Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!sun-barr!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!bmc.uu.se!heap
From: heap@bmc.uu.se
Newsgroups: comp.windows.x.motif
Subject: Re: Problem using the WorkingDialog
Message-ID: <1990Oct10.091924.3527@bmc.uu.se>
Date: 10 Oct 90 08:19:23 GMT
References: <1990Oct1.111721.3499@bmc.uu.se> <901004143230.998@alphalpha> <1990Oct5.134155.3518@bmc.uu.se>
Distribution: inet
Organization: Biomedical Center, University of Uppsala, Sweden
Lines: 67

I received another solution of my problem, it doesn't use Xt-calls but
is more compact and reliable than "my own" solution.
It was (most kindly) mailed to me by cuweiss.US2.oramail@us.oracle.com.
She didn't think that the original author would have anything against it being
posted.
So here it comes :

===============================================================================
Received: 06-01-90 21:07                                 Sent: 06-02-90 00:03
From:     kit@expo.lcs.mit.edu <DVLSEQ:kit@expo.lcs.mit.edu>
To:       cuweiss.US2.oramail@us.oracle.com 
Subject:  Re: Code for working around timing problems in X 
Cc:       kit@expo.lcs.mit.edu kit@expo.lcs.mit.edu 
Reply-To: DVLSEQ:kit@expo.lcs.mit.edu
In-Reply-To:  Your message of Fri, 25 May 90 15:51:20 -0700.


Anything like this is a kludge at best, and if you are not very careful you can
get into trouble.  Bad things can happen, like you application will hang waiting
for an event that will never come.  Keeping that in mind, here is one method of
coding that will block until an expose event occures in the widget specified. 
No remember that an obscured widget will never receive an expose event, so it is
important that you KNOW that the widget in question will be visable.  Not just
mapped, but it can also no be obscured by any other widget.

This code also only returns one expose event.  Expose events may come in groups,
since they contain a rectangle that is the region that has been exposed. 
Consider the case of when an "L" shaped region has been uncovered.  There are
two possibilities, you can either return two expose events One for this part of
the L "|" and one for this part "_".  Or you could return a rectangle containing
the entire box that contines the L (this also gives you some region that does
not need to be repainted).  Because you only get one expose event your widget
may not repaint the entire widget, but just part of it.  

I know this all sounds like pretty ominous, but I just want you to understand
that you are breaking the rules here a bit, so you had better know what you are
doing.  I have used this code in one of my applicaions, and it works just fine.

Without further adoo...

  Widget widget;
  XEvent event;

  while ( !XCheckTypedWindowEvent(XtDisplay(widget), XtWindow(widget), 
				  Expose, &event) );
  XtDispatchEvent( &event );
  XFlush(XtDisplay(widget));


This is by no means the only way to do this, using the Xlib functions that let
you peek into the event queue, you can see that there are many ways to
accomplish the same task.  I hope this helps you solve your problem.


						Chris D. Peterson     
						MIT X Consortium 

Net:	 kit@expo.lcs.mit.edu
Phone:   (617) 253 - 9608	
Address: MIT - Room NE43-213
-- 
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Per Bengtsson, Dept. of Scientific Computing, Univ. of Uppsala, Sweden

Internet:       heap@tdb.uu.se
Sunet/Decnet:   tdb::heap
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