menu: lazily generate menu scenes

This removes the need to call update_client_list_combined_menu()
and update_client_send_to_menu() every time a root menu is opened.

This commit also fixed the incorrect menu position with following
configuration:
  <menu id="foo" label="foo">
    <item label="aaaaaa"/>
    <item label="bbbbbb"/>
  </menu>
  <menu id="root-menu">
    <menu id="foo" />
    <menu id="foo" />
  </menu>

include/menu/menu.h

@@ -127,7 +127,4 @@ void menu_close_root(struct server *server);
 /* menu_reconfigure - reload theme and content */
 void menu_reconfigure(struct server *server);
 
-void update_client_list_combined_menu(struct server *server);
-void update_client_send_to_menu(struct server *server);
-
 #endif /* LABWC_MENU_H */

src/action.c

@@ -664,16 +664,6 @@ show_menu(struct server *server, struct view *view, struct cursor_context *ctx,
 		return;
 	}
 
-	/*
-	 * We always refresh client-list-combined-menu and client-send-to-menu
-	 * so that they are up-to-date whether they are directly opened as a
-	 * top-level menu or opened as a submenu which we don't know at this
-	 * point. It is also needed to calculate the proper width for placement
-	 * as it fluctuates depending on application/workspace titles.
-	 */
-	update_client_list_combined_menu(menu->server);
-	update_client_send_to_menu(menu->server);
-
 	int x = server->seat.cursor->x;
 	int y = server->seat.cursor->y;
 

src/menu/menu.c

@@ -362,19 +362,30 @@ title_create_scene(struct menuitem *menuitem, int *item_y)
 	*item_y += theme->menu_header_height;
 }
 
-/* (Re)creates the scene of the menu */
+static void item_destroy(struct menuitem *item);
+
 static void
-menu_update_scene(struct menu *menu)
+reset_menu(struct menu *menu)
+{
+	struct menuitem *item, *next;
+	wl_list_for_each_safe(item, next, &menu->menuitems, link) {
+		item_destroy(item);
+	}
+	if (menu->scene_tree) {
+		wlr_scene_node_destroy(&menu->scene_tree->node);
+		menu->scene_tree = NULL;
+	}
+	/* TODO: also reset other fields? */
+}
+
+static void
+menu_create_scene(struct menu *menu)
 {
 	struct menuitem *item;
 	struct theme *theme = menu->server->theme;
 
-	if (menu->scene_tree) {
+	assert(!menu->scene_tree);
-		wlr_scene_node_destroy(&menu->scene_tree->node);
+
-		wl_list_for_each(item, &menu->menuitems, link) {
-			item->tree = NULL;
-		}
-	}
 	menu->scene_tree = wlr_scene_tree_create(menu->server->menu_tree);
 	wlr_scene_node_set_enabled(&menu->scene_tree->node, false);
 
@@ -420,22 +431,6 @@ menu_update_scene(struct menu *menu)
 	wlr_scene_node_lower_to_bottom(&bg_buffer->scene_buffer->node);
 }
 
-static void
-post_processing(struct server *server)
-{
-	/*
-	 * Create menu scene after all of its contents is determined
-	 * (e.g. when finished reading menu.xml or received output from
-	 * pipemenu program).
-	 */
-	struct menu *menu;
-	wl_list_for_each(menu, &server->menus, link) {
-		if (!menu->scene_tree) {
-			menu_update_scene(menu);
-		}
-	}
-}
-
 /*
  * Handle the following:
  * <item label="">
@@ -916,8 +911,6 @@ get_item_anchor_rect(struct theme *theme, struct menuitem *item)
 static void
 menu_reposition(struct menu *menu, struct wlr_box anchor_rect)
 {
-	struct theme *theme = menu->server->theme;
-
 	/* Get output usable area to place the menu within */
 	struct output *output = output_nearest_to(menu->server,
 		anchor_rect.x, anchor_rect.y);
@@ -962,15 +955,6 @@ menu_reposition(struct menu *menu, struct wlr_box anchor_rect)
 	wlr_scene_node_set_position(&menu->scene_tree->node, box.x, box.y);
 
 	menu->align_left = (box.x < anchor_rect.x);
-
-	struct menuitem *item;
-	wl_list_for_each(item, &menu->menuitems, link) {
-		if (!item->submenu) {
-			continue;
-		}
-		anchor_rect = get_item_anchor_rect(theme, item);
-		menu_reposition(item->submenu, anchor_rect);
-	}
 }
 
 static void
@@ -1006,20 +990,13 @@ init_client_send_to_menu(struct server *server)
  * with the workspace names that can be used with
  * SendToDesktop, left/right options are included.
  */
-void
+static void
 update_client_send_to_menu(struct server *server)
 {
-	struct menu *menu = menu_get_by_id(server,
+	struct menu *menu = menu_get_by_id(server, "client-send-to-menu");
-			"client-send-to-menu");
+	assert(menu);
 
