Path: utzoo!attcan!uunet!husc6!uwvax!umn-d-ub!gandreas
From: gandreas@umn-d-ub.D.UMN.EDU (Glenn Andreas)
Newsgroups: comp.sys.mac.programmer
Subject: Re: flicker-free drawing
Message-ID: <424@umn-d-ub.D.UMN.EDU>
Date: 26 Jul 88 14:40:53 GMT
References: <5727@orstcs.CS.ORST.EDU> <12549@agate.BERKELEY.EDU>
Reply-To: gandreas@ub.d.umn.edu.UUCP (Glenn Andreas)
Organization: University of Minnesota, Duluth
Lines: 33

In article <12549@agate.BERKELEY.EDU> lippin@math.berkeley.edu writes:
>Recently jasmerb@orstcs.CS.ORST.EDU (Bryce Jasmer) said:
>>I am writing a DA that needs to have flicker free drawing...
[ stuff deleted ]
>A better way to avoid flicker is to skip the erasing that causes it,
>like this:

>TextMode(srcCopy);
>DrawString(whatever);
[more deleted ]

>The only hitch is that srcCopy for text doesn't exist for the most
>ancient hardware/system software combinations.

>					--Tom Lippincott
>					..ucbvax!bosco!lippin

There are more problems than that.  When you (or at least when I) use
srcCopy for text, it will often erase more than just to the end of the last
letter.  It seems that it erases up to the next byte/word boundary (?), and
so if you have your end of the text near say a line you've drawn, it may
erase a path through the line as well.  This may or may not be a problem,
depending on the situation (I wanted to draw text over a detailed, filled
map and by using srcCopy I got ugly results.  I ended up with EraseRect, but
I didn't need it flicker free).  You could always draw off screen and use
CopyBits :-).


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= "When I was young, all I wanted was to be  | - gandreas@ub.d.umn.edu -    =
=  ruler of the universe.  Now that isn't    |   Glenn Andreas              =
=  enough" - Alex P. Keaton                  |                              =
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