[PATCH libinput 1/2] Document LIBINPUT_CALIBRATION_MATRIX properly
spitzak at gmail.com
Tue Sep 9 18:14:05 PDT 2014
On 09/09/2014 04:40 PM, Peter Hutterer wrote:
> + * The udev property is parsed as 6 floating point numbers separated by a
> + * single space each (scanf(3) format "%f %f %f %f %f %f").
> + * The 6 values represent the first two rows of the calibration matrix as
> + * described in libinput_device_config_calibration_set_matrix().
Six-entry affine matricies are more commonly done as columns, such that
the list (a,b,c,d,x,y) describes the following matrix:
| a c x |
| b d y |
| 0 0 1 |
This is used by Cairo and PostScript, and probably by SVG and anything
else influenced by PostScript.
You are describing (a,c,x,b,d,y). This is not often used because of the
unexpected splitting of x,y.
Unfortunately I have also seen (a,c,b,d,x,y). Don't do that...
If it is possible to change this now without breaking any existing code
it may be a good idea.
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