[Interest] QTouchEvents correctly placed only when the windows is on the primary screen?

[Rutledge Shawn]

On 25 Sep 2013, at 11:46 PM, Andrea Franceschini wrote:

> 2013/9/25 Casimiro, Daniel C CIV NUWC NWPT <daniel.casimiro at navy.mil>:
> 
>> 1. How to associate the TUIO device with the correct QScreen? (maybe QScreen::name and the TUIO device name)
>> 2. How is QWindowSystemInterface::handleTouchEvent supposed to handle multiple screens?
> 
> That's actually the same thing I was wondering. As for 1, I'd say that
> sounds plausible, but is it feasible? As for 2, in my case I don't
> need multiple touch screens, but I suppose that you could somehow
> extend the approach from 1, maybe via on/off-line config?

FWIW XInput permits setting an arbitrary transform to map the touchscreen to part of the entire desktop.  It's a bit cumbersome for the most common use case but also very flexible.  So I have

/etc/X11/xorg.conf.d/52-acer-touchscreen-options.conf
Section "InputClass"
	# This is for human-readable purposes only.
	Identifier "Acer touchscreen options"
	# Match all devices with either Wacom or Waltop in their product name
	MatchProduct "Advanced Silicon S.A CoolTouch(TM) System"
	# AND match devices with a device path of /dev/input/eventX.
	MatchDevicePath "/dev/input/event*"
	Option "Transformation Matrix" "0.5 0 0.5 0 0.9 0 0 0 1"
EndSection

which goes with my desktop configuration having a 1920x1200 monitor on the left and 1920x1080 touchscreen on the right: on the x axis the touchscreen is at 0.5 and on the y axis the touchscreen is simply shorter than the entire desktop: 1080/1200 = 0.9.  They could at least have used pixel units instead of normalized coordinates, but maybe they were worried about mismatched resolutions or something.

Anyway, I think global touch coordinates should be w.r.t. the desktop, not the screen.  If you want to simplify and say that tuio only permits mapping the touch area to an entire screen, you can still offset the coordinates according to the screen's position on the desktop.