Path: utzoo!news-server.csri.toronto.edu!rutgers!dimacs.rutgers.edu!seismo!uunet!olivea!oliveb!amiga!boing!dale
From: dale@boing.UUCP (Dale Luck)
Newsgroups: comp.windows.x
Subject: Re:  PC X servers / backing store
Message-ID: <951@boing.UUCP>
Date: 3 Mar 91 01:17:23 GMT
References: <9103020232.AA05738@lightning.McRCIM.McGill.EDU>
Reply-To: dale@boing.UUCP (Dale Luck)
Organization: Boing, Milpitas, Ca.
Lines: 32

In article <9103020232.AA05738@lightning.McRCIM.McGill.EDU> mouse@lightning.mcrcim.mcgill.EDU writes:
>> The client software I am using is GRAFIT running on an HP 9000/825.
>
>> A problem encountered with both products is that if a graphics window
>> is overlaid ( e.g. by a menu ), the overlaid portion is not restored.
>> The suppliers of Grafit informed me that the X server implementation
>> probably did not support backing store  - a requirement for their
>> package ( or for the HP Starbase/X implementation? ).
>
>Then their package is buggy.

This is absolutely untrue. Backing store is a feature just like colors,
visuals, shape extensions, pex and everything else. There is nothing
wrong with a package requiring properly working backstore for that
package to work. The graphics that are being generated maybe entirely
to complex to redraw efficiently if an expose event occurs. I can think
of just about any ray tracing program that would have that problem.
Also most raster paintprograms are not really in the mood to have to retrace
all the users steps to recreate a particular image every time a menu pops
up on the drawable and the server goes oops.
Saying that the clients should do it's own backing store if the xserver
can't do it is like saying the client should map colors to dither patterns
if it sees a b/w color terminal, or automatically scale a drawing down
if the terminal's resolution is not large enough to present a satisfactory
Sure these are nice things to have but sometimes the resulting product
in such a degraded state on a X server that just does not have the right
capabilities is just a waste of programmer effort.


-- 
Dale Luck     GfxBase/Boing, Inc.
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