dict() accessor.
- Moved NodeEditor.acquire() to NodeSetEditor.acquire(). This allows it to be used to acquire an editor of any type.
- Added fallbackResult to WeakMethod.
- Fixed CompoundPlug plugSetSignal() emission when children change.

0.92.1
======

#### Scene

- Improved shader assignment reporting in SceneInspector (#335)
- Improved shader handle generation

0.92.0
======

#### Core

- Made Plug flags serialisation more future proof (#684).
- Removed redundant serialisation of default values. This reduced file sizes by 25% and load times by nearly 20% for a large production script. Note that changing the default value for a plug or shader parameter now represents a backwards compatibility break with old scripts.
- Optimised python bindings, giving speedups in many areas, including file loading and shader generation.
- Removed parameter mapping from ObjectReader
- Fixed threading bugs in ObjectReader.
- Fixed bugs preventing expressions being used with filenames in ObjectReader.

#### UI

- Improved plug "Edit Input..." menu item. It now ensures that the input plug widget is directly visible on screen, whereas before it could only show the node editor for the input node.
- Prevented nodes from being created offscreen (#640).
- Exposed "enabled" plugs in a new Node Editor "Node" tab (#759).
- Fixed MessageWidget crashes encountered in Maya.
- Fixed bug preventing positioning of new nodes within backdrops (#769).
- Added workaround for PyQt/uuid crashes (#775).
- Added filtering so that DirNameParameter file browsers will only show directories and not files (#774).
- Fixes image viewer colour swatches when the image doesn't contain an alpha channel.
- Improved scene preview support to include .abc, .cob, and .pdc files (any files for which Cortex has a Reader implementation).

#### Scene

- Options and Attributes nodes now have sensible default values for their plugs.

#### Image

- Fixed bugs associated with negative display window origins.
- Fixed crash when creating ImageWriters with another image node selected (#681 #255).

#### Arnold

- Arnold shader names are now prefixed with "ai" within the node search menu, to aid finding them amongst the other nodes.

#### API

- Added Widget.reveal() method (#503).
- Added extend argument to NodeGraph.frame(). The default value of false behaves exactly as before - the specified set of nodes are framed in the viewport. A value of true still causes the nodes to be included in the framing, but in addition to the original contents of the frame.
- Properly implemented CompoundNumericPlugValueWidget.childPlugValueWidget().
- Removed MessageWidget.textWidget() method. The internal text widget should now be considered private. The currently displayed messages may be cleared using the new MessageWidget.clear() method.
- Removed deprecated MessageWidget.appendException() method.
- Added control over the default button to the OpDialogue. This controls whether the OK or Cancel button is focussed by default when displaying the Op. The default value is as before, focussing the OK button, but the value can be controlled either by user data in the Op or by passing an alternative argument to the OpDialogue constructor.
- Adopted new Python wrapping mechanism from Cortex.
- Fixed pollution of GafferUI namespace with IECore module.
- Added DirNameParameterValueWidget.
- PathPreviewWidget now respects registration order.

#### Build

- Requires Cortex 8.2.0.

0.91.0
======

#### Apps

- Fixed gui startup error in ocio.py.

#### Core

- Fixed copy/paste problems where inappropriate values would be copied for plugs with inputs, where the input was not in the selection being copied (#740).

#### UI

- Added a first implementation of an automatic node layout algorithm. This is available via the Edit/Arrange menu item (#638).
- Fixed image viewer data window display in the presence of an offset display window.
- Fixed TextGadget vertical bound. It was slightly different depending on the text contents, causing different nodes to appear with slightly different heights.
- Moved OSLObject and OSLImage shader inputs to the left of the node.
- Added message filtering to MessageWidget.

#### Scene

- Fixed AlembicSource refresh failure (#737).
- Fixed errors when AlembicSource filename is "".

#### RenderMan

- Added support for multiple types in RSL "coshaderType" annotation (#621).

#### OSL

- Added support for arbitrary image channels to the OSLImage node. The InChannel and InLayer shaders should be used to fetch channels and layers from the input image, and the OutChannel and OutLayer shaders may be used to write values to the output channels and layers. The Out* shaders should be plugged into an OutImage shader which is then plugged into the OSLImage node.
- Added support for arbitrary primitive variables to the OSLObject node. The InFloat, InColor, InNormal, InPoint and InVector shaders provide access to vertex primitive variables on the input primitive, and the corresponding Out* shaders
can be used to write values to the output primitive variables. The Out* shaders should be pluggined into an OutObject shader which is then plugged in to the OSLObject node.
- Added V3fVectorData support to OSLRenderer user data queries.
- Fixed dirty propagation through OSLShader closure outputs.
- Improved OSL processor shader input acceptance.
	- Only accepts OSLShader nodes if they hold a surface shader, as other shader types can't be used directly.
	- Also accepts Box and ShaderSwitch connections so that shaders can be connected indirectly.
- Revised shader naming convention to UpperCamelCase. The names of existing shaders have therefore changed.

#### API

- Moved OSLImage::shadingEngine() method to OSLShader::shadingEngine().
- Removed FormatPlugSerialiser from the public interface - it was not intended to be subclassed.
- Removed FormatBindings namespace and moved formatRepr() into the GafferImageBindings namespace.
- Switched formatRepr() signature to take a reference rather than a pointer.
- Added MessageWidget setMessageLevel() and getMessageLevel() methods.

0.90.0
======

#### Scene

- Fixed off-by-one error in scene cache preview frame ranges.

#### UI

- Fixed slight jump when connections are first drawn.
- Removed PathFilter paths plug representation in the NodeGraph. There aren't really any nodes we would connect to it.
- Improved OpDialogue warning display. If an Op completes successfully, but emits error or warning messages in the process, these will now always be flagged before the user can continue.

#### API

- Refactored ConnectionGadget into an abstract base class with a factory, to allow for the creation of custom subclasses. A new StandardConnectionGadget class contains the functionality of the old ConnectionGadget. Config files may register creation function for connections to control the type of gadget created, and its style etc.
- Added MessageWidget.messageCount() method. This returns the number of messages currently being displayed.
- Added OpDialogue.messageWidget() method. This provides access to the message display for the Op being executed.
- Added MessageWidget.forwardingMessageHandler(), to allow messages received by the widget to be propagated on to other handlers. This can be useful for connecting the OpDialogue to a centralised logging system.
- Deprecated MessageWidget appendMessage() and appendException() methods. The same result can be achieved by passing messages via the message handler instead.

0.89.0
======

#### Core

- Added Support for NumericPlug->BoolPlug and BoolPlug->NumericPlug connections.

#### UI

- Added additional types to the user plug creation menu.
- Added pre-selection highlighting in the NodeGraph (#94).
- Added "Create Expression..." menu option for bool plugs.
- Fixed NodeGraph resizing to crop rather than scale (#10).
- Fixed read only CompoundPlug labels.
- Added workarounds for Qt OpenGL problem on OS X (#404 and #396).

#### Scene

- Added Parent node. This allows one hierarchy to be parented into another (#91).
- Fixed bug which could cause incorrect bound computation at the parent node in the Instancer.
- Seeds and Instancer classes now preserve existing children of the parent location, renaming the new locations to avoid name clashes if necessary.
- Added tag filtering to the SceneReader node.
- Enabled input connections to PathFilter "paths" plug. This allows it to be promoted to box level and be driven by expressions etc (#704).

#### Apps

- Updated view app to contain tabs with different views (info, header, preview etc).
- Added scene cache previews to the browser and view apps (#416).

#### API

- Removed BranchCreator name plug - derived classes are now responsible for generating the entirety of their branch.
- Modified BranchCreator hashing slightly to improve performance - derived classes hashBranch*() methods are now responsible for calling the base class implementation.
- Fixed Box::canPromotePlug( readOnlyPlug ) to return false.
- Fixed Box::canPromotePlug() to check child plugs too.
- Fixed bug in read only Plugs with input connections.
- Added Gadget setHighlighted() and getHighlighted() methods.
- Added supportedExtensions() methods to ImageReader and SceneReader.
- Added Viewer.view() and Viewer.viewGadgetWidget() methods.
- Added NodeToolbar and StandardNodeToolbar classes.

#### Build

- Updated public build to use OpenEXR 2.1.
- Updated public build to use OpenImageIO 1.3.12.
- Updated public build to use OpenShadingLanguage 1.4.1.
- Removed pkg-config from the dependency requirements.

0.88.1
======

#### Core

- Added env app which mimics /usr/bin/env
- Enabled Python threading by default in Gaffer python module

#### UI

- Renaming is available for promoted children of CompoundDataPlugs
- Moved scene node filter plugs to the right hand side of the node

#### Image

- Fixed threading issue in Display node

0.88.0
======

#### Core

- Fixed threading issue in caching code.
- Implemented per-instance metadata for Box nodes. This will provide the basis for the user to make further customisations to Boxes, like setting descriptions for plugs and so on.
- Fixed bug in Switch node which could cause crashes when promoting the index plug.
- Added pivot to TransformPlug.

#### UI

- NodeGraph node tooltips now display a helpful description for the node. Node authors can define this text using the "description" Metadata entry (which is intended to provide a static description of the node's purpose) and the "summary" Metadata which may optionally be computed dynamically to describe the current state of the node (#157).
- Fixed initial value jump in viewer gamma/exposure virtual sliders.
- NodeGraph nodes may now display plugs on all sides, rather than just top/bottom or left/right as before. Node authors may control plug placement by defining a "nodeGadget:nodulePosition" Metadata entry.
- ShaderAssignment nodes now receive their shader input from the left (#82).
- Fixed OpDialogue hangs caused by the rapid output of many messages from an Op.
- Fixed strange browser behaviour when editing a path which is no longer valid (#64).
- Improved image viewer responsiveness, especially when used as a render viewer.
- Fixed position of plugs in the NodeGraph when the node gadget was very narrow.
- Made Box nodule positions match internal nodule positions (#608).
- Simplified OpDialogue error display - long error messages are now only visible in the Details view, rather than cluttering up the main window, and potentially making it very large on screen.

#### Scene

- Added a ParentConstraint node (#26).
- Added "includeRoot" plug to GafferScene::SubTree. This means that when choosing /path/to/theNewRoot as the root, the subtree will be output under /theNewRoot rather than /. Previously this was only possible by using an Isolate node followed by a Subtree (#565).
- Added "targetOffset" plug to the Constraint node. This is of most use for offsetting the aim point in the AimConstraint node (#278).
- Fixed bug in copying a node which has an input from an unselected PathFilter.
- Fixed bug in ShaderAssignment node which could cause crashes when querying for acceptable inputs.
- Improved the transform node
	- Added a pivot plug (#156)
	- Added a space plug to specify whether the transform is applied in World or Object space.

#### Image

- Fixed ImageReader problem which caused the green and blue channels of non-float images to be offset horizontally.
- Fixed bug which could cause the OpenColorIO node to output greyscale images.
- Optimised Display node.
- Optimised ChannelDataProcessor::channelEnabled().

#### OSL

- Updated for compatibility with OSL 1.3, 1.4 and 1.5 (master branch).
- Removed unsupported closures from OSLRenderer.
- Added debug() closure support to OSLRenderer to allow the output of multiple values via ShadingEngine::shade(). The closure takes an optional "type" keyword argument to define the type of the resulting output.

#### API

- Added GafferUI.SpacerGadget class.
- Reimplemented GafferUI.Metadata in C++, so it can be used from C++ code as well as from Python.
- Fixed bug in Widget.mousePosition() with GLWidget overlays.
- Fixed GafferScene.ScenePath.isValid() to only consider a path as valid if all parents up to the root exist according to ScenePlug.childNames().
- Added space conversion methods to GafferImage::Format. These are useful for converting between the Cortex and OpenEXR Y-down space to the Gaffer y-up space.
- Fixed GafferImage::FormatData serialisation.
- Removed deprecated ImageView( name, inputPlug ) constructor.  This was being used by old View subclasses which would pass their own input plug and then use setPreprocessor() to insert some conversion network. Subclasses should now use insertConverter(), following the example in GafferImageUITest.ImageViewTest.testDeriving.
- Moved Metadata class from libGafferUI module to libGaffer.

#### Build

- Fixed compilation with GCC 4.4.

0.87.1
======

#### UI

- Constrained slider positions inside range by default (#99). Shift modifier allows slides to exceed range.
- Key modifiers are now correctly updated during drags.
- Fixed PySide incompatibility in Slider.

#### Image

- Added ImageSampler node to GafferImage
- Fixed colour space used for ImageView colour sampling (now in linear space).

0.87.0
======

#### UI

- Added visualisation of clipping colours in the image viewer (#572).

#### Core

- Boxes now export all non-hidden plugs for referencing. Prior to this they only exported "in", "out" and user plugs.
- Fixed unwanted plug promotion when nesting Boxes inside Boxes.

#### Scene

- Fixed Subtree update problem.
- Added enabling/disabling support to SceneTimeWarp and SceneContextVariables.
- Added a SceneSwitch node. This can be used to choose between different scene hierarchies.
- Added a ShaderSwitch node. This can be used to switch between different shaders being fed into a ShaderAssignment. It is also compatible with RenderMan coshaders, so can be used to switch between different coshaders in a network.

#### Image

- Added a Clamp node
- Fixed bug in Display node which caused problems when using multiple Displays at once.
- Added ImageTimeWarp, ImageContextVariables and ImageSwitch nodes - these are equivalent to their Scene module counterparts.

#### API

- Added missing IntrusivePtr typedefs to GafferImage
- Added RecursionPredicate to FilteredRecursiveChildIterator. This allows the definition of iterators which automatically prune the recursion based on some condition.
- Redefined RecursivePlugIterators so that they do not recurse into nested nodes - instead they just visit all the plugs of the parent node.
- Improved Node::plugSetSignal() behaviour. The signal is now emitted for all the outputs of the plug being set in addition to the source plug - otherwise plugSetSignal() could not be used effectively for plugs which had been promoted to Box level.
- Renamed SceneContextProcessorBase to SceneMixinBase.

#### Build

- Fixed build for Ubuntu 12.04.
- Updated public build to use Arnold 4.1.
- Removed OIIO versioning workaround - previously we had to rename the OIIO library to avoid conflicts with Arnold, but since Arnold 4.1 such conflicts no longer exist.
- Updated default boost version to 1.51.0.
- Added dependenciesPackage build target. This can be used to make a package of prebuilt dependencies to seed a build. from.
- Updated default Cortex version to 8.0.0b5.

