[Development] Extending touch semantic information and Qt backends

[Rutledge Shawn]

> On 11 Feb 2016, at 11:35, Александр Волков <a.volkov at rusbitech.ru> wrote:
> 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.

TUIO models the touchpoint as a rotated ellipse though, right?  http://www.tuio.org/?specification  And I think that’s nice, for finger touchpoints at least (although markers could be any shape).  It can be assumed to be the ellipse inscribed in a rect; but I don’t think for the next-gen API that it makes sense to change the dimensions just because it’s rotated, because that makes it hard to visualize the ellipse, and hard to turn the size of the contact patch into a pressure (if you have hardware which gives you the contact patch but not the pressure).

Typical capacitive touchscreens (or window-system APIs) don’t provide the contact patch either, do they?  I’m not sure why it’s not more common.