calibrate touchscreen

[Jens Harms]

Hello, i created a simple calibration widget to calculate the CTM but
xinput refused to apply the CTM.
When i start X without any X Application running  and then (over ssh shell)
type

xinput set-prop 'my touch' 'Coordinate Transformation Matrix' a b c d e f g
h i

without any error, NOTHING happens. no error, no change to the property.

BUT: when I start X, then aterm and after the aterm window is visible,
i can succesfully apply the matrix with  "xinput set-prop 'my touch'
'Coordinate Transformation Matrix' a b c d e f g h i"

Is this intended behavior?

re,
Jens Harms

For the curious, i uploaded the full source:

git clone https://github.com/xtforever/xtcal.git

you can add as many calibration points as you wish, the least sqare
algo will calculate the correct matrix.


2016-10-20 7:52 GMT+02:00 Peter Hutterer <peter.hutterer at who-t.net>:

> On Wed, Oct 19, 2016 at 03:52:56PM +0200, Jens Harms wrote:
> > Hi. I try to calibrate  a resisitive Touchscreen.
> > The touchscreen is a bit rotatated (3-5 degree), therefore i can not use
> > xinput_calibrator. I try to understand how the the evdev driver works.
> >
> > Do i need to set "Evdev Axis Calibration" and "Coordinate Transformation
> > Matrix" ? Or is it sufficent to set the CTM alone?
>
> don't use the axis calibration, use the matrix only.
>
> > How are Touch coordinates calculated? Which transformations are applied
> to
> > the raw data?
>
> the matrix is a basic transformation matrix, so you can use your normal
> rotational elements, etc. The values are normalized to [0, 1] where 1
> represents "total width" or "total height".
>
> https://wiki.archlinux.org/index.php/Calibrating_Touchscreen
> https://wiki.ubuntu.com/X/InputCoordinateTransformation
>
> Cheers,
>    Peter
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.x.org/archives/xorg-devel/attachments/20161116/d5b867df/attachment.html>