[Myrsloik]

Originally Posted by stax76

I'm not sure what's the focus of this thread because my question is about vs host application development.

There is a weird exception happening here:

    case WM_DESTROY:
        DiscardGraphicsResources();
        SafeRelease(&g_D2D_Factory);

        g_vsapi->freeNode(g_vsnode);
        vsscript_freeScript(g_vsscript);
        vsscript_finalize();

        PostQuitMessage(0);
        return 0;

Exception thrown at 0x00007FFAFC5B448D (vapoursynth.cp37-win_amd64.pyd) in VapourSynth Direct2D Rendering.exe: 0xC0000005: Access violation writing location 0x0000000000000000.

Weird thing is it crashes only inside WM_DESTROY and not when this code is executed before WM_DESTROY !

How can this issue be debugged?

It's with a trivial script (BlankClip only)?

Are there any restrictions on what you're allowed to do when handling a WM_DESTROY message? If not then I'd simply see what the call stack is in a debugger. Maybe there's a hint in there.