Xref: utzoo comp.sys.mac:35128 comp.sys.mac.programmer:7749
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!mcvax!kth!draken!tut!santra!kampi.hut.fi!jmunkki
From: jmunkki@kampi.hut.fi (Juri Munkki)
Newsgroups: comp.sys.mac,comp.sys.mac.programmer
Subject: Re: Quickdraw efficiency question
Message-ID: <23899@santra.UUCP>
Date: 21 Jul 89 23:02:40 GMT
References: <1681@neoucom.UUCP> <2803@internal.Apple.COM>
Sender: news@santra.UUCP
Reply-To: jmunkki@kampi.hut.fi (Juri Munkki)
Organization: Helsinki University of Technology, Finland
Lines: 30

In article <2803@internal.Apple.COM> maxie@apple.com (Keith G. Nemitz) writes:
>Another method for drawing characters to the screen (and quite legal)
>is to predraw the the characterset into an offscreen buffer and use
>copybits to blast their images to screen.  This is what Red Ryder
>does.

Yuk. I have never (ever) heard anyone calling Red Ryder fast. To make this
method really effective would require you to keep your whole terminal screen
in an offscreen bitmap.

>It is very fast because in the long run DrawString and DrawChar both
>call copybits eventually. If your character set is a mono-spaced font
>you can use the byte itself as an index into the offscreen bitmap.

I think DrawString & DrawChar never call CopyBits. They might call something
similar, but I think they do something much smarter. It is faster to process
a font a single scanline at a time. I would guess that QD draws a single
scanline into offscreen RAM and then blasts it onto the screen. It can then
forget that line even exists in the font bitmap and move onto the next one.
This saves you some indexing/registers when compared to the approach where
you write a character and then forget about it when you move onto the next.

P.S.	I would appreciate it if people would append informative signatures.
	A lot of people at apple.com are actually not working for Apple and
	even might not have any experience in programming Macs.

_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
|     Juri Munkki jmunkki@hut.fi  jmunkki@fingate.bitnet        I Want   Ne   |
|     Helsinki University of Technology Computing Centre        My Own   XT   |
^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^