clutter/paint-context: Add 'no-cursors' paint flag

Will be used by the stage to not paint the overlays. We skip all
overlays since overlays are only ever used for pointer cursors when the
hardware cursors cannot or should not be used.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1207

clutter/clutter/clutter-paint-context.h

@@ -32,6 +32,7 @@ typedef struct _ClutterPaintContext ClutterPaintContext;
 typedef enum _ClutterPaintFlag
 {
   CLUTTER_PAINT_FLAG_NONE = 0,
+  CLUTTER_PAINT_FLAG_NO_CURSORS = 1 << 0,
 } ClutterPaintFlag;
 
 #define CLUTTER_TYPE_PAINT_CONTEXT (clutter_paint_context_get_type ())

src/backends/meta-stage.c

@@ -206,8 +206,12 @@ meta_stage_paint (ClutterActor        *actor,
 
   g_signal_emit (stage, signals[ACTORS_PAINTED], 0);
 
+  if (!(clutter_paint_context_get_paint_flags (paint_context) &
+        CLUTTER_PAINT_FLAG_NO_CURSORS))
+    {
       for (l = stage->overlays; l; l = l->next)
         meta_overlay_paint (l->data, paint_context);
+    }
 
   if (view)
     {