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

Joerg Reisenweber joerg at openmoko.org
Tue Mar 24 16:07:10 CET 2009

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 
There have been many different opinions about feasibility of this approach, I 
for one think it won't work.


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.
> -- 
>                                   .-.
> =------------------------------   /v\  ----------------------------=
> Keep in touch                    // \\     (yoh@|www.)onerussian.com
> Yaroslav Halchenko              /(   )\               ICQ#: 60653192
>                    Linux User    ^^-^^    [175555]
> _______________________________________________
> Openmoko community mailing list
> community at lists.openmoko.org
> http://lists.openmoko.org/mailman/listinfo/community

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: This is a digitally signed message part.
Url : http://lists.openmoko.org/pipermail/community/attachments/20090324/f00ecd88/attachment.pgp 

More information about the community mailing list