0.86.0
======

#### UI

- Added exposure and gamma controls to the image viewer (#571).
- Added colourspace management to the image viewer (#573). By default display colourspaces are taken from the OCIO config, but any image processing node (or Box containing them) can be registered via config files to provide alternative methods of colour management.
- Added auto expand option to the scene viewer (#163).
- Added Shift+Down shortcut for full expansion in the scene viewer (#556).
- Added "look through camera" in the scene viewer (#49).
- Added global Left/Right keyboard shortcuts for frame increment/decrement (#52).
- Added background operation to op dialogues in the op and browser apps. The UI now remains responsive during execution and displays IECore messages and results (#591).
- Objects can now be dragged from the Viewer and SceneHierarchy into path fields such as the AimConstraint target or the StandardOptions camera.
- Buttons now accept Return and Enter keypresses in addition to the space bar and clicking.
- Confirmation dialogues now focus the default button so they can be dismissed using the keyboard.
- Tarted up the About dialogue with a nice new logo courtesy of Tiziana Beretta.
- Fixed MenuButton bug whereby menus could be shown partially offscreen.
- Fixed Timeline bugs
	- Wraparound during playback would remove the fractional part of the frame number
	- Entering a value in the frame field which was outside the frame range would make it impossible to subsequently enter a fractional frame number.
    - Changing the frame number via the numeric field didn't update until focus left the field.
- Fixed clipping problem in BusyWidget drawing, and removed overhead of invisible BusyWidgets.
- Fixed GadgetWidget overlay event handling problems.
- Fixed crashes when MultiSelectionMenu was used in GLWidget overlay.
- Viewer toolbar now omits labels when Metadata value is "".
- Made the NodeGraph save and restore its framing when entering and leaving Boxes (#626).
- Fixed PathWidget menu positioning when used as a GLWidget overlay.

#### Scene

- Added a UnionFilter node (#594).
- Optimised SceneReader. It now computes constant hashes where data is not animated, resulting in significant speedups and reduced memory consumption. Approximately 2x speedup and 50% memory usage reduction has been seen in animated production assets (#545).
- Optimised SceneHierarchy update for improved playback performance (#545). 4x speedups have been seen with animated production assets.
- Fixed the laggy node dragging seen after expanding the SceneHierarchy contents and moving the current frame a few times (#209).
- Disabled StandardOptions camera and resolution by default.

#### Image

- Optimised OpenColorIO node performance.
- Optimised grade node performance and memory usage (through improved hash implementation).
- Set Grade node's gamma plug minimum value to 0.
- Fixed threading related OpenColorIO crashes on OS X.
- Fixed ImagePrimitiveSource hashing bug. This would manifest itself as a corrupted image when connecting a disabled node downstream from a Display node (#420).
- Fixed miscellaneous hashing bugs.

#### Core

- Optimised StringPlug::getValue() and StringPlug::hash() for cases where the string doesn't contain substitutions.
- Fixed bug in Path inequality operator.
- Renamed python deprecation warning output - Python2.7 disabled this by default.

#### API

- Added a new Playback class. This provides a central controller for all clients who wish to initiate playback or react when playback occurs.
- Added ColorProcessor base class. This makes it easier to implement image processing nodes which mix across channels.
- DependencyNode::affects() is now called for output plugs too. This can trip up poorly implemented DependencyNode::affects() overrides - see f1e9cb3bf20430b7889795dcb5eccec863f1e2e7 for details.
- Resolved ambiguities in Widget auto-parenting keyword arguments. Parenting arguments should now be passed as "parenting = { ... }" rather than just "...".  The old style of argument passing will be deprecated (#655).
- Added ViewportGadget::set/getCameraEditable() methods.
- Added previous root node to GraphGadget::rootChangedSignal().
- Added set/getTextSelectable() method to GafferUI.Label.
- Added Dialogue set/getModal() methods.
- Added Path._emitPathChanged() protected method.  This can be used by derived classes to emit the pathChangedSignal(), avoiding emitting it if nothing is listening. All subclasses should use this in preference to self.pathChangedSignal()( self ).
- Added Context::hasSubstitutions() method. This can be used to query if a string contains any substitutions supported by Context::substitute().
- Added Slider set/getPositionIncrement() methods. These allows the cursor key position nudging behaviour to be controlled.
- Added const version of GafferUI::View::getPreprocessor.
- Added EnumPlugValueWidget.selectionMenu() method.
- Renamed ImageNode::hash*Plug() methods to hash*(), for consistency with the rest of the framework.
- Refactored ImageNode hashing for improved performance and clarity - see 78b8739f1867ecd3b660838d384cdd6083734d92 for details.
- Added many missing IntrusivePtr typedefs.
- Added support for "divider" Metadata in viewer toolbars.

0.85.1
======

#### Scene

- Compatibility with Cortex 8.0.0b1

0.85.0
======

#### API

- Added Bookmarks API for storing Path bookmarks by application, path type, and category (#55)
 - Configs can define custom bookmarks on startup (https://github.com/ImageEngine/gaffer/wiki/Custom-Bookmarks)
 - Parameters can specify the bookmarks category with a ["UI"]["bookmarksCategory"] user data entry
 - Support in the gui, browser, and op apps
 - Support in File menu, PathChooserDialogue, PathChooserWidget, PathParameter, PathVectorParameter, RenderMan shader parameter, Box, and Reference node UIs
- Added Style::changedSignal()
- Added Window set/getIcon and setting GafferLogoMini as the default window icon
- Added TextWidget set/getPreferredCharacterWidth methods
- Fixed ParameterisedHolder parameterChanged() crashes
- Fixed Widget.bound() on OS X
- Fixed some bugs with null plugs in Box's plug promotion methods

#### GL

- Fixed GLSL shaders used by the UI for OpenGL 2.1 (requires Cortex 8.0.0-a23)
- Fixed OpenGL drawing when embedded in Houdini (requires Cortex 8.0.0-a22)

#### UI

- Added ColorSwatchPlugValueWidget (#625)
- Added new Gaffer logos (though only using them for window icons currently)
- Increased preferred width of PathWidgets (#515)
- Improved PathChooserDialogue handling of invalid selections (#628)
- Fixed Dialogue positioning and focussing on Linux (#220, #642, #62)
- Fixed SectionedCompoundDataPlugValueWidget child widget bugs (#588)
- Fixed Timeline start/end field sizing bug (#111)

#### Scene

- Added DeleteAttributes node and AttributeProcessor base class (#587)
- Fixed PrimitiveVariableProcessor::affects()

#### RenderMan

- Fixed RenderManShader.acceptsInput() crash

#### OSL

- Added closure parameter support to OSLShader

0.84.0
======

#### UI

- Added shift+drag of node to panel to create duplicate editor (#575).
- Added HSV readout for pixel below mouse in image viewer (#576).
- Improved the UI for Attributes and Options, to distinguish between the boolean used to enable a setting and the boolean used to define the value (#65).
- Fixed unwanted scaling of Button images.
- Added a toolbar to the viewer, initially with only a single button for specifying the 3D display style (#114).
- Improved MenuButton menu positioning.
- Fixed bug where searchable menus kept keyboard focus after closing.
- Fixed focus stealing problems apparent in Viewer and NodeGraph. They still take focus on mouse enter, but will not steal focus from text entry widgets (#555, #439).
- Added per-column visibility for CompoundVectorParameterValueWidget. Visibility is specified using the standard ["UI"]["visible"] userData entries on the child parameters which provide the columns (#526).
- Stopped plug controls accepting drags from themselves. This was causing trouble for users who were accidentally dragging and dropping a single line from a PathVectorDataPlugValueWidget onto itself, thus removing all the other lines.
- Added drag start threshold, to make it harder to accidentally start a drag (#593).
- Disabled "Remove input" menu item for read only plugs and uis.
- Disabled Box promotion menus on read only UIs (#604).
- Disabled ganging menu items for read only UIs.
- Stopped standard graph layout reconnecting invisible nodes.

#### Scene

- Prevented rogue connections being made to Shader "parameters" Plug.
- Fixed bugs in computing hashes for transform, object and attributes at the scene root.

#### OSL

- Added support for struct parameters.
- Added shaders for doing basic vector arithmetic.
- Added support for N global variable in OSLRenderer.
- Fixed OSLShader hash bug. Because OSL shaders are the first shader type we've supported where a single shader can have multiple outputs, we weren't taking into account _which_ particular output was connected when computing the hash.
- Prevented vector->color connections for OSLShader nodes. OSL itself doesn't allow such connections so we mustn't either. Also added a vectorToColor shader to help work around the restriction.

#### Documentation

- Started versioning documentation releases - they follow the app release version.
- Changed modifier key styling in documentation content to match that used in interface.
- NodeEditor content expanded.
- NodeGraph content expanded.
- New images.
- New screen grab setups.
- Simplified example light shader.

#### API

- Renamed CheckBox to BoolWidget and added different display modes. CheckBox remains as an alias to BoolWidget for backwards compatibility.
- Added stream insertion operator for GafferScene::ScenePlug::ScenePath.
- Fixed RunTimeTyped declaration for SceneView. It was declared as deriving from View rather than View3D.
- Fixed bug in Widget.widgetAt().
- Added widget overlays to GLWidget. This allows any Widget subclass to be displayed as an overlay on top of the OpenGL contents.
- Added setColumnVisible/getColumnVisible methods to VectorDataWidget.
- Implemented VectorDataPlugValueWidget.setHighlighted().
- Fixed StandardNodeUI.setReadOnly() to properly affect plug labels.
- Implemented setPlug on a SectionedCompoundDataPlugValueWidget.
- Fixed DependencyNode::enabledPlug() python bindings.
- Added python binding for ValuePlug::setFrom().

0.83.0
======

#### UI

- Added support for framing nodes and plugs dragged to the NodeGraph.
- Fixed overzealous pinning of nodes dragged to editors. Specifically, a node dragged from within an editor would be accepted as a pinning-drag into that very same editor. Now a drag must originate from outside the editor to be considered for pinning.
- Stopped GafferUI.Frame from expanding beyond the min/max of its contents. It now behaves like the other containers in this respect. Frames can still expand, but now only when their contents want to. Updated ErrorDialogue for this fix by adding some appropriate Spacers, and updated it to use the newer "with" syntax for building UIs at the same time.
- Added highlighted rendering for frames.
- Added ConnectionPlugValueWidget. This is a fallback widget for plugs that otherwise have no value to display. It shows the input connection to the plug, and provides means of navigation to that input (#130).
- Added post-execution behaviours to OpDialogue. These allow the UI writer, the Op writer or the user to choose whether or not the dialogue should be closed after the Op has executed (#560).
- Fixed PathListingWidget errors when "/" path is invalid.  Invalid root paths occur quite frequently in the SceneHierarchy editor when an invalid filename has been entered in a SceneReader or AlembicReader. Those nodes will still display an error, but the SceneHierarchy now won't output a confusing stacktrace which distracts people from the root cause (#528).
- Added Alt click modifier for selecting upstream nodes in GraphGadget. Alt+Shift click adds all upstream nodes to the selection. Alt+Ctrl click removes all upstream nodes from the selection (#437).
- Fixed launching of external URLs on OS X.

#### Scene

-  Fixed Prune node's forward declarations of lights and cameras. Previously it would not correctly remove the forward declaration for an object whose ancestor had been pruned.
- Added Isolate node type.  This removes all paths which are not directly above or below the chosen location - particularly useful for singling out certain assets from a large scene (#564).
- Improved default values for Seeds and Instancer nodes. The new defaults mean there are less steps to perform to get something happening.
- Stopped annoying startup errors when 3delight or arnold are missing (#486).

#### OSL

- Introduced a new gaffer module which integrates Open Shading Language.
	- OSLShader node represents OSL shaders and allows them to be connected into shading networks.
	- OSLImage node executes OSL shaders in the context of an input image to perform arbitrary image processing.
	- OSLObject node executes OSL shaders in the context of an object's primitive variables to perform geometry deformation.

#### API

- Added custom formatters and name depth control to NameLabel.
- Added Widget.isAncestorOf() method.
- Added ButtonEvent.button field.
- Improved path matching to provide more complete information.
- Added GraphGadget::upstreamNodeGadgets() method.

#### Support apps

- Added ability to specify Widget to be grabbed in the screenGrab app.

####################################################################################################

0.82.0
======

#### Core

- Made Plug::acceptsInput() consider current output connections (#532).

#### UI

- Added even-more-simplified mode to StandardNodeUI (#549).
- Fixed GraphGadget for NULL return from NodeGadget::create(). This allows NodeGadget::registerNodeGadget() to be used with functions that will return NULL to signify that the node should be hidden.

#### Scene

- Fixed errors reading polygon normals from Alembic files (courtesy of Cortex 8.0.0-a18).
- Added MapOffset node for offsetting texture coordinates.

#### RenderMan

- Fixed output of multiple displays (courtesy of Cortex 8.0.0-a18) (#357).
- Added automatic instancing capabilities (courtesy of Cortex 8.0.0-a18).

0.81.0
======

Core
----

- Improved dirtiness propagation mechanism to remove duplicate signal emission.

UI
--

- Backdrop improvements
	- Backdrop contents can now be scaled, so large backdrops can still have readable text when zoomed out.
	- Fixed bug which meant that empty backdrops didn't immediately redraw as highlighted when selected.
	- Improved resizing behaviour.
	- Fixed cut and paste bug.

Scene
-----

- Added doublesided attribute to StandardAttributes node (#275).

Arnold
------

- Fixed packaging of Arnold plugins.
- Fixed problem where light shaders weren't being created as lights.

RenderMan
---------

- Fixed public build to work with older 3delight versions where RiProceduralV isn't available.
- Added support for several new attributes in RenderManAttributes node (#275).

API
---

- The plugDirtiedSignal() is now emitted when a value has been edited with ValuePlug::setValue() - this means that observers need only ever use plugDirtiedSignal() instead of also having to use plugSetSignal() as well.
- Added Style::characterBound(). This returns a bounding box guaranteed to cover the largest character in the font. It is useful for correctly positioning the text baseline among other things.


0.80.0
======

UI
--

- NodeGraph now only drag-selects nodes that are wholly contained in the drag area, not merely intersecting it.
- Added a Backdrop node (#153).

RenderMan
---------

- Added support for "help" shader annotation in RenderManShaderUI (#536). This provides help for the shader as a whole and is mapped into the MetaData as the node description, appearing in the NodeEditor as a tooltip.

API
---

- Added optional continuous update to string PlugValueWidgets, controlled by the continuousUpdate parameters to the constructor. This transfers the text from the ui to the plug on every keypress.

Core
----

- Fixed serialisation of dynamic BoxPlugs.

Documentation
-------------

- Improvements too numerous to mention.

0.79.0
======

UI
--

- Added additional plug types to the CompoundDataPlug new plug menu (#522).
- Fixed bug in searchable Menus with no entries (#527).

Scene
-----

- Added CustomAttributes and CustomOptions nodes. These will be used instead of the old Attributes and Options nodes, and exist to better distinguish their use from the Standard, RenderMan and Arnold options and attributes nodes.

RenderMan
---------

-  Enabled hosting of RenderManShaders inside custom Box classes. Previously it only worked inside Boxes and not classes derived from Box.

API
---

- Added python subclassing ability to Serialisation::Serialiser (#520).


0.78.0
======

API
---

- Added python bindings for signal::num_slots and signal::empty().
- Added Gadget::idleSignal(). This allows Gadgets to do things during the idle times of the host event loop.
- Added NodeEditor.nodeUI() method.
- Added CompoundEditor.editorAddedSignal().
- Enabled subclassing of Box from Python.
- Made RenderManShaderUI public.

