commit 8fdf857

compositor: Fix damage calculation on attach

We only need to damage the region that was newly covered or uncovered
during a resize.

 1@@ -1,6 +1,6 @@
 2 /* swc: libswc/compositor.c
 3  *
 4- * Copyright (c) 2013, 2014 Michael Forney
 5+ * Copyright (c) 2013-2020 Michael Forney
 6  *
 7  * Based in part upon compositor.c from weston, which is:
 8  *
 9@@ -292,8 +292,8 @@ renderer_flush_view(struct compositor_view *view)
10 /* Surface Views {{{ */
11 
12 /**
13- * Adds damage from the region below a view, taking into account it's clip
14- * region, to the region specified by `damage'.
15+ * Adds the region below a view to the compositor's damaged region,
16+ * taking into account its clip region.
17  */
18 static void
19 damage_below_view(struct compositor_view *view)
20@@ -362,22 +362,38 @@ static int
21 attach(struct view *base, struct wld_buffer *buffer)
22 {
23 	struct compositor_view *view = (void *)base;
24+	pixman_box32_t old_extents;
25+	pixman_region32_t old, new, both;
26 	int ret;
27 
28 	if ((ret = renderer_attach(view, buffer)) < 0)
29 		return ret;
30 
31-	if (view->visible && view->base.buffer) {
32-		damage_below_view(view);
33-		update(&view->base);
34-	}
35+	/* Schedule updates on the screens the view was previously
36+	 * visible on. */
37+	update(&view->base);
38 
39 	if (view_set_size_from_buffer(&view->base, buffer)) {
40+		/* The view was resized. */
41+		old_extents = view->extents;
42 		update_extents(view);
43 
44-		if (view->visible && buffer) {
45+		if (view->visible) {
46+			/* Damage the region that was newly uncovered
47+			 * or covered, minus the clip region. */
48+			pixman_region32_init_with_extents(&old, &old_extents);
49+			pixman_region32_init_with_extents(&new, &view->extents);
50+			pixman_region32_init(&both);
51+			pixman_region32_intersect(&both, &old, &new);
52+			pixman_region32_union(&new, &old, &new);
53+			pixman_region32_subtract(&new, &new, &both);
54+			pixman_region32_subtract(&new, &new, &view->clip);
55+			pixman_region32_union(&compositor.damage, &compositor.damage, &new);
56+			pixman_region32_fini(&old);
57+			pixman_region32_fini(&new);
58+			pixman_region32_fini(&both);
59+
60 			view_update_screens(&view->base);
61-			damage_below_view(view);
62 			update(&view->base);
63 		}
64 	}