Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!uxc!tank!ra_robert@gsbacd.uchicago.edu
From: ra_robert@gsbacd.uchicago.edu
Newsgroups: comp.sys.mac.programmer
Subject: Re: Saving area under dialog boxes (Re: WingZ)
Message-ID: <2993@tank.uchicago.edu>
Date: 29 Apr 89 18:52:50 GMT
Sender: news@tank.uchicago.edu
Distribution: na
Organization: University of Chicago Graduate School of Business
Lines: 25

In article <29827@apple.Apple.COM>, keith@Apple.COM (Keith Rollin) writes...

> 
>Saving data from your own window into an offscreen buffer is not much of a 
>problem _right now_. It should even work in the forseeable future. However, I 
>would recommend against it in favor of doing it the other way around; keep 
>the master image in an offscreen buffer, and refresh from it exclusively.
[...]


What about in a paint type program?  I've been working on one, and when someone
"draws" on the screen I first draw it on the screen (e.g. on the simplest level
with calls such as LineTo)  and then blit it to my offscreen buffer (from which
I refresh my image) for permanent storage when the drawn object is done (i.e,
on MouseUp).  Wouldn't there be times when you need to CopyBits from screen
memory to your offscreen buffer?  I suppose one _could_ draw to your offscreen
bugger and CopyBits it on screen constantly, but that sounds fairly awful in
terms of speed, etc.


Robert
------
ra_robert@gsbacd.uchicago.edu
------
generic disclaimer: all my opinions are mine