Re: [PATCH v3 0/5] MR944: win32u: Make desktop resize logic asynchronous.

[Rémi Bernon (＠rbernon)]

On Thu Sep 29 09:17:32 2022 +0000, Zhiyi Zhang wrote:
> This might break clipping. Note that in X11DRV_resize_desktop(),
> ungrab_clipping_window() is called. In ungrab_clipping_window(),
> XUngrabPointer() is called when clipping_cursor is FALSE. Also notice
> that in grab_clipping_window() clipping is rejected in the desktop
> process. So clipping_cursor in the desktop process will always be FALSE
> and clipping will not be released as before. You need to keep the
> clipping logic the same as the old one.

Hmm, I think that's the same logic as how it is currently done:

`X11DRV_resize_desktop` is already sending a message to the desktop window if it's not called from the desktop thread, so its actual logic is only executed from the desktop thread:

https://gitlab.winehq.org/wine/wine/-/blob/master/dlls/winex11.drv/desktop.c...

```c
    if (NtUserGetWindowThread( hwnd, NULL ) != GetCurrentThreadId())
    {
        send_message( hwnd, WM_X11DRV_RESIZE_DESKTOP, 0, 0 );
    }
    else
    {
        /* ... */
        ungrab_clipping_window();
    }
```

From that thread, `ungrab_clipping_window` indeed skips the `XUngrabPointer`, but sends a `WM_X11DRV_CLIP_CURSOR_NOTIFY` message to the desktop window (so the thread itself):

https://gitlab.winehq.org/wine/wine/-/blob/master/dlls/winex11.drv/mouse.c#L...

```c
void ungrab_clipping_window(void)
{
    /* ... */
    if (clipping_cursor) XUngrabPointer( display, CurrentTime );
    clipping_cursor = FALSE;
    send_notify_message( NtUserGetDesktopWindow(), WM_X11DRV_CLIP_CURSOR_NOTIFY, 0, 0 );
}
```

Which is later use to reset some desktop clip_hwnd variable, and forwarded to the previously clipping window:

https://gitlab.winehq.org/wine/wine/-/blob/master/dlls/winex11.drv/mouse.c#L...

```c
    if (hwnd == NtUserGetDesktopWindow())  /* change the clip window stored in the desktop process */
    {
        static HWND clip_hwnd;
        HWND prev = clip_hwnd;
        clip_hwnd = new_clip_hwnd;
        if (prev) send_notify_message( prev, WM_X11DRV_CLIP_CURSOR_NOTIFY, (WPARAM)prev, 0 );
    }
```

This then translates, in the currently clipping thread, to the cursor being ungrabbed and the clipping window being destroyed:

https://gitlab.winehq.org/wine/wine/-/blob/master/dlls/winex11.drv/mouse.c#L...

```c
    else if (hwnd == data->clip_hwnd)  /* this is a notification that clipping has been reset */
    {
        disable_xinput2();
        NtUserDestroyWindow( hwnd );
    }
```

**Then however**, I think you're right that the changes can break clipping, but I think it's because of https://gitlab.winehq.org/wine/wine/-/merge_requests/944/diffs?commit_id=1cf... instead:

Moving that part to `X11DRV_resize_desktop` makes it likely never match the condition, because the desktop is unlikely to be the foreground process. Instead I think it can simply send the `WM_X11DRV_CLIP_CURSOR_REQUEST` to the foreground window without even checking the thread id / pid.

```c
    /* forward clip_fullscreen_window request to the foreground window */
    if ((foreground = NtUserGetForegroundWindow()) &&
        (tid = NtUserGetWindowThread( foreground, &pid )) && pid == GetCurrentProcessId())
    {
        if (tid == GetCurrentThreadId()) clip_fullscreen_window( foreground, TRUE );
        else send_notify_message( foreground, WM_X11DRV_CLIP_CURSOR_REQUEST, TRUE, TRUE );
    }
```

That should still asynchronously restore clipping from the foreground process if fullscreen clipping is enabled, and always after the reset logic described above.