WPF TextBox not accepting Input when in ElementHost in Window Forms

Question

We are developing a UI Control in WPF to be consumed within an existing Windows Forms / MFC application engine (Rhino 3D).

The application engine exposes the ability

Answer 1

Check out my own question about this very same thing. in the end though, all you need is something like this:

Window window1 = new Window();
ElementHost.EnableModelessKeyboardInterop(window1);
window1.Show();

Why is my WPF textbox "kinda" readonly?

Answer 2

It is not necessary to create derived TextBox. The code for IOTextBox can be used in a UserControl hosting textboxes. I have successfully tested it with WPF control used for custom options page used in VS2010 package.

Answer 3

I have a similar issue with a wxWidgets parent window and embedded WPF TextBox controls. I found that although attaching ChildHwndSourceHook does solve the problem of not receiving keyboard input, I ended up with occasional duplicate space characters. It seems the WM_KEYDOWN message handles the space characters reliably, but a duplicate WM_CHAR message is also received for some of the spaces. To solve this I added the following clause to the body of the ChildHwndSourceHook function, which simply ignores the WM_CHAR space character:

        const UInt32 WM_CHAR = 0x0102;

        if (msg == WM_CHAR)
        {
            // avoid duplicated spaces when parent window is a native window
            if (wParam.ToInt32() == 32)
                handled = true;
        }

Answer 4

I finally figured it out after 2 days of head scatching...

The MFC Dialog window was taking the WM_CHAR messages and preventing the control from handling the input. So in order to prevent this, I hook the HwndSource and whenever I receive the WM_GETDLGCODE message I respond back with the types of input to accept, and then mark the event as handled.

I created my own TextBox in order to prevent having to fix every textbox (see Below):

    /// <summary>
    /// Interop Enabled TextBox : This TextBox will properly handle WM_GETDLGCODE Messages allowing Key Input
    /// </summary>
    class IOTextBox : TextBox
    {
        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;

        public IOTextBox() : base()
        {
            Loaded += delegate
                          {
                              HwndSource s = HwndSource.FromVisual(this) as HwndSource;
                              if (s != null)
                                  s.AddHook(new HwndSourceHook(ChildHwndSourceHook));
                          };
        }

        IntPtr ChildHwndSourceHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            if (msg == WM_GETDLGCODE)
            {
                handled = true;
                return new IntPtr(DLGC_WANTCHARS | DLGC_WANTARROWS | DLGC_HASSETSEL);
            }
            return IntPtr.Zero;
        }
    }