Fwd: UI long term development perspective: physics engine

Al Johnson openmoko at mazikeen.demon.co.uk
Mon Apr 2 19:43:32 CEST 2007

On Monday 02 April 2007 00:38, Florent THIERY 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.

The synaptics touchpad driver for X supports 2- and 3-finger taps but requires 
hardware support for this. The apple touchpad appears to be a variant on this 
(see http://www.popies.net/atp/). I've never tried a 2-finger drag on my 
synaptics pad so I don't know what it would do.

Of course the apple/synaptics pad may have a similar hack in firmware, so the 
questions are still valid.

> Regards
> Florent
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