Avalonia window (textboxes) embedded in Autodesk Inventor not accepting input

[Basnederveen]

See my post on StackOverflow: https://stackoverflow.com/questions/77543411/avalonia-window-textboxes-embedded-in-autodesk-inventor-not-accepting-input

Creating an Autodesk Inventor plugin. Have a small avalonia app which I want to host in the dockable window in Inventor.

https://stackoverflow.com/questions/835878/wpf-textbox-not-accepting-input-when-in-elementhost-in-window-forms

Similar problem to above. There is something I'm missing about how to forward the keystrokes to the avalonia component.

The key events are fired in the MainWindow code-behind, but they are not forwarded to the AvaloniaWpfHost control.

[MrJul]

I'm not sure why you're creating a WPF window as an intermediate if you only want Avalonia controls? Thatintermediate layer doesn't seem necessary. As far as I can tell, Inventor seems to only need a standard Win32 HWND.

You can create an Avalonia Window and get its HWND through Window.TryGetPlatformHandle().Handle, that you should be able to pass directly to Inventor's DockableWindow.AddChild().

Then, to handle the WM_GETDLGCODE message, you have two choices:

• You're willing to use latest 11.1 nightly builds: use Win32SpecificOptions.AddWndProcHookCallback()
• You're on stable 11.0.x: use the standard Win32 SetWindowLongPtr function with GWLP_WNDPROC to change the window procedure.

[Basnederveen]

Hi MrJul,

Thank you so much for the reply. I've just created the WPF window because I hoped it would fix the problem. I can indeed add the avalonia window to the DockableWindow by its handle.

Since I'm on 11.0.x I tried the SetWindowLongPtr function. But this crashes Inventor..

I'm calling the function straight after adding the child to the dockable window.

[MrJul]

That's probably a bad usage of SetWindowLongPtr, like wrong argument types defined for your WndProc callback, corrupting the stack. Also make sure to call the old window proc for messages others than WM_GETDLGCODE, or your window won't work correctly.

If you're not comfortable with P/Invoke, I'd suggest to try the nightly builds since you'll get the nice AddWndProcHookCallback instead of having to replace the WndProc manually. This way you'll be able to validate whether handling the message solves the problem in Inventor. Then you can figure the P/Invoke stuff to port that to 11.0.

[Basnederveen]

That's probably likely. This is all quite new for me so I thought you meant I should just call the SetWindowLongPtr in my initialization code.

This crashes. I see now you wrote GWLP_WNDPROC not GWL_WNDPROC. I thought at first you meant to use the function as it is used in the SetParent function of https://github.com/AvaloniaUI/Avalonia/blob/master/src/Windows/Avalonia.Win32/WindowImpl.cs#L656

With the WindowLongParam GWL_WNDPROC (-4).

private void InitializePropertyEditor()
{
    propertyWindow = TryGetDockableWindow();
    services = Builder.BuildLauncherServices();
    builder = Builder.BuildAvaloniaAppWithServices(services).SetupWithoutStarting();

    MainWindow = new EmbeddedWindow()
    {
        DataContext = services.GetService<MainViewModel>()
    };

    MainWindow.Show();

    var hwnd = MainWindow.TryGetPlatformHandle().Handle;
    propertyWindow.AddChild(hwnd);

    //SetWindowLongPtr(hwnd, -4, propertyWindow.HWND);
}

I'm at the moment trying the nightly build. But the latest one I see in the nuget source is 11.0.999. It contains the AddWndProcHookCallback, so I guess this is the one you mean.

[MrJul]

Note: 11.0.999 is a "wrong" release (well for your needs, it already works), almost 2 months old. You have to check the Pre-release checkbox when adding a NuGet package and use the latest one, whose version should be something like 11.1.999-cibuild00XXXXX-beta.

[Basnederveen]

Got it, thanks!

[Basnederveen]

It works!!!! Thanks again!! Had a feeling it would be a one-line fix..

private void InitializePropertyEditor()
{
    propertyWindow = TryGetDockableWindow();
    var services = Builder.BuildLauncherServices();
    var builder = Builder.BuildAvaloniaAppWithServices(services).SetupWithoutStarting();

    MainWindow = new EmbeddedWindow()
    {
        DataContext = services.GetService<MainViewModel>()
    };

    MainWindow.Show();

    var hwnd = MainWindow.TryGetPlatformHandle().Handle;
    propertyWindow.AddChild(hwnd);
    
    Win32SpecificOptions.AddWndProcHookCallback(TopLevel.GetTopLevel(MainWindow), WndProc);
}

private DockableWindow TryGetDockableWindow()
{
    var internalName = "BasAutomation.PropertyEditor";
    var windowName = "Properties";

    DockableWindow propertyWindow;
    try
    {
        propertyWindow = app.UserInterfaceManager.DockableWindows[internalName];
    }
    catch (Exception ex)
    {
        propertyWindow = app.UserInterfaceManager.DockableWindows.Add(AddInClientId, internalName, windowName);
    }

    return propertyWindow;
}

private const UInt32 DLGC_WANTARROWS = 0x0001;
private const UInt32 DLGC_WANTTAB = 0x0002;
private const UInt32 DLGC_WANTALLKEYS = 0x0004;
private const UInt32 DLGC_HASSETSEL = 0x0008;
private const UInt32 DLGC_WANTCHARS = 0x0080;
private const UInt32 WM_GETDLGCODE = 0x0087;

private static IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
    if (msg == WM_GETDLGCODE)
    {
        handled = true;
        return new IntPtr(DLGC_WANTCHARS | DLGC_WANTARROWS | DLGC_HASSETSEL | DLGC_WANTTAB | DLGC_WANTALLKEYS);
    }

    return IntPtr.Zero;
}

}

[MrJul]

You're welcome. Happy you could get it working!