[Pixman] [PATCH] _intersect_rect should return an empty region when intersecting with an empty rect

Bill McCloskey wmccloskey at mozilla.com
Wed Jan 13 13:43:39 PST 2016

When you call _intersect_rect and pass it an empty rectangle,
it creates an invalid region from that rectangle. The only valid
empty region is the one where the data pointer points to
pixman_region_empty_data. The region created by _intersect_rect has
a null data pointer, and so _not_empty returns true for it even if
the extents are empty.

This patch uses code similar to what's in _union_rect to handle empty
 pixman/pixman-region.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/pixman/pixman-region.c b/pixman/pixman-region.c
index 59bc9c7..95911db 100644
--- a/pixman/pixman-region.c
+++ b/pixman/pixman-region.c
@@ -1329,16 +1329,25 @@ PREFIX(_intersect_rect) (region_type_t *dest,
     region_type_t region;

     region.data = NULL;
     region.extents.x1 = x;
     region.extents.y1 = y;
     region.extents.x2 = x + width;
     region.extents.y2 = y + height;

+    if (!GOOD_RECT (&region.extents))
+    {
+        if (BAD_RECT (&region.extents))
+            _pixman_log_error (FUNC, "Invalid rectangle passed");
+        FREE_DATA (dest);
+        PREFIX (_init) (dest);
+        return TRUE;
+    }
     return PREFIX(_intersect) (dest, source, &region);

 /* Convenience function for performing union of region with a
  * single rectangle
 PIXMAN_EXPORT pixman_bool_t
 PREFIX (_union_rect) (region_type_t *dest,
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