clip: Restrict composite extents to clip extents

Fixes test/clip-rectangle-twice.

1 files changed, 84 insertions, 0 deletions

diff --git a/src/cairo-clip.c b/src/cairo-clip.c
index abcf6595..fdb94701 100644
--- a/src/cairo-clip.c
+++ b/src/cairo-clip.c
@@ -1335,6 +1335,90 @@ _cairo_clip_get_boxes (cairo_clip_t *clip,
     return CAIRO_STATUS_SUCCESS;
 }
 
+static cairo_bool_t
+box_is_aligned (const cairo_box_t *box)
+{
+    return
+	_cairo_fixed_is_integer (box->p1.x) &&
+	_cairo_fixed_is_integer (box->p1.y) &&
+	_cairo_fixed_is_integer (box->p2.x) &&
+	_cairo_fixed_is_integer (box->p2.y);
+}
+
+static void
+intersect_with_boxes (cairo_composite_rectangles_t *extents,
+		      cairo_box_t *boxes,
+		      int num_boxes)
+{
+    cairo_rectangle_int_t rect;
+    cairo_box_t box;
+    cairo_bool_t is_empty;
+
+    box.p1.x = box.p1.y = INT_MIN;
+    box.p2.x = box.p2.y = INT_MAX;
+    while (num_boxes--) {
+	if (boxes->p1.x < box.p1.x)
+	    box.p1.x = boxes->p1.x;
+	if (boxes->p1.y < box.p1.y)
+	    box.p1.y = boxes->p1.y;
+
+	if (boxes->p2.x > box.p2.x)
+	    box.p2.x = boxes->p2.x;
+	if (boxes->p2.y > box.p2.y)
+	    box.p2.y = boxes->p2.y;
+    }
+
+    _cairo_box_round_to_rectangle (&box, &rect);
+    is_empty = _cairo_rectangle_intersect (&extents->bounded, &rect);
+    is_empty = _cairo_rectangle_intersect (&extents->unbounded, &rect);
+}
+
+cairo_status_t
+_cairo_clip_to_boxes (cairo_clip_t **clip,
+		      cairo_composite_rectangles_t *extents,
+		      cairo_box_t **boxes,
+		      int *num_boxes)
+{
+    cairo_status_t status;
+    const cairo_rectangle_int_t *rect;
+
+    rect = extents->is_bounded ? &extents->bounded : &extents->unbounded;
+
+    if (*clip == NULL)
+	goto EXTENTS;
+
+    status = _cairo_clip_rectangle (*clip, rect);
+    if (unlikely (status))
+	return status;
+
+    status = _cairo_clip_get_boxes (*clip, boxes, num_boxes);
+    switch ((int) status) {
+    case CAIRO_STATUS_SUCCESS:
+	intersect_with_boxes (extents, *boxes, *num_boxes);
+	if (rect->width == 0 || rect->height == 0 ||
+	    extents->is_bounded ||
+	    (*num_boxes == 1 && box_is_aligned (*boxes)))
+	{
+	    *clip = NULL;
+	}
+	goto DONE;
+
+    case CAIRO_INT_STATUS_UNSUPPORTED:
+	goto EXTENTS;
+
+    default:
+	return status;
+    }
+
+  EXTENTS:
+    status = CAIRO_STATUS_SUCCESS;
+    _cairo_box_from_rectangle (&(*boxes)[0], rect);
+    *num_boxes = 1;
+  DONE:
+    return status;
+}
+
+
 static cairo_rectangle_list_t *
 _cairo_rectangle_list_create_in_error (cairo_status_t status)
 {