Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!uvm-gen!chaffee
From: chaffee@uvm-gen.UUCP (Alex D. Chaffee,,,6581273)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Slightly more elaborate offscreen bitmap prob.
Message-ID: <1240@uvm-gen.UUCP>
Date: 25 Jul 89 02:55:33 GMT
References: <14324@swan.ulowell.edu>
Sender: nobody@uvm-gen.UUCP
Organization: EMBA Computer Facility, Univ. of Vermont, Burlington.
Lines: 26

From article <14324@swan.ulowell.edu>, by jkeegan@hawk.ulowell.edu (Jeff Keegan):
>   I'm writing a program that will have as part of it a "time line". For
> various reasons I have decided that I want to save it as a very long (wide)
> offscreen bitmap (7200 pixels), and when an update event comes along I
> read my scrollbar and calculate which part of the offscreen bitmap I want to
> copy to my screen.
> 
>   This SEEMS to work fine at first. I have (for the sake of debugging) drawn
> offscreen to my offscreen bitmap multiples of 25 up to 7200. Scrolling shows
> that the bitmap is fine up to around 600 pixels, and then becomes garbage.
                                       ^^^ probably 512?

If I remember right, Inside Mac (I, p.149) is wrong; the default ClipRgn is
set to the screen.  Try putting a ClipRect(&meterRect) in your creation code.
For good measure, also do RectRgn(...->visRgn, &meterRect).

Disclaimer: I may be wrong; all my offscreen maps have been puny.


			"Gee, Batman... is there anything you don't know?"

				"Yes, Robin.  Several things, in fact."
____________________________
Alex Chaffee
chaffee@emily.uvm.edu
____________________________