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From: apratt@atari.UUCP (Allan Pratt)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: Line A Considered Harmful (was Re: Closing AES boxes interfering with VDI drawing)
Message-ID: <2790@atari.UUCP>
Date: 27 Dec 90 23:18:52 GMT
References: <1990Dec19.034923.291@convex.com> <13510006@hplsla.HP.COM>
Organization: Atari Corp., Sunnyvale CA
Lines: 25

To clear up any confusion, when we talk about line-A we're talking
about graphics.  Line-F was a hack in the ST ROMs to save space, and
that's not what we're talking about here.

The blanket statement "Line A doesn't work on the TT" is actually a
little misleading.  The actual statement from Atari is more like this:
"Line A is maintained for compatibility with existing programs only,
and should not be used in new programs, and will not be maintained for
new features of the ST/TT line of computers."

This "new stuff not supported though line-A" is already in evidence in
the TT: you can't use line-A in 256-color mode, because you only have
access to four color bits.  New programs should not use line-A.

If you use VDI correctly, it is no slower than line-A.  This is obvious
when you realize that line-A is just a back door to the same routines
that the VDI uses!  There is a little overhead from VDI, but it's small
compared to the time to do anything remotely complicated, like drawing
a line.  Two things can make VDI seem slow: using clipping when it's
not necessary, and using some versions of GDOS.  In the latter case,
it's GDOS's fault, not VDI's, and newer GDOSes are faster.

============================================
Opinions expressed above do not necessarily	-- Allan Pratt, Atari Corp.
reflect those of Atari Corp. or anyone else.	  ...ames!atari!apratt