From: Geert Uytterhoeven <Geert.Uytterhoeven@cs.kuleuven.ac.be>
  To  : ggi-develop@eskimo.com
  Date: Thu, 30 Jul 1998 11:49:28 +0200 (CEST)

Re: I've seen the stars too... [Re: kgicon, etc]

On Thu, 30 Jul 1998, Andrew Apted wrote:
> Martin Eli Erhardsen writes:
> >  How is it possible to write a scroller which is so slow.
> >  Does it copy the whole screen in the framebuffer every time.
>   
> Yes, and apparently _reading_ the framebuffer is a lot slower than
> writing it.  Once we change to the smart scrolling, it should be a lot
> faster.

Smart scrolling _is_ already available if you enable it:

    display->scrollmode = FBCON_REDRAW

> >  would speed up the scrolling. The VGA splitline helps too, but you can
> 
> Splitline is no good.  I've tried it, but what happens is that when you
> _move_ the splitline (e.g. up 8 lines), you often miss the VGA's line
> counter.  It is an exact comparison, so no ywrap occurs for that frame,
> resulting in a flash of garbage on the screen.  Real ugly.

You could do it during the vblank. On Amiga, the copper lists are changed
during the vblank only to prevent this kind of annoying effects.

Greetings,

						Geert

--
Geert Uytterhoeven                     Geert.Uytterhoeven@cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}  http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium