InspectorColumn : Allow toggling of edit enabled state

Changes.md

@@ -21,6 +21,7 @@ Improvements
   - Improved formatting of column headers containing whitespace.
   - The "Double-click to toggle" tooltip is no longer displayed while hovering over non-editable cells, and a "Double-click to edit" tooltip is now displayed while hovering over other non-toggleable but editable cells.
 - Spreadsheet : Added yellow underlining to the currently active row.
+- LightEditor, RenderPassEditor : The "Disable Edit" right-click menu item and <kdb>D</kdb> shortcut now act as a toggle, where edits disabled in the current session via these actions can be re-enabled with <kbd>D</kbd> or by selecting "Enable Edit" from the right-click menu.
 
 Fixes
 -----

python/GafferSceneUI/_InspectorColumn.py

@@ -162,9 +162,10 @@ def __editSelectedCells( pathListing, quickBoolean = True ) :
 
 		__inspectorColumnPopup.popup( parent = pathListing )
 
-def __disablableInspectionTweaks( pathListing ) :
+def __toggleableInspectionTweaks( pathListing ) :
 
-	tweaks = []
+	enabledTweaks = []
+	disabledTweaks = []
 
 	path = pathListing.getPath().copy()
 	for columnSelection, column in zip( pathListing.getSelection(), pathListing.getColumns() ) :
@@ -176,18 +177,57 @@ def __disablableInspectionTweaks( pathListing ) :
 
 			with inspectionContext :
 				inspection = column.inspector().inspect()
-				if inspection is not None and inspection.canDisableEdit() :
-					tweaks.append( inspection )
+				if inspection is None :
+					return [], True
+
+				if inspection.canDisableEdit() :
+					enabledTweaks.append( inspection )
 				else :
-					return []
+					edit = inspection.acquireEdit( createIfNecessary = False )
+					if isinstance( edit, ( Gaffer.NameValuePlug, Gaffer.OptionalValuePlug, Gaffer.TweakPlug ) ) and Gaffer.Metadata.value( edit, "inspector:disabledEdit" ) :
+						disabledTweaks.append( inspection )
+					else :
+						# The selection includes a cell that is not viable candidate for enabling or disabling,
+						# we don't allow toggling of any of the selected cells in this case.
+						return [], True
+
+	if len( enabledTweaks ) > 0 :
+		return enabledTweaks, True
+
+	return disabledTweaks, False
 
-	return tweaks
+def __toggleEditEnabled( pathListing ) :
 
-def __disableEdits( pathListing ) :
+	global __inspectorColumnPopup
+
+	inspections, tweaksEnabled = __toggleableInspectionTweaks( pathListing )
+
+	nonEditable = [ i for i in inspections if not i.editable() ]
+
+	if len( nonEditable ) > 0 :
+		with GafferUI.PopupWindow() as __inspectorColumnPopup :
+			with GafferUI.ListContainer( GafferUI.ListContainer.Orientation.Horizontal, spacing = 4 ) :
+				GafferUI.Image( "warningSmall.png" )
+				GafferUI.Label( "<h4>{}</h4>".format( nonEditable[0].nonEditableReason() ) )
+
+			__inspectorColumnPopup.popup( parent = pathListing )
+
+		return
 
 	with Gaffer.UndoScope( pathListing.ancestor( GafferUI.Editor ).scriptNode() ) :
-		for inspection in __disablableInspectionTweaks( pathListing ) :
-			inspection.disableEdit()
+		for inspection in inspections :
+			if tweaksEnabled :
+				inspection.disableEdit()
+				# We register non-persistent metadata on disabled edits to later determine
+				# whether the disabled edit is a suitable candidate for enabling. This allows
+				# investigative toggling of edits in the current session while avoiding enabling
+				# edits the user may not expect to exist, such as previously unedited spreadsheet
+				# cells in EditScope processors.
+				Gaffer.Metadata.registerValue( inspection.source(), "inspector:disabledEdit", True, persistent = False )
+			else :
+				edit = inspection.acquireEdit( createIfNecessary = False )
+				edit["enabled"].setValue( True )
+				Gaffer.Metadata.deregisterValue( edit, "inspector:disabledEdit" )
 
 def __removableAttributeInspections( pathListing ) :
 
@@ -360,11 +400,12 @@ def __contextMenu( column, pathListing, menuDefinition ) :
 			"command" : functools.partial( __editSelectedCells, pathListing, toggleOnly ),
 		}
 	)
+	tweaks, tweaksEnabled = __toggleableInspectionTweaks( pathListing )
 	menuDefinition.append(
-		"Disable Edit",
+		"{} Edit{}".format( "Disable" if tweaksEnabled else "Enable", "s" if len( tweaks ) > 1 else "" ),
 		{
-			"command" : functools.partial( __disableEdits, pathListing ),
-			"active" : len( __disablableInspectionTweaks( pathListing ) ) > 0,
+			"command" : functools.partial( __toggleEditEnabled, pathListing ),
+			"active" : len( tweaks ) > 0,
 			"shortCut" : "D",
 		}
 	)
@@ -402,8 +443,8 @@ def __keyPress( column, pathListing, event ) :
 			return True
 
 		if event.key == "D" :
-			if len( __disablableInspectionTweaks( pathListing ) ) > 0 :
-				__disableEdits( pathListing )
+			if len( __toggleableInspectionTweaks( pathListing )[0] ) > 0 :
+				__toggleEditEnabled( pathListing )
 			return True
 
 		if event.key in ( "Backspace", "Delete" ) :