Path: utzoo!mnetor!uunet!nuchat!peter
From: peter@nuchat.UUCP (Peter da Silva)
Newsgroups: comp.sys.amiga
Subject: Re: Scrolling bitmaps (help needed)
Message-ID: <699@nuchat.UUCP>
Date: 28 Feb 88 12:09:13 GMT
References: <595NU105451@NDSUVM1> <795@sdcc8.ucsd.EDU>
Organization: Public Access - Houston, Tx
Lines: 23
Keywords: Bitmap scroll graphics
Summary: A solution to the page-flipping dillemma?

In article <795@sdcc8.ucsd.EDU>, cs178abu@sdcc8.ucsd.EDU (John Schultz) writes:
>   For vertical scrolling, allocate a bitmap twice as high as the
> display (for 200 lines, allocate a bitmap with a height of 400,
> etc).  Set up a Dwidth of 200 lines.  Make the RP handle 400 lines.
> You now have a drawing area 400 pixels tall, but you can only see
> 200 pixels.  Increment RyOffset then call ScrollVPort().
> Notice no flicker, incredible speed and smoothness; the result of
> hardware scrolling. (you don't need WaitTOF() or WaitBOVP())

Is this a solution to the double-buffering page-flipping dillemma?

A quick review.

Programs that use double buffering have a problem: if they are well behaved
they have to call a RethinkDisplay when they switch. That's real slow, but
if they are badly behaved they produce weird effects like the ones you can
see when you mouse around in Halfbrite Hill or ShowAnim.

Is ScrollVPort fast enough for the job? Does it work right under Intuition?
-- 
-- a clone of Peter (have you hugged your wolf today) da Silva  `-_-'
-- normally  ...!hoptoad!academ!uhnix1!sugar!peter                U
-- Disclaimer: These aren't mere opinions... these are *values*.