Crashing menus, event handling broken?

Jukka Heinonen jhei at
Thu Nov 22 05:11:57 CST 2001

While playing Civilization 2, I noticed that Wine crashes
if I click menu bar twice while the game is thinking.

The reason for this is that raw hardware messages get processed 
before menu event loop starts. Raw event processing turns raw events 
into cooked events and because menu event loop has not started yet,
game window is not capturing events and thus clicks on menu bar
are turned into nonclient messages. These cooked messages are
put back into message queue. When menu event loop starts,
it receives the second nonclient button press event and
passes it to DispatchMessage. Default window procedure creates
a new menu event loop and since the nonclient message was still
in the event queue (it would have been removed if DispatchMessage
had returned), we get a nice stack overflow.

The real problem is not in menu event loop but in the fact that
Wine event handling forgets that we can't determine whether
a mouse event is nonclient event or not unless we have already
called window procedure for all previous mouse events. This is
because one of those calls might have for example captured
mouse input after which we no longer report nonclient events.

Since event handling is quite complicated and this flaw looks
more like a design error than coding bug, I would like to get
some discussion about what should be done to fix this problem.

Jukka Heinonen <>

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