libweston: Skip views without a layer assignment in output_mask calculations

Surface views that are not assigned to a layer are not going to be
rendered, and thus should not participate in determining the outputs the
surface is on.

There are other view properties that may determine if the view should be
considered in output_mask calculations, e.g., is_mapped, but checking
for this currently breaks tests. Such additional checks are left for
future fixes or reworkings of the view infrastructure.

Fixes #646

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>

libweston/compositor.c

@@ -1300,6 +1300,14 @@ weston_view_set_output(struct weston_view *view, struct weston_output *output)
 	}
 }
 
+static struct weston_layer *
+get_view_layer(struct weston_view *view)
+{
+	if (view->parent_view)
+		return get_view_layer(view->parent_view);
+	return view->layer_link.layer;
+}
+
 /** Recalculate which output(s) the surface has views displayed on
  *
  * \param es  The surface to remap to outputs
@@ -1325,7 +1333,9 @@ weston_surface_assign_output(struct weston_surface *es)
 	mask = 0;
 	pixman_region32_init(&region);
 	wl_list_for_each(view, &es->views, surface_link) {
-		if (!view->output)
+		/* Only views that are visible on some layer participate in
+		 * output_mask calculations. */
+		if (!view->output || !get_view_layer(view))
 			continue;
 
 		pixman_region32_intersect(&region, &view->transform.boundingbox,
@@ -1605,14 +1615,6 @@ weston_view_update_transform_enable(struct weston_view *view)
 	return 0;
 }
 
-static struct weston_layer *
-get_view_layer(struct weston_view *view)
-{
-	if (view->parent_view)
-		return get_view_layer(view->parent_view);
-	return view->layer_link.layer;
-}
-
 WL_EXPORT void
 weston_view_update_transform(struct weston_view *view)
 {