Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!snorkelwacker!bloom-beacon!MAPS.CS.CMU.EDU!Matthew.Diamond
From: Matthew.Diamond@MAPS.CS.CMU.EDU
Newsgroups: comp.windows.x
Subject: Forcing application to process events
Message-ID: <9002011609.AA05640@ATHENA.MIT.EDU>
Date: 1 Feb 90 16:08:03 GMT
Sender: root@athena.mit.edu (Wizard A. Root)
Organization: The Internet
Lines: 39


> Re: Beginner question: forcing update of labelWidget display 
>                    ...
> The problem is that the XtSetValues() call clears the Label Widget's window,
> and tells that X Server to generate an exposure event for that window.  The
> window will not actually get painted until your code drops back into
> XtAppMainLoop() and resumes processing events.
> 
> Can you work around this?  Yes, but its pretty ugly, and could cause your
> application to hang.  I would suggest that you would be better served by
> looking to a more event-driven model for you application.  
> 

Speaking for myself, I would be interested in hearing what the work-around
is.  I am writing a user-interface which is supposed to be
interchangeable with an existing user-interface.  The idea is that we take
applications that use the old, textual interface, link them with my
libraries instead, and then they have a mouse-driven, graphical interface,
with no change to the application's code.

The problem is that these applications were not written to the event-driven
model.  I can process events whenever my code is called (most user I/O is
handled by me, since I am replacing keyboard procedures with code that accepts
input from the mouse too).  But there are times when my code is not being
called and the application's display freezes for a while.

I attempted to use XtAddTimeOut() to add an event-loop that would be run
periodically, but of course I found that timeouts are handled in the
event-loop, they are not true interrupts.

Our group may find that we can live with this problem, or I may try using
Unix interrupts to periodically interrupt the application, forcing it to
process certain events (i.e. Expose) before continuing.

But if there is another way, I'd like to hear it.

Matthew Diamond
MAPS Project, Carnegie-Mellon University
matt@maps.cs.cmu.edu