Core
---

- Fixed serialisation of ExecutableOpHolder.
- Added dynamic requirement plugs to Executable.
-

UI
--

- Added middle mouse drag for dragging nodules to the script editor without dragging a connection.
- Further increased width of plug labels in NodeEditor (#98).
- Fixed read-only RenderManShader UIs.
- Fixed bug whereby read-only PlugValueWidgets were accepting drags.
- Added Help menu.
- Added NodeGraph auto-scrolling.
- Added support for "presets" parameter type hint.

OS X
----

- Fixed GafferImageUI linking.

0.77.0
======

- Added alignment support and addSpacer method to ListContainer.
- Fixed an update bug in the pixel value inspector (#401).
- Added the pinned status to saved layouts (#444).
- Added read-only mode to NodeUIs and NodeEditor (#414). Note that this currently interacts poorly with activators on RenderManShader node, and will be fixed in a future release.
- Fixed read-only MultiLineTextWidget bugs.
- Implemented tag reading in SceneReader node. Tags are represented as BoolData attributes called "user:tag:tagName" (#494).
- Increased width of plug labels in NodeEditor (#98).
- Improved the default layout to include SceneHierarchy and SceneInspector and Timeline editors.
- Fixed TabbedContainer sizing when tabs not visible.
- Fixed crashes when loading old scripts where coshader array parameters were stored as Compound plugs.
- Fixed propagation of shader hashes through Boxes.
- Allowed shaders to accept inputs from Boxes, even if the Box doesn't currently output a shader.
- Changed internal image coordinate system to have 0,0 at bottom left (formerly at top left).

0.76.0
======

- Added Application._executeStartupFiles() method (#354).
- Added RemoveChannels image node.
- Added a PointConstraint node (#482).
- Fixed framing error when entering a Box.
- Image viewer now displays channels in grey scale.
- Added Widget.widgetAt() method.
- Added ability to hide tabs in layouts.
- Fixed bug converting coshader array from fixed to variable length.
- Added Serialiser::postScript() method.

0.75.0
======

- Added a channel mask feature to GafferImageUI::ImageView. Use the r,g,b and a keys to isolate individual channels (#403).
- Updated for compatibility with Cortex 8.0.0a14.
- Updated screengrab app to allow the execution of a commands file.
- Added a node find dialogue, accessible via the Edit/Find.. menu item (#454).
- Added NodeGraph.frame( nodes ) method. This can be used to frame specific nodes within the viewport of the NodeGraph.
- Addressed thread related hangs when using an InteractiveRenderManRender and deleting or connecting nodes.

0.74.0
======

- Added a multitude of miscellaneous documentation improvements.
- Implemented parameterName.type RenderManShader annotation (#456).
- Implemented parameterName.coshaderType RenderManShader annotation (#460).
- Fixed disabled Shader pass-through bugs.
- Added variable length coshader array support to RenderManShader (#462).

0.73.0
======

- Implemented connection hiding for the NodeGraph. This is accessed by right clicking on a node in the Node Graph and using the new "Show Input Connections" and "Show Output Connections" menu items (#429).
- Fixed const correctness of GraphGadget::getNodePosition().
- Fixed connection drag bug. Dragging the endpoint of a connection around and then placing it back where it started was breaking the connection, whereas it should have been having no effect.
- Replaced Enabled/Disable node menu item with Enabled checkbox.
- Added titles to the node graph context menus.

0.72.2
======

- Fixed Box creation with nested connected plugs. This allows the creation of Boxes with shader nodes with input connections.
- Fixed removal of nodules from nodes in the graph ui when Plugs are removed.
- Fixed InputGenerator bugs and added python bindings and tests.
- Fixed Group bugs involving dynamically generated inputs and undo (#179, #210, #302).
- Tidied up node menu labels.
- Renamed WriteNode to ObjectWriter and ReadNode to ObjectReader (#17).
- Fixed minimum height of ramp editor (#445).
- Fixed empty messages from ErrorDialogue.ExceptionHandler.
- Added popup error dialogues for file save failures (#449).
- Fixed context used by interactive render nodes.

0.72.1
======

- Updated PySide build.
- Fixed bug expanding objects in viewer when a custom variable was needed by the computation (#438).
- Fixed boxing of RenderMan coshaders (#440).
- Fixed Qt 4.6 compatibility.

0.72.0
======

- Added workaround for weird focus-stealing behaviour in Maya.
- Added application variable to the scope available to the screen grab command.
- Added support for empty and relative paths in Gaffer.Path. ( #432, #324 )

    - Added root parameter to all path constructors. This is used to define the root when the path parameter is passed a list of items. Because python doesn't allow overloaded functions this is slightly awkward - see documentation of Path.__init__ for discussion of how this would break down into overloaded constructors when we move the implementation to C++.
    - Added Path.root() and Path.isEmpty() methods.
    - Added Path.setFromPath() method, which copies the elements and the root from another path. This should be used in place of code which formerly did path[:] = otherPath[:].

    Note that the new root parameter changes the parameter order for all Path (and derived class) constructors - if you were formerly passing a filter as a non-keyword argument you should now pass it as a keyword argument to avoid problems. Additionally, if you implemented a custom Path subclass, you need to add the root parameter to your constructor and update your copy() and children() implementations. The DictPath changes provide a minimal example of what needs changing.

0.71.0
======

- Variable substitution improvements
	- Added standard ${script:name} variable (#407)
	- Added custom script-wide variables accessible via the File->Settings menu (#407)
	- Added support for variable references within variables (recursive substitution)
	- Added environment variable and ~ substitution
	- Added standard ${project:name} and ${project:rootDirectory} variables.
- Fixed save and load of ReadOnly plugs.
- Removed Escape hotkey for leaving full screen mode. The same function is served by the ` hotkey.
- Defined default locations for ribs, ass files and rendered images.
- Added automatic directory creation for display, rib and ass locations (#59)
- Added GraphComponent::clearChildren() method
- Greyed out File->RevertToSaved menu item when it doesn't make sense
- Improved CompoundDataPlug data representation
- CompoundPlugValueWidget using PlugValueWidget.hasLabel() to avoid unecessary labelling
- Fixed UI for promoted plugs (#264)
- Fixed bug where deleted children of Boxes weren't removed from the selection (#430)
- Fixed bug where pinned nodes were still visible in the UI after being deleted (#308)
- Fixed hangs caused by adjusting colours while rerendering
- Tidied up some test cases

0.70.0
======

* Added Ganging for CompoundNumericPlugs (#402)
* Added menu item for loading renderman shaders from file (#125)
* Added color ramp editing support (#286)
* Added spline parameter support to RenderManShader::loadShader()
* Added shader annotations for passing default values to RenderManShader splines
* Added dividers in the NodeEditor, available to RenderMan shaders via the annotation "parameterName.divider" (#288)
* Added API for undo merging.
* Added ScriptNode::undoAddedSignal() (#103)
* Fixed hiding of Menu when using the search box
* Fixed tab focus ordering in NodeEditor (#107)
* Improved GadgetWidget focus behaviour (#119)
* Fixed redundant CompoundNumericPlug serialisation (#2)
* Fixed scrubbing of values for IntPlugs
* Fixed size issues caused by TabbedContainer size policy (Settings and About window)
* Fixed bug in Random::affects()
* Fixed multiple undo entries in virtual sliders, cursor up/down nudging, color choser, and ramps (#400)
* Fixed Ctrl+C copy shortcut in non-editable MultiLineTextWidgets
* Hid Shader enabled plug in the UI (#398)

0.69.1
======

* Fixed bug with top level actions breaking searchable menus
* Fixed node reconnection crashes in ScriptNode::deleteNodes and StandardGraphLayout::ConnectNodeInternal

0.69.0
======

* Implemented drag and drop between plugs in the NodeEditor (#285)
    Drags are initiated on the label for the plug.
    Left drag initiates a drag for connecting plugs.
    Shift-left drag and middle drag initiate a drag for transferring values between plugs.
    Colours may now also be dragged from the viewer onto a plug.
    There are custom pointer icons for each type of drag (#44)
* Added blinking indication for plugs preventing the opening of a colour picker (#185).
* Implemented enabling/disabling for shader nodes (#327).
    By default disabled shaders behave as if their output connections didn't exist.
    RenderMan shaders may act as a pass-through by defining a "primaryInput" annotation naming an input coshader parameter.
* LinkedScene files (.lscc) are now previewable in the browser
* ImageReader only reads the necessary channel from the OpenImageIO cache
* Reverted non-gui ExecutableRender::execute() to block until the render is complete (#353).
* Fixed Nuke link error
* Fixed browser op mode
* Fixed missing Recent Files bug (#378).
* Fixed some bugs with extraneous dragBegins
* Removed namespace prefixes from typenames for displaying to the user (#389).
* Removed deperecated ModelCacheSource

0.68.0
======

* Improved speed of renderman shader menu.
* Image stats node in ImageView now uses the preprocessed input plug if the raw input is not an ImagePlug
* Removed right-click layout context menu.
* Added "Unpromote from Box" item to plug popup menu.
* Fixed menu title so it doesn't interfere with menu keyboard navigation.

0.67.0
======

* Fixed potential lockup with NumericPlugs.
* Fixed RenderMan ShaderMenu match expressions (broken in 0.66.0)
* Reintroduced the node name into the NodeEditor header.
* Exposed LayoutMenu submenu callable publicly.
* Implemented in-place renaming for user plugs (#213).
* Added support for RSL "parameterName.label" annotation (#372).
* Added a MapProjection node.
* Added sample window to the ImageViewer.
* Fixed UI test cases broken by the per-application menu commits.
* Can once again build for OS X.
* Added support for packaging as .dmg on OS X.

0.66.0
======

* Fixed interactive display.
* Fixed APIs to make UI resources per-application. When applications are updated to use these new APIS, they will no longer pollute each other's interfaces (#351, #225).
* Refactored GafferImage::Filter to have a better interface whilst removing the need for the construct() method.
* Added python bindings and enhancements for the GafferImage::Filter class.
* Fixed hash() bug in RenderMan coshader, which in turn fixes an interactive rerendering bug.
* Reduced occurences of accidental connection snatching (#313, #325).
* Fixed escape-to-close menu bug.
* Added an ImageStats node.
* Fixed deadlock when writing image files to disk.
* Op. Procedural and RenderMan shader menus may now be filtered to show fewer options.
* Added "cmd" parameter to screen grab app.
* Fixed GafferImage::FormatPlug::hash()
* Fixed duplicate typename errors (#330).
* Prevented promotion of non-serialisable plugs to Box level (#347).
* Fixed a bug in ImageProcessor that was causing a segfault when the node has an output that is not an ImagePlug.

0.65.0
======

* Added divisions plug to Plane node.
* Added Cube and Sphere scene sources (#97).
* Added a Text node to GafferScene.
* Added labelling support to TabbedContainer auto-parenting mechanism.
* Added ImageViewer pixel inspection by dragging pixels to the script editor (#245).
* Added python bindings for Views (#323).
* Added screengrab app.
* Implemented Gaffer->About menu item (#6).
* Improved ImageView to allow subclassing (#323).
* Set the name attribute for lights properly in the Render node (#326).
* Fixed GLWidget for use inside Maya 2013.
* Fixed Recent Files menu bug (#333).
* Fixed a bug in ViewportGadget drag event propogation.

0.64.0
======

* Added support for displaying RenderMan shader color parameters as plain numbers. This can be achieved by setting the "parameterName.widget" annotation to a value of "number".

* Added support for RenderManShader array parameters, including arrays of coshaders.

* Fixed redraw issue in searchable menus.

0.63.1
======

* Using Boost Filesystem version 3 (for compatibility with Cortex 8)

0.63.0
======

* Fixed promotion of dynamic colour plugs to Boxes.

* Fixed crash creating Merge node (#253).

* Fixed Gaffer module dependency on GafferImage.

* Display now obeys the default format (#280).

* Fixed circular references in plug popup menus.

* Fixed NumericWidget dragBegin errors.

* Newly created nodes are now connected in-stream where possible (#257).

* Fixed editability of user plugs.

* Added error handling for bad RenderManShader activator annotations.

* Improved automatic placement of filter nodes (#86).

* Fixed empty tab creation in Node Editor.

* Added interactive search for node menu.

* Reordered image filters so that they are displayed from most soft to most sharp.

* Added the Lanczos image filter.

* Fixed a bug with the Sinc image filter.

* Fixed the "streaking" issues when using the ImageTransform.

* Added subpixel filtering to the image Sampler.

* Implemented snapping during Graph Editor drags.

* Optimised node dragging in the Graph Editor.

0.62.1
======

* Fixed gl sharing widget bug when launching gaffer in maya

* ExecutableRenderer now always launches the render asynchronously to avoid locking the maya UI

0.62.0
======

* Fixed bug with promotion of CompoundPlugs to Boxes.

* Fixed ImageNode paste error (#251).

* Fixed BoolPlugValueWidget._updateFromPlug() to avoid setting plug value (#266).

* Fixed bug in Group operation (#269).

* Implemented RenderMan shader parameter activation via annotation expressions (#226).
    An activator is defined by a global annotation of this form :
        pragma annotation "activator.name.expression" "pythonExpression"
    The python expression may reference current parameter values by name, and also use the connected( "parameterName" ) function to query whether or not a parameter is connected.
    Activators are then assigned to specific parameters using annotations of this form :
        pragma annotation "parameterName.activator" "name"

* Implemented annotation-based uis for RenderManLight node.

* Added a ComputeNode class, and refactored DependencyNode so it can be a useful base class for shaders as well.

* Fixed dirty propagation of Shaders through ShaderAssignments.

* Fixed 3delight workaround. GafferRenderMan now requires 3delight 10.0.138 or newer.

* Added rudimentary shader updates to InteractiveRender. Note that there are still problems whereby deadlocks sometimes occur so this isn't in a state where you'd want to bet the success of any public performances on it.

* Fixed an issue with the glBlendingMode that was causing the result to be pre-multiplied twice.

* Fixed an image rendering issue with data/display window mismatches.

* Fixed banding and dark edges evident in 2D viewer (#74).

* Improved speed issues when moving single nodes in the NodeGraph by refactoring GraphGadget::connectionGadgetAt (#283).

0.61.0
======

* Fixed bug in MultiSelectionMenu so that if only one selection is available, it is displayed by name rather than as "All".

* Added image Sampler and Filter API classes.

* Added an image Reformat node.

* Added an ImageWriter node.

* Added RecursiveChildIterator API class.

* Fixed noodle-snatching to work with Shader nodes.

* Node Graph label now uses "/" as a separator for Box paths, rather than ".".

* Fixed layouts to allow panels to be collapsed fully and smoothly - addresses issue #93.

* Added workaround for PyQt/PySide pyqtSignal/Signal differences.

* Fixed "CameraController not in motion" errors. These occurred when the user accidentally moved the mouse scroll wheel while performing a drag to move the camera. We now ignore wheel events when dragging the camera.

* Removed unecessary collapsible section in Group UI.

* Fixed ImageReader to work with offset data windows.

