[mutter/wip/carlosg/invalid-constraint-region: 12/12] wayland: Ensure pointer constraint region consistency

[Carlos Garnacho <carlosg src gnome org>]

commit dd02e8209c9bbe1f0bb7d00fc3f7a8859d13c1bf
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Dec 23 18:58:48 2020 +0100

    wayland: Ensure pointer constraint region consistency
    
    Changes in games between fullscreen and windowed modes may trigger
    chaotic situations where the buffer and the frame size temporarily
    disagree, producing rectangles with negative width/height. This is
    usually followed by other updates that bring the pointer constraint
    up to date.
    
    This makes cairo panic and return an "error" empty region, which breaks
    deeper down when using the region rectangles to apply the pointer
    constraint.
    
    If we hit this situation, ignore the frame rectangle, and just go with
    the buffer rectangle.

 src/wayland/meta-wayland-pointer-constraints.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)
---
diff --git a/src/wayland/meta-wayland-pointer-constraints.c b/src/wayland/meta-wayland-pointer-constraints.c
index d7033e3ef6..f5ed5b9a5f 100644
--- a/src/wayland/meta-wayland-pointer-constraints.c
+++ b/src/wayland/meta-wayland-pointer-constraints.c
@@ -624,12 +624,15 @@ meta_wayland_pointer_constraint_calculate_effective_region (MetaWaylandPointerCo
                                                   frame->right_width);
       actual_height = window->buffer_rect.height - (frame->child_y +
                                                     frame->bottom_height);
-      cairo_region_intersect_rectangle (region, &(cairo_rectangle_int_t) {
-                                          .x = frame->child_x,
-                                          .y = frame->child_y,
-                                          .width = actual_width,
-                                          .height = actual_height
-                                        });
+      if (actual_width > 1 && actual_height > 1)
+        {
+          cairo_region_intersect_rectangle (region, &(cairo_rectangle_int_t) {
+                                              .x = frame->child_x,
+                                              .y = frame->child_y,
+                                              .width = actual_width,
+                                              .height = actual_height
+                                            });
+        }
     }
 
   return region;