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From: daveh@cbmvax.cbm.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: BlitzFonts query reply
Message-ID: <1867@cbmvax.cbmvax.cbm.UUCP>
Date: Wed, 13-May-87 16:55:09 EDT
Article-I.D.: cbmvax.1867
Posted: Wed May 13 16:55:09 1987
Date-Received: Sat, 16-May-87 05:49:27 EDT
References: <8705130700.AA24705@cory.Berkeley.EDU>
Organization: Commodore Technology, West Chester, PA
Lines: 49

in article <8705130700.AA24705@cory.Berkeley.EDU>, dillon@CORY.BERKELEY.EDU (Matt Dillon) says:
> 
>>> What is BlitzFonts?  You mentioned using it to make text scroll faster...
>>
>>That's exactly what it is ... a program that "hooks" itself into AmigaDOS
>>(the console.device ?) that speeds up the display of text output.  I dunno
> 
> 	Definately not the console device.  DME makes calls to the graphics
> library directly (Text()) and Blitzfonts speeds DME up 600%!  I'm just as
> interested in finding out what it does as you.  Anybody know?  It can't be
> too complicated. ..
> 
> 			-Matt

I haven't looked at BlitzFonts specifically, but I'd imagine that it doesn't
do anything to DOS.  By the way, console.device isn't part of DOS.  In fact,
anything that'll called a "device" is an EXEC managed device.  The "device"
name, as usual, is overused.  You speak of DOS objects like DF0:, RAM:,
PAR:, SER:, etc. as DOS devices.  Which they are, in DOS terminology.  But
as far as the Amiga OS goes, things like RAM: and PAR: are DOS interfaces
to EXEC supported devices.  Generally, DOS will have a process, called a
handler, that comunicates directly to a device.  Devices accept standard
and device specific commands, specified in the ROM Kernal Manual.  Handlers
can be given any of a set of about 30 or so commands, each of which is a
DOS interface into a particular EXEC device.  A handler can do the thing
specified by a handler command (called an action), or it can tell you the
particular action is not supported (like files or directories on the SER:
device).

What I'd expect BlitzFonts to be is the same thing that MicroSmith's 
FastFonts is: an alternate Text() function.  All library based functions
(except those in the DOS library, which is a weird library) are kept as
offsets into various run-time libraries.  The offsets are in the form
of jump commands that lead to the particular function required (note that
functions can move about, based on what was requested first from disk
loaded libraries).  An EXEC function, called SetFunction(), is provided
to re-vector any of the calls in a standard library.  So if I write a 
very fast version of Text(), then SetFunction() this version into the
graphics library, all programs that use the Text() routine will do their
text display faster.  I know that's what the FastFonts program does, and
I expect that's just what BlitzFonts does.  The shortcoming of BlitzFonts
seems to be that it trades generality for speed.  The program can display
Topaz8 characters at a fast rate; but it can't support arbitrary fonts as
can the normal Text() function (and the FastFonts function, from what
I've heard).
-- 
Dave Haynie     Commodore-Amiga    Usenet: {ihnp4|caip|rutgers}!cbmvax!daveh
"The A2000 Guy"                    BIX   : hazy
	"These are the days of miracle and wonder" -P. Simon