UI long term development perspective: physics engine

Florent THIERY fthiery at gmail.com
Sat Mar 24 15:38:42 CET 2007

I'll add here sotg from an off-list msg;

In fact we have the position given by the touchscreen : [ x(t) ; y(t) ]
speed is: [ (x(t') - x(t)) / (t' -t) ; (y(t') - y(t)) / (t' -t) ] -
friction_factor*(t' - t)

... Where the friction_factor is in [0 ; 1]

If we want acceleration, then we have to integrate the equation once.

Shit, i gotta look into my college courses, it's terrible how fast it
fades away :-p

I'm not sure we really need to take acceleration into account.

The changes to bring to the standard gtk scrolling are:
- consider the list as scrollable (not just the scroll item)
- change the scrolling "stop" behaviour (when the user stops touching
the screen) like this: if (last_cursor_speed > 0),
- when touching the moving list again, stop the scrolling immediately
- addition of friction may be a plus, for a more
"wheel-of-fortune"-like experience

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