Is there a way to set the Window (frame) minimum height/width? (WinUI 3)

[jeromelaban]

from discord

The only thing I found online was this (microsoft/microsoft-ui-xaml#2945 (comment)) which seems very overcomplicated, and it only works on Windows.

[jeromelaban]

Indeed, at this time, the WinUI 3 APIs are very specific to windows. Fortunately, most of those APIs were available as part of WinRT and can be used for the other platforms (where Window sizing is applicable):

ApplicationView.GetForCurrentView().SetPreferredMinSize(new Size(640, 480));

[ArchLeaders]

Very well. Thank you for your time.

[ArchLeaders]

The solution in that discussion brings about two compiler errors for me.

1. 'ShellView' does not contain a definition for 'As' and no accessible extension method 'As' accepting a first argument of type 'ShellView' could be found (are you missing a using directive or an assembly reference?)

2. The name 'PInvoke' does not exist in the current context (this error is duplicated many times throughout) the snippet.

The only difference between my code and the snippet is that the derived type is Page not Window. But I cannot derive from Window without getting another compiler error: 'ShellView': cannot derive from sealed type 'Window'.

[jeromelaban]

You need to make that code conditional to windows, by using #if !HAS_UNO for instance,

[ArchLeaders]

Ah right, didn't know that was crucial to the code. My bad.
Using the #if WINDOWS statement leaves just one error when getting the HWND. Member 'Page.As<ShellView.IWindowNative>()' cannot be accessed with an instance reference; qualify it with a type name instead. (Same error when using !HAS_UNO as well)

[ArchLeaders]

Using the static type Page to satisfy the compiler results in the same memory read access error as before.

[EvarDion]

This code didn't work for me

ApplicationView.GetForCurrentView().SetPreferredMinSize()

But another option which works in WINUI3 under windows is to handle the AppWindow.Changed event that fires when the window changes check if the new size is bellow MinWidth or MinHeight and then resize it back to the MinHeight or MinWidth.

This isn't an elegant solution as it causes the window to flicker a bit but it does prevent the user from resizing the window smaller than is desired and I use it to set the startup size for my app.

        /// <summary>
        /// Sets the size of the Application Window when running in Windows.
        /// </summary>
        /// <param name="window"></param>o
        /// <param name="width"></param>
        /// <param name="height"></param>
        /// <returns></returns>
        public static bool Resize(Window window, int width, int height)
        {

            try
            {

#if NET7_0_WINDOWS10_0_18362
                // Use 'this' rather than 'window' as variable if this is about the current window.
                IntPtr hWnd = WinRT.Interop.WindowNative.GetWindowHandle(window);
                Microsoft.UI.WindowId windowId = Microsoft.UI.Win32Interop.GetWindowIdFromWindow(hWnd);
                AppWindow = Microsoft.UI.Windowing.AppWindow.GetFromWindowId(windowId);
                AppWindow.Resize(new Windows.Graphics.SizeInt32 { Width = width, Height = height });
                AppWindow.Changed += AppWindow_Changed;
#else
                _ = Log.Warn($"{nameof(WindowHelper)}.{nameof(Resize)}() is not currently supported on this platform.");

#endif

                return true;
            }
            catch (Exception ex)
            {
                _ = Log.Error(ex);
            }
            return false;
        }

        private static void AppWindow_Changed(Microsoft.UI.Windowing.AppWindow sender, Microsoft.UI.Windowing.AppWindowChangedEventArgs args)
        {
            try
            {
#if NET7_0_WINDOWS10_0_18362
                if (AppWindow == null)
                    return;

                if (AppWindow.Size.Height < MinHeight && AppWindow.Size.Width < MinWidth)
                    AppWindow.Resize(new Windows.Graphics.SizeInt32 { Width = MinWidth, Height = MinHeight });
                else if (AppWindow.Size.Height < MinHeight)
                    AppWindow.Resize(new Windows.Graphics.SizeInt32 { Width = AppWindow.Size.Width, Height = MinHeight });
                else if (AppWindow.Size.Width < MinWidth)
                    AppWindow.Resize(new Windows.Graphics.SizeInt32 { Width = MinWidth, Height = AppWindow.Size.Height });
#endif

            }
            catch (Exception ex)
            {
                _ = Log.Error(ex);
            }
        }

[elibroftw]

Easy as pie for WinUI 3 in 2026 if you know what you are doing. Just install WinUIEx

public MainWindow()
{
    InitializeComponent();
  var manager = WinUIEx.WindowManager.Get(this);
  manager.PersistenceId = "MainWindow";
  manager.MinWidth = 500;
  manager.MinHeight = 550;
}