QT4 applications not receiving clicks

[louis at museresearch.com]

Hi,
  I'm looking at a WINE issue in which some QT-based software isn't getting
mouse clicks.  The program in question is a VST plug-in.  The plug-in, in
our host, creates its UI in a child window.  Now, in QT, HWNDs are created
several layers deep-- seemingly one HWND per widget (QWidget), and then a
few others like "QEventDispatcher".  I think in doing this, I may have
uncovered a bug in which grandchild HWNDs do not receive mouse-down events.
 
  To summarize before I dive into the details:  On these mouse-down events,
WINE attempts to bring the HWND to the front, but fails because the HWND in
question is not a top-level window or a top-level window's child and
subsequently eats the message.
  Now for the gory details.  Let's start at process_mouse_messages in
user32/message.c.  If the event in question is a button-down event, WINE
tries to activate the window it's for.  In the switch statement near the
bottom of the function, there is a case MA_ACTIVATE.  This calls
FOCUS_MouseActivate which in turn
calls set_foreground_window (both in user32/focus.c).  Jump to the
wineserver's set_foreground_window function (in server/queue.c).  There is
a line which reads:

if (is_top_level_window( req->handle ) && . . . )

  What this is_top_level_window function says (in server/window.c) is to
return true only if the HWND is_desktop_window or a child of the desktop
window.  is_desktop_window says to return true if there is no parent
(because "only desktop windows have no parent").  So, if the HWND has no
parent or is the parent of a window with no parent, WINE deems the window
top level and the HWND receives the click.  If this test fails,
set_foreground_window returns an error and causes process_mouse_messages to
eat the click instead of passing it on.
  So, I have a couple questions about WINE operation.  My first question is
whether the click really should be passed on even if WINE can't bring the
HWND to the front in this case.  My second question is whether the
top-level window test works as expected-- my instinct was that the
top-level window is just a window without a parent and that the check might
not need to involve the desktop.  

Thanks,
Louis Gorenfeld
Muse Research