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Path: utzoo!mnetor!lsuc!sq!hobie
From: hobie@sq.uucp (Hobie Orris)
Newsgroups: comp.sys.amiga
Subject: Re: Overscan and Blink
Message-ID: <1987Sep22.012059.20532@sq.uucp>
Date: Tue, 22-Sep-87 01:20:59 EDT
Article-I.D.: sq.1987Sep22.012059.20532
Posted: Tue Sep 22 01:20:59 1987
Date-Received: Wed, 23-Sep-87 07:13:14 EDT
References: <2967@aspvax.UUCP>
Reply-To: hobie@sq.UUCP (Hobie Orris)
Organization: SoftQuad Inc., Toronto
Lines: 48
Checksum: 14988


eraps2@aspvax.UUCP writes:
>
>Hi all,
>Could someone post a summary of overscan to the net.  I looked through
>the RKM manuals, the hardware reference, and intuition manuals and was
>unable to ascertain how to use it.  Also, is there some special way to
>code so that my programs will be compatable with overscan screens?  If 
>this is described somewhere, please tell me where.
>
>"We want information ... information"       Rob Ginn 
>	- No. 2

"You'll not get it!"
	- No. 6
	
	Overscan cannot be summed up, since it is unofficial and its usage
is varied. DPaint 2 uses 672x444 for hi-res overscan because Dan Silva devel-
oped it on a buggy Workbench that crashed if he tried anything bigger. Aegis
uses 704x480 (?) which works, but is wasteful.  I find that the best dimensions
for overscan (as used in PageFlipper 1.0) are 352x222 for lo-res and 704x444
for hi-res.  Other resolutions use combinations of these values.  These have
been confirmed by my testing to be the best combinations for filling the screen
with a minimum of wasted memory.  So first you want to open a screen with 
these dimensions and then you want to push it up and to the left so there are
no unsightly borders on the left (as in DPaint 2 "full video") and on the top.
This is the trick:

	BigScreen->ViewPort.DxOffset = -16;	/* push 1 word left */
	BigScreen->ViewPort.DyOffset = -12;	/* yank it up a little */
	MakeScreen(BigScreen);
	RethinkDisplay();

This works great if you use Intuition.  If you don't, then you're on your own.
When you do this your pixels are still numbered from zero (don't need negative
offsets!) so that's no sweat, but your menus will be off the screen, and the
pointer will not point to them like it did in the good old days, so it might
be a good idea to re-do your pointer so it's offset too.

	I would like to see some overscan standard thrashed out and observed by
developers, and blessed by the Commodore (you know the one!).  I submit this 
as a starting point.  So let's argue :-) 


 Hobie Orris			 	| Jesus was a leprechaun
 guest of SoftQuad Inc., Toronto, Ont.	| A twinkle in his eye
 {ihnp4 | decvax | ? }!utzoo!sq!hobie	| Always smiling sweetly
                                        | But he never expected to die.
                                        |     - Snakefinger