Cryptomatte : Rename __manifestScene plug

This becomes necessary now that we make the Hierarchy View ignore private plugs. `__manifestScene` will now be ignored, resulting in the Hierarchy View no longer displaying the Cryptomatte manifest, so we rename the plug to `manifestScene` and hide both its nodeGadget and plugValueWidget.

python/GafferSceneTest/CryptomatteTest.py

@@ -438,7 +438,7 @@ def testSceneValid( self ) :
 		c["in"].setInput( r["out"] )
 
 		c["layer"].setValue( "crypto_object" )
-		self.assertSceneValid( c["__manifestScene"] )
+		self.assertSceneValid( c["manifestScene"] )
 
 	def testChildNames( self ) :
 
@@ -450,10 +450,10 @@ def testChildNames( self ) :
 
 		cs = GafferTest.CapturingSlot( c.plugDirtiedSignal() )
 		c["layer"].setValue( "crypto_object" )
-		self.assertTrue( c["__manifestScene"]["childNames"] in [ x[0] for x in cs ] )
+		self.assertTrue( c["manifestScene"]["childNames"] in [ x[0] for x in cs ] )
 
 		self.assertEqual(
-			c["__manifestScene"].childNames( "/GAFFERBOT/C_torso_GRP" ),
+			c["manifestScene"].childNames( "/GAFFERBOT/C_torso_GRP" ),
 			IECore.InternedStringVectorData( [ "C_head_GRP", "C_key_GRP", "C_torso_CPT", "L_armUpper_GRP", "L_legUpper_GRP", "R_armUpper_GRP", "R_legUpper_GRP" ] )
 		)
 

python/GafferSceneUI/CryptomatteUI.py

@@ -282,6 +282,18 @@ def __layerPresetValues( plug ) :
 
 		],
 
+		"manifestScene" : [
+
+			"description",
+			"""
+			A scene containing locations representing the contents of the Cryptomatte manifest.
+			""",
+
+			"plugValueWidget:type", None,
+			"nodeGadget:type", None,
+
+		],
+
 	}
 
 )
@@ -410,7 +422,7 @@ def __selectAffected( node, context ) :
 	if not isinstance( node, GafferScene.Cryptomatte ) :
 		return
 
-	scene = node["__manifestScene"]
+	scene = node["manifestScene"]
 
 	with context :
 		pathMatcher = IECore.PathMatcher()

src/GafferScene/Cryptomatte.cpp

@@ -344,7 +344,7 @@ Cryptomatte::Cryptomatte( const std::string &name )
 	addChild( new FloatVectorDataPlug( "__matteValues", Gaffer::Plug::Out, new FloatVectorData() ) );
 	addChild( new AtomicCompoundDataPlug( "__manifest", Gaffer::Plug::Out, new CompoundData() ) );
 	addChild( new PathMatcherDataPlug( "__manifestPaths", Gaffer::Plug::Out, new PathMatcherData ) );
-	addChild( new ScenePlug( "__manifestScene", Gaffer::Plug::Out ) );
+	addChild( new ScenePlug( "manifestScene", Gaffer::Plug::Out ) );
 	addChild( new FloatVectorDataPlug( "__matteChannelData", Gaffer::Plug::Out, GafferImage::ImagePlug::blackTile() ) );
 
 	outPlug()->formatPlug()->setInput( inPlug()->formatPlug() );