Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!bloom-beacon!EXPO.LCS.MIT.EDU!jim
From: jim@EXPO.LCS.MIT.EDU (Jim Fulton)
Newsgroups: comp.windows.x
Subject: Re: XGetWindowAttributes: documentation/reality clash
Message-ID: <8904242147.AA11700@expo.lcs.mit.edu>
Date: 24 Apr 89 21:47:09 GMT
References: <8904240439.AA12537@Larry.McRCIM.McGill.EDU>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: X Consortium, MIT Laboratory for Computer Science
Lines: 16


The Xlib document is a little misleading.  The routines in section 4.1 (titled
"Obtaining Window Information", pages 62-67 in Scheifler, Gettys, and Newman)
still require you to have an error handler (which you always need in critical
applications, especially window managers).  Since these routines normally only
return an error when there is an invalid window or drawable identifier (well,
not quite: BadAlloc could crop up but your client would probably be hosed
shortly), your handler simply needs to not crap out in order for your calling
program to get a Status of 0 or a Bool of False. 


> What *is* the proper way to tell whether a window still exists?

Select for SubstructureNotify on the root and keep track of DestroyNotify
events.  Or else, just use one of the routines mentioned above once you've
written your error handler!  :-)