ArnoldShaderUI : Use help parameter metadata

This is now provided by the Arnold core in Arnold 7.3, rather than being duplicated in each of the official DCC plugins (and not existing at all in poor old Gaffer).

Changes.md

@@ -13,6 +13,7 @@ Improvements
 
 - EditScope : Added a summary of edits in the NodeEditor, with the ability to select the affected objects and quickly navigate to the processor nodes.
 - Arnold : OSL shaders with connections from multiple outputs are no longer duplicated on export to Arnold.
+- ArnoldShader : Added parameter tooltips based on `help` metadata provided by Arnold.
 
 Fixes
 -----

python/GafferArnoldUI/ArnoldShaderUI.py

@@ -205,6 +205,8 @@ def __translateNodeMetadata( nodeEntry ) :
 
 	# Shader description. We support Arnold-style "desc" and
 	# OSL style "help".
+	## \todo It seems that Arnold's standard is now "help", so
+	# we may be able to remove "desc".
 
 	description = __aiMetadataGetStr( nodeEntry, None, "desc",
 		defaultValue = __aiMetadataGetStr( nodeEntry, None, "help" )
@@ -245,7 +247,10 @@ def __translateNodeMetadata( nodeEntry ) :
 
 		# Parameter description
 
-		description = __aiMetadataGetStr( nodeEntry, paramName, "desc" )
+		description = __aiMetadataGetStr(
+			nodeEntry, paramName, "desc",
+			defaultValue = __aiMetadataGetStr( nodeEntry, paramName, "help" )
+		)
 		if description is not None :
 			__metadata[paramPath]["description"] = description