Keys are not coming through to the plugin window.
The problem was that the window style was set to WS_CHILD. I don't know why, but this was causing the issue. Once I removed this, the problem went away.
Obiwan, I got this code from WpfControlWrapper in the project Jacobi.Vst.Samples.CorePlugin. I'd suggest that this might be wrong and causing the same issue if other people use this code. I hadn't changed the code, but you can see it here:
public void Open(IntPtr hWnd)
_instance = new T();
_instance.Width = _width;
_instance.Height = _height;
HwndSourceParameters hwndParams = new HwndSourceParameters("VST.NET Wpf Editor");
hwndParams.ParentWindow = hWnd;
hwndParams.Height = _height;
hwndParams.Width = _width;
hwndParams.WindowStyle = 0x10000000|0x40000000; // WS_VISIBLE|WS_CHILD
_hwndSource = new HwndSource(hwndParams);
_hwndSource.RootVisual = _instance;
I actually removed the Windows Style WS_CHILD completely and now there is no issue! Yes! Another hurdle jumped over.