From: <postmaster_at_diffenbach.org>
Date: Thu, 22 Jun 2006 23:38:10 -0400

A beta build for video ipod with accelerated scrolling is available.

This build more or less approximates the accelerated scrolling on the
retail OS; in particular, no visual indication of the scroll factor is
shown to the user (other than the speed up of the scrolling itself).

Three discrete acceleration levels ("fast", "faster", "fastest"), plus
the standard unaccelerated level, are recognized. The user can adjust
the thresholds at which each acceleration level is reached by accessing:
  Menu|General Settings|System|Ipod Scroll Wheel Acceleration

For each of the three acceleration levels, the scale is in scroll
ticks per second; the ipod 5G's scroll wheel recognizes 96 discrete
ticks per rotation, so value of 96 means that acceleration is reached
if the user's finger travels 360 degrees around the wheel in one second.

If the user's scrolling speed exceeds the threshold for any level,
then that level's acceleration is applied. (When the threshold is no
longer exceeded, the level falls. There's no need to "turn off"
acceleration; just move your finger more slowly.)

The speed is calculated simply as distance/time, but the distance and
time are measured from the time the scroll event ("button") was
generated to the time other code reads that event ("button").

Bugs and known issues: the menu threshold values are shown in the
parent menu (this departs form Rockbox practice); these values are not
updated after the sub-menu is exited, until the parent menu itself is
exited.

The values should be monotonic increasing, that is, the fast
acceleration threshold should be less than the faster threshold should
be less than the fastest threshold. The software, however, does not
enforce this.

Only lists scrolling is actually accelerated. Lists however, include
all menus, directories, and dbcache listings, so most use is covered.
Plugins, however, are not accelerated.

The following accelerations are applied. These cannot be changed by
the user in this release:
unaccelerated: advances/retreats by one line per scroll
fast: advances/retreats by one page per scroll, default threshold: 55
faster: advances/retreats by eight pages per scroll, default
threshold: 110
fastest: advances/retreats by 10 percent of the list per scroll,
default threshold: 165

But if 10% is less than 8 pages, fastest scrolls 8 pages instead; and
if the list is less than a page long, no acceleration takes place.

Also, the standard button handling has been to require a movement of
four scroll ticks before a button event is generated. In his release,
that's changed to three ticks. You may initially find the scrolling a
little too jumpy -- this has nothing to do with the
[I]acceleration[/I], but with this separate change to the button
generation threshold.

[b]This build is not free! You must pay for it![/b] As "payment", I
ask that you occasionally access the debug menu, select "logfdump",
and send me a copy of the file logf.txt in the .rockbox directory on
your ipod. Please send copies to
rockboxscrollaccelbeta AT diffenbach.org

The code for this isn't yet released as a patch, I want to keep
looking at it a bit before releasing it.

For 60GB ONLY video ipods, install this zip file:
http://diffenbach.org/rockbox/scrollaccelbeta/64/rockbox.zip
For 30GB video ipods, install this zip file:
http://diffenbach.org/rockbox/scrollaccelbeta/32/rockbox.zip
Received on 2006-06-23