layersurface: create a dedicated scene tree for popups

this tree should be always above the top layer

Fixes: #328

dwl.c

@@ -152,6 +152,7 @@ typedef struct {
 	struct wlr_box geom;
 	Monitor *mon;
 	struct wlr_scene_node *scene;
+	struct wlr_scene_node *popups;
 	struct wl_list link;
 	int mapped;
 	struct wlr_layer_surface_v1 *layer_surface;
@@ -583,6 +584,7 @@ arrangelayer(Monitor *m, struct wl_list *list, struct wlr_box *usable_area, int
 					state->margin.top, state->margin.right,
 					state->margin.bottom, state->margin.left);
 		wlr_scene_node_set_position(layersurface->scene, box.x, box.y);
+		wlr_scene_node_set_position(layersurface->popups, box.x, box.y);
 		wlr_layer_surface_v1_configure(wlr_layer_surface, box.width, box.height);
 	}
 }
@@ -823,10 +825,14 @@ commitlayersurfacenotify(struct wl_listener *listener, void *data)
 	if (layers[wlr_layer_surface->current.layer] != layersurface->scene->parent) {
 		wlr_scene_node_reparent(layersurface->scene,
 				layers[wlr_layer_surface->current.layer]);
+		wlr_scene_node_reparent(layersurface->popups,
+				layers[wlr_layer_surface->current.layer]);
 		wl_list_remove(&layersurface->link);
 		wl_list_insert(&layersurface->mon->layers[wlr_layer_surface->current.layer],
 				&layersurface->link);
 	}
+	if (wlr_layer_surface->current.layer < ZWLR_LAYER_SHELL_V1_LAYER_TOP)
+		wlr_scene_node_reparent(layersurface->popups, layers[LyrTop]);
 
 	if (wlr_layer_surface->current.committed == 0
 			&& layersurface->mapped == wlr_layer_surface->mapped)
@@ -920,10 +926,11 @@ createlayersurface(struct wl_listener *listener, void *data)
 	layersurface->mon = wlr_layer_surface->output->data;
 	wlr_layer_surface->data = layersurface;
 
-	layersurface->scene = wlr_layer_surface->surface->data =
-			wlr_scene_subsurface_tree_create(layers[wlr_layer_surface->pending.layer],
-			wlr_layer_surface->surface);
+	layersurface->scene = wlr_scene_subsurface_tree_create(
+			layers[wlr_layer_surface->pending.layer], wlr_layer_surface->surface);
 	layersurface->scene->data = layersurface;
+	layersurface->popups = wlr_layer_surface->surface->data =
+			&wlr_scene_tree_create(layers[wlr_layer_surface->pending.layer])->node;
 
 	wl_list_insert(&layersurface->mon->layers[wlr_layer_surface->pending.layer],
 			&layersurface->link);
@@ -1011,12 +1018,6 @@ createnotify(struct wl_listener *listener, void *data)
 		LayerSurface *l = toplevel_from_popup(xdg_surface->popup);
 		xdg_surface->surface->data = wlr_scene_xdg_surface_create(
 				xdg_surface->popup->parent->data, xdg_surface);
-		/* Raise to top layer if the inmediate parent of the popup is on
-		 * bottom/background layer, which will cause popups appear below the
-		 * x{dg,wayland} clients */
-		if (wlr_surface_is_layer_surface(xdg_surface->popup->parent) && l
-				&& l->layer_surface->current.layer < ZWLR_LAYER_SHELL_V1_LAYER_TOP)
-			wlr_scene_node_reparent(xdg_surface->surface->data, layers[LyrTop]);
 		/* Probably the check of `l` is useless, the only thing that can be NULL
 		 * is its monitor */
 		if (!l || !l->mon)