Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!gatech!bbn!diamond.bbn.com!mlandau
From: mlandau@bbn.com (Matt Landau)
Newsgroups: comp.windows.x
Subject: Re: Contents of windows
Summary: Backing store is a *hint* -- don't propagate false information
Message-ID: <12792@diamond.BBN.COM>
Date: 23 Apr 89 21:46:39 GMT
References: <890422145257.00001135181@grouch.JPL.NASA.GOV> <1438@rpi.edu>
Reply-To: mlandau@bbn.com (Matt Landau)
Organization: BBN Systems and Technologies Corporation, Cambridge, MA
Lines: 18

In comp.windows.x (<1438@rpi.edu>), mcintyrd@cs.rpi.edu (David McIntyre) writes:
>Yes, that takes care of the problem.  Backing store keeps the current
>contents of the window, and will re-expose damaged portions.

Please remember that asking an X server for backing store on a window is 
merely a *hint* that you'd like to minimize redraw requests for that window.

An X server is under no obligation to provide backing store, and is free to
ignore requests for backing store on windows.  Moreover, a server that does
choose to provide backing store may stop providing it at any time during a
session if it decides it's running out of resources.

A correctly written X client that wishes to be portable to different servers
MUST assume that it may be called on to regenerate any or all of its display
at any time, subject to the rules laid out in the protocol spec for X11.  
--
 Matt Landau			Oblivion gallops closer,
 mlandau@bbn.com		    favoring the spur, sparing the rein.