How do I get a WPF Window "from" an HwndSource I create directly?

Question

If I create an HwndSource directly, have I then also created a WPF Window that I can now access from code? If so, how can I access it?

Or do I now need to somehow "add" a WPF Window to that HwndSource? If so, how do I do this?

I have studied the HwndSource documentation thoroughly, and this part is not explained well at all. I understand that I can get the HwndSource from an existing WPF Window, but that does not help me. I need to intercept the creation of the Window, so I can force it to WS_CHILD style and set its parent directly; and the docs say you must create the HwndSource directly if you want to force its parent.

Edit: I've been studying every question I can find with HwndSource in it; it looks like you "add" the WPF object to the HwndSource object by setting the RootVisual property of the HwndSource object to the WPF object you want displayed; or maybe by calling the HwndSource AddSource method? Will examine those next. Hope this is useful to other questioners.

Answer 1

As I suspected, the solution is to add your WPF object to the HwndSource.RootVisual object. In the example below, NativeMethods is my class for PInvoke of Win32 APIs. Use SetLastError and GetLastError to check for Windows errors.

Note that in this case you must use a User Control or Page or the like; you can NOT set HwndSource.RootVisual to be an existing or "new" WPF Window, as WPF Windows already have a Parent, and it won't accept an object with a Parent.

    private void ShowPreview(IntPtr hWnd)
    {
        if (NativeMethods.IsWindow(hWnd))
        {
            // Get the rect of the desired parent.
            int error = 0;
            System.Drawing.Rectangle ParentRect = new System.Drawing.Rectangle();
            NativeMethods.SetLastErrorEx(0, 0);
            bool fSuccess = NativeMethods.GetClientRect(hWnd, ref ParentRect);
            error = System.Runtime.InteropServices.Marshal.GetLastWin32Error();

            // Create the HwndSource which will host our Preview user control
            HwndSourceParameters parameters = new HwndSourceParameters();
            parameters.WindowStyle = NativeMethods.WindowStyles.WS_CHILD | NativeMethods.WindowStyles.WS_VISIBLE;
            parameters.SetPosition(0, 0);
            parameters.SetSize(ParentRect.Width, ParentRect.Height);
            parameters.ParentWindow = hWnd;
            HwndSource src = new HwndSource(parameters);

            // Create the user control and attach it
            PreviewControl Preview = new PreviewControl();
            src.RootVisual = Preview;
            Preview.Visibility = Visibility.Visible;
        }
    }