-	if (menu) {
+	reset_menu(menu);
-		struct menuitem *item, *next;
-		wl_list_for_each_safe(item, next, &menu->menuitems, link) {
-			item_destroy(item);
-		}
-	}
-
-	menu->size.height = 0;
 
 	struct workspace *workspace;
 
@@ -1036,7 +1013,7 @@ update_client_send_to_menu(struct server *server)
 		fill_item("to.action", workspace->name);
 	}
 
-	menu_update_scene(menu);
+	menu_create_scene(menu);
 }
 
 static void
@@ -1054,23 +1031,13 @@ init_client_list_combined_menu(struct server *server)
  * separator label and the titles of the view, if any, below each workspace
  * name. Active view is indicated by "*" preceding title.
  */
-void
+static void
 update_client_list_combined_menu(struct server *server)
 {
 	struct menu *menu = menu_get_by_id(server, "client-list-combined-menu");
+	assert(menu);
 
-	if (!menu) {
+	reset_menu(menu);
-		/* Menu is created on compositor startup/reconfigure */
-		wlr_log(WLR_ERROR, "client-list-combined-menu does not exist");
-		return;
-	}
-
-	struct menuitem *item, *next;
-	wl_list_for_each_safe(item, next, &menu->menuitems, link) {
-		item_destroy(item);
-	}
-
-	menu->size.height = 0;
 
 	struct workspace *workspace;
 	struct view *view;
@@ -1108,7 +1075,7 @@ update_client_list_combined_menu(struct server *server)
 		fill_item("to.action", workspace->name);
 	}
 	buf_reset(&buffer);
-	menu_update_scene(menu);
+	menu_create_scene(menu);
 }
 
 static void
@@ -1191,7 +1158,6 @@ menu_init(struct server *server)
 	init_windowmenu(server);
 	init_client_list_combined_menu(server);
 	init_client_send_to_menu(server);
-	post_processing(server);
 	validate(server);
 }
 
@@ -1358,6 +1324,23 @@ menu_close(struct menu *menu)
 	_close(menu);
 }
 
+static void
+open_menu(struct menu *menu, struct wlr_box anchor_rect)
+{
+	if (!strcmp(menu->id, "client-list-combined-menu")) {
+		update_client_list_combined_menu(menu->server);
+	} else if (!strcmp(menu->id, "client-send-to-menu")) {
+		update_client_send_to_menu(menu->server);
+	}
+
+	if (!menu->scene_tree) {
+		menu_create_scene(menu);
+		assert(menu->scene_tree);
+	}
+	menu_reposition(menu, anchor_rect);
+	wlr_scene_node_set_enabled(&menu->scene_tree->node, true);
+}
+
 void
 menu_open_root(struct menu *menu, int x, int y)
 {
@@ -1369,8 +1352,7 @@ menu_open_root(struct menu *menu, int x, int y)
 
 	assert(!menu->server->menu_current);
 
-	menu_reposition(menu, (struct wlr_box){.x = x, .y = y});
+	open_menu(menu, (struct wlr_box){.x = x, .y = y});
-	wlr_scene_node_set_enabled(&menu->scene_tree->node, true);
 	menu->server->menu_current = menu;
 	selected_item = NULL;
 	seat_focus_override_begin(&menu->server->seat,
@@ -1402,9 +1384,7 @@ create_pipe_menu(struct menu_pipe_context *ctx)
 				ctx->top_level_menu->id);
 		}
 		menu_level--;
-		post_processing(ctx->server);
 		validate(ctx->server);
-		menu_update_scene(current_menu);
 		return;
 	}
 
@@ -1445,12 +1425,9 @@ create_pipe_menu(struct menu_pipe_context *ctx)
 	 * operate from current point onwards
 	 */
 
-	/* Set menu-widths before configuring */
-	post_processing(ctx->server);
-
 	struct wlr_box anchor_rect =
 		get_item_anchor_rect(ctx->server->theme, ctx->item);
-	menu_reposition(pipe_menu, anchor_rect);
+	open_menu(pipe_menu, anchor_rect);
 
 	validate(ctx->server);
 
@@ -1625,8 +1602,9 @@ menu_process_item_selection(struct menuitem *item)
 		/* Ensure the submenu has its parent set correctly */
 		item->submenu->parent = item->parent;
 		/* And open the new submenu tree */
-		wlr_scene_node_set_enabled(
+		struct wlr_box anchor_rect =
-			&item->submenu->scene_tree->node, true);
+			get_item_anchor_rect(item->submenu->server->theme, item);
+		open_menu(item->submenu, anchor_rect);
 	}
 
 	item->parent->selection.menu = item->submenu;