Le 17 août 10 à 12:55, Chase Douglas a écrit :

On Tue, 2010-08-17 at 09:49 +0200, Stéphane Chatty wrote:

quoted

Le 16 août 10 à 17:30, Henrik Rydberg a écrit :

  - the single touch emulation is highly device dependent. I was (and
still am) pretty proud of my choice of tracking the 'oldest' finger
on the panel: this turns multitouch panels into single touch panels
that are impervious to parasite touches. But the drawback is that
currently there is no generic method for this tracking: I used
whatever device-specific information I could use (order of fingers in
a message, tracking id, etc).

Stéphan,

Can you explain in more detail why you chose an 'oldest' finger  
approach
for single touch emulation? I wonder if it's the best mechanism. Take
the following example:

1. User touches with one finger and intends to drag an object on  
screen
2. User touches another finger down, either accidentally or
intentionally, while dragging the first finger
3. User releases first finger to end the drag
4. Object suddenly is dragged under the second finger

As I'm implementing support for the Magic Trackpad right now, I'm  
having
to figure out the best way to do single-touch emulation. What I'm
currently doing is converting the first finger touched for single- 
touch
emulation, and when that finger is released no single-touch emulation
can occur until all fingers have left the screen again.

Yes, the debate is what to do when the 'actual oldest' finger is  
released: should the 'second oldest' take its place or should this be  
a release or should somthing else occur.

Some arguments in favour of the first option:
- My experience is that 'accidental' touches are transient.  
Therefore, the conjunction of having an accidental touch and a  
release is not very frequent.
  - At the opposite, on very large screens, it may sometimes be  
comfortable to "replace one finger with another", thus 'moving' the  
dragged object from one hand to the other.

More or less, the debate is about statistics and user experience  
design...

Cheers,

St.

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