Prevent opening an empty menu

examples/example-dockpanel/src/index.ts

@@ -280,10 +280,15 @@ function main(): void {
  menu3.title.label = 'View';
  menu3.title.mnemonic = 0;
 
+ let emptyMenu = new Menu({ commands });
+ emptyMenu.title.label = 'Empty Menu';
+ emptyMenu.title.mnemonic = 0;
+
  let bar = new MenuBar();
  bar.addMenu(menu1);
  bar.addMenu(menu2);
  bar.addMenu(menu3);
+ bar.addMenu(emptyMenu);
  bar.id = 'menuBar';
 
  let palette = new CommandPalette({ commands });

packages/widgets/src/menubar.ts

@@ -405,6 +405,9 @@ export class MenuBar extends Widget {
  for (let i = 0, n = menus.length; i < n; ++i) {
  let title = menus[i].title;
  let active = i === activeIndex;
+ if (active && menus[i].items.length == 0) {
+ active = false;
+ }
  content[i] = renderer.renderItem({
  title,
  active,
@@ -607,7 +610,9 @@ export class MenuBar extends Widget {
  let { left, bottom } = (itemNode as HTMLElement).getBoundingClientRect();
 
  // Open the new menu at the computed location.
- newMenu.open(left, bottom, this._forceItemsPosition);
+ if (newMenu.items.length > 0) {
+ newMenu.open(left, bottom, this._forceItemsPosition);
+ }
  }
 
  /**

packages/widgets/tests/src/menubar.spec.ts

@@ -288,6 +288,16 @@ describe('@lumino/widgets', () => {
  expect(menu.isAttached).to.equal(false);
  bar.dispose();
  });
+
+ it('should be a no-op if the active menu is empty', () => {
+ let bar = new MenuBar();
+ let menu = new Menu({ commands });
+ bar.addMenu(menu);
+ bar.activeMenu = menu;
+ bar.openActiveMenu();
+ expect(menu.isAttached).to.equal(false);
+ bar.dispose();
+ });
  });
 
  describe('#addMenu()', () => {