CallWndProc16From32.cs

// Call a 16-bit window procedure
public IntPtr CallWndProc16from32(uint pfnProc, IntPtr hWnd, uint message, IntPtr wParam, IntPtr lParam, bool dlgProc)
{
    // Put it into structure
    var msg32 = new Win32.MSG()
    {
        hWnd = hWnd,
        message = message,
        wParam = wParam,
        lParam = lParam,
    };

    // Get message semantics
    ushort message16;
    var sem = TryGetMessageSemantics32(hWnd, message, out message16);

    // Convert the easy stuff
    var msg16 = new Win16.MSG()
    {
        hWnd = HWND.Map.To16(hWnd),
        message = message16,
    };


    // Bypass?
    if (sem!=null && sem.ShouldBypass(_machine, ref msg32))
    {
        // Bypassed messages to a dialog box procedure can just return FALSE
        if (dlgProc)
            return IntPtr.Zero;

        // Unsupported message - sneak it through
        var bpm = AllocBypassMessage(message, wParam, lParam);
        var ret = _machine.CallWndProc16(pfnProc, HWND.Map.To16(hWnd), Win16.WM_WIN3MU_BYPASS16, 0, bpm.id);
        return FreeBypassMessage(bpm);
    }

    // Postable?
    var postable = sem as MessageSemantics.Postable;
    if (postable != null)
    {
        // Convert it
        postable.To16(_machine, ref msg32, ref msg16);

        // Call it
        var x = _machine.CallWndProc16(pfnProc, msg16.hWnd, msg16.message, msg16.wParam, msg16.lParam);

        // Return it
        return BitUtils.DWordToIntPtr(x);
    }

    // Callable?
    var callable = sem as MessageSemantics.Callable;
    if (callable != null)
    {
        // Call it
        var retv = callable.Call16from32(_machine, false, dlgProc, ref msg32, ref msg16, () =>
        {
            return _machine.CallWndProc16(pfnProc, msg16.hWnd, msg16.message, msg16.wParam, msg16.lParam);
        });

        if (dlgProc)
            retv = (IntPtr)(x.ToInt32().Loword());
        return retv;
    }

    // Unsupported
    throw new VirtualException($"Unknown windows message {MessageNames.NameOfMessage(message)} for window class '{User.GetClassName(hWnd32)}'");
}