"Multitouch" on FR ... imho should be possible to mimic

[Joerg Reisenweber]

This has been discussed multiple times since last ~15months.
The basic assumption a "middle-point" when touching with 2 fingers might be 
anyway exactly in the middle is incorrect. It depends on pressure of each 
touchpoint.
There have been many different opinions about feasibility of this approach, I 
for one think it won't work.

cheers
jOERG

Am Do  19. März 2009 schrieb Yaroslav Halchenko:
> Hi All,
> 
> I've been cherishing the idea for a while but got no spare time to even
> code a proof of concept. so I decided to share it with you so someone
> could do that for the common advantage ;)
> 
> Indeed we can't register both touches -- as a result hardware returns
> midpoint. BUT what if
> 
>  you touch screen with two fingers (at some inter-finger distance like
>  half of screen width) not at the same time but within
> lets say 100-200ms. Ie you "click" with one finger just slightly before
> the other one.
> 
>  then driver reports 2 coordinates where there is a significant
>  immediate jump from first coordinate to the midpoint between the two,
>  which would be as much as 1/2 of distance between the fingers.
> 
>  such behavior would signal that 2 fingers are on the screen!
> 
>  then if you move 2nd finger somewhere, midpoint would move and that
>  movement can be taken as a multitouch gesture, ie  if you are expanding
>  2nd finger away from first one -- it is like 'zoom-out' or increase of
>  smth. analogously, by comparing to the first coordinate (of 1st finger)
>  rotations / horizontal zoomin/ vertical zooming etc could be derived
>  
>  multitouch gesture mode would stop when fingers leave the screen or
>  there is once again a singificant jump from prev coordinate (like you
>  raise one finger up prior to the other one)
> 
> alternative mode can be that after 'two finger' non-synchroneous touch
> which switches to "multitouch mode" you drive your gesture with only
> second finger (ie raise the first one off the screen) -- that would
> allow for better control over the gesture since no averaging of
> coordinates between two points would happen. And again, multitouch mode
> is left whenever finger is raised of the screen.
> 
> if someone is to implement/test such approach, qwo might be a nice code
> base to start from... alternatively I guess tslib for those with
> debian+fbdev xserver.
> 
> -- 
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> 
> 
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