[mutter/gnome-3-38] surface-actor: Fix unobscurred_fraction calculation

[Robert Mader <rmader src gnome org>]

commit 15ac84da2da518850e9c247b81d23becad223195
Author: Robert Mader <robert mader posteo de>
Date:   Sun Dec 19 23:42:57 2021 +0100

    surface-actor: Fix unobscurred_fraction calculation
    
    This calculation wrongly applied a `x2 - x1` pattern.
    
    Closes https://gitlab.gnome.org/GNOME/mutter/-/issues/1971
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2169>
    
    
    (cherry picked from commit 6204769fdb8a048ee23f49be0ca532f8ff1d557a)

 src/compositor/meta-surface-actor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/compositor/meta-surface-actor.c b/src/compositor/meta-surface-actor.c
index bdf42720fc..75622f6bbf 100644
--- a/src/compositor/meta-surface-actor.c
+++ b/src/compositor/meta-surface-actor.c
@@ -523,7 +523,7 @@ meta_surface_actor_is_obscured_on_stage_view (MetaSurfaceActor *self,
           cairo_rectangle_int_t rect;
 
           cairo_region_get_rectangle (intersection_region, i, &rect);
-          intersection_size += (rect.width - rect.x) * (rect.height - rect.x);
+          intersection_size += rect.width * rect.height;
         }
       cairo_region_destroy (intersection_region);