Will software patents stop us having multitouch?

Helge Hafting helge.hafting at hist.no
Wed Feb 18 16:41:26 CET 2009

Tim Dobson wrote:
> I recently came across this blog post which, interesting explains that the
> Android G1 is *capable* of multitouch but chose not to use it for some
> reason - some suggest, for fear of litigation from Apple.
> http://osswatch.jiscinvolve.org/2009/01/30/what-does-that-two-finger-gesture-mean/
> I don't live in the USA so it may not be such an issue for me but it could
> still cause problems for Openmoko...
> What are your thoughts?

I don't think this will cause trouble for openmoko - for the neo phone 
screen doesn't support multitouch. It doesn't matter what the software 
might be able to do with a multitouch-screen, when it isn't available.

To get in patent trouble, you actually have to infringe on the patent in 

Most touchscreens can't do multitouch, and new screens likely won't have 
it either because manufacturers will worry about that patent. Some 
screens, such as the neo, can do "fake multitouch":

If you touch with two fingers, the screen first notices the location of 
the first finger. When the second finger lands, the screen notices a new 
location, somewhere between the two fingers. The location of the second 
finger is never seen, unless the first finger is released.

So when two touches happens with no release inbetween, it could be a 
drag. If the jump distance is too long for a regular drag, then assume a 
second finger landed somewhere further out along the line between first 
and second touch.

The location of the second finger will not be very precise, for the 
screen doesn't necessarily register the exact midpoint between the 
fingers. The midpoint will be closer to the bigger finger or the finger 
that is pressing hardest. This is a problem, for the second finger will 
necessarily touch lightly with a small area in the beginning. So the 
movement of the "weighted average" position may resemble a drag. Perhaps 
some careful study of such drags and two-finger touchdowns will reveal 
systematic differences so the software can be written that usually gets 
this right. Some averaging and a screen with good bandwith *may* be able 
to get a reasonable position for the second finger in reasonable time.
But then apple might get irritated.

Also, it might be hard to see the difference between a two-finger touch 
  and tapping two places in rapid succession - unless you can be sure 
you always get a release event.

Helge Hafting

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