Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!bloom-beacon!SUN.COM!dshr
From: dshr@SUN.COM (David Rosenthal)
Newsgroups: comp.windows.x
Subject: Re: Contents of windows
Message-ID: <8904251538.AA00185@devnull.sun.com>
Date: 25 Apr 89 13:30:45 GMT
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 25

Dave "mr question" McIntyre writes:

> >Suppose I have backing store supported and enabled.  Does X automatically
> >restore the contents of the window in this case?
> 
> Yes, that takes care of the problem.  Backing store keeps the current
> contents of the window, and will re-expose damaged portions.
> 
This is seriously misleading.  Backing-store is a HINT,  not a command.
The server may stop maintaining backing-store at any time,  for any
reason.

The use of backing store makes no difference to program structure.  The
client still has to be capable of restoring the contents of a window.
All the backing store does is to reduce the frequency with which the
code that restores the window will be executed.

There is no escape.  It is a fundamental requirement of X that the client
respond to Expose events by re-painting the exposed area.  If you don't
like this requirement,  go find yourself some other window system.  This
requirement is one of the reasons why X is simple and portable to a wide
range of displays,  so the other window system you find is not likely
to be as widespread or successful as X.

	David.