compositor: forbid sub-surface nesting loops

The only way to create a sub-surface loop by recursive nesting is to
make the main surface (which does not have a role) a sub-surface of any
of its sub-surfaces. All other cases should already be cought.

This change checks for that exact case, and sends a protocol error.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

diff --git a/src/compositor.c b/src/compositor.c
index ed250ba..f67028e 100644 (file)
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -2295,6 +2295,14 @@ subcompositor_get_subsurface(struct wl_client *client,
                return;
        }
 
+       if (weston_surface_get_main_surface(parent) == surface) {
+               wl_resource_post_error(resource,
+                       WL_SUBCOMPOSITOR_ERROR_BAD_SURFACE,
+                       "%s%d: wl_surface@%d is an ancestor of parent",
+                       where, id, surface_resource->object.id);
+               return;
+       }
+
        /* make sure the parent is in its own list */
        if (wl_list_empty(&parent->subsurface_list)) {
                if (!weston_subsurface_create_for_parent(parent)) {