clip: Report the surface offset when retrieving the clip mask

Stop the callers from guessing the origin of the clip surface by
reporting it explicitly! This enables the clip to bypass any rectangles
overlaid on top of the clip surface, which is common when the backends
limit the clip to the extents of the operation -- but irrelevant to the
actual content of the clip mask

1 files changed, 20 insertions, 6 deletions

diff --git a/src/cairo-clip.c b/src/cairo-clip.c
index fca47597c..ff4aeb636 100644
--- a/src/cairo-clip.c
+++ b/src/cairo-clip.c
@@ -942,7 +942,8 @@ _cairo_clip_path_to_boxes (cairo_clip_path_t *clip_path,
 
 static cairo_surface_t *
 _cairo_clip_path_get_surface (cairo_clip_path_t *clip_path,
-			      cairo_surface_t *target)
+			      cairo_surface_t *target,
+			      int *tx, int *ty)
 {
     const cairo_rectangle_int_t *clip_extents = &clip_path->extents;
     cairo_bool_t need_translate;
@@ -950,9 +951,19 @@ _cairo_clip_path_get_surface (cairo_clip_path_t *clip_path,
     cairo_clip_path_t *prev;
     cairo_status_t status;
 
+    while (clip_path->prev != NULL &&
+	   clip_path->flags & CAIRO_CLIP_PATH_IS_BOX &&
+	   clip_path->path.maybe_fill_region)
+    {
+	clip_path = clip_path->prev;
+    }
+
+    clip_extents = &clip_path->extents;
     if (clip_path->surface != NULL &&
 	clip_path->surface->backend == target->backend)
     {
+	*tx = clip_extents->x;
+	*ty = clip_extents->y;
 	return clip_path->surface;
     }
 
@@ -1046,16 +1057,17 @@ _cairo_clip_path_get_surface (cairo_clip_path_t *clip_path,
 	{
 	    cairo_surface_pattern_t pattern;
 	    cairo_surface_t *prev_surface;
+	    int prev_tx, prev_ty;
 
-	    prev_surface = _cairo_clip_path_get_surface (prev, target);
+	    prev_surface = _cairo_clip_path_get_surface (prev, target, &prev_tx, &prev_ty);
 	    if (unlikely (prev_surface->status))
 		goto BAIL;
 
 	    _cairo_pattern_init_for_surface (&pattern, prev_surface);
 	    pattern.base.filter = CAIRO_FILTER_NEAREST;
 	    cairo_matrix_init_translate (&pattern.base.matrix,
-					 clip_extents->x - prev->extents.x,
-					 clip_extents->y - prev->extents.y);
+					 clip_extents->x - prev_tx,
+					 clip_extents->y - prev_ty);
 	    status = _cairo_surface_paint (surface,
 					   CAIRO_OPERATOR_IN,
 					   &pattern.base,
@@ -1071,6 +1083,8 @@ _cairo_clip_path_get_surface (cairo_clip_path_t *clip_path,
 	prev = prev->prev;
     }
 
+    *tx = clip_extents->x;
+    *ty = clip_extents->y;
     cairo_surface_destroy (clip_path->surface);
     return clip_path->surface = surface;
 
@@ -1158,11 +1172,11 @@ _cairo_debug_print_clip (FILE *stream, cairo_clip_t *clip)
 }
 
 cairo_surface_t *
-_cairo_clip_get_surface (cairo_clip_t *clip, cairo_surface_t *target)
+_cairo_clip_get_surface (cairo_clip_t *clip, cairo_surface_t *target, int *tx, int *ty)
 {
     /* XXX is_clear -> all_clipped */
     assert (clip->path != NULL);
-    return _cairo_clip_path_get_surface (clip->path, target);
+    return _cairo_clip_path_get_surface (clip->path, target, tx, ty);
 }
 
 cairo_status_t