SplitView Proposed Architecture

Jeff Booher edited this page May 15, 2014 · 102 revisions
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Refactoring Brackets to Support Split View with Multiple Documents requires quite a bit of hacking on the plumbing but there are only a few places that need to be heavily refactored to do so. To break this work up in to smaller pieces, an accompanying document SplitView Architecture Tasking has been created.

Proposed Implementation

This proposal calls for anything that wants to show a view in the "Editor Workspace Area" must be a Registered View Provider. There are other ways to get views into this area but deserialization requires a method for views to be reconstructed at startup and this is done through a Registered View Provider. Registered View Providers expose methods to create a view for a given URI. A ViewFactory will be responsible for maintaining the View Provider registry and invoke the Registered View Provider's createView method when a Registered View Provider indicates that it can create a viewer for a given URI.

Initially there will be 2 Registered View Providers: an Image View Provider and a Document Editor provider. EditorManager will be the Registered View Provider for creating all document editors.

Workingset management moves from DocumentManager to MainViewManager -- although some legacy APIs, Events, Functions, Commands, etc..., will remain for some time to maintain backwards compatibility. The concept of Workingset is going away and all Workingset APIs are going to be renamed PaneViewList and WorkingSetView is renamed PaneViewListView.

Those items that are needed to maintain backwards compatibility have been identified and documented in the SplitView Extension Migration Guide and are detailed in the section below on Deprecating Legacy APIs

This proposal is an overview of the system along with functional details and implementation changes needed to build the SplitView feature.

High Level Block Diagram

SplitView Architecture

EditorManager APIs

These EditorManager APIs that exist will remain for backwards compatibility and convenience but their implementation will move as described.


Reimplemented by moving the current implementation into Editor and invoking Editor.getFocusedEditor() for the Editor object of the focused pane. The API will continue to work as it does today.


Reimplemented by moving the current implementation into Editor and invoking Editor.getCurrentlyViewedPath for the Editor object of the focused pane. The API will continue to work as it does today.


Reimplemented by moving the current implementation into Editor and invoking EditorManager.getFocusedEditor().getCurrentFullEditor() The API will continue to work as it does today.

View Layout APIs


This API will change the layout to match rows and columns.

MainViewManager.setColumnWidth(column, width)

MainViewManager.setRowHeight(row, height)

Update pane height/width.

View APIs

MainViewManager.addView(paneID, view, context)

This is how the viewFactory will add views to the layout but components can add views as necessary by calling addView and passing it the relevant data. This gives the framework the flexibility to be able to create arbitrary views on the fly without a URI. Calling this method directly, however, means that deserialization will not be able to reconstruct the view since there is no factory method for doing so. See MainViewManager.registerViewProvider() to register a view provider so that views can be reconstructed during the deserialization process.

This method will return a viewID that is used to address the view.

view is an object with the following interface:

/** @type {string} **/
var title;

/** @type {boolean} **/
var modified;

function getUI();
/** @returns {{!jQueryObject}} **/


provder is an object with the following interface:

/** @type {string} **/
var displayname;

function canDecode(uri)
/** @returns {boolean} **/

function createViweFor(uri)
/** @return {!jQueryObject} **/


Call this when the view's title has changed and you need to update it in the workingset and titlebar of the application.


Removes a view from the pane and PaneViewList.


This will return any context data associated with the view when it was created

PaneViewList API

The Implementation of these functions will move from DocumentManager to MainViewManager. See the section at the bottom of this document for a list of deprecated Workingset APIs that need to be kept for backwards compatibility.

Moving this functionality to MainViewManager is being done primarily because each view pane will have its own PaneViewList and MainViewManager manages the view panes so it makes sense to move it there. But, architecturally, it makes sense that this list is a property of the view because it's really a UI structure.

Extension Authors and 3rd party developers are encouraged to use other methods whenever possible to work with the set of open documents. See the SplitView Extension Migration Guide and the section below on Workingset Alternatives for more information.

PaneViewList APIs

PaneViewList APIs will replace the WorkingSet APIs and their implementation will be migrated from DocumentManager. Some of the WorkingSet APIs will continue to exist in DocumentManager to maintain backwards compatibility. The PaneViewList APIs have the same functionality as the Workingset APIs from previous versions of Brackets except they will take a paneId to identify which PaneViewList to work on.

Most of the PaneViewList APIs will take one of these Special Pane IDs for paneId in addition to valid paneIds:

Constant                | Usage
ALL_PANES               | Perform the operation on all panes (e.g. search for fullpath in all Pane View Lists)
FOCUSED_PANE            | Perform the operation on the currently focused pane (can also use MainViewManager.getFocusedPane())


MainViewManager.addToPaneViewList(paneId, file, open)

MainViewManager.addListToPaneViewList(paneId, files)

MainViewManager.removeFromPaneViewList(paneId, file)

MainViewManager.removeListFromPaneViewList(paneId, files)

MainViewManager.swapPaneViewListIndexes(paneId, files)

MainViewManager.sortPaneViewList(paneId, files)

MainViewManager.findInPaneViewList(paneId, file)

MainViewManager.findInPaneViewListAddedOrder(paneId, file)

Returns {paneId: paneId, index: index) or undefined if not found

PaneViewList Events

MainViewManager Events will add paneId to event data









Pane Events





EditorManager Events

provided for backwards compatibility but adds PaneId as Event Data



ProjectManager Events


Implementing the Layout Manager

The initial implementation will be mostly handled by MainViewManager but a MainViewLayoutManager object will be created just to help handle the layout. We shouldn't need to build for advanced layout mechanics since we only need, at most, 2 panes. Support for arbitrary rows and columns can be built into the MainViewLayoutManager builder at a later date.

Whether or not the initial implementation uses a MainViewLayoutManager object is an implementation detail that will be decided when the feature is implemented.

Layout Rules:

  • Only 1 pane or 1 row and 2 columns or 2 rows and 1 column are initially supported
  • Panes, when created, will initially show the Brackets logo interstitial screen until the corresponding view for that pane has loaded its content.
  • When a pane is destroyed, all views in the corresponding PaneViewList for that pane are moved to another pane and that pane's PaneViewList is updated. Since there are, at most, 2 panes in the initial implementation, this is just a matter of combining the ViewPaneList with the remaining Pane's ViewPaneList. This will generate a viewPaneListRemoveList event is generated for the pane losing views and a corresponding viewPaneListAddList event is generated for the pane who is receiving the the views.

WorkspaceManager computes the new size of #editor-holder in its the window.resize event handler and triggers an event to resize that the MainViewManager object subscribes to. Currently WorkspaceManager only computes the Height and passes that as data but it needs to also compute Width and pass that as well so that the MainViewLayoutManager object can verify that the editor holder doesn't get too narrow to handle 2 editor instances. At the point that it is too narrow then it will need to start resizing other columns to get a decent layout. This algorithm becomes more complex with more columns and rows. For now it can be a matter of going to something like 50%. We may want to bump up the shell's minimum width as well to avoid getting too small.

Column Width/Row Height Rules

height and width are expressed in percentages when affixing the CSS to the columns (e.g. width: 40%). Doing it in a percentage and only applying to all except the rightmost column and bottom most row will yield a fluid layout. The API will reject setting the width on the rightmost column. For the initial implementation we may just go with 50% splits all around without the ability to resize.

#Implementing Pane Management ViewManager will manage a PaneViewList for each of its View Panes. This may be abstracted and delegated into a Pane object if implementation starts to get to messy but the API to get the PaneViewList will be through the MainViewManager object. Because the ViewPaneList is being decoupled from DocumentManager, the list will no longer be a collection of Document objects. It will be a collection of file names.

NOTE: To abstract the PaneViewList's location, each view pane is addressed by paneId rather than row,col. Valid paneId values cannot be false, 0, null, undefined or "" so that they can be used in truthy tests.

Clients can use the Special Pane IDs for PaneViewList APIs to avoid having to maintain a reference to the pane in which a view belongs.

Implementing PaneViewListViews

PaneViewListView objects are created when the event viewPaneCreated is handled. SideBarView will handle this event and create a PaneViewListView object (which is bound to the pane's PaneViewList object) for the pane (passed as event data).

#open-files-container is a container which contains one or more .working-set-container divs in the DOM. Several 3rd Party Extensions rely or use the #open-files-container div. The extensions which style the elements will continue to work.

Supporting Images in PaneViewLists

To support images in split view, we will need to change the rules to allow for images in PaneViewLists. This means that callers of the new PaneViewList APIs will need to check to ensure they can operate on a file by getting its file type from the language manager or by checking its extension.

PaneViewLists will basically just be a list of files that may or may not have a Document object owned by the DocumentManager. The deprecated API, DocumentManager.getWorkingSet(), will use the PaneViewList APIs to filter out any files that do not have an associated Document object.

Implementing PaneViewListView Context Menus

This currently works by listening to contextmenu events on the #open_files_container. This will change to listen to contextmenu events on an .open_files_container and the PaneViewListView will maintain the paneId from the EventData it was passed during creation so the menu can operate on the correct pane's ViewPaneList.

