Implement saved window positioning per target

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

@@ -10,9 +10,11 @@
 
 // $FlowFixMe[unclear-type] We have no Flow types for the Electron API.
 const {BrowserWindow, Menu, app, shell, ipcMain} = require('electron') as any;
+const SettingsStore = require('./SettingsStore.js');
 const path = require('path');
 const util = require('util');
 
+const appSettings = new SettingsStore();
 const windowMetadata = new WeakMap<
   typeof BrowserWindow,
   $ReadOnly<{
@@ -53,10 +55,11 @@ function handleLaunchArgs(argv: string[]) {
       }, 1000);
     }
   } else {
-    // Create the browser window.
     frontendWindow = new BrowserWindow({
-      width: 1200,
-      height: 600,
+      ...(getSavedWindowPosition(windowKey) ?? {
+        width: 1200,
+        height: 600,
+      }),
       webPreferences: {
         partition: 'persist:react-native-devtools',
         preload: require.resolve('./preload.js'),
@@ -66,6 +69,8 @@ function handleLaunchArgs(argv: string[]) {
     });
     // Auto-hide the Windows/Linux menu bar
     frontendWindow.setMenuBarVisibility(false);
+    // Observe and update saved window position
+    setupWindowResizeListeners(frontendWindow, windowKey);
   }
 
   // Open links in the default browser instead of in new Electron windows.
@@ -119,6 +124,37 @@ function configureAppMenu() {
   Menu.setApplicationMenu(menu);
 }
 
+function getSavedWindowPosition(
+  windowKey: string,
+): ?{width: number, height: number, x?: number, y?: number} {
+  return appSettings.get('windowArrangements', {})[windowKey];
+}
+
+function saveWindowPosition(
+  windowKey: string,
+  position: {x: number, y: number, width: number, height: number},
+) {
+  const windowArrangements = appSettings.get('windowArrangements', {});
+  windowArrangements[windowKey] = position;
+  appSettings.set('windowArrangements', windowArrangements);
+}
+
+function setupWindowResizeListeners(
+  browserWindow: typeof BrowserWindow,
+  windowKey: string,
+) {
+  const savePosition = () => {
+    if (!browserWindow.isDestroyed()) {
+      const [x, y] = browserWindow.getPosition();
+      const [width, height] = browserWindow.getSize();
+      saveWindowPosition(windowKey, {x, y, width, height});
+    }
+  };
+  browserWindow.on('moved', savePosition);
+  browserWindow.on('resized', savePosition);
+  browserWindow.on('closed', savePosition);
+}
+
 app.whenReady().then(() => {
   handleLaunchArgs(process.argv.slice(app.isPackaged ? 1 : 2));
   configureAppMenu();

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

@@ -0,0 +1,130 @@
+/**
+ * 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.
+ *
+ * @flow
+ * @format
+ * @oncall react_native
+ */
+
+// $FlowFixMe[unclear-type] We have no Flow types for the Electron API.
+const {app} = require('electron') as any;
+const fs = require('fs');
+const path = require('path');
+
+type Options = $ReadOnly<{
+  name?: string,
+  defaults?: Object,
+}>;
+
+/**
+ * A data persistence layer for storing application settings, modelled after
+ * [`electron-store`](https://www.npmjs.com/package/electron-store).
+ *
+ * Values are saved in a `config.json` file in `app.getPath('userData')`.
+ *
+ * Compatibility:
+ * - Maintains API and file format compatibility with `electron-store@8.2.0`.
+ * - Supports the Electron main process only.
+ */
+class SettingsStore {
+  #defaultValues: Object = {};
+  path: string;
+
+  constructor(options: Options = {}) {
+    options = {
+      name: 'config',
+      ...options,
+    };
+    this.#defaultValues = {
+      ...this.#defaultValues,
+      ...options.defaults,
+    };
+    this.path = path.resolve(
+      app.getPath('userData'),
+      `${options.name ?? 'config'}.json`,
+    );
+  }
+
+  get(key: string, defaultValue?: any): any {
+    const store = this.store;
+    return store[key] !== undefined ? store[key] : defaultValue;
+  }
+
+  set(key: string, value: any): void {
+    const {store} = this;
+    if (typeof key === 'object') {
+      const object = key;
+      for (const [k, v] of Object.entries(object)) {
+        store[k] = v;
+      }
+    } else {
+      store[key] = value;
+    }
+    this.store = store;
+  }
+
+  has(key: string): boolean {
+    return key in this.store;
+  }
+
+  reset(...keys: Array<string>): void {
+    for (const key of keys) {
+      if (this.#defaultValues[key] != null) {
+        this.set(key, this.#defaultValues[key]);
+      }
+    }
+  }
+
+  delete(key: string): void {
+    const {store} = this;
+    delete store[key];
+    this.store = store;
+  }
+
+  clear(): void {
+    this.store = {};
+    for (const key of Object.keys(this.#defaultValues)) {
+      this.reset(key);
+    }
+  }
+
+  get store(): {[string]: mixed} {
+    try {
+      const data = fs.readFileSync(this.path, 'utf8');
+      const deserializedData = this._deserialize(data);
+      return {
+        ...((deserializedData: any): {[string]: mixed}),
+      };
+    } catch (error) {
+      if (error?.code === 'ENOENT') {
+        this._ensureDirectory();
+        return {};
+      }
+      throw error;
+    }
+  }
+
+  set store(value: mixed): void {
+    this._ensureDirectory();
+    this._write(value);
+  }
+
+  _deserialize = (value: string): mixed => JSON.parse(value);
+  _serialize = (value: mixed): string =>
+    JSON.stringify(value, undefined, '\t') ?? '';
+
+  _ensureDirectory(): void {
+    fs.mkdirSync(path.dirname(this.path), {recursive: true});
+  }
+
+  _write(value: mixed): void {
+    const data = this._serialize(value);
+
+    fs.writeFileSync(this.path, data, {mode: 0o666});
+  }
+}
+
+module.exports = SettingsStore;