[mutter] background-content: Assume background clones are always transformed

[verdre <jonasd src gnome org>]

commit a24b2f4b0fc72ebe262988a14a6fcd58d531e2bb
Author: Daniel van Vugt <daniel van vugt canonical com>
Date:   Tue Oct 20 17:49:26 2020 +0800

    background-content: Assume background clones are always transformed
    
    Because clones may not have identical geometry to their source actors.
    So we can't use the geometry of the source actor to decide to take the
    more optimized (more clipped) path.
    
    Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1480

 src/compositor/meta-background-content.c | 41 +++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 17 deletions(-)
---
diff --git a/src/compositor/meta-background-content.c b/src/compositor/meta-background-content.c
index ce6ee2fff1..7990ad47b5 100644
--- a/src/compositor/meta-background-content.c
+++ b/src/compositor/meta-background-content.c
@@ -511,29 +511,36 @@ meta_background_content_paint_content (ClutterContent      *content,
   if ((self->clip_region && cairo_region_is_empty (self->clip_region)))
     return;
 
-  clutter_actor_get_transformed_position (actor,
-                                          &transformed_x,
-                                          &transformed_y);
-  rect_within_stage.x = floorf (transformed_x);
-  rect_within_stage.y = floorf (transformed_y);
-
-  clutter_actor_get_transformed_size (actor,
-                                      &transformed_width,
-                                      &transformed_height);
-  rect_within_stage.width = roundf (transformed_width);
-  rect_within_stage.height = roundf (transformed_height);
-
   clutter_actor_get_content_box (actor, &actor_box);
   rect_within_actor.x = actor_box.x1;
   rect_within_actor.y = actor_box.y1;
   rect_within_actor.width = actor_box.x2 - actor_box.x1;
   rect_within_actor.height = actor_box.y2 - actor_box.y1;
 
-  untransformed =
-    rect_within_actor.x == rect_within_stage.x &&
-    rect_within_actor.y == rect_within_stage.y &&
-    rect_within_actor.width == rect_within_stage.width &&
-    rect_within_actor.height == rect_within_stage.height;
+  if (clutter_actor_is_in_clone_paint (actor))
+    {
+      untransformed = FALSE;
+    }
+  else
+    {
+      clutter_actor_get_transformed_position (actor,
+                                              &transformed_x,
+                                              &transformed_y);
+      rect_within_stage.x = floorf (transformed_x);
+      rect_within_stage.y = floorf (transformed_y);
+
+      clutter_actor_get_transformed_size (actor,
+                                          &transformed_width,
+                                          &transformed_height);
+      rect_within_stage.width = roundf (transformed_width);
+      rect_within_stage.height = roundf (transformed_height);
+
+      untransformed =
+        rect_within_actor.x == rect_within_stage.x &&
+        rect_within_actor.y == rect_within_stage.y &&
+        rect_within_actor.width == rect_within_stage.width &&
+        rect_within_actor.height == rect_within_stage.height;
+    }
 
   if (untransformed) /* actor and stage space are the same */
     {