[Vm-dev] bug in X11 focus event handling

Martin Kuball martinkuball at web.de
Tue Feb 24 20:36:54 UTC 2009


When I build a new VM some weeks ago I found the following bug in the focus 
event handling:

My environment is KDE 3.5 on linux x86.

When I switch from squeak to another application via alt-tab everything is 
fine. If I switch to another app by selecting one from the taskbar squeak 
receives a focus in event (which seems to me quite strange given the fact 
that I just transferred it to another app) with detail NotifyNonlinear. 
Now we call the method XSetInputFocus which triggers a new focus in event 
and we are stuck in an endless loop.
Actually with alt-tab, squeak receives a focus in event, too. But the call 
to XSetInputFocus does not trigger the loop.

Well, the looping stops if I alt-tab back to squeak. And I must do this, 
because with the loop running the app I switched to is behaving a bit 

Now I just inserted a break after the "case NotifyNonlinear:" target. This 
made the bug go away. But I don't know if this has some unwanted side 
effects. Couldn't find one, yet. But I would like to hear the opinion of 
someone more proficient in X than me.


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