Hi Torsten, Esteban, I try to use OS-Windows (not OSWindow :) ) with latest spur VM and UnifiedFFI. As far as I can see, you (Torsten) already ported some parts to UnifiedFFI - great, thanks! I now try to open a new window with WinWindow>>createWindowEx .... as I took this example originally from NBOpenGL, it seems I have to define a Window Class first, with WinWndClassEx This seems to work in the old NBOpenGL/NBWin32 code but not with OS-Windows WinWndClassEx first, NBOpenGL uses NativeBoostWin32 getVMModuleHandle for an HModule instance there is a similar call in OS-Windows, WinProcess getVMModuleHandle (I needed to define a missing type, HMODULE, but that works). What does not work is this part: | hInst wndClass | hInst := WinProcess getVMModuleHandle. wndClass := WinWndClassEx new. wndClass hInstance: hInst. FF complains about pointerAt: byteOffset put: value "Store a pointer object at the given byte address" value isExternalAddress here value is not a handle, but a small integer, and it does not define isExternalAddress I tried to put the handle instead of the handles value, but this does not work either. Any Idea what is missing here, I need a way to store the HMODULE handle in the structure of the WinWNdClassEx Thanks in advance.