Bug 1050788 - Fix a bug where cairo's region clipping code incorrectly handled empty clips. r=jrmuizel

--HG--
extra : rebase_source : 653c04da802a5e6598638baaaab05c059b46709d

gfx/cairo/cairo-region-clip.patch

@@ -0,0 +1,34 @@
+# HG changeset patch
+# User Matt Woodrow <mwoodrow@mozilla.com>
+# Date 1408674084 -43200
+#      Fri Aug 22 14:21:24 2014 +1200
+# Node ID 2b819b882c3b26c02d821e8d713591a9b56f1728
+# Parent  ffd1fc7e7d5a85e4823b5f2067b4a24d358a0e41
+Bug 1050788 - Fix cairo clip path region construction when the first path generates no traps. r=jrmuizel
+
+diff --git a/gfx/cairo/cairo/src/cairo-clip.c b/gfx/cairo/cairo/src/cairo-clip.c
+--- a/gfx/cairo/cairo/src/cairo-clip.c
++++ b/gfx/cairo/cairo/src/cairo-clip.c
+@@ -590,16 +590,22 @@ static cairo_int_status_t
+     status = _cairo_path_fixed_fill_rectilinear_to_traps (&clip_path->path,
+ 							  clip_path->fill_rule,
+ 							  &traps);
+     if (unlikely (_cairo_status_is_error (status)))
+ 	return status;
+     if (status == CAIRO_INT_STATUS_UNSUPPORTED)
+ 	goto UNSUPPORTED;
+ 
++    if (unlikely (traps.num_traps == 0)) {
++	clip_path->region = cairo_region_create ();
++	clip_path->flags |= CAIRO_CLIP_PATH_HAS_REGION;
++	return CAIRO_STATUS_SUCCESS;
++    }
++
+     if (traps.num_traps > ARRAY_LENGTH (stack_boxes)) {
+ 	boxes = _cairo_malloc_ab (traps.num_traps, sizeof (cairo_box_t));
+ 	if (unlikely (boxes == NULL))
+ 	    return _cairo_error (CAIRO_STATUS_NO_MEMORY);
+     }
+ 
+     for (n = 0; n < traps.num_traps; n++) {
+ 	boxes[n].p1.x = traps.traps[n].left.p1.x;

gfx/cairo/cairo/src/cairo-clip.c

@@ -595,6 +595,12 @@ _cairo_clip_path_to_region_geometric (cairo_clip_path_t *clip_path)
     if (status == CAIRO_INT_STATUS_UNSUPPORTED)
 	goto UNSUPPORTED;
 
+    if (unlikely (traps.num_traps == 0)) {
+	clip_path->region = cairo_region_create ();
+	clip_path->flags |= CAIRO_CLIP_PATH_HAS_REGION;
+	return CAIRO_STATUS_SUCCESS;
+    }
+
     if (traps.num_traps > ARRAY_LENGTH (stack_boxes)) {
 	boxes = _cairo_malloc_ab (traps.num_traps, sizeof (cairo_box_t));
 	if (unlikely (boxes == NULL))