Re: Smooth Scrolling

[Michael L Torrie <torriem chem byu edu>]

On Tue, 2007-03-27 at 15:54 +0200, Xavier Bestel wrote:
> On Tue, 2007-03-27 at 07:37 +0100, Alex Jones wrote:
> > A few years ago there used to be a distributor patch in Gentoo to enable
> > this, and it was sweet. What happened, here?
> 
> I dunno, but it's more than sweet. Whoever remember the text editor
> CygnusED, which had a very smooth scrolling, vblank-synchronized,
> progressive, knows that this helps wonderfully to "know where you are"
> once you have scrolled. Currently in GTK+, after hitting the scrollbar
> you have to think for a moment to let your eyes find the cursor again.
> 
> To me, smooth scrolling is the same improvement than compiz/beryl is wrt
> virtual desk switching. Except it was already implemented on low-end
> hardware 15 years before :)

Smooth scrolling is only good if it is very fast (as fast as without
smooth scrolling) and totally synchronized with both the redraw and the
mouse wheel's speed, in order to eliminate tearing and stuttering.  I
think we're finally to the point where it could be done right.

IE 5,  if I recall correctly, had smooth scrolling and it was the first
thing most I turned off because it was so annoying.  It had a constant
lag and, because of the scroll "steps" (ie one click of the scroll wheel
is so many lines) it would hesitate and appear to stutter.  Half the
time it would have to catch up to you.  Was awful. 

I think the fundamental problem is that the mouse scroll wheel is really
a low-resolution input device, with discreet jumps that have to be
mapped to pixels or lines somehow.  Whether or not smooth scrolling is
actually smooth depends entirely on how it can react to various scroll
wheel speeds.  Slowly moving the scroll wheel, for example, causes the
scroll bar to jump in discreet jumps, and smooth scrolling amplifies
that motion and makes it jumpy (well it's jumpy without smooth-scroll
too), from my experience.  Fast scrolling is where smooth scrolling
looks the best, so long as it doesn't lag behind where the user expects
to be.  If the scroll wheel was ultra-high resolution, then it would
always work well.  But most scroll wheels are not high-resolution
(except for may Apple's mighty mouse).

> 
> 	Xav
> 
> 
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