Double Hierarchy View Crash

[danieldresser-ie]

This is a bizarrely specific bug showing up in production at IE, but with help from Linas, we do seem to have a reproducible case. I'll try to describe the steps of the incantation quite exactly, because any slight deviation seems to make it not occur the same way.

1. paste in the scene listed at the bottom of this issue
2. in your top right UI pane, create a second hierarchy view, and set it to also follow the focus node, so you have two identical hiearchy views. I will refer to this new hierarchy view as <H>
3. focus the bottom group of the scene
4. using <H>, shift click on the root group to fully expand the scene
5. using <H>, collapse location A
6. using <H>, click in the right column to set A as excluded
7. using <H>, collapse location B
8. using <H>, click in the left column to set B as expanded
9. using <H>, collapse the root "/group"
10. using the Viewer, click on the background to make sure nothing is selected
11. using the Viewer, click on the visible cube. This should expand the hierarchy to show the location clicked, but if you've done this all right, you should see a crash.

This crashes on both Gaffer 1.2 and 1.3, and I think is consistent - I've been wondering if there's an element of randomness to it, but I think any of the times it didn't fail, I deviated slightly in the incantation.

In Linas's testing, the crash seems to occur in GafferSceneUI.ContextAlgo.getVisibleSet. It looks like the only way this could crash is if the context passed in is null or invalid. We probably ought to guard against null, but when Linas instrumented it, he sees it always getting called on the same address, including the time it crashes ... suggesting that somehow the context it's using has been deallocated? ( Though this is a bit complicated by there being two Hierarchy Views going at once ).

Linas also found that he was unable to reproduce the crash if he moved the getVisibleSet inside __transferExpansionFromContext to inside of the BlockedConnection - I don't really understand this code, and he was mostly just going based on intuition based on the getVisibleSet in __expansionChanged being inside of a different BlockedConnection. Maybe this is the solution, or maybe it just shifts the problem around ... either way, we probably need someone who understands this code better than I do to take a look.

import GafferScene
import imath

Gaffer.Metadata.registerValue( parent, "serialiser:milestoneVersion", 1, persistent=False )
Gaffer.Metadata.registerValue( parent, "serialiser:majorVersion", 2, persistent=False )
Gaffer.Metadata.registerValue( parent, "serialiser:minorVersion", 8, persistent=False )
Gaffer.Metadata.registerValue( parent, "serialiser:patchVersion", 0, persistent=False )

__children = {}

__children["Cube"] = GafferScene.Cube( "Cube" )
parent.addChild( __children["Cube"] )
__children["Cube"].addChild( Gaffer.V2fPlug( "__uiPosition", defaultValue = imath.V2f( 0, 0 ), flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group"] = GafferScene.Group( "Group" )
parent.addChild( __children["Group"] )
__children["Group"]["in"].addChild( GafferScene.ScenePlug( "in1", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group"]["in"].addChild( GafferScene.ScenePlug( "in2", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group"].addChild( Gaffer.V2fPlug( "__uiPosition", defaultValue = imath.V2f( 0, 0 ), flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group1"] = GafferScene.Group( "Group1" )
parent.addChild( __children["Group1"] )
__children["Group1"]["in"].addChild( GafferScene.ScenePlug( "in1", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group1"]["in"].addChild( GafferScene.ScenePlug( "in2", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group1"].addChild( Gaffer.V2fPlug( "__uiPosition", defaultValue = imath.V2f( 0, 0 ), flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group2"] = GafferScene.Group( "Group2" )
parent.addChild( __children["Group2"] )
__children["Group2"]["in"].addChild( GafferScene.ScenePlug( "in1", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group2"]["in"].addChild( GafferScene.ScenePlug( "in2", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Group2"].addChild( Gaffer.V2fPlug( "__uiPosition", defaultValue = imath.V2f( 0, 0 ), flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )
__children["Cube"]["__uiPosition"].setValue( imath.V2f( 58.457634, 4.66671658 ) )
__children["Group"]["in"][0].setInput( __children["Cube"]["out"] )
__children["Group"]["in"][1].setInput( __children["Cube"]["out"] )
__children["Group"]["name"].setValue( 'A' )
__children["Group"]["__uiPosition"].setValue( imath.V2f( 59.9567871, -3.49734592 ) )
__children["Group1"]["in"][0].setInput( __children["Cube"]["out"] )
__children["Group1"]["in"][1].setInput( __children["Cube"]["out"] )
__children["Group1"]["name"].setValue( 'B' )
__children["Group1"]["transform"]["translate"].setValue( imath.V3f( 2, 0, 0 ) )
__children["Group1"]["__uiPosition"].setValue( imath.V2f( 77.3576279, -3.49734569 ) )
__children["Group2"]["in"][0].setInput( __children["Group"]["out"] )
__children["Group2"]["in"][1].setInput( __children["Group1"]["out"] )
__children["Group2"]["__uiPosition"].setValue( imath.V2f( 69.757637, -14.233284 ) )


del __children