[mutter] Revert "clutter/offscreen-effect: Use the paint volume origin as the FBO offset"

[Marge Bot <marge-bot src gnome org>]

commit 7de5f79ddb078e35494514745fe2c8554926386d
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Wed Dec 16 19:39:35 2020 +0100

    Revert "clutter/offscreen-effect: Use the paint volume origin as the FBO offset"
    
    This change broke the color picker in gnome-shell, let's revert it for
    now until a correct solution can be figured out.
    
    This reverts commit 0bace8dbde4945f8f8d4b633934bbdb50e1200d0.
    
    Closes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3494
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1645>

 clutter/clutter/clutter-offscreen-effect.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)
---
diff --git a/clutter/clutter/clutter-offscreen-effect.c b/clutter/clutter/clutter-offscreen-effect.c
index 6d4f095fbc..42e5238c44 100644
--- a/clutter/clutter/clutter-offscreen-effect.c
+++ b/clutter/clutter/clutter-offscreen-effect.c
@@ -298,7 +298,7 @@ clutter_offscreen_effect_pre_paint (ClutterEffect       *effect,
   ClutterOffscreenEffect *self = CLUTTER_OFFSCREEN_EFFECT (effect);
   ClutterOffscreenEffectPrivate *priv = self->priv;
   CoglFramebuffer *offscreen;
-  ClutterActorBox box;
+  ClutterActorBox raw_box, box;
   ClutterActor *stage;
   graphene_matrix_t projection, modelview;
   const ClutterPaintVolume *volume;
@@ -334,18 +334,19 @@ clutter_offscreen_effect_pre_paint (ClutterEffect       *effect,
       ClutterPaintVolume mutable_volume;
 
       _clutter_paint_volume_copy_static (volume, &mutable_volume);
-      _clutter_paint_volume_get_bounding_box (&mutable_volume, &box);
+      _clutter_paint_volume_get_bounding_box (&mutable_volume, &raw_box);
       clutter_paint_volume_free (&mutable_volume);
     }
   else
     {
-      clutter_actor_get_allocation_box (priv->actor, &box);
+      clutter_actor_get_allocation_box (priv->actor, &raw_box);
     }
 
+  box = raw_box;
   _clutter_actor_box_enlarge_for_effects (&box);
 
-  priv->fbo_offset_x = box.x1;
-  priv->fbo_offset_y = box.y1;
+  priv->fbo_offset_x = box.x1 - raw_box.x1;
+  priv->fbo_offset_y = box.y1 - raw_box.y1;
 
   clutter_actor_box_scale (&box, ceiled_resource_scale);
   clutter_actor_box_get_size (&box, &target_width, &target_height);