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From: ewhac@well.UUCP (Leo L. Schwab)
Newsgroups: comp.sys.amiga.tech
Subject: Re: WaitTOF in interlace mode
Message-ID: <6639@well.UUCP>
Date: 27 Jul 88 11:14:16 GMT
References: <4860@killer.DALLAS.TX.US>
Reply-To: ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab)
Organization: Loudmouth Software, Inc.
Lines: 35
Quote: "OO BABY YEAH!  ROCK AND ROLL!  I KNEAD YOU LIKE FRESH PIZZA DOUGH!"

In article <4860@killer.DALLAS.TX.US> ltf@killer.DALLAS.TX.US (Lance Franklin) writes:
>When running a window on a screen that's interlaced, is there any way, in
>a non-hardware-specific, intuition-friendly way to tell whether you're 
>starting an even or odd scan when you return from a call to WaitTOF.  [ ... ]

	An inspection of GfxBase structures reveals a lot of intersting and
promising locations for inspection.  However, since they're undocumented (no
comments describing what they do), they are most likely private, subject to
change, don't even think about it, etc etc etc.  So we are left with a
hardware solution.

	The hardware solution is to look at custom.vposr and examine bit #15.
If it is set, you are in the long field (whatever that means).  If it is
unset, you are in the short field.  It is unclear which is the even field
and which is the odd field.  Dale?

	Code to examine this would look like:

#include <hardware/custom.h>
#ifndef MANX
extern struct Custom custom;
#endif
	:
	:
	if (custom.vposr & 0x8000)
		/*  Long field  */
	else
		/*  Short field  */

	Hope it helps.

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