Clip composite region against the destination alpha map extents.

Otherwise we can end up writing outside the alpha map.

diff --git a/pixman/pixman.c b/pixman/pixman.c
index cdf4b75..285bbfc 100644 (file)
--- a/pixman/pixman.c
+++ b/pixman/pixman.c
@@ -315,14 +315,27 @@ pixman_compute_composite_region32 (pixman_region32_t * region,
            return FALSE;
     }
 
-    if (dst_image->common.alpha_map && dst_image->common.alpha_map->common.have_clip_region)
+    if (dst_image->common.alpha_map)
     {
-       if (!clip_general_image (region, &dst_image->common.alpha_map->common.clip_region,
-                                -dst_image->common.alpha_origin_x,
-                                -dst_image->common.alpha_origin_y))
+       if (!pixman_region32_intersect_rect (region, region,
+                                            dst_image->common.alpha_origin_x,
+                                            dst_image->common.alpha_origin_y,
+                                            dst_image->common.alpha_map->width,
+                                            dst_image->common.alpha_map->height))
        {
            return FALSE;
        }
+       if (!pixman_region32_not_empty (region))
+           return FALSE;
+       if (dst_image->common.alpha_map->common.have_clip_region)
+       {
+           if (!clip_general_image (region, &dst_image->common.alpha_map->common.clip_region,
+                                    -dst_image->common.alpha_origin_x,
+                                    -dst_image->common.alpha_origin_y))
+           {
+               return FALSE;
+           }
+       }
     }
 
     /* clip against src */