Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!sun!quintus!pds
From: pds@quintus.UUCP (Luis Jenkins)
Newsgroups: comp.windows.x
Subject: Re: PC X servers / backing store
Message-ID: <1494@quintus.UUCP>
Date: 5 Mar 91 21:31:48 GMT
References: <9103041710.AA12610@asl.dl.nec.com>
Reply-To: pds@quintus.UUCP (Peter Schachte)
Organization: Quintus Computer Systems, Inc.
Lines: 24

In article <9103041710.AA12610@asl.dl.nec.com> ekberg@asl.dl.nec.COM (Tom Ekberg) writes:
>	Backing-stores indicates when the server supports backing stores for
>	this screen, although it may be storage limited in the number of
>	windows it can support at once.  If save-unders is True, the server can
>	support the save-under mode in CreateWindow and ChangeWindowAttributes,
>	although again it may be storage limited.

This doesn't make a lot of sense.  If I know I can't count on the server
to provide backing store, then I'll have to keep a pixmap the size of my
window to back it myself (asuming that this is the sort of application
where it just doesn't make sense to redraw the window from first
principles).  If I allocate that pixmap, then that much server memory is
occupied, so if the server would have been unable to maintain backing
store for me, it certainly will be unable to give me my pixmap (or else
it won't allow some other process to have the resources it needs).  If
it guaranteed me backing store, it would only have to allocate resources
for the part of my window that is occluded.

Besides, if I have to back up my window myself, I have to do 2 drawing
operations for every one I would do if I had backing store.
-- 
-Peter Schachte
pds@quintus.com
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