compositor: fix endless recursion in scene-graph printing

If a surface has subsurfaces then the surface itself is in the subsurface
list. To avoid printing it again there is a check to skip the child view,
if it is the same as the current view.

However, this fails when a surface with subsurfaces has two (or more) views:
The check to skip the parent fails for the other view and the two views are
printed again and again until a stack overflow occurs.

So instead check if the parent view of the subsurface view is the current
view. This way, any view that does not belong to a real subsurface is
skipped.

As a side effect, this ensures that each view of the subsurfaces is only
printed once at the correct place in the hierarchy.

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>

libweston/compositor.c

@@ -7162,8 +7162,8 @@ debug_scene_view_print_tree(struct weston_view *view,
 
 	wl_list_for_each(sub, &view->surface->subsurface_list, parent_link) {
 		wl_list_for_each(ev, &sub->surface->views, surface_link) {
-			/* do not print again the parent view */
-			if (view == ev)
+			/* only print the child views of the current view */
+			if (ev->parent_view != view)
 				continue;
 
 			(*view_idx)++;