How to specify window size for a MAUI application in case of Windows platform?

Question

I'm working on a .NET MAUI app which I'd like to deploy on Windows beside Android.

My goal is to specify a minimal window width and a minimal window height only

affecting Windows as a platform.

My attempt to set the aforementioned properties inside App.xamls.cs:

public App()   
{
        InitializeComponent();

        Microsoft.Maui.Handlers.WindowHandler.WindowMapper[nameof(IWindow)] = (handler, view) =>
        {
#if WINDOWS
                    var nativeWindow = handler.NativeView;
                    nativeWindow.Activate();
                    IntPtr windowHandle = PInvoke.User32.GetActiveWindow();

                    PInvoke.User32.SetWindowPos(windowHandle, 
                    PInvoke.User32.SpecialWindowHandles.HWND_TOP,
                                        0, 0, width, height,  // width and height are ints
                                        PInvoke.User32.SetWindowPosFlags.SWP_NOMOVE);

#endif
        };
}

Unfortunately, it does not work as I'm receiveing the following error:

Error CS0117 'WindowHandler' does not contain a definition for 'WindowMapper

Any help is greatly appreciated!

no answer accepted, but take a look https://stackoverflow.com/questions/72399551/maui-net-set-window-size — kenny, Dec 25 '22 at 14:41

score 3 · Accepted Answer · answered Dec 26 '22 at 07:27

If you want to specify a minimal window width and a minimal window height only, you can make the project's target framwork as .net 7.0. And then override the App's CreateWindow method:

    protected override Window CreateWindow(IActivationState activationState)
      {
            var window = base.CreateWindow(activationState);
            window.MinimumHeight = 600; // set minimal window height
            window.MinimumWidth = 800; // set minimal window width
            return window;
      }

And you can also use the handler to resize the window. In the page.cs:

protected override void OnHandlerChanged()
      {
            base.OnHandlerChanged();
#if WINDOWS
            Microsoft.UI.Xaml.Window window = (Microsoft.UI.Xaml.Window)App.Current.Windows.First<Window>().Handler.PlatformView;
            IntPtr windowHandle = WinRT.Interop.WindowNative.GetWindowHandle(window);
            Microsoft.UI.WindowId windowId = Microsoft.UI.Win32Interop.GetWindowIdFromWindow(windowHandle);
            Microsoft.UI.Windowing.AppWindow appWindow = Microsoft.UI.Windowing.AppWindow.GetFromWindowId(windowId);
            appWindow.Resize(new Windows.Graphics.SizeInt32(800,600));
#endif
      }

I retargeted my project to .net 7 and tried the first code but I'm getting 'Window' does not contain a definition for 'Width'... I looked at what is available and Width and Height do not exist for base.CreateWindow — Zonus, Jan 30 '23 at 16:29

score 1 · Answer 2 · answered Jun 14 '23 at 01:47

You could take advantage of .NET MAUI support for partial classes to avoid the usage of the #if WINDOWS preprocessor directive.

Here is an idea with a partial method that is only implemented in Window
Note: App.cs Windows file should have the same namespace as the platform independent App.cs

In App\App.xaml.cs

namespace App;

public partial class App : Application
{
    public App()
    {
        InitializeComponent();
    }

    protected override Window CreateWindow(IActivationState activationState)
    {
        var window = new Window(new AppShell());
        UpdateWindow(window);

        return window;
    }

    partial void UpdateWindow(Window window);
}

In App\Platforms\Windows\App.cs

namespace App
{
    public partial class App : Application
    {
        partial void UpdateWindow(Window window)
        {
            window.MinimumWidth = 800;
            window.MinimumHeight = 600;

            window.Width = 1024;
            window.Height = 800;
        }
    }
}

How to specify window size for a MAUI application in case of Windows platform?

2 Answers2