* Fixed node auto-connection to work with Shader nodes (and other nodes with nested plugs).

* Added auto-connection and auto-positioning for pasted nodes (#13).

* Added inherit argument to Metadata query functions (#232).

* Fixed negative data window origins in image module.

* Added subdivision attributes to ArnoldAttributes node.

* Renamed Assignment node to ShaderAssignment.

* Added Reference node, providing the ability to reference in external scripts to facilitate collaborative workflows (#228).

* Added popup plug labelling to the NodeGraph (#138).

* Added connection snapping to the NodeGraph - connections dragged onto a node will snap to the nearest compatible plug.

* Added ImageTransform node (#96).

0.60.0
======

* Expansion state of collapsible plug grouping is now remembered for the duration of a session (#87).

* Current tab in Node Editor is now remembered for the duration of a session (#87).

* Fixed a bug in the NodeGraph where setTitle() was having no effect.

* Slowed wheel zooming (#200).

* Fixed crash when dragging nodes (#211).

* Improved NodeEditor node labelling (#151).

0.59.0
======

* Fixed save/load of user plugs created via the UI (#174).

* Fixed UI for generic Options and Attributes nodes.

* Removed collapsibility of Transform node's transform plug as it just cluttered up the UI.

* Removed collapsibility of Attribute node's attributes plug as it just cluttered up the UI.

* Removed collapsibility of Lights node's parameters plug as it just cluttered up the UI.

* Fixed MeshType::affects() (#175).

* Fixed SceneInspector update (#176).

* Improved SceneInspector shader representation (#147).

* Improved SceneInspector numeric formatting (#88).

* Added drag and drop node connection re-wiring (#78).

* Added virtual slider for NumericWidgets, engaged using LeftClick + Control or ShiftControl (#79).

* Fixed dirty propagation for Light nodes.

* Added first implementation of interactive rerendering in the InteractiveRenderManRender node. (#141)

* Deleting nodes attempts to rebuild the network to act as if the deleted nodes had been disabled (#95).

* Viewports can be panned/tracked using middle mouse with no modifier key (#28).

0.58.0
======

* Fixed creation of nodes within Boxes - previously they were added below the root of the script rather than inside the box.

* Fixed unstable scene hierarchy expansion (issue #120).

* Fixed highlighting bugs whereby widgets inside a highlighted tab would incorrectly display an inherited highlight state. This could be seen when dragging a node into the node editor with either nested tabs or a nested VectorDataWidget.

* Fixed PathPlugValueWidget bug where it would attempt to change the value of a read only plug.

* Fixed PathWidget bug where it would still do autocompletion and popup menus even when non-editable.

* Added TabbedContainer.insert() method.

* Generalised the Metadata system to store arbitrary values rather than just descriptions.

* Fixed CompoundPlugValueWidget bug whereby it would error if a summary was provided on a non-collapsible UI.

* Added right-click context menus to enum and checkbox plug uis.

* Added Box plug-promotion feature (#142).

* Removed Gaffer.GroupNode (#164).

* Fixed ordering of parameters in RenderManShader UI (#136).

* Fixed banding and dark edges evident in 2D viewer (#74).

* Fixed awkward zooming of Viewers and NodeGraph (#46).

0.57.0
======

* Renamed ColorPlug child names to rgba rather than xyzw (issue #133).

* File->SaveAs... menu item now adds the file to the recent files list.

* Fixed unwanted vertical expansion of color plug widgets.

* Removed the unwanted visualisation of the "name" plug on shaders in the Node Graph.

* Added NodeGraph plugContextMenuSignal() and connectionContextMenuSignal() to allow customisable right click menus for plugs and connections (issue #122).

* RenderManShader annotations are now correctly reloaded when the shader itself is reloaded.

* RenderManShader UI produces more sensible errors when bad annotations are discovered.

* Fixed parameter ordering in RenderManShader UI (issue #136).

* Fixed bug which prevented numeric plug entry fields from showing the correct value when values outside the allowable range were entered.

0.56.0
======

* RenderManShader node now supports the use of annotations within the shader to define the node UI. Annotations follow the OSL specification for shader metadata.

* Added the GafferUI.Metadata class, which will be used to provide things such as node and plug descriptions for the generation of tooltips and reference documentation.

* Added a Prune node, for removing whole branches from a Scene (issue #70).

* The Menu class now supports the description field of menu items, displaying descriptions as tooltips.

* The Menu class now supports the passing of the menu to callables registered as subMenus.

* Added a "File/Open Recent" menu item (issue #118).

* Added the ability to reload RenderManShader nodes, updating them to reflect any changes to the shader on disk. This is done automatically on file load and can be performed manually at any time using the new button in the node editor.

0.55.0
======

* Fixed graphical glitches caused by icons overlapping the edge of the editors on the Gnome desktop.

* SceneProcedural now renders general VisibleRenderables too.

* Fixed SceneReader to read animation at the correct speed (issue #68).

* File->Quit and the window close icon now prompt the user to confirm before closing if there are unsaved changes (issue #19).

* Added support for shader parameters of type "shader" in the RenderManShader node - these are mapped to plugs which accept connections to other RenderManShaders, allowing the creation of networks of coshaders.

0.54.0
======

* Added base classes Executable and Despatcher and two derived Node classes: ExecutableNode and ExecutableOpHolder.

* Added an enabled/disabled plug to all SceneNodes. Nodes with no inputs output an empty scene when disabled, and SceneProcessors output the first input unchanged. The enabled/disabled state can be toggled using the node right click menu or the "d" hotkey in the Graph Editor.

* Added SceneNode::hash*() methods to match the GafferScene::compute*() methods. This was necessary for the enabled plug to be implemented, and also makes the implementation of derived classes more readable. Matching pairs of hash*() and compute*() methods should be reused as a pattern throughout Gaffer where appropriate in the future.

* Renamed SceneElementProcessor::process*() methods to SceneElementProcessor::computeProcessed*() and SceneElementProcessor::hash*() methods to SceneElementProcessor::hashProcessed*(). This was necessary to resolve conflicts with the name hash*() methods at the SceneNode level.

* Removed the ability to return distant descendants from the GraphComponent::getChild() function. Also modified GraphComponent method signatures to use InternedString where appropriate. This change alone gives a 10-15% speedup in evaluating a benchmark GafferScene network.

* Added GraphComponent::descendant() method to replace the lost functionality in GraphComponent::getChild().

* Fixed bug whereby ViewportGadget sent keyReleaseSignal() to the keyPressSignal() of child Gadgets.

* Added Style::renderLine() method.

* VectorDataWidget now supports InternedStringVectorData. This makes it possible to view InternedStringVectorData in the browser app.

* Fixed errors caused by trying to view a SceneReader with an empty filename.

* The currently active tab for each panel is now saved with each layout.

* Renamed GraphEditor to NodeGraph - the previous name was confusing to users. Renaming all the classes rather than just changing the label, because we want a fairly straightforward mapping from UI->API to help users make the transition into scripting.

* Multiple shortcuts may now be specified for each menu item by passing a comma separated list of shortcuts in the "shortCut" field of the menu item.

* EditMenu now uses both backspace and delete as shortcuts for the delete action.

* Double-clicking a node in the Node Graph now makes any Node Editor tabs editing that node visible by making them the current tab.

* The ` key (left of the 1 on the keyboard) may now be used to toggle in and out of fullscreen mode.

* Renamed SceneEditor to SceneHierarchy to be more explicit that it visualises the scene graph and doesn't really provide much in the way of editing.

* Renamed TimeEditor to a more user friendly Timeline.

* The File->SaveAs... menu item now ensures that the file saved always has a ".gfr" extension.

* Added Scene->Object->Modifiers->MeshType node for converting meshes between polygons and subdivs, and optionally adding normals when converting to polygons.

* The Scene Inspector now displays mesh interpolation.

* Fixed bugs which could prevent the UI updating appropriately when plug values were changed.

* Optimised redundant updates in the SceneHierarchy editor.

0.53.0
======

* Added the concept of a global format for disconnected nodes along with a format plug.

* Added the Constant node for GafferImage.

* Added the Select node for GafferImage.

* Fixed a bug which prevented Assignment nodes from being connected to Shaders outside the Box containing the Assignment.

* Improved formatting in NumericWidgets.

* Added NumericWidget.valueChangedSignal().

* Fixed bug where editing a numeric plug value using cursor up/down didn't immediately update.

* Added CompoundDataPlug::addMember() and CompoundDataPlug::addOptionalMember() overloads which take a ValuePlug instead of Data to provide the value for the member.

0.52.0
======

* The Gaffer clipboard now synchronizes with the global system clipboard, allowing nodes to be cut and pasted between external applications.

* Fixed a bug which meant that the Viewer didn't update if a view became dirty while it wasn't the currently active view.

0.51.0
======

* Switched Arnold import in ArnoldRender.py to a deferred import, to allow 3delight renders of scenes containing Arnold nodes

* Added a Grade node to GafferImage

* Added a Merge node to GafferImage

* Added option to disable highlight in GafferUI.Button

* Fixed exception caused by undefined subMenuDefinition in GafferUI.Menu

* Catching all exception types in ErrorDialogue

* Image nodes can now be disabled.

* Renamed ExpressionNode to simply Expression.

* Multithreaded the ImagePlug class.

* Fixed ParameterValueWidget.create() so that it always returns either None or an instance of ParameterValueWidget. Previously it was returning PlugValueWidget instances where no specific ParameterValueWidget registration had been made.

* Added PlugValueWidget setReadOnly/getReadOnly methods. These can be used to force a ui to be read only when the plug itself allows editing. Note that they can not be used to force editing when the plug itself is not editable.

* Fixed BoolPlugValueWidget so that it correctly disables the checkbox if the plug is not writable for any reason, or is setReadOnly( True ) has been called.

* PlugValueWidget.popupMenuSignal() now passes the PlugValueWidget itself to slots rather than the Plug as it did before. The plug can retrieved by calling plugValueWidget.getPlug().

* ParameterValueWidget.popupMenuSignal() now passes the ParameterValueWidget itself to slots rather than the ParameterHandler as it did before. The parameter handler can be retrieved using parameterValueWidget.parameterHandler().

* Added readOnly parameter to ParameterisedHolderNodeUI constructor.

* ParameterValueWidget now requires that the topLevelWidget passed to the constructor is always an instance of PlugValueWidget. This is made available via a new plugValueWidget() method.

* CompoundPlugValueWidget now requires that the result of _childPlugWidget either derives from PlugValueWidget or must have a plugValueWidget() method which returns a PlugValueWidget. This allows it to implement a new childPlugValueWidget() method which can be used to get access to the widget for a child plug. This is building towards a time when the NodeUI class provides a single method for retrieving the PlugValueWidget for a given plug.

* Added ValuePlug::settable() method.

* The VectorDataWidget now allows tooltips to be specified on a per-column basis using the columnToolTips argument to the constructor.

* The CompoundVectorParameterValueWidget now constructs tooltips for the columns using the descriptions for the child parameters.

* Added drag support to PathListingWidget and VectorDataWidget.

* ViewportGadget now forwards the keyPress and keyRelease signals to its child.

* GadgetWidget now allows the viewport to be changed using setViewportGadget(), and the previous viewportGadget() accessor has been renamed to getViewportGadget().

* ParameterisedHolder now calls the parameterChanged() methods of the classes held by ClassParameters and ClassVectorParameters when their parameters change, rather than calling the method on the top-level parameterised class.

* CompoundPlugs now accept input CompoundPlugs with more plugs than necessary, provided that the first N input child plugs match the N child plugs of the output. This allows Color3fPlugs to receive input directly from Color4fPlugs and arnold COLOR3 parameters to receive input from arnold COLOR4 outputs.

* ArnoldOptions node now allows the specification of texture, shader and procedural searchpaths.

* ArnoldRender node no longer specifies procedural location using a full path, allowing the procedural searchpath to be used if it has been set by an ArnoldOptions node.

* Fixed crash when evaluating a ContextProcessor containing an entry with an empty name.

* Added CompoundDataPlug::addOptionalMember(). This works as for addMember(), but adds an additional BoolPlug to allow the user to enable/disable that member. Both methods also take an additional parameter to specify the name of the plug used to represent the member.

* ArnoldOptions and ArnoldAttributes nodes now create their plugs with sensible names, and allow options and attributes to be enabled and disabled - by default they are all disabled.

* Added a File/Settings... menu option which opens a window for editing the plugs of the ScriptNode.

* Gaffer::CompoundDataPlug now handles Color4fData.

* Added a GafferScene::OpenGLAttributes node for controlling the drawing of objects in OpenGL.

* Gaffer::TypedObjectPlug::setValue() now references the value directly rather than taking a copy.

* Fixed bugs which prevented the ColorChooser working with colour types with an alpha channel.

* Added a procedural app for visualising Cortex procedurals.

* Plug::getInput() now returns a raw rather than reference counted pointer.

* Added RenderableGadget::selectionBound() method which returns the bounding box of all selected objects.

* Added View::framingBound() method which can be overridden by derived classes to control the framing behaviour when "F" is pressed.

* SceneView now frames the current selection when "F" is pressed.

* IndividualContainer::getChild() now returns raw pointers rather than smart pointers and uses a direct method of indexing.

* Gadget::getToolTip() now takes a line in gadget space, allowing the tooltip to be varied with the position of the mouse.

* RenderableGadget implements getToolTip() to display the name of the object under the mouse.

* PathMatcher is now editable after construction, with addPath() and removePath() methods. Because of this the copy constructor also now performs a full deep copy which can be expensive.

* Added PathMatcherData to make sharing PathMatchers easy, and to introduce the possibility of storing them in Plugs and Contexts. Copying is lazy-copy-on-write which can be used to avoid the expensive PathMatcher copy constructor where possible.

* Added Context::names() method.

* EditorWidget._updateFromContext() is now passed a set containing the names of items changed since the last call to _updateFromContext().

* Fixed bug which caused PathListingWidget.selectionChangedSignal() to fire far too frequently.

* Added a GraphLayout class, used in conjunction with the GraphGadget to perform automatic node connections and graph layout. This replaces ad-hoc code from NodeMenu.py. Still needs a decent fully automatic layout implementation for situations where the user doesn't build the graph manually.

* Added Plug::source() method.

* Added GraphGadget::nodeGadgetAt() method.

* GraphGadget now uses middle mouse drag for sending nodes to other widgets - left mouse drag is for moving nodes only. Shift drags can be used to add nodes to the current selection.

* TabbedContainer switches tabs automatically on drag enter, to allow drags to access targets that aren't current at the start of the drag.

* Expression node now supports calls to context.getFrame() and context.get() in addition to context["name"] dictionary style access. The get( name, defaultValue ) method is particularly useful when an expression may be executed in a context without the required entry.

* ScriptEditor no longer displays the result of execution if the result is None.

* Replaced RenderCamera node with more general StandardOptions node, which will define all the render globals type stuff that can be shared between renderers. Fixed bug in hash computation of GlobalsProcessor. Removed resolution from camera, putting it on the StandardOptions node instead.

