Bring RNDT shell to front when paused on breakpoint (#51748)

Summary:
Pull Request resolved: #51748

Changelog: [Internal]

Implements the first RNDT shell-specific feature based on facebook/react-native-devtools-frontend#168 - namely, the ability for RNDT to foreground itself when certain events occur. This is most noticeable when pausing on a breakpoint.

Reviewed By: huntie, vzaidman

Differential Revision: D75795689

fbshipit-source-id: a073bf8ea96ba70d835007f5af6069d49a693d81

Author: motiz88

packages/debugger-shell/src/electron/MainInstanceEntryPoint.js

@@ -9,7 +9,7 @@
  */
 
 // $FlowFixMe[unclear-type] We have no Flow types for the Electron API.
-const {BrowserWindow, app, shell} = require('electron') as any;
+const {BrowserWindow, app, shell, ipcMain} = require('electron') as any;
 const util = require('util');
 
 const windowMetadata = new WeakMap<
@@ -66,6 +66,7 @@ function handleLaunchArgs(argv: string[]) {
     height: 600,
     webPreferences: {
       partition: 'persist:react-native-devtools',
+      preload: require.resolve('./preload.js'),
     },
   });
 
@@ -102,3 +103,16 @@ app.whenReady().then(() => {
 app.on('window-all-closed', function () {
   app.quit();
 });
+
+ipcMain.on('bringToFront', (event, title) => {
+  const webContents = event.sender;
+  const win = BrowserWindow.fromWebContents(webContents);
+  if (win) {
+    win.focus();
+  }
+  if (process.platform === 'darwin') {
+    app.focus({
+      steal: true,
+    });
+  }
+});

packages/debugger-shell/src/electron/preload.js

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+const {contextBridge, ipcRenderer} = require('electron');
+
+contextBridge.executeInMainWorld({
+  func: ipcDevTools => {
+    let didDecorateInspectorFrontendHostInstance = false;
+    // reactNativeDecorateInspectorFrontendHostInstance was introduced in
+    // https://github.com/facebook/react-native-devtools-frontend/pull/168
+    globalThis.reactNativeDecorateInspectorFrontendHostInstance =
+      InspectorFrontendHostInstance => {
+        didDecorateInspectorFrontendHostInstance = true;
+        InspectorFrontendHostInstance.bringToFront = () => {
+          ipcDevTools.bringToFront();
+        };
+      };
+
+    document.addEventListener('DOMContentLoaded', () => {
+      if (!didDecorateInspectorFrontendHostInstance) {
+        console.error(
+          'reactNativeDecorateInspectorFrontendHostInstance was not called at startup. ' +
+            'This version of the DevTools frontend may not be compatible with @react-native/debugger-shell.',
+        );
+      }
+    });
+  },
+  args: [
+    {
+      bringToFront() {
+        ipcRenderer.send('bringToFront');
+      },
+    },
+  ],
+});