31.43 Flutter Desktop Window Manager

20230805

The window_manager package for Linux, MacOS, and Windows, allows various desktop options to be managed for the flutter app. For example, the default window title is the app name as specified in the pubspec.yaml. The default (startup) window size is specified in the operating system specific files in the linux (??), windows (??), and macos (??) directories.

Technically, to set things up for the windowManager, the so-called method call handler has to be set up before the binary messenger has been initialized. Thus when we call setMethodCallHandler() below, before the WidgetsFlutterBinding has been initialized we need to ensure the WidgetsFlutterBinding is initialized. We do this in the sample code below as the content for main.dart.

To support all platforms we need to check if we are running in a web browser (which could be on any of the platforms) and not undertake any window manager activity if so.

import 'dart:io' show Platform;

import 'package:flutter/foundation.dart' show kIsWeb;

import 'package:window_manager/window_manager.dart';

void main() async {

  // Identify if Desktop or Mobile app.

  bool isDesktop = Platform.isLinux || Platform.isMacOS || Platform.isWindows;

  // Tune the window manager before runApp to avoid a lag in the UI. For desktop
  // (non-web) versions re-size to mimic mobile (as the main target platform).

  if (isDesktop && !kIsWeb) {

    WidgetsFlutterBinding.ensureInitialized();

    await windowManager.ensureInitialized();

    WindowOptions windowOptions = WindowOptions(
      alwaysOnTop: true,
      // The size is overriden in the first instance by, for example,
      // linux/my_application.cc. The size here takes effect when Retarting the
      // app.
      size: Size(450, 700),
      title: 'MyApp - test out some functionality of an app.',
      alwaysOnTop: true,
      backgroundColor: Colors.transparent,
      center: true,
      skipTaskbar: false,
      titleBarStyle: TitleBarStyle.hidden,
    );

    windowManager.waitUntilReadyToShow(windowOptions, () async {
      await windowManager.show();
      await windowManager.focus();
      await windowManager.setAlwaysOnTop(false);
    });
  }

  runApp(const MyExperienceApp());
}

I was also finding that the app window on my linux desktop was being displayed underneath my other windows, which was annoying. So a little trick in the above is to set alwaysOnTop and then to turn that off after getting focus. That seems to achieve what I wanted. Keeping isAlwaysOnTop active is not useful as the window is then always on top of every other window.

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