* CompoundPlugValueWidget can now display a summary of the plug values in the collapsible header. Used this to provide useful summaries for all options and attributes nodes in GafferScene. Renamed in OpenGLAttribute plug for consistency with the others.

* Fixed SceneEditor bug which meant that items were only displayed if the first selected node contained them.

* Added TransformPlugValueWidget which provides a useful summary of the transform in the collapsible header.

* Added ScenePlug::fullAttributes() method which returns the full set of inherited attributes at a particular scene path.

0.36.0
======

* Improved bindings by removing macros and replacing them with proper wrapper classes.

* Added Window.childWindows() method.

* Added initial (and limited) support for Parameterised::parameterChanged() methods. Currently only modifying parameter values is supported in parameterChanged() - support for modifying user data and presets will be added in later revisions.

* The input and output connections for selected nodes are now drawn highlighted.

* Added BlockedConnection class in C++. This handles the blocking and unblocking of connections in an exception-safe manner.

* Added Node::plugFlagsChangedSignal().

* Added Plug::ReadOnly flag, to allow plugs to be locked against modification of the input or value.

* Added support for ["gaffer"]["readOnly"] bool parameter user data, mapping it to the Plug::ReadOnly flag. This user data may be modified in a ParameterModificationContext or in a Parameterised::parameterChanged() callback.

* StringPlugValueWidget and PathPlugValueWidget now correctly set their text entry field to read only when the plug is read only.

* PresetsOnlyParameterValueWidget now displays in a disabled state when a plug is not writable.

* Fixed C/C++ Object already deleted test messages caused by DeferredPathPreview.

* Fixed lifetime issues with ScriptWindows - they may now be constructed directly or acquire()d directly and their lifetime will be as expected (managed by the caller). ScriptWindow.connect() continues to operate as before - managing the lifetime of windows to correspond with the lifetime of scripts in the application.

* Fixed problems caused by serialising plug flags as All - they would then acquire new values when loaded in a future where there are new flags available.

* Added a SubTree node, for taking a branch of the tree and rerooting it back to /.

* Fixed bug in ConnectionGadget::bound() which meant that sometimes the graph would not be framed correctly when first displaying a GraphEditor.

* Fixed ColorChooserDialogue to actually use the colour passed to the constructor.

* Window.addChildWindow() now always causes the child window to remain on top of the parent. Previously, this was documented as the behaviour, but it only worked for child dialogues which subsequently went into a modal state. This is achieved by setting the QtCore.Qt.Tool window flag - this is much better than WindowStaysOnTopHint because it hides the child window when the application becomes inactive on the mac - otherwise the window would remain on top of the windows for the newly activated application.

* Fixed bug where colour chooser would remain after the parent swatch died, but be inoperative. It now remains but is still functional.

* Added GafferScene::PathMatcher class, which provides accelerated path matching for use in the PathFilter.

* PathFilter now supports * as a wildcard to match any portion of a name.

* PathFilter now supports ... as a path entry, to match any number of entries.

* Added a ParameterPath class for navigating Parameter hierarchies.

* Fixed bug which prevented CompoundVectorParameters from being saved in presets.

0.35.7
======

* Fixed bug which caused Windows to be hidden when being added as the child of another Window.

* Window.setVisible( True ) now ensures that the Window is unminimized and raised where necessary.

* Added NodeEditor.acquire() method, to allow other UI elements to request that a Node editor be shown in some way for a specific node.

* Double clicking a node in the graph now shows a floating Node Editor for that node.

* Added MultiLineTextWidget.dropTextSignal(), making it easy to implement drag and drop for different datatypes. This simplifies the ScriptEditor implementation somewhat.

* Added an improved ui for editing expressions. Context menu on plugs allows for creation and editing of expressions, and the expression editor accepts drag and drop of plugs.

* Random node no longer errors when context items are missing - this prevents the UI from erroring when scene:path etc is not available.

* NumericSlider now allows specification of hardMin and hardMax values to control what happens when the slider is dragged outside of the widget area.

* Slider now draws the position differently to indicate when the position is outside of the widget area.

* Fixed ColorChooser bugs caused by dragging sliders outside of sensible ranges - the ranges are now enforced.

* Added GafferUI.DisplayTransform class for managing colour transformations from linear to display space. Updated ColorSwatch and ColorChooser classes to use this, and added ocio.py config file to set up the transform using PyOpenColorIO.

* Added GafferUI.ExecuteUI module with functionality for executing nodes, repeating previous executions etc. This provides a new execute menu in the main menu, and a right click menu item in the graph editor.

* Fixed bug which meant that dynamic CompoundNumericPlugs would fail to restore their connections upon script load.

* Arnold shaders may now be connected together to form networks, and they may have non-shader inputs (such as the Random node) which can be evaluated on a per-object basis to provide additional variation.

* Fixed error caused by browser preview tab.

0.35.6
======

* Fixed problem where VectorDataWidget would grow to claim size it couldn't use.

* VectorDataWidget now scrolls to show the new rows when rows have been added.

* RenderableGadget now implements click and drag signal handlers to manage a set of selected objects.

* Fixed bug where MultiLineTextWidget would emit textChangedSignal whenever setText was called, regardless of whether or not it made any changes.

* Added insertText, setCursorPosition, getCursorPosition, cursorPositionAt, setFocussed and getFocussed methods to MultiLineTextWidget.

* ScriptEditor now accepts drops for scene objects, plugs, and nodes, which can be dragged from the Viewer and the GraphEditor.

* Added Widget.parentChangedSignal(), which does what you'd expect from the name.

* Improved default sizing for OpDialogue.

* Fixed CompoundParameter UIs to respect the ["UI"]["collapsed"] user data entry.

* CompoundPlugValueWidget now has a collapsed constructor argument to replace the previous collapsible argument. This takes None, True or False as values, allowing the ui to be created as non-collapsible, collapsed or expanded.

* Disallowing null values in plugs. This fixes bugs in the computation of hashes (all null values hashed the same, regardless of type, or what the actual default value was), and also simplifies coding (no more need for tests against null before using an Object).

* Fixed bug where setting SplinePlug to a value with less points than before raised an Exception.

* Fixed bug where SplinePlug::setToDefault did not work as expected.

* Added ValuePlug::setCacheMemoryLimit() and ValuePlug::getCacheMemoryLimit(), to allow management of cache memory usage. Added startup/gui/cache.py to expose this to the user via the preferences.

* Fixed bug which prevented user preferences from loading.

* Improved drawing of very thin/small selection boxes - they had a tendency to disappear before.

* Added Widget setHighlighted() and getHighlighted() methods, implementing highlight-on-hover for buttons and sliders.

* Implemented drop of items into VectorDataWidget. This allows objects from the viewer to be dragged and dropped into a filter to perform assignments.

* PlugValueWidget.popupMenuSignal now passes the PlugValueWidget to slots instead of the Plug.

* Fixed bug where ColorPlugValueWidget would attempt to show colour pickers for non-editable plugs, resulting in errors.

* NodeUI now also shows output plugs. They can be removed as necessary by registering None with PlugValueWidget.registerCreator().

* ModelCacheSource now uses the new ModelCache class provided by Cortex.

* Added a Random node, for producing random floats and colours based on a seed and a context item.

* Fixed bug where plug popup menus tried to edit plugs which were not editable.

* Fixed bug where the effects of TextWidget.setEditable() did not update the appearance of the widget.

* Fixed bug which caused ExpressionNode to crash when the expression was changed while the output plug was being viewed by the UI.

* Fixed bug which caused errors when connecting compatible children of CompoundPlugs together, if the CompoundPlugs were not themselves compatible enough for a complete connection between all child plugs to be made.

* Fixed bug which prevents ExpressionNode from accepting a Plug with direction()==In as an input to the expression.

* Fixed bug whereby GadgetWidget was passing buttonDoubleClick signals to buttonPress signals on the held gadget.

* Added GraphEditor.nodeDoubleClickSignal().

0.35.5
======

* Fixed graphical glitches caused by incorrectly applying visibility to children of TabbedContainer - this affected the preview section of the browser app particularly badly.

* Added a reportErrors parameter to the OpMatcher constructor - this defaults to True (same behaviour as before) but can be set to False to silence error reporting while loading ops. Note that the OpMatcher used by the BrowserEditor may be customised by implementing the Mode._createOpMatcher() method - this would be the place to pass reportErrors=True.

0.35.4
======

* Added a GafferBindings::NodeClass class, which simplifies the binding of Node derived classes. It is now a one liner to bind a typical extension node.

* The op app now has an arguments parameter which can be used to specify the parameter values for the op.

* The op app now has a gui parameter. When this is true a gui is presented, when it is false the op is executed directly on the command line.

* Added the GafferScene and GafferSceneUI modules. These will allow the generation and editing of scene graphs.

* Fixed RunTimeTyped registration of Gaffer::CompoundPlug.

* Fixed behaviour when a Widget doesn't have a tooltip - it now correctly looks for tooltips on parent Widgets until one is found.

* Added a GafferUI.NumericSlider widget.

* The Viewer now correctly updates when the context has changed. The EditorWidget no longer calls _updateFromContext() at awkward times.

* Added a simple TimeEditor for manipulating the current frame.

* Fixed GIL problems caused by passing multithreaded python procedurals to RenderableGadget.

* Fixed GIL problems when emitting signals with python slots from a thread which does not currently hold the GIL.

* Added an ExpressionNode class.

* PlugValueWidgets now have setContext and getContext methods, and update correctly when the context changes if a plug has input connections.

* Added a Gaffer.TransformPlug class, for specifying transformations.

* Removed NodeUI.createPlugValueWidget() registeredWidgets only parameter.

* Added PathListingWidget setPathExpanded, getPathExpanded, setExpandedPaths, getExpandedPaths and expansionChangedSignal methods.

* Added the GafferImage and GafferImageUI modules, for tile based image processing.

* Removed deprecated StandardNodeGadget::acceptsNodule() method, and associated StandardNodeGadget( node, deferNoduleCreation ) constructor. Nodule creation should now be controlled entirely by the Nodule factory mechanism.

* The Application base class now automatically creates an ApplicationRoot and makes it available via the root() method. Derived classes should use this rather than create their own. The Application base class now also makes sure that all startup files have been executed before the application is run, so derived classes may not now call _executeStartupFiles themselves (it is now protected). Additionally the doRun() method has
been renamed to _run, to be more in keeping with general python philosophy.

* The WeakMethod class now throws a more useful exception when called on expired instances.

* Fixed bug whereby menus were never destroyed due to a circular reference. This masked other bugs whereby some uis weren't maintaining a reference to their menus to keep them alive - it's now essential that this is done.

* Fixed bug which prevented dynamic output CompoundNumericPlugs serialising correctly.

* Fixed problems caused by PlugValueWidget.__init__ calling _updateFromPlug() at a point when the derived class is not fully constructed. PlugValueWidget.__init__ no longer calls _updateFromPlug(), so derived classes should now call it at the end of their __init__ method.

* ColorPlugValueWidget now has numeric fields for editing the colour, in addition to the
swatch.

* ContainerGadget can now add padding around the children, accessed using the new setPadding() and getPadding() methods.

* StandardNodeGadget can now be used in a vertical orientation as well as a horizontal one. This will be useful for making graphs which better suit a horizontal flow (shaders for example).

* Fixed IECore::RunTimeTyped registration for CompoundNumericPlug types.

* Added GafferArnold module.

* Added Label.linkActivatedSignal(), for reacting to HTML links in label text.

* Fixed flickering caused by MenuBars appearing briefly on screen before being parented.

* Added MultiLineTextWidget setWrapMode, getWrapMode, appendHTML, linkAt and linkActivatedSignal methods.

* Added a PopupWindow class.

* Fixed the Slider button press handler to swallow the events it uses.

* Added Window setPosition() and getPosition() methods.

* Moved NodeUI.registerPlugValueWidget() functionality into PlugValueWidget.registerCreator().

* Removed NodeUI._build() method. Derived classes should instead pass a topLevelWidget to the constructor if they wish to be in control of the ui construction.

* GafferUI.EventLoop now disables any idle callbacks which error during execution.

* Added Node::acceptsInput virtual method, to allow nodes to reject connections.

* Added a Widget.bound() method.

* Added GadgetWidget.positionToGadgetSpace() method, for converting Widget-relative positions into Gadget-relative lines.

* Added a GraphEditor.graphGadgetWidget() method.

* Nodes created via the NodeMenu are now automatically connected to the selected nodes, and positioned based on those connections.

* Parameter help for CompoundParameters (and derived classes) is now available as a tooltip on the label of the Collapsible ui.

* The op application now has an arguments parameter, which can be used to specify the initial values for the parameters of the op (backported from trunk).

* The python application now has an arguments parameter, which can be used to specify an arbitrary list of strings to be provided to the python script in a variable called argv.

* VectorDataWidget now allows a minimum number of visible rows to be passed in the constructor. Previously a similar behaviour was implemented internally with the minimum hardcoded to 1 - the new default is now 8. This improves the layout of CompoundVectorDataParameters.

* Added workaround for Qt problems which caused VectorDataWidget to sometimes be clipped on the right hand edge.

0.35.3
======

* Fixed LayoutMenu delete function

0.35.2
======

* Added a minimum size of the OpDialogue

0.35.1
======

* Removed ParameterValueWidget._addPopupMenu and _popupMenuDefinition, replacing them with PlugValueWidget._addPopupMenu and _popupMenuDefinition. This makes the parameter preset menus automatically available on all parameter uis, and provides for easy extension in the future (menus for manipulating plug inputs, expressions, locking etc). Note that if you previously had a custom ParameterValueWidget class with a _popupMenuDefinition() override, then it will no longer work - use ParameterValueWidget.popupMenuSignal() instead.

* Removed ToolParameterValueWidget, replacing it with ToolPlugValueWidget which has identical functionality (but applicable to Plugs too).

* Fixed bug which caused the filename column to become too wide when switching to Op browsing mode in the browser and then back to files.

0.35.0
======

* Sequence Path displays file sequences with a single frame

* Reverted changes made in Widget class about "apply visiblity"

* OpDialogue now supports op.userData()["UI"]["buttonLabel"], for specifying a custom label for the OK button.

* Removed requirement of the boost build having a patched python library capable of participating in garbage collection.

* Fixed bug in Collapsible when calling setChild() with a widget currently parented elsewhere.

* Fixed various GafferUI.Container bugs which prevented successful transfer of Widgets between containers.

* Added workarounds for unwanted Qt behaviours - parentless Widgets becoming top-level windows, and widgets being hidden when reparented.

* Added setClassLoader and getClassLoader methods to the op application. These may be used by configuration files to customise the loading of ops (the application is available as an "application" variable to the startup scripts).

* Calling BrowserEditor.registerMode() with the label of an existing mode now overrides the previous registration, rather than adding a second with an identical name.

* The standard BrowserEditor modes are now accessible publicly as BrowserEditor.FileSystemMode, BrowserEditor.FileSequenceMode and BrowserEditor.OpMode.

* The browser OpMode now takes an additional classLoader argument to the constructor, allowing the use of custom class loaders.

