Merge pull request #5621 from johnhaddon/expandHeaderVariables

RendererAlgo : Expand string substitutions in context image metadata

Changes.md

@@ -16,6 +16,7 @@ Improvements
 - OpenColorIOContext : Added file browser for `config` plug.
 - Layouts : Added the ability to load layouts containing editors that aren't currently available. This allows layouts containing new editors introduced in Gaffer 1.4 to be loaded in Gaffer 1.3.
 - LightTool : Changed the color of the non-highlighted handles to orange and the highlighted handles to cyan for consistency with other highlight colors.
+- Outputs : Variable substitutions are now applied to `gaffer:context:*` image metadata values. This is needed when the value of a context variable contains references to other variables, with the default value for `project:rootDirectory` being one example.
 
 Fixes
 -----

python/GafferSceneTest/InteractiveRenderTest.py

@@ -118,6 +118,7 @@ def testMetadata( self ) :
 
 		s = Gaffer.ScriptNode()
 		s["variables"].addChild( Gaffer.NameValuePlug( "a", "A", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic ) )
+		s["variables"].addChild( Gaffer.NameValuePlug( "b", "${a}", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic ) )
 
 		s["s"] = GafferScene.Sphere()
 
@@ -148,6 +149,7 @@ def testMetadata( self ) :
 		self.assertEqual( headers["gaffer:version"], IECore.StringData( Gaffer.About.versionString() ) )
 		self.assertEqual( headers["gaffer:sourceScene"], IECore.StringData( "r.__adaptedIn" ) )
 		self.assertEqual( headers["gaffer:context:a"], IECore.StringData( "A" ) )
+		self.assertEqual( headers["gaffer:context:b"], IECore.StringData( "A" ) )
 
 	def testAddAndRemoveOutput( self ):
 

src/GafferScene/RendererAlgo.cpp

@@ -1605,12 +1605,16 @@ ConstOutputPtr addGafferOutputParameters( const Output *output, const ScenePlug
 			case IECore::BoolDataTypeId :
 			case IECore::IntDataTypeId :
 			case IECore::FloatDataTypeId :
-			case IECore::StringDataTypeId :
 			case IECore::V3fDataTypeId :
 			case IECore::Color3fDataTypeId :
 			case IECore::Color4fDataTypeId :
 				param->writable()["header:gaffer:context:" + name.string()] = data;
 				break;
+			case IECore::StringDataTypeId :
+				param->writable()["header:gaffer:context:" + name.string()] = new StringData(
+					context->substitute( static_cast<const StringData *>( data.get() )->readable() )
+				);
+				break;
 			default :
 				IECore::msg(
 					IECore::Msg::Debug,