Example of registering a custom menu node.

`MenuModelRegistry#registerMenuNode`

Signed-off-by: Akos Kitta <kittaakos@typefox.io>

examples/api-samples/package.json

@@ -11,6 +11,10 @@
     {
       "frontend": "lib/browser/api-samples-frontend-module"
     },
+    {
+      "frontend": "lib/browser/menu/sample-browser-menu-module",
+      "frontendElectron": "lib/electron-browser/menu/sample-electron-menu-module"
+    },
     {
       "electronMain": "lib/electron-main/update/sample-updater-main-module",
       "frontendElectron": "lib/electron-browser/updater/sample-updater-frontend-module"

examples/api-samples/src/browser/menu/sample-browser-menu-module.ts

@@ -0,0 +1,97 @@
+/********************************************************************************
+ * Copyright (C) 2020 TypeFox and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the Eclipse
+ * Public License v. 2.0 are satisfied: GNU General Public License, version 2
+ * with the GNU Classpath Exception which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ ********************************************************************************/
+
+import { injectable, ContainerModule } from 'inversify';
+import { Menu as MenuWidget } from '@phosphor/widgets';
+import { Disposable } from '@theia/core/lib/common/disposable';
+import { MenuNode, CompositeMenuNode } from '@theia/core/lib/common/menu';
+import { BrowserMainMenuFactory, MenuCommandRegistry, DynamicMenuWidget } from '@theia/core/lib/browser/menu/browser-menu-plugin';
+import { PlaceholderMenuNode } from './sample-menu-contribution';
+
+export default new ContainerModule((bind, unbind, isBound, rebind) => {
+    rebind(BrowserMainMenuFactory).to(SampleBrowserMainMenuFactory).inSingletonScope();
+});
+
+@injectable()
+class SampleBrowserMainMenuFactory extends BrowserMainMenuFactory {
+
+    protected handleDefault(menuCommandRegistry: MenuCommandRegistry, menuNode: MenuNode): void {
+        if (menuNode instanceof PlaceholderMenuNode && menuCommandRegistry instanceof SampleMenuCommandRegistry) {
+            menuCommandRegistry.registerPlaceholderMenu(menuNode);
+        }
+    }
+
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    protected createMenuCommandRegistry(menu: CompositeMenuNode, args: any[] = []): MenuCommandRegistry {
+        const menuCommandRegistry = new SampleMenuCommandRegistry(this.services);
+        this.registerMenu(menuCommandRegistry, menu, args);
+        return menuCommandRegistry;
+    }
+
+    createMenuWidget(menu: CompositeMenuNode, options: MenuWidget.IOptions & { commands: MenuCommandRegistry }): DynamicMenuWidget {
+        return new SampleDynamicMenuWidget(menu, options, this.services);
+    }
+
+}
+
+class SampleMenuCommandRegistry extends MenuCommandRegistry {
+
+    protected placeholders = new Map<string, PlaceholderMenuNode>();
+
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    registerPlaceholderMenu(menu: PlaceholderMenuNode): void {
+        const { id } = menu;
+        if (this.placeholders.has(id)) {
+            return;
+        }
+        this.placeholders.set(id, menu);
+    }
+
+    snapshot(): this {
+        super.snapshot();
+        for (const menu of this.placeholders.values()) {
+            this.toDispose.push(this.registerPlaceholder(menu));
+        }
+        return this;
+    }
+
+    protected registerPlaceholder(menu: PlaceholderMenuNode): Disposable {
+        const { id } = menu;
+        const unregisterCommand = this.addCommand(id, {
+            execute: () => { /* NOOP */ },
+            label: menu.label,
+            icon: menu.icon,
+            isEnabled: () => false,
+            isVisible: () => true
+        });
+        return Disposable.create(() => unregisterCommand.dispose());
+    }
+
+}
+
+class SampleDynamicMenuWidget extends DynamicMenuWidget {
+
+    protected handleDefault(menuNode: MenuNode): MenuWidget.IItemOptions[] {
+        if (menuNode instanceof PlaceholderMenuNode) {
+            return [{
+                command: menuNode.id,
+                type: 'command'
+            }];
+        }
+        return [];
+    }
+
+}

examples/api-samples/src/browser/menu/sample-menu-contribution.ts

@@ -14,7 +14,7 @@
  * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
  ********************************************************************************/
 
-import { Command, CommandContribution, CommandRegistry, MAIN_MENU_BAR, MenuContribution, MenuModelRegistry } from '@theia/core/lib/common';
+import { Command, CommandContribution, CommandRegistry, MAIN_MENU_BAR, MenuContribution, MenuModelRegistry, MenuNode, SubMenuOptions } from '@theia/core/lib/common';
 import { injectable, interfaces } from 'inversify';
 
 const SampleCommand: Command = {
@@ -59,16 +59,36 @@ export class SampleMenuContribution implements MenuContribution {
             order: '2'
         });
         const subSubMenuPath = [...subMenuPath, 'sample-sub-menu'];
-        menus.registerSubmenu(subSubMenuPath, 'Sample sub menu', { order: '1' });
+        menus.registerSubmenu(subSubMenuPath, 'Sample sub menu', { order: '2' });
         menus.registerMenuAction(subSubMenuPath, {
             commandId: SampleCommand.id,
-            order: '0'
+            order: '1'
         });
         menus.registerMenuAction(subSubMenuPath, {
             commandId: SampleCommand2.id,
-            order: '2'
+            order: '3'
         });
+        const placeholder = new PlaceholderMenuNode([...subSubMenuPath, 'placeholder'].join('-'), 'Placeholder', { order: '0' });
+        menus.registerMenuNode(subSubMenuPath, placeholder);
     }
+
+}
+
+/**
+ * Special menu node that is not backed by any commands and is always disabled.
+ */
+export class PlaceholderMenuNode implements MenuNode {
+
+    constructor(readonly id: string, public readonly label: string, protected options?: SubMenuOptions) { }
+
+    get icon(): string | undefined {
+        return this.options?.iconClass;
+    }
+
+    get sortString(): string {
+        return this.options?.order || this.label;
+    }
+
 }
 
 export const bindSampleMenu = (bind: interfaces.Bind) => {

examples/api-samples/src/electron-browser/menu/sample-electron-menu-module.ts

@@ -0,0 +1,41 @@
+/********************************************************************************
+ * Copyright (C) 2020 TypeFox and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the Eclipse
+ * Public License v. 2.0 are satisfied: GNU General Public License, version 2
+ * with the GNU Classpath Exception which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ ********************************************************************************/
+
+import { injectable, ContainerModule } from 'inversify';
+import { CompositeMenuNode } from '@theia/core/lib/common/menu';
+import { ElectronMainMenuFactory, ElectronMenuOptions } from '@theia/core/lib/electron-browser/menu/electron-main-menu-factory';
+import { PlaceholderMenuNode } from '../../browser/menu/sample-menu-contribution';
+
+export default new ContainerModule((bind, unbind, isBound, rebind) => {
+    rebind(ElectronMainMenuFactory).to(SampleElectronMainMenuFactory).inSingletonScope();
+});
+
+@injectable()
+class SampleElectronMainMenuFactory extends ElectronMainMenuFactory {
+
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    protected handleDefault(menuNode: CompositeMenuNode, args: any[] = [], options?: ElectronMenuOptions): Electron.MenuItemConstructorOptions[] {
+        if (menuNode instanceof PlaceholderMenuNode) {
+            return [{
+                label: menuNode.label,
+                enabled: false,
+                visible: true
+            }];
+        }
+        return [];
+    }
+
+}