* The ParameterValueWidget.registerType() method now accepts an optional uiTypeHint argument, which allows the registration of custom uis, which parameters can request using the standard ["UI"]["typeHint"] userData entry.

* Added ValueType class members to TypedObjectPlug bindings, so that appropriate values
can be constructed easily.

* GraphComponent.children() python method now accepts a typeId to filter the result.

* Fixed bug which meant that colour swatches for plugs had the wrong colour when first shown.

* Simplified EditorWidget implementations by removing setScriptNode() method - now the scriptNode is always provided at construction and cannot be subsequently changed. Renamed ScriptWindow.getScript() to ScriptWindow.scriptNode() and EditorWidget.getScriptNode() to EditorWidget.scriptNode() for consistency.

* Menus now support a "shortCut" entry in the MenuItemDefinition to provide keyboard shortcuts. The standard application, file and edit menus now provide the expected shortcuts, and are greyed out appropriately when they cannot be used for whatever reason.

* Added ScriptNode undoAvailable() and redoAvailable() methods.

* CompoundNodule now supports a vertical orientation, specified using a new argument to the constructor.

* GafferUI.LinearContainer now supports decreasing as well as increasing child ordering, controlled with the setDirection() and getDirection() methods.

* Fixed ordering of nodules in vertically oriented NodeGadgets.

* PathPlugValueWidget doesn't update the plug value as you type any more - this was causing constant computation with invalid values. The value is now only set when editing finishes.

* Fixed problems with PathChooserWidget which meant the wrong file/directory was displayed on opening (truncated by one).

* ParameterValueWidget popup menus may now be customised by external code, using the ParameterValueWidget.popupMenuSignal().

* The Path class now implements a much more readable __repr__.

* The DictPath class now accepts an additional "dictTypes" argument to the constructor, which can be used to define what types it considers to be branches in the path (all other types are considered leaves).

* The OpMatcher.defaultInstance() function now takes an optional classLoader argument, which is used to create the shareable OpMatcher.

* The BrowserEditor.Mode class now has a _createOpMatcher() method which may be overridden by derived classes. Typically this would be overridden to use a custom ClassLoader for the ops.

* Moved Label.VerticalAlignment and Label.HorizontalAlignment enums to GafferUI namespace - to allow their use in other parts of the API. They are temporarily available under their old names for backwards compatibility.

* GridContainer.addChild() now accepts an alignment parameter to control alignment of the child within its cells.

* Path setFromString, append and truncateUntilValid methods now return self, to allow easy chaining and use in list comprehensions.

* Fixed problem which could cause MultiLineTextWidget to raise an Exception when losing focus as part of a ui being destroyed.

* Fixed SelectionMenu so that standard python strings (and not QStrings) are returned from the getCurrentItem() and getItem() methods.

* Added support for loading and saving presets for ops and other Parameterised classes.

* The OpPathPreview is now more flexible in what it considers to be a ClassLoader for ops, to provide better support for custom ClassLoaders.

* The PathListing widget now allows multiple levels of hierarchy to be expanded, by holding either Shift (all levels) or Control (one level) while expanding a level. In addition, expansionChangedSignal() is not emitted only once for batched changes, such as those caused by setExpandedPaths() and the new recursive expansion/collapsing.

* Layouts now remember their correct splitting ratios when they're saved. Added a useful layout for use with scenes.

* The ExpressionNode now supports string as well as numeric output types.

* The execute app now operates over frame ranges defined using the -frames command line argument.

* When not in gui mode, the Render node waits for the render subprocess to complete before returning from execute().

* StringPlug inputs now automatically substitute $name, ${name} and ### tokens using values from the current context when their value is accessed during a computation. This behaviour can be controlled using the new PerformsSubstitutions plug flag.

* Node computations are now cached in memory and reused when possible. Hashes representing computations are available using the ValuePlug::hash() method, and Node implementations must now implement the new Node::hash() method to assist in computing hashes.

* Added GraphComponent::getChild( childIndex ) method, providing constant-time access to children by index. This improved the implementation of SplinePlug, ChildSet and the GraphComponent __getitem__ method in Python.

* The op application now supports the loading of presets at launch, using the new "-preset presetName" command line option.

* Added a simple ConfirmationDialogue class.

* Presets are now stored in subdirectories based on class name, to avoid clashes between presets for different classes.

* Added a small UI for deleting presets.

* Resolved browser errors caused by broken symlinks. FileSystemPath now returns True for isValid() if a path is a broken symlink (it seems unreasonable for children() to return invalid paths) and falls back to os.lstat() to generate path info if os.stat() fails due to a broken link.

* Fixed problem where SequencePath would error in info() when given an invalid base path. Now it returns None as expected.

0.34.0
======

* Added support for ClassVectorParameters.

* Added a -help flag to the gaffer command line.

* Fixed parameter menu bug introduced in version 0.33.2.

* Added support for TimeCodeParameters.

* Menu.popup() method now takes an optional grabFocus parameter - if this is False and a key is pressed then the menu will close and pass the key to the previous focus widget.

* PathWidget's helpful popup menus are now more helpful because they don't steal keypresses from the PathWidget itself.

* TextWidget now supports having a fixed width defined in characters using the setCharacterWidth() and getCharacterWidth() methods.

* NumericPlugValueWidget now sets maximum field width for integer plugs where max values has been set - this slightly improves the ui for the TimeCodeParameterValueWidget.

0.33.2
======

* Fixed the delete order of ListContainer that was causing popup windows

* Fixed circular reference in menu that was causing popup windows

0.33.1
======

* Fixed bug in Menu

0.33.0
======

* Added a MenuButton class to GafferUI.

* The GafferUI.Spacer class now specifies a maximumSize in addition to the previous minimumSize.

* Added support for ClassParameters.

* Improved formatting of Parameter tooltips, and worked around Qt crash caused by having "\n\n" in the tooltip text.

* Fixed bug which meant that Labels were always aligned to the right and centre. Note that this changes the behaviour of default constructed Labels, which have always specified left alignment, but have been ignored till now.

* ListContainer now supports slices when setting children. For instance container[2:4] = [ list, of, children ]. ListContainer also now implements the index() method in the same way a list would, and allows access to the expand attribute of children using the new setExpand() and getExpand() methods.

* Improved WeakMethod behaviour when called after the instance has expired. Now a descriptive ReferenceError exception is thrown rather than the previous cryptic exception. Also added instance() and method() member functions to return the underlying member data.

* GafferUI.Menu now allows WeakMethods to be used for the command field of a menu item.

* Improved file selector for PathVectorParameters, and added custom file selector for FileSequenceVectorParameters.

* Fixed problem where the automatic Widget parenting mechanism was attempting to parent Menus unnecessarily.

0.32.1
======

* Added workaround for problems where string values were not always committed into parameters before the Execute button of the OpDialogue was clicked.

0.32.0
======

* Added GafferUI.NotificationMessageHandler, for displaying IECore messages in a little window.

* Added a ParameterHandler and ParameterValueWidget for DateTimeParameters.

* VectorDataWidget size behaviour now works much better for large amounts of data. It is now possible to use the browser's FileIndexedIO preview tab to view large amounts of data
from .cob and .fio files.

* Fixed bug in VectorDataWidget, whereby the vertical header would disappear when rows were deleted.

* Multiple fields may now be edited simultaneously in the VectorDataWidget, by selecting several fields before editing one of the selected fields. Changes are automatically copied to the rest of the selection. Columns may be selected by clicking on the horizontal header
and rows by clicking on the vertical header.

* The enter and return keys can now be used to edit the checkbox fields of a VectorDataWidget.

* The MultiLineTextWidget now has setEditable, getEditable, textChangedSignal, editingFinishedSignal and activatedSignal methods equivalent to the existing methods on TextWidget.

* Added a MultiLineStringPlugValueWidget class.

* StringParameterValueWidget now supports the ["UI"]["multiLine"] user data item.

* The browser app now has an "initialPath" parameter to allows the browsing location to be set from the command line.

* Added Gaffer.AttributeCachePath and GafferUI.AttributeCachePathPreview classes, to allow browsing of attribute caches.

* Browsing for paths from a PathPlugValueWidget where the path is presumed empty now starts from the current working directory.

0.31.0
======

* Fixed getText method of Label widget.

* TextInputDialogue now has all text in the textfield selected by default.

* Fixed "RuntimeError: underlying C/C++ object has been deleted" error triggered by removing a panel from a ScriptWindow.

* Fixed bug which meant that removing a panel would only keep a single subpanel of the panel that remained.

* Fixed bug which meant that sometimes the remaining layout buttons would cease to work after removing a panel from the CompoundEditor.

* PathListingWidget now has a displayModeChangedSignal() method.

* Added PathChooserWidget setPath() and getPath() methods.

* Added customisable modes to the BrowserEditor. Current modes allow the browsing of either files or ops.

* Added Gaffer.SequencePath class and used it to implement a file sequence browsing mode for the BrowserEditor and a FileSequenceParameterValueWidget.

* Added PathListingWidget setColumns() and getColumns() methods.

* Added a Gaffer.OpMatcher class, to provide lists of ops which are suitable for application to particular objects.

* Added a contextMenuSignal() to the Widget class.

* Added a right click menu to the BrowserEditor, allowing suitable ops to be applied to
files and file sequences.

0.30.0
======

* Fixed problem trying to call QLineEdit.setPlaceholderText within Nuke.

* Gaffer.BlockedConnection now supports reentrancy, with the connection only becoming unblocked when the outermost block has been exited.

* Fixed bug which prevented selection using the up/down cursor keys from working in the PathChooserWidget.

* ImageGadgets now have a linear to srgb conversion applied when they are drawn. This means they now match the Image widget behaviour.

* PathChooserWidget and PathChooserDialogue now accept a new allowMultipleSelection argument to the constructor. Use the new PathChooserDialogue.waitForPaths() method to wait for paths selected in this way.

* VectorDataWidget has a new protected _createRows() method which may be overridden by derived classes to customise the addition of new rows. The PathVectorDataWidget implements this by displaying a dialogue where the user may select multiple paths to be added. This improves the parameter ui for PathVectorParameters.

0.29.0
======

* The Gaffer.BlockedConnection constructor now accepts a list of connections to block, as an alternative to just a single connection.

* Added a Gaffer.LeafPathFilter class, which filters out leaf Paths.

* Fixed problem with Dialogue.waitForButton() which meant that the keyboard focus would be in the wrong place if a parent window was provided.

* PathListingWidget now supports user resizing of the columns. The existing automatic resizing behaviour remains, but any changes made by the user are remembered and applied as offsets to future automatic resize events.

* PathListingWidget.Column.lessThanFunction has been replaced with PathListingWidget.Column.sortFunction. The former was a function to compare two items, whereas the latter now simply returns the data in a form that should be passed to a standard less than comparison.

* Added PathListingWidget.selectionChangedSignal().

* Added PathListingWidget.scrollToPath() method.

* PathListingWidget now supports a tree view mode in addition to the existing list mode. This is exposed in the PathChooserWidget and PathChooserDialogue via a button to toggle between the modes.

* Deprecated PathListingWidget.selectedPaths() and introduced a pair of getSelectedPaths()/setSelectedPaths() methods.

* Added the ability to remove children from the TabbedContainer using del[start:end] notation.

* Added GafferUI.EventLoop.executeOnUIThread().

* Added Gaffer.DictPath, to allow browsing of dictionaries, IECore.CompoundData and IECore.CompoundObjects using the GafferUI Path components.

* Added GafferUI.BusyWidget, for saying "i might be some time but i don't really know how long so just twiddle your thumbs please".

* Fixed bug in GafferUI.Frame.removeChild.

* PathListingWidget now copes if a field in the Path.info() is missing.

* Added a Gaffer.IndexedIOPath class, to allow browsing inside Cortex files using the GafferUI Path components.

* GafferUI.EventLoop in Houdini mode now pumps 5 times rather than once per hou.ui.eventLoop idle. This makes typing in text fields interactive.

* GafferUI.TabbedContainer now has setTabsVisible() and getTabsVisible() methods.

* Added a frame() method to GafferUI.GadgetWidget, to frame a particular bounding box in the viewport, and fixed a bug whereby setGadget() didn't request a redraw.

* Added setPath and getPath methods to PathListingWidget, and PathWidget.

* Added setPathCollapsed and getPathCollapsed to PathListingWidget to allow programmatic control of the tree view.

* Added Gaffer.ClassLoaderPath class to allow browsing of ops and suchlike.

* GafferUI.SplitContainer.setSizes() can now be called before the SplitContainer has become visible.

* Added GafferUI.ErrorDialogue.ExceptionHandler class to simplify error handling.

* Added classes for previewing paths. General file information, headers, images, meshes, ops, and indexed io files and contents may all be previewed.

* Added a BrowserEditor class for embedding a file browser into a Gaffer layout.

* Added a browser app to browse the filesystem and display previews.

* Renamed ScriptNode::application() method to ScriptNode::applicationRoot() and changed return type to a raw pointer in keeping with the rest of Gaffer. Added python binding.

* Added ApplicationRoot::preferencesLocation() method to return an appropriate directory into which settings can be saved.

* Added Widget.visibilityChangedSignal().

* Fixed crash in python bindings for TypedObjectPlug::defaultValue, for the case of the default value being null.

* TypedObjectPlug bindings now support the serialisation of the value and default value, provided that the bindings for the types they hold implement __repr__ appropriately.

* Fixed bug in GafferBindings::Serialiser which meant that serialisers were called twice unecessarily.

0.28.1
======

* Changed the default resize mode of OpDialogue/ErrorDialogue to be manual

* Removed assert warning

* Fixed juddering resize events when opening the OpDialogue, by optimising out unecessary calls in Widget.setVisible().

0.28.0
======

* Added an InfoPathFilter, which allows filtering with an arbitrary match function applied to an arbitrary field of Path.info(). Used this to implement a filter text box for path choosers.

* PathParameterWidget now applies path filters, and has an _filter() method which can be overridden in derived classes to define the filter.

* GridContainer now supports the automatic parenting mechanism

* Window now support the addition of child windows using the automatic parenting mechanism.

* Keyword arguments can now be passed to the ContainerWidget.addChild() call generated by the automatic parenting mechanism. To properly support this, all Widget subclasses must take a **kw constructor argument, and pass it to their parent class constructor. An example use follows :

	with GafferUI.GridContainer() :
		# index is automatically passed to GridContainer.addChild() to specify the position of the button
		GafferUI.Button( "myButton", index = ( 0, 2 ) )

	with GafferUI.ListContainer() :
		# expand is automatically passed to ListContainer.addChild()
		GafferUI.Spacer( IECore.V2i( 10 ), expand=True )

* Added the ability to easily profile any gaffer application using the cPython profiling module, by specifying the -profileFileName command line flag. Use the pstats module to examine the resulting file.

* Optimised the Widget event filter.

* Fixed circular reference in GafferUI.CompoundParameterValueWidget which could cause "Underlying C/C++ object has been deleted" errors.

* The displayFunction in GafferUI.PathListingWidget.Columns may now return a GafferUI.Image or (as an optimisation) a QtGui.QIcon.

