xcb: track fallback damage

And only upload the parts of the image that are modified during the
fallback. I have to keep reminding myself that the goal is always to
reduce the amount of fallbacks required...

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/cairo-composite-rectangles.c b/src/cairo-composite-rectangles.c
index c66d3d628..7fc0f5fe5 100644
--- a/src/cairo-composite-rectangles.c
+++ b/src/cairo-composite-rectangles.c
@@ -436,3 +436,21 @@ _cairo_composite_rectangles_can_reduce_clip (cairo_composite_rectangles_t *compo
     _cairo_box_from_rectangle (&box, &extents);
     return _cairo_clip_contains_box (clip, &box);
 }
+
+cairo_int_status_t
+_cairo_composite_rectangles_add_to_damage (cairo_composite_rectangles_t *composite,
+					   cairo_boxes_t *damage)
+{
+    cairo_int_status_t status;
+    int n;
+
+    for (n = 0; n < composite->clip->num_boxes; n++) {
+	status = _cairo_boxes_add (damage,
+			  CAIRO_ANTIALIAS_NONE,
+			  &composite->clip->boxes[n]);
+	if (unlikely (status))
+	    return status;
+    }
+
+    return CAIRO_INT_STATUS_SUCCESS;
+}