Fix node UI not using translation context correctly.

Now that some node types may have custom context, we need to handle that
in the (convoluted :| ) UI code of nodes as well.

Reported in T43295 by Gabriel Gazzán (@gab3d), thanks.

release/scripts/modules/nodeitems_utils.py

@@ -61,13 +61,19 @@ class NodeItem:
             # if no custom label is defined, fall back to the node type UI name
             return getattr(bpy.types, self.nodetype).bl_rna.name
 
+    @property
+    def translation_context(self):
+        if self._label:
+            return bpy.app.translations.contexts.default
+        else:
+            # if no custom label is defined, fall back to the node type UI name
+            return getattr(bpy.types, self.nodetype).bl_rna.translation_context
+
     # NB: is a staticmethod because called with an explicit self argument
     # NodeItemCustom sets this as a variable attribute in __init__
     @staticmethod
     def draw(self, layout, context):
-        default_context = bpy.app.translations.contexts.default
-
-        props = layout.operator("node.add_node", text=self.label, text_ctxt=default_context)
+        props = layout.operator("node.add_node", text=self.label, text_ctxt=self.translation_context)
         props.type = self.nodetype
         props.use_transform = True
 

source/blender/blenkernel/intern/node.c

@@ -3174,12 +3174,20 @@ void nodeSynchronizeID(bNode *node, bool copy_to_id)
 
 void nodeLabel(bNodeTree *ntree, bNode *node, char *label, int maxlen)
 {
-	if (node->label[0] != '\0')
+	if (node->label[0] != '\0') {
 		BLI_strncpy(label, node->label, maxlen);
-	else if (node->typeinfo->labelfunc)
+	}
+	else if (node->typeinfo->labelfunc) {
 		node->typeinfo->labelfunc(ntree, node, label, maxlen);
-	else
-		BLI_strncpy(label, IFACE_(node->typeinfo->ui_name), maxlen);
+	}
+	else {
+		/* Kind of hacky and weak... Ideally would be better to use RNA here. :| */
+		const char *tmp = CTX_IFACE_(BLT_I18NCONTEXT_ID_NODETREE, node->typeinfo->ui_name);
+		if (tmp == node->typeinfo->ui_name) {
+			tmp = IFACE_(node->typeinfo->ui_name);
+		}
+		BLI_strncpy(label, tmp, maxlen);
+	}
 }
 
 static void node_type_base_defaults(bNodeType *ntype)