* Added GafferUI.PathListingWidget.defaultFileSystemIconColumn, which can be added to the list of columns passed to GafferUI.PathListingWidget to obtain an icon view.

* Optimised Widget implementation so that the event filter is only applied when it is absolutely needed - either when a connection to one of the signals has been made or when getToolTip has been overridden. Investigations with the standard gaffer ui revealed that only about one third of widgets meet these criteria.

* Optimised Widget implementation by lazily constructing signals when they are first accessed. This improves construction times but also reduces the memory footprint of a freshly constructed Widget by 40%.

* Added Gaffer.lazyImport function, which imports modules in such a way that they aren't actually loaded until first accessed.

* Optimised startup of gaffer applications which don't use any GL functionality, by using the new Gaffer.lazyImport functionality for PyOpenGL, IECoreGL and QtOpenGL.

* Added buttonDoubleClickSignal() to GafferUI.Widget and GafferUI.Gadget.

* Added setSelection() and getSelection() methods to GafferUI.TextWidget, along with a selectionChangedSignal() method. An additional selectingFinishedSignal() uses heuristics to determine when the user has finished making a selection. This is useful in Widgets which wish to provide easy methods of acting on the selection.

* The Menu.popup() method now takes optional position and forcePosition arguments.

* Improved PathWidget popup listing behaviour.

* GafferUI.ScrolledContainer now always asks for enough size to completely show its contents, regardless of the scroll mode in use.

* Deprecated GafferUI.Window setResizeable() and getResizeable() methods in favour of new setSizeMode() and getSizeMode() methods. These provide three modes - Manual (the same as the previous resizeable), Fixed (the same as the previous non-resizeable) and Automatic, whereby the window always tries to fit its child. Added a resizeToFitChild() method for cases where sizeMode is not Automatic and you know the child has been resized.

* The OpDialogue now resizes automatically to fit the parameters initially, and adjust as parameter sections are shown and hidden.

* The Widget class now has a keyReleaseSignal, and the GadgetWidget propagates events on this signal to the existing Gadget::keyReleaseSignal.

* Added support for "label" attributes in menu definitions to GafferUI.Menu. This is really just a workaround for the fact that IECore.MenuDefinition uses / characters to delineate between menu entries, and sometimes we want a / in the entry name itself.

* The VectorDataWidget now sizes itself to fit its contents.

0.27.0
======

* Keeping the same font dpi no matter where gaffer is running.

* Fixed bug which caused NameError to be thrown when loading a script containing an OpHolder.

* NodeUI widgets can now be customised on a per-plug basis using the NodeUI.registerPlugValueWidget call.

* Fixed bug which could cause crashes if a plug managed by VectorTypedParameterHandler had a null value.

* Fixed bug which caused additional parameters1, parameters2 etc plugs to be created on the ReadNode. Added an additional test to check that the ReadNode works following serialisation.

* Implemented keys(), values(), items() and __getitem__( long ) for GraphComponent bindings.

* Added a simple Write node.

* Added an execute application which can be used to execute Write nodes, or any other node with an execute() method.

* The Gaffer headers are now installed in the include directory in the Gaffer distribution.

* The Cortex procedural stubs are now installed as part of the Gaffer distribution.

* GafferUI.TabbedContainer now has an index() method for retrieving the index of a given child, and a currentChangedSignal() method for signalling when the current tab has been changed.

* GafferUI.NodeSetEditor now has a nodeSetChangedSignal() method, to notify listeners when the node set the editor is using has changed.

* GafferUI.CompoundEditor now houses a couple of useful buttons alongside the tabs in the layout. One brings up the menu to edit the layout, and the other locks the currently viewed nodes for the current editor.

* Added Serialisable flag to Gaffer.Plug, to control whether or not plugs and their values are serialised.

* The gui app now has a fullScreen command line flag.

* NodeEditor now displays the node type.

* The Plug base class may now be serialised.

* Fixed bug which meant that plug flags were not correctly serialised.

* Fixed bug in the automatic Widget parenting mechanism, which meant Widgets could be parented inappropriately when being created from the constructor of another Widget.

* The Path.addFilter() and Path.removeFilter() methods have been deprecated and replaced with Path.setFilter() and Path.getFilter() methods. Use the new CompoundFilter class if you wish to use more than one filter.

* The Path and FileSystemPath constructors now accept an optional filter argument.

* The PathFilter class now has setEnabled() and getEnabled() methods to turn the filter on and off. Derived classes should now implement the _filter() method rather than the filter() method.

* The PathFilter class now has a changedSignal(), which issues notifications when the filter is changed in some way. The Path class uses this to correctly trigger its own pathChangedSignal()

* The PathFilter classes now accept a dictionary userData argument to the constructor, which can be used for storing arbitrary data with the filter.

* The CheckBox class now has setText() and getText() accessors.

* Added PathFilterWidget class to allow uis to be built for the filters on paths. Added filter ui to PathChooserWidget, along with a button to refresh the listing.

* The Path class now adds "name" and "fullName" entries to the info() dictionary.

* The Menu class now accepts booleans as well as callables for the checkBox MenuItemDefinition entry.

0.26.0
======

* Gaffer.Application._executeStartupFiles() now takes an optional contextDict to allow variables to be passed to the startup scripts.

* GafferBindings.Serialiser now has a public constructor and can be used directly. It still needs some refactoring.

* Gaffer.ApplicationRoot now has a preferences() method which returns a node used to represent preferences. It also has a savePreferences() method to save the user preferences into a startup script. The GafferUI.ApplicationMenu
provides access to this via a menu item.

* Default stylesheet now does a better job of aligning the corner widget for the TabbedContainer.

0.25.0
======

* Changed in NumericPlugValueWidget the methods __keypress and __textChanged to be protected

* Added alternate color as new entry in widget style sheet

* The GafferUI.Image class now uses a more sensible cache size to eliminate thrashing when loading images from disk. The cache size defaults to 100 MB but can be specified directly using the GAFFERUI_IMAGECACHE_MEMORY environment variable, which is also interpreted as being a number in MB.

0.24.0
======

* ParameterisedHolder now correctly loads an instance of the held class
following serialisation.

* ParameterisedHolder::setParameterised() and OpHolder::setOp() now accept
an optional keepExistingValues parameter which defaults to false. Passing
true preserves existing plug values in preference to the values in the
incoming Parameterised object.

* TabbedContainer now allows the addition of a custom Widget to the top
right corner using the setCornerWidget() and getCornerWidget() methods.

* Fixed a bug which meant that the ButtonEvent::line field was incorrectly
transformed when delivering events to Gadgets.

* Fixed tab sizing issue on OS X.

* Fixed crashes in ObjectParameterHandler triggered by plugs with null values.

* Added enterSignal(), leaveSignal(), dragEnterSignal() and dragLeaveSignal() methods to Gadget. Nodules now highlight themselves when entered using this
new functionality.

* Fixed GafferUI to work with qt 4.6 as well as 4.7.

* Gaffer can now be run embedded in Nuke.

0.23.0
======

* Fixed a bug which prevented keypresses in GadgetWidget from being propagated to the parent widget if they were not processed by the GadgetWidget.

* Can now exit full screen mode by hitting Escape.

* OpDialogue.waitForResult() now never returns Exceptions if execution fails. Instead it gives the user the chance to try again or cancel.

* CompoundParameterValueWidget and CompoundVectorParameterValueWidget now support the ["UI"]["collapsible"] and ["UI"]["collapsed"] parameter userData. The collapsible argument to the constructor now defaults to None, it can be specified explicitly as True or False to override the userData request.

* Fixed a bug which prevented the GafferUI.Widget owner for empty QTabWidgets from being found with PyQt4. This caused errors during event handling.

* The Widget.setVisible() and Widget.getVisible() methods have been modified to match the behaviour of Widget.setEnabled() and Widget.getEnabled(), and an addition Widget.visible() method has been introduced to query visibility relative to an ancestor. See documentation for further details.

* Added SplitContainer getSizes(), setSizes() and handle() methods. See documentation for details.

* ListContainer.__init__() orientation parameter now defaults to vertical.

* CompoundEditor now provides dynamic behaviour for expanding and collapsing child editors. Hit space to expand the current editor one level, double space for two levels and so on. Space then collapses back one level, double space two levels and so on. When an editor is fully collapsed, hovering over the splitter handle will dynamically show it.

0.22.1
======

* Changed events keyPress and textChanged to be protected

0.22.0
======

* Collapsible Widget now supports corner widget expanded

* Changed Error Window to be resizable as default

* Added selectedSignal in SelectionMenu

* Added CurrentIndexChangedSignal test in SelectionMenuTest

* Fixed StringParameterValueWidget to create a PlugValueWidget using the registered Type

* Added enterSignal and leaveSignal in Widget


0.21.0
======

* Added a selectionMenu widget.

* Stylesheet restructured, enabling style overrides in widgets.

* Improved stylesheet performance applying styles only in Window and Menu widgets.

* Buttons can optionally have the frame removed using the setHasFrame() method or the hasFrame argument to the constructor. Additionally they no longer have minimum sizes defined by the stylesheet.

* Minor style changes.

* Disabled Qt's automatic merging of menubars with the OS X system menu. This was causing crashes and wasn't compatible with fullscreen mode either.

* Added a simple ProgressBar widget.

* Removing a node from a parent using removeChild() now automatically disconnects the node from the graph. Fixes issue #38.

* Fixed a number of test failures which occurred only in the Image Engine build, due to the fact that we install the cortex ops with different version numbers than a standard install.

* CompoundParameterValueWidget now updates the ui appropriately when plugs are added and removed. This can be seen in the Read node when switching between different file types.

* File menu items now open file browsers in a more sensible location.

* File browser now has a button to go up one directory level.

* Containers may now be used in the python with statement to make the creation of nested layouts more straightforward. For example :

	with GafferUI.Collapsible() :
		with GafferUI.ScrolledContainer() :
			with GafferUI.ListContainer( GafferUI.ListContainer.Orientation.Vertical ) :
				GafferUI.TextWidget( "Making uis is easier now" )
				GafferUI.Button()

* Nodule::registerNodule now accepts regular expressions for plug names.

* StandardNodeGadget::acceptsNodule is deprecated. Use Nodule::registerNodule in preference. Default implementation of StandardNodeGadget::acceptsNodule now always returns true.

* Graph editor ui for ParameterisedHolders now only shows connections for ObjectPlugs, this prevents the interface being cluttered with connections for all the other parameter types.

* Viewer is no longer hardcoded to display the result of the "output" plug - it now displays the result of the first output ObjectPlug. This allows it to view the results of procedurals and ops.

* The node creation menus for Ops and Procedurals now create OpHolder and ProceduralHolder nodes rather than generic ParameterisedHolder nodes. Ops and procedurals may now be run in Gaffer.

0.20.0
======

* GafferUI.EventLoop supports Houdini using hou.ui.addEventLoopCallback

* Support for boost 1.37.0

* Using future to import with_statement for python 2.5 compatibility

0.19.0
======

* Added a BoolVectorDataPlug and a BoolVectorDataParameterHandler.

* GafferUI._Variant.fromVariant() now supports booleans.

* VectorDataWidget now accepts a list of VectorData objects to the constructor and in setData(). This allows larger tables to be constructed consisting of columns from several VectorData objects. As a result VectorData.getData() always returns a list of objects, even when operating on only a single object. VectorDataWidget now accepts custom header labels specified by passing a list of strings to the header parameter in the constructor.

* Using an officially allocated TypeId range, and not one that might conflict with internal projects.

* CompoundValueParameterWidget can now be usefully subclassed, and the _buildChildParameterUIs method reimplemented to change behaviour.

* Added a CompoundVectorParameterValueWidget.

* Fixed a bug in GafferUI.Menu which prevented dynamically generated submenus from displaying correctly.

* Plugs representing parameters are now correctly identified as being dynamic, and can therefore be saved and loaded to scripts. Custom ParameterHandler classes should now call setupPlugFlags() in their setupPlug() implementation to support this behaviour.

* Added OpHolder and ProceduralHolder node types. The ui still needs work to make these useable.

* Fixed problem which caused artifacts in GafferUI.Images when using PySide.

* Reduced default font size to fit more on screen.

* Fixed problem with GafferUI.Button positioning on OS X.

0.18.0
======

* Renamed ArrayNodule to CompoundNodule.

* Bug fix for PathListingWidget with allowMultipleSelection==True. When selecting more than one item, the path being edited is now always set the current directory. This avoids problems where setting the path to the last selected leaf could cause the current selection to be destroyed.

0.17.0
======

* Fixed a bug in NumericPlug::setValue() which meant it was possible to set value outside the Plug's min/max range.

* Changed ParameterHandler interface to allow the same ParameterHandler instance to be used repeatedly even when Parameters are being added and remove or are changing type. This should be more efficient but more importantly will be necessary to allow the CompoundParameterValueWidget to adjust the ui when Parameters are edited in this way. The following changes need to be made to a ParameterHandler implementation :

	* Remove the plugParent argument to the constructor, and move the plug creation code to an implementation of the new setupPlug() pure virtual function.
	* Stop passing the parameter to the base class constructor, but instead store it as a member variable, and implement the pure virtual parameter() method to return it.

See python/GafferTest/ParameterHandlerTest.py for an example.

* The path argument to the PathPlugValueWidget is now optional, with a FileSystemPath being used if no path is specified.

* ValuePlug now emits plugSetSignal() before calling Node::dirty(), rather than vice versa.

* The ReadNode now exposes the parameters of the IECore::Readers it uses as plugs on the node.

* The PathListingWidget contents can now be customised by passing a column specification to the constructor. See PathListingWidget.defaultFileSystemColumns for an example. Also added support for sorting the listing by clicking on the headers, and allowed the column specification to provide a sorting function to be used in this case.

* The PathListingWidget now allows multiple selection of files using the allowMultipleSelection argument to the constructor, and provides a list of the currently selected paths using the selectedPaths() method.

* Implemented the ParameterisedHolder::setParameterised( className, classVersion, searchPathEnvVar ) overload. Still needs some work so nodes can be serialised to a script and reloaded properly.

* Fixed a bug in the Node bindings which meant that the C++ base class implementations weren't called when a python class didn't provide overrides.

* ParameterHandler::setupPlug now takes an argument specifying the plug direction required.

* Added an ObjectParameterHandler.

* Added Widget setEnabled(), getEnabled() and enabled( relativeTo ) methods - see documentation for details. Signals are not emitted for Widgets which have been disabled.

* Fixed a bug in the RunTimeTyped registration for TypedPlug.

0.16.0
======

* Added a StandardNodeGadget::acceptsNodule() method which may be reimplemented by derived classes to control exactly which plugs are represented by the gadget. See GafferUITest.StandardNodeGadgetTest.testSubclassing() for an example.

* GafferUI.StringPlugValueWidget now exposes the internal TextWidget with a textWidget() method.

* GafferUI.TextWidget now supports password style text display, settable with the displayMode constructor parameter, or the setDisplayMode() method.

* New StringParameterValueWidget supports ["UI"]["password"] parameter userData.

