[Bug 43009] TIM message manager window covered by an unresponsive window

https://bugs.winehq.org/show_bug.cgi?id=43009

--- Comment #22 from Dmitry Timoshkov  ---
In short: the unresponsive window in question is a layered window with
an assigned color key. I guess that the window surface bitmap is used
as a layer mask, and is supposed to be "transparent" both visually and
for mouse clicks. winex11.drv calculates the mask shape and instructs
the WM about it, so WM sends the button click event to an underlying
window. But user32 side is not aware about that masked shape, and
currently there is no way to check for it from WINPOS_WindowFromPoint.