Fixed confirmExit behaviour for Electron apps

dev-packages/application-manager/src/generator/frontend-generator.ts

@@ -125,44 +125,14 @@ process.env.LC_NUMERIC = 'C';
 const electron = require('electron');
 const { join, resolve } = require('path');
 const { fork } = require('child_process');
-const { app, shell, BrowserWindow, ipcMain, Menu } = electron;
+const { app, dialog, shell, BrowserWindow, ipcMain, Menu } = electron;
 
 const applicationName = \`${this.pck.props.frontend.config.applicationName}\`;
 
 const nativeKeymap = require('native-keymap');
 const Storage = require('electron-store');
 const electronStore = new Storage();
 
-let canPreventStop = true;
-const windows = [];
-
-app.on('before-quit', async event => {
-    if (canPreventStop) {
-        // Pause the stop.
-        event.preventDefault();
-        let preventStop = false;
-        // Ask all opened windows whether they want to prevent the \`close\` event or not.
-        for (const window of windows) {
-            if (!preventStop) {
-                window.webContents.send('prevent-stop-request');
-                const preventStopPerWindow = await new Promise((resolve) => {
-                    ipcMain.once('prevent-stop-response', (_, arg) => {
-                        if (!!arg && 'preventStop' in arg && typeof arg.preventStop === 'boolean') {
-                            resolve(arg.preventStop);
-                        }
-                    })
-                });
-                if (preventStopPerWindow) {
-                    preventStop = true;
-                }
-            }
-        }
-        if (!preventStop) {
-            canPreventStop = false;
-            app.quit();
-        }
-    }
-});
 app.on('ready', () => {
     const { screen } = electron;
 
@@ -243,13 +213,20 @@ app.on('ready', () => {
         newWindow.on('close', saveWindowState);
         newWindow.on('resize', saveWindowStateDelayed);
         newWindow.on('move', saveWindowStateDelayed);
-        newWindow.on('closed', () => {
-            const index = windows.indexOf(newWindow);
-            if (index !== -1) {
-                windows.splice(index, 1);
-            }
-            if (windows.length === 0) {
-                app.quit();
+
+        // Fired when a beforeunload handler tries to prevent the page unloading
+        newWindow.webContents.on('will-prevent-unload', event => {
+            const preventStop = 0 !== dialog.showMessageBox(newWindow, {
+                type: 'question',
+                buttons: ['Yes', 'No'],
+                title: 'Confirm',
+                message: 'Are you sure you want to quit?',
+                detail: 'Any unsaved changes will not be saved.'
+            });
+
+            if (!preventStop) {
+                // This ignores the beforeunload callback, allowing the page to unload
+                event.preventDefault();
             }
         });
 
@@ -267,7 +244,6 @@ app.on('ready', () => {
         if (!!theUrl) {
             newWindow.loadURL(theUrl);
         }
-        windows.push(newWindow);
         return newWindow;
     }
 

packages/core/package.json

@@ -62,9 +62,6 @@
       "frontend": "lib/browser/keyboard/browser-keyboard-module",
       "frontendElectron": "lib/electron-browser/keyboard/electron-keyboard-module",
       "backendElectron": "lib/electron-node/keyboard/electron-backend-keyboard-module"
-    },
-    {
-      "frontendElectron": "lib/electron-browser/shutdown-hook/electron-shutdown-hook-module"
     }
   ],
   "keywords": [

packages/core/src/browser/window/default-window-service.ts

@@ -36,9 +36,7 @@ export class DefaultWindowService implements WindowService, FrontendApplicationC
         this.frontendApplication = app;
         window.addEventListener('beforeunload', event => {
             if (!this.canUnload()) {
-                event.returnValue = '';
-                event.preventDefault();
-                return '';
+                return this.preventUnload(event);
             }
         });
     }
@@ -66,4 +64,14 @@ export class DefaultWindowService implements WindowService, FrontendApplicationC
         return confirmExit !== 'always';
     }
 
+    /**
+     * Ask the user to confirm if they want to unload the window. Prevent it if they do not.
+     * @param event The beforeunload event
+     */
+    protected preventUnload(event: BeforeUnloadEvent): string | void {
+        event.returnValue = '';
+        event.preventDefault();
+        return '';
+    }
+
 }

packages/core/src/electron-browser/window/electron-window-service.ts

@@ -17,20 +17,11 @@
 import { injectable } from 'inversify';
 import { ipcRenderer } from 'electron';
 import { NewWindowOptions } from '../../browser/window/window-service';
-import { FrontendApplication } from '../../browser/frontend-application';
 import { DefaultWindowService } from '../../browser/window/default-window-service';
 
 @injectable()
 export class ElectronWindowService extends DefaultWindowService {
 
-    onStart(app: FrontendApplication): void {
-        this.frontendApplication = app;
-        // We do not want to add a `beforeunload` listener to the `window`.
-        // Why? Because by the time we get into the unload handler, it is already too late. Our application has quit.
-        // _Emitted when the `window` is going to be closed. It's emitted before the `beforeunload` and `unload` event of the DOM._
-        // https://github.com/electron/electron/blob/master/docs/api/browser-window.md#event-close
-    }
-
     openNewWindow(url: string, { external }: NewWindowOptions = {}): undefined {
         if (external) {
             ipcRenderer.send('open-external', url);
@@ -40,4 +31,9 @@ export class ElectronWindowService extends DefaultWindowService {
         return undefined;
     }
 
+    protected preventUnload(event: BeforeUnloadEvent): string | void {
+        // The user will be shown a confirmation dialog by the will-prevent-unload handler in the Electron main script
+        event.returnValue = false;
+    }
+
 }