* The appearance of disabled buttons is now less confusing.

0.15.1
======

* Fixed layout problems caused by adding larger items into existing rows of a GridLayout.

0.15.0
======

* Added a GridContainer class.

* Fixed bug which meant that connections were temporarily offset from their endpoint if a nodule was added to a node immediately after them being made (as the Group node does).

* Fixed bugs in the GroupNode which meant that compute() was called each time the node was moved in the GraphEditor, and that compute() could error if an input plug contained None.

* Gaffer can now be run embedded in maya versions which use Qt natively.

0.14.0
======

* The parameter userData ["UI"]["visible"] is now supported.

* Fixed failing test GafferTest.ParameterisedHolderTest.testAddAndRemoveParameters. Parameters may now be added or removed within a ParameterisedHolder::ParameterModificationContext.

* Fixed a few stylesheet issues that appeared when running under Gnome.

* Added a GraphComponent::setChild() method - this operates in the same way as the __setitem__ python method. See documentation for the distinction between addChild() and setChild().

* Fixed a bug whereby GraphComponent::getChild( "" ) would return the GraphComponent itself rather than nothing.

* Fixed a bug dealing with parameters changing type within a ParameterisedHolder::ParameterModificationContext.

* GraphComponent::parentChangedSignal() now also provides the previous parent to connected slots in addition to the child argument.

* Fixed a bug where transferring a child from one parent to another would emit parentChangedSignal() twice, once with the child unparented from the old parent, and once with the child reparented to the new parent. Now the signal is only emitted once, omitting the bogus temporary unparenting signal.

* Plugs now automatically disconnect their inputs and outputs when they are removed from their parent.

* Plugs may no longer implement acceptsInput( 0 ) to return false - this was illogical as it prevents the undoing of a connection made by the user.

0.13.0
======

* Fixed a bug whereby a node would be offset from the mouse position when dragging if starting the drag was delayed while other uis (particularly the NodeEditor) were updating.

* Fixed a bug which meant that connections were not correctly represented in the GraphEditor for children of the ArrayNodule.

* The ParameterHandler classes now correctly define the Ptr and ConstPtr member typedefs required for all IECore::RefCounted subclasses.

* The ParameterHandler classes now have a plug() method which returns the plug which was created to represent the parameter().

* The ParameterisedHolder class now exposes the internal ParameterHandler with a parameterHandler() method.

* The CompoundParameterHandler class now provides access to the handlers it uses for child parameters using the childParameterHandler() method.

* The CompoundParameterHandler now has python bindings.

* The Image widget no longer expands to fill space if it is available.

* The Label widget now has setText() and getText() methods.

* The PathWidget class now has a path() method returning the path being displayed.

* The Window.addChildWindow( window ) call now results in the parent window holding a reference to the python object representing the child. This avoids situations whereby the child python object would die but the QWidget representing the child on the C++ side would continue to live. Use Window.removeChild() to remove a child window when you wish to destroy it, or use setVisible( False ) to hide the child until you need it again.

* Fixed bug in PathWidget which meant that the path display would be incorrect until the path changed for the first time.

* PathListingWidget fixes :

	* Error when double clicking an item.
	* Selection was not being cleared when the current path wasn't valid.
	* Path wasn't being set when a leaf item was selected, which meant that hitting Enter in the PathChooserDialogue chose the wrong path.
	* Double clicking a directory when the current path wasn't valid created another invalid path, rather than replacing the invalid section.

* Added a "python" application which simply executes a python file in the Gaffer environment.

* Added a GafferUI._Variant class which has helper function for dealing with differences in PySide and PyQt4 with respect to QVariant handling.

* Fixed VectorDataWidget to work with PySide.

* Added a BoxParameterHandler covering Box2i, Box2f, Box3i and Box3f parameter types.

* GraphComponent now supports the len() function in python, returning the number of children for the instance. The __nonzero__ method is also implemented so that queries of the type "if graphComponent : " will return True as before, even if there are no children.

* The sizing behaviour of the PathListingWidget is no longer quite as annoying.

* GafferUI.Menu now optionally passes a "menu" argument to the checkBox callback of a menu item, in the same way as it does for the command callback.

* Fixed bug in GafferUI.ColorSwatch.getColor().

* Added Window.[gs]etFullScreen() methods, and added a menu item to the Layout menu to use them. Added a parentWindow argument to the Dialogue*.waitFor*() methods, and used it appropriately to keep dialogues on top even when in full screen mode.

* The Image class now uses the Cortex PNGImageReader for loading png files, and correctly converts linear data to sRGB for display.

* Added a basic framework for parameter-specific uis. Initially there are only specific uis for compound parameters, presets only parameters and path parameters - all others fall back to using the default plug widgets. A UI may be easily instantiated for all the parameters of a ParameterisedHolderNode using the GafferUI.CompoundParameterValueWidget - see GafferUI.ParameterisedHolderNodeUI for an example.

* The MultiLineTextWidget now has much more sensible tab spacing.

* The Collapsible container can now display an optional widget in the top right corner of the header. Use the setCornerWidget() and getCornerWidget() methods to manipulate this widget.

* Removed font parameter from GafferUI.Label - it wasn't doing anything anyway. Font control will likely return in the form of some support for text markup.

* Fixed variable scope issues which meant that the following code would fail if executed in a script editor :

		class A() :

			def __init__( self ) :

				print A

		a = A()

0.12.0
======

* Added a VectorDataWidget and a VectorDataPlugValueWidget, handling plugs of type StringVectorPlug, IntVectorPlug, FloatVectorPlug and V3fVectorPlug. Still needs file selector support.

* Added a V3fVectorDataPlug and a V3fVectorDataParameter handler.

* All gaffer applications now include a call to IECore.registerRunTimeTyped.

* Fixed bug which would cause the base class doRender() method to be called in addition to the overridden one when subclassing from Gadget in python.

* Plug::setInput() now calls acceptsInput() even when the new input is null. This allows plugs to reject the removal of existing connections. The connection gadget has been updated to respect the new rejection possibility, preventing the dragging of the destination end of a connection to a plug whose acceptsInput( 0 ) returns false, and not attempting to set the input if the source end of source a connection is dragged off into space. Currently no Gaffer plug type returns false from acceptsInput( 0 ), but custom plugs are free to do so and Gaffer plugs may return false in the future based on the content of a ReadOnly or Locked flag on the plug.

* Window constructor now accepts an additional "child" keyword argument which is passed to a call to setChild().

* Fixed problem whereby the hover colour for the SplitContainer handles wouldn't work on all platforms.

* The GraphEditor now provides access to its internal GraphGadget with the graphGadget() method.

* Refactored the Set class into an abstract base class and a StandardSet class containing the previous functionality. The members() and sequencedMembers() methods have been removed as they didn't generalise well to other potential Set subclasses (such as a NameFilteredSet). Instead a new member( i ) method provides ordered access and the contains( member ) method provides membership queries.

* Added a ChildSet class whose membership tracks the children of a given GraphComponent.

* Added python bindings for Nodule::plug and Connection::srcNodule() and Connection::dstNodule().

* Added CompoundEditor.editors() method, which returns all the child editors, optionally filtered by type.

* GraphGadget can now show arbitrary Sets of nodes, specified using the GraphGadget::setGraphSet() method.

* GafferBindings::SignalBinder now supports signals of arity 0.

* GafferBindings::SignalBinder now returns the class that was bound, so that additional method bindings may be added by calling code.

* A generic set of python signals are now bound as Signal0, Signal1, Signal2 and Signal3, where the number denotes the number of arguments the Signal takes. Python callables may be used to provide custom result combiners - see GafferTest.SignalsTest for examples.

* The GraphEditor now allows custom right click menus to be displayed for nodes in the graph. See GraphEditor.nodeContextMenuSignal() for brief documentation.

0.11.0
======

* GafferUI.Image() constructor now accepts unicode strings.

* Gadget, NodeGadget and StandardNodeGadget may now be derived from in Python.

* NodeGadget.registerNodeGadget() may now be called from Python, passing a callable for the creation function.

* New GafferUI.ImageGadget class allows images to be displayed in zoomable gadget uis.

* GafferUI.StandardNodeGadget can now be customised using a new setContents() method. This allows the central region of the node to be replaced with custom gadgets on a per-node basis. See startup/gui/graphs.py for example code for customising with an icon (note that this is waiting for a PNGImageReader to be available in cortex).

0.10.0
======

* Fixed flickering in the Viewer - enabled double buffering in same way as GraphEditor.

* The view application has been ported from gtk to Qt.

* The Collapsible widget no longer changes width when its collapse state is changed.

* Window.addChildWindow() has been ported from gtk to Qt. This means that dialogues can be made to stay on top of the windows that launch them.

* GafferUI.Dialogue.__init__ now accepts borderWidth and resizeable arguments.

* Collapsible constructor now accepts borderWidth argument.

* MultiLineTextWidget now accepts text argument to constructor.

* OpDialogue now reliably closes itself following execution or cancel. A future version may stay open if userData on the Op requests it.

* All signal connections are now made to Gaffer.WeakMethod objects where appropriate. Updated the Widget documentation to encourage the use of WeakMethod.

* GafferUI.Frame class now accepts a child argument to the constructor, actually uses the borderWidth argument, and Frame.setChild( None ) no longer errors.

* Rationalised Window close behaviour. Added Window.close() method which may be called to request that a window be closed - this is also called when the user clicks the close icon. Window subclasses may override Window._acceptsClose to reject or defer closing. Window.closeSignal() has been renamed to Window.closedSignal() and now is now used purely for notification when a window has closed (the return value from attached slots is irrelevant).

* GafferUI.Frame has a borderStyle argument, defaulting to drawing a rather plain border.

* OpDialogue now reports errors using a new ErrorDialogue class.

* GafferUI.CamelCase has been removed as it was ported into IECore some time ago.

* Fixed bug which prevented GraphComponent::commonAncestor<T>() from compiling.

* Gadgets and Widgets may now have tooltips. Client code can set the tooltip using setToolTip(), and classes may provide default dynamic values by implementing getToolTip() appropriately. Currently the NodeGadget, Nodule and ConnectionGadget implement getToolTip to return information about the Nodes, Plugs and Connections they represent.

* Widgets now have a wheelSignal() for responding to mouse wheel events. The Viewer and GraphEditor use this to implement zooming.

* Fixed bug which prevented Collapsible containers from toggling state correctly when multiple instances shared a parent.

* Node UIs now use a ScrolledContainer for their top level container.

* Label widget now allows the alignment to be specified.

* Fixed alignment issues in NodeUIs.

* OpDialogue has a better default size.

* Added handlers for the following parameter types :

	IECore.V2iParameter
	IECore.V3iParameter
	IECore.V2fParameter
	IECore.V3fParameter
	IECore.Color3fParameter
	IECore.Color4fParameter

* Fixed TypeError: invalid argument to sipBadCatcherResult() messages coming from ColorSwatch widget.

0.9.0
=====

* Can now access the internal QPixmap for a GafferUI.Image widget using the _qtPixmap() method. This is to assist in implementing other widget types and should be considered off limits for user code (along with all the other protected _qt* function).

* GafferUI.Button can now display an optional GafferUI.Image in addition to text, and has setText(), getText(), setImage() and getImage() accessors. Note that the label keyword parameter has been renamed to text. The GafferUI.Dialogue._addButton() method now accepts a Button directly (as well as still accepting a string for backwards compatibility) to allow buttons with images to be used in Dialogues.

* GraphEditor flicker should now be fixed (enabled double buffering for GL display).

* Fixed bug which would cause Ops to be executed twice in OpDialogue.waitForResult().

0.8.0
=====

* GafferUI.Image now falls back to using Qt image loading code if no IECore.Reader is available. This provides support for PNG images among others. Also fixed some bugs whereby images would fail to load if a full path wasn't provided - now the GAFFERUI_IMAGE_PATHS are used appropriately.

* OpDialogue can now be used non-modally without waitForResult(). The new OpDialogue.opExecutedSignal() can be used to tell when the op has been executed, and to get the result.

* GafferUI.EventLoop addIdleCallback() and removeIdleCallback() have been ported from the old gtk code to the new Qt code.

* Reworked GafferUI.EventLoop to support embedding of Gaffer in Maya. See documentation in GafferUI/EventLoop.py and apps/gui/gui-1.py for details.

0.7.0
=====

* Can now derive from ScriptNode in python and override acceptsChild etc as expected.

* ScrolledContainer and viewer classes have now been ported to the Qt based GafferUI.

* Added a GafferUI.Image class for displaying images in a widget.

* GafferUI.Menu class now supports checkBox menu items again.

* GafferUI.CheckBox widget now displayed with a tick rather than a blank yellow box.

* CompoundNumericPlugValueWidget has now been ported to the Qt based GafferUI, providing uis for V2f, V3f, V2i and V3i plug types.

* GafferUI.Widget derived classes may now pass a GafferUI.Widget instead of a QtGui.QWidget instance to the base class constructor. This makes it possible to develop a wider variety of custom widgets without resorting to Qt APIs.

0.6.0
=====

* Can now specify whether to use PySide or PyQt for Qt python bindings, using the GAFFERUI_QT_BINDINGS environment variable.

0.5.0
=====

* Added a new OpDialogue class to make it easy to run ops.

* Added a new op application, to allow users to run ops in a gui.

* NodeEditor.registerNodeUI has been moved to NodeUI.registerNodeUI, and a NodeUI.create factory functiona added. This allows NodeUIs to be used in places other than the NodeEditor.

0.4.0
=====

* Can now derive from GraphComponent in python and override acceptsParent and acceptsChild methods. These methods can also be overridden in other python-derivable classes such as Plug and Node.

* Can now derive from CompoundPlug in python.

0.3.0
=====

* ParameterisedHolders now allow some Parameters to opt out of representation as a Plug by adding a "noHostMapping" user data item with a value of BoolData( True ).

* Can now implement and use ParameterHandlers in python.

* Ctrl-C now correctly kills Gaffer

* Fixed type registration for TypedObjectPlugs.

* Fixed NodeEditor lag when selecting several nodes in the GraphEditor.

* Added a factory mechanism for Nodules, allowing different nodules to be used for different plugs. Used this to implement an ArrayNodule type which allows connections to the children of a CompoundPlug to be managed. The code below can be used to demonstrate this :

	import GafferUI
	GafferUI.Nodule.registerNodule( Gaffer.Node.staticTypeId(), "c", GafferUI.ArrayNodule )

	n = Gaffer.Node()

	n.addChild( Gaffer.CompoundPlug( "c" ) )
	n["c"].addChild( Gaffer.IntPlug( "a" ) )
	n["c"].addChild( Gaffer.IntPlug( "b" ) )
	n["c"].addChild( Gaffer.IntPlug( "c" ) )

	addChild( n )

	n2 = Gaffer.Node()
	n2.addChild( Gaffer.IntPlug( "o", Gaffer.Plug.Direction.Out ) )

	addChild( n2 )

* Fixed bug which caused "RuntimeError: Internal C++ object (PySide.QtGui.QLineEdit) already deleted." messages to be displayed.