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From: kit@EXPO.LCS.MIT.EDU (Chris D. Peterson)
Newsgroups: comp.windows.x
Subject: Re: Contents of windows
Message-ID: <8904241530.AA02631@expo.lcs.mit.edu>
Date: 24 Apr 89 15:30:20 GMT
References: <890422145257.00001135181@grouch.JPL.NASA.GOV>
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> But from my reading it appears that redisplay is the responsibility of 
> the programmer.

Yep.

> Let me get this straight.  If, for instance, I am writing
> a painting program, then either I have to keep a journal of all the user's
> paint commands, and replay them whenever I am redisplayed, or I have to
> save the bitmap for the window each time the window is modified, and
> restore from that if I am obscured?

Those are two ways of doing it, personally I would like to see you keep a
list of those things that make visable changes to the window, and then
redraw this list.  This will be the most memory efficient method of 
doing it.  Performace is another matter entirely.

> Suppose I have backing store supported
> and enabled.  Does X automatically restore the contents of the window in
> this case?

Maybe.  You should still be able to refresh the contents of your window since
you can never count on backing store being avaliable.  That is why it is a hint
the server can choose to ignore your request for backing store at any time.
Remeber that backing store is a convience, DON'T RELY ON BACKING STORE TO
BE AVALIABLE.

                                               Chris D. Peterson
                                               MIT X Consortium