UI long term development perspective: physics engine

adrian cockcroft adrian.cockcroft at gmail.com
Mon Apr 2 17:41:13 CEST 2007

If the touchscreen reports the last touch and two fingers cause the
position to hop between two points then the driver just needs an
algorithm that reports the last two places and has some smoothing and
clustering built in.  Given low level access to the hardware this
shouldn't be too difficult to code and test. How does the "pointer"
device driver report position? Is there a provision to report chords
in some standard way? This isn't specific to OpenMoko, it could be a
generic Linux trackpad capability.


On 4/1/07, Florent THIERY <fthiery at gmail.com> wrote:
> > > i'm pretty curious to know what exactly the touchscreen sees when  you touch the screen with 2 fingers at the same time, when you move them, when you move only one of the 2, etc...., ...).
> > The output is the center of the bounding box of the touched area.
> > Pressure has little, but not no effect. Almost no effect on a single
> > touch, on a double touch, the relative pressures will have a slight
> > skewing effect towards the harder touch.
> > (from theory).
> > The touch point skips instantly on double touch.
> Thank you. I added your report to the wiki, and reorganized the mails
> so that a human being can try to contribute :p
> http://wiki.openmoko.org/wiki/UI_Improvements
> Please take a look if interested to help.
> If you have some spare time to continue reporting about the
> touchscreen, there are some questions on the wiki, but anybody having
> access to hardware can do it.
> Why do i keep asking for this? Because i'm not sure apple's ibooks
> have multi-touch pads, but if you slide 2 fingers in parallel, it
> makes scrolling. Which means: if it's not multitouch at it's base
> (and, if it was, there would be more of it), then they detect it using
> a hack. So can we do too, but we have to know exactly how the
> touchscreen reports "exotic" uses.
> Regards
> Florent
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