Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Quickdraw efficiency question
Message-ID: <7943@hoptoad.uucp>
Date: 11 Jul 89 04:45:18 GMT
References: <1681@neoucom.UUCP>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 34

In article <1681@neoucom.UUCP> sam@neoucom.UUCP (Scott A. Mason) writes:
>Question:
>
>Which would be faster when drawing multiple characters to a window?
>
>  1) repeated calls to DrawChar
>  2) building a string and calling DrawString.

DrawString.  Smaller trap overhead, fewer internal calls to the Font
Manager, some built-in heuristics to speed things up.  DrawText is
even better,m supposedly.

>While I'm at it, how does Mackermit achieve such speedy screen drawing??

I don't know for sure, but a lot of terminal emulators use a
reprehensible technique sometimes called "bit-blasting".  This involves
bypassing both Quickdraw and the Font manager and copying the bits of
characters directly into the screen.  It *is* fast, but there are
serious portability problems.  Drawing straight into the screen bitmap
is a major no-no these days, and of course when fonts change in System
7.0, there is a good chance many of these programs will break.  You
also have to figure your own clipping and visible regions usage, no
easy task to do correctly.  The early generation of bit-blasters were
mostly incompatible with MultiFinder, and the new generation will
probably be incopmpatible with some add-on screens and with System
7.0.  Caveat implementor, in Kari Dubbelman's clever phrase....
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com
Postal: 424 Tehama, SF CA 94103; Phone: (415) 495-2934

"When errors are found in old research, the relevant theories are
 re-examined.  When facts contradict theory, theory gets dumped.  Is
 that why the NLP people are unwilling to research their facts?"
	-- Jerry Hollombe on sci.psychology