Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!quintus!pds
From: pds@quintus.uucp (Peter Schachte)
Newsgroups: comp.windows.x
Subject: Re: changing menu widget behavior
Message-ID: <146@quintus.UUCP>
Date: 29 Jun 88 20:20:29 GMT
References: <11393@steinmetz.ge.com> <19880628120158.9.RWS@KILLINGTON.LCS.MIT.EDU>
Sender: news@quintus.UUCP
Reply-To: pds@quintus.UUCP (Peter Schachte)
Organization: Quintus Computer Systems, Inc.
Lines: 21

In article <19880628120158.9.RWS@KILLINGTON.LCS.MIT.EDU> RWS@ZERMATT.LCS.MIT.EDU (Robert Scheifler) writes:
>    I would like to be able to save and 
>    restore the random contents of my graphic window
>Save-under and backing-store are the right thing to use.

Unfortunately, there's a flaw with backing store:  you can't insist on
it.  So when you write your application, you have to allocate your own
bitmap to back up your window, and have to blt it to the window every
time it changes.  The server could implement backing store much more
efficiently, since IT knows when part of your window is going to be
obscured, and can copy out the contents first.  User programs can't do
that, so they have to keep their own backing bitmap up-to-date all the
time.

Am I missing something?  Is there a better way to maintain a window
that's too complex for display lists?  Is there a reason the server
can't do backing store as efficiently as I've indicated?

-Peter Schachte
pds@quintus.uucp
..!sun!quintus!pds