Comment 3 for bug 978378

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Mohamed IKBEL Boulabiar (boulabiar) wrote : Re: [Bug 978378] Re: A window can be moved even when some fingers are not over it

Hi Chase,

On Tue, Apr 17, 2012 at 9:19 PM, Chase Douglas
<email address hidden>wrote:

> On a touchscreen, if you put on finger over the target window and two
> other fingers over other windows, then the intention is ambiguous.
> Currently, the code looks at the centroid of the touches to determine
> which window to interact with. By requiring all the touches to hit the
> same window, we remove all ambiguity about which window is really
> targeted.
>

Yep, I remember a discussion about how to recognize this and the related
use of combinatorial gestures to avoid ambiguity.

> This is really a design decision. To me it makes sense. If you disagree,
> we can escalate this to the Unity designers and confirm which is correct
> according to their designs.
>

I've only found this decision strange as it has changed from the old point
of view.
You know that fingers are not always very well aligned on the
window/widget, and because of this some people invented the probabilistic
matching[1].
Anyway, some later end-user testing may confirm this decision to require
fingers inside the window.

Thanks for the answer and keep the good work !

[1] http://notjulie.com/research/probinput/paper.pdf