Re: w32-pass-lwindow-to-system does not work as expected

[Lennart Borgman <lennart.borgman.073@student.lu.se>]

Eli Zaretskii wrote:

>Watch out for the caveats of using low-level keyboard interfaces: what
>the hook gets is the scan code of the key and various bit masks for ...
>  
>
I took a look at the code in w32fns.c again. It looks to me everything 
is in place to handle the <lwindow> key, except for that low level 
keyboard hook. Everything the keyboard hook has to to is to avoid 
sending anything to the system when <lwindow> is typed and Emacs wants it.

So if it works at all it should perhaps be very little trouble:

1) add the hook at thread startup
2) the hook prevents sending any VK_LWIN events further if Emacs wants 
them, otherwise not.
3) remove the hook at thread termination.

Below is code for doing this. I have assumed that NILP and 
Vw32_pass_lwindow_to_system are actually available in the input thread. 
(Or did I read that wrong?)

But as I said I am not a guru on this, I just read the docs and the 
code. Am I misunderstanding something here?

*** Adding the low level keyboard hook to the main thread at thread startup:
hLowKBhook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, NULL, dwMainThreadId);

*** Removing the low level keyboard hook at the main thread tear down:
UnhookWindowsHookEx(hLowKBhook);

*** The hook procedure. This runs in the context of the thread.

LRESULT LowLevelKeyboardProc(INT nCode, WPARAM wParam, LPARAM lParam)
{
    BOOL fHandled = FALSE;

    if (nCode == HC_ACTION)
    {
        KBDLLHOOKSTRUCT *pkbdllhook = (KBDLLHOOKSTRUCT *)lParam;

        switch (wParam)
        {
            case WM_KEYUP:
            case WM_KEYDOWN:  // This was not in the MS example, why??
            case WM_SYSKEYUP:
            case WM_SYSKEYDOWN:
                switch (pkbdllhook->vkCode)
                {
                    case VK_LWIN:
                    {
                        // the user pressed the <lwindow> key
                	if (!NILP (Vw32_pass_lwindow_to_system))
                        fHandled = TRUE;
                        break;
                    }
                }
        }
    }

    return (fHandled ? TRUE : CallNextHookEx(hhook, nCode, wParam, lParam));
}