What's this?

Basically, I'm trying to build a dockable window using wxWidgets. At the moment I'm able to create windows but docking doesn't work yet. I already managed to have reg->hwnd_main as parent window (a bit tricky since it's no intended use of wxWidgets), but DockWindowAdd() gives the error message shown above. What went wrong? Here's a piece of code: Code:

Have you checked from wxwidgets documentation what you get from dlg->GetHandle() is a win32 window handle, not some internal handle from wxwidgets? The cast would seem to indicate the types are maybe not compatible in the first place and thus what is returned from dlg->GetHandle() isn't a valid Windows handle at all. DockWindowAdd((HWND)dlg->GetHandle(), "Hello World", 40400, true); A similar problem appears to be in the call : wxWindow *window = w->CreateWindowFromHWND(0, (WXHWND) g_hwndParent); You are casting a win32 window handle to what would maybe appear to be wxwidget's own window handle type.

GetHandle() returns a WXHWND which can be safely cast to your platform's window handle - HWND in Windows, GtkWindow* in Linux and so on. Maybe Reaper expects a HWND of a CDialog but wxWidgets uses a CWnd even for dialogs...