Right clicking on a ViewPaneList item will also trigger a focus action on view for that ViewPaneList item causing the view to gain focus.

The core extension, CloseOthers, will be retooled to work on the PaneViewList for the pane associated with the PaneViewListView that it manages.

        $("#open-files-container").on("contextmenu", function (e) {

        $(".working-set-container").on("contextmenu", function (e) {
            e.paneId = this._paneId;

Workingset Alternatives

Although they aren't called Workingsets anymore, extensions making use of the WorkingSet APIs today are encouraged to migrate to these new convenience methods rather than just accessing ViewList directly if possible.


Returns a list of all open files


Returns a list of all open documents -- including documents which are in a PaneViewList but not yet opened, documents which have been opened in inline editors but not part of a PaneViewList and opened but not modified or added to any PaneViewList.

Deprecating Legacy APIs

API                                  | Calls...
DocumentManager.getCurrentDocument() | EditorManager
                                     |    .getFocusedEditor()
                                     |    .getDocument();
DocumentManager.getWorkingSet()      | $.map(ViewManager.getPaneViewList(ALL_PANES, …),
                                     |        function(fullPath) {
                                     |           if (DocumentManager.isDocument(fullPath)) {
                                     |               return fullPath; 
                                     |        }
                                     | });
DocumentManager.findInWorkingSet()   | return ViewManager
*only used by pflynn                 |    .findInPaneViewList(ALL_PANES, ...).index || -1;
DocumentManager.addToWorkingSet()    | return ViewManager
                                     |    .addToPaneViewList(FOCUSED_PANE, ...);
DocumentManager.addListToWorkingSet  | return ViewManager
                                     |    .addListToPaneViewList(FOCUSED_PANE, ...);
DocumentManager.removeFromWorkingSet | return ViewManager
                                     |    .removeFromPaneViewList(ALL_PANES, ...);

Deprecating Legacy Events

The following Events will be kept on the DocumentManager object to maintain backwards compatibility but will just republish MainViewManager events.





Fired when handling EditorManager.fullEditorChanged

Stubbing Modules

Both WorkingSetView and PanelManager will need to be stubbed and deprecation warnings will be added to them when used.

Opportunistic Cleanup

The following EditorManager functions will move to Editor and are opportunistic refactorings since we're working in that code. These refactorings aid in the overall implementation but aren't necessary.

 Name                   | Usage                             | Disposition                  
_openInlineWidget       | Internal Inline Widget Management | Moves to Editor without impunity
_toggleInlineWidget     | Command Handler                   | Current Implementation moves to 
                        |                                   | Editor
                        |                                   | Command handler will call
                        |                                   | Editor
					    |                                   |   .getFocusedEditor()
						|                                   |    .toggleInlineWidget()
closeInlineWidget       |                                   | Moves to Editor
						|                                   | calls hostEditor.closeInlineWidget()
getInlineEditors        |                                   | Moves to Editor
						|                                   | calls hostEditor.getInlineEditors()
getFocusedInlineWidget  |                                   | Doesn't move but passes through to
                        |                                   |    getFocusedEditor()
						|                                   |      .getFocusedInlineWidget();

Break up Editor up into Editor and EditorModule

The community has suggested splitting Editor into 2 parts. One with only the Editor class and all prototype methods (EditorModule). Another for the non-prototype methods including the ones added in as part of the refactorings described above. These would remain as Editor. This is how Document is split and make sense to do the same for the Editor.

Refactor Editor into logical groupings

  • Move all the tab/indent code into a new utility module. (If we eventually do auto-indent-size sniffing, we could put that code there too).
  • Hoist out some of the selection-related APIs into a new SelectionRanges object or a SelectionUtils module (stuff like convertToLineSelections() and selectWordAt().
  • Move most of the displayErrorMessageAtCursor() into a more UI-oriented popover module.
  • Make an OuterEditor/FullEditor subclass and move all the inline widget management APIs into that.
  • Move the getMode/LanguageFor*() APIs into TokenUtils, perhaps.
  • Deprecate & eventually move all the per-preference static APIs? Or move them into a separate EditorPreferences module?

Commands (opportunistic cleanup)

The following list of commands will move from DocumentCommandHandlers along with their corresponding implementation into a new module -- ViewCommandHandlers. We will also remove "file." from the command name and rename the commands to "cmd.", deprecating the old command ids in the same fashion the find commands were deprecated using getters.











Raw data can be found here: splitview architecture notes