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Date: 1 Jun 90 09:56:23 GMT
From: convex!uunet.uu.net!vyncke%esat%kulesat%kulcs%ub4b%mcsun
Organization: Katholieke Universiteit Leuven,ESAT - dep. Elect. Engineering, Belgium
Subject: again : avoiding event loops
Message-Id: <2998.26663bc7@esat.kuleuven.ac.be>
Sender: convex!expo.lcs.mit.edu!xpert-request
To: xpert@expo.lcs.mit.edu

I'm writing an application where the graphical interface is not the main
part of the program. Since I want my windows to be updated after expose
events, I need a kind of asynchrounous behaviour.
I first build the program on a VAX station 3100 and there I had a
routine called XSelectAsyncInput(...) . This worked fine. But two
months ago I switched to a Sun Sparc with X11R4. There I tried to catch
the events in a background process. This however was not failsafe.
Now I implemented the method of John Bruner :

> My approach is to get the file descriptor for the X server (with
> ConnectionNumber(display)) and catch SIGIO.

This works fine but there is still one problem : If I catch an interrupt
when I'm in a X-call, my programm crashes. I worked around this by
postponing the interrupt handling while I'm doing X-calls. This is however
elaborate, and I'm wondering if there is not an other way to prevent the
Xserver from receiving two concurrent X-calls
Please send any reply by Email

-- Frank Vyncke . Department of Robot Vision, KU Leuven, Belgium
                  vyncke@esat.kuleuven.ac.be