[Development] Extending touch semantic information and Qt backends

[Ariel Molina]

>
>
>> There is QTouchEvent::device(). Isn't it enough?
>


>
> - Area & rotation. There is TouchPoint::area() and ::pressure() but
>> currently there is no support for ::angle(). Angle can be zero when not
>> supported.
>>
> Angle is not enough, because for compatibility with older apps
> TouchPoint::rect() should be as close as possible to the rotated rect.
> See https://codereview.qt-project.org/#/c/114238/
> In other words it should be a projection of the rotated rect, so you
> should introduce a separate method to get the rotated rect.
>

I see the patch refers to a fix making it rotate to the closest angle. Then
there is the blob definition from http://tuio.org/?specification (scroll to
the bottom), by using the diagram on the bottom of that page, you mean
TouchPoint::blob() and TouchPoint::blobAngle() might be more appropriate?


>
> - Unique identification. On research and advanced interactive surfaces the
>> usage of "markers" [3] is quite common. This is just a code extracted
>> either visually or by other mechanisms which is passed along the touch
>> information. I conjunction with area, rotation and uuid this paves the way
>> for very rich interaction.
>>
> How does it differ from TouchPoint::id()?
>
AFAIK ::id() is a temporary ID for unique identification of current live
touchpoints. This means the same object/finger gets different id() every
time it is released and come to touch again.
Im talking about marked objects such as the used in Samsung SUR40
(Microsoft Pixelsense), Fidtrack, Reactivision [1][2] and several others
including magnetic object detection[3] where devices can uniquely identify
objects, their position and rotation.

Ariel


[1] Fiducials and finger touchs.
http://reactivision.sourceforge.net/images/reactivision01.png
[2] https://www.youtube.com/watch?v=Mgy1S8qymx0
[3] https://www.youtube.com/watch?v=qlr-15Oto6s

-- 
Ariel Molina R.

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Movil: +521 2226 758874
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