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doc: improve absolute axis documentation a bit

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Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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Peter Hutterer 2016-01-05 12:35:49 +10:00
parent 9114054fa2
commit 665daba9a9
1 changed files with 12 additions and 6 deletions
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18
doc/absolute-axes.dox
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@ -10,7 +10,7 @@ libinput supports three types of devices with absolute axes:
- multi-touch screens
- single-touch screens
- graphics tablets (currently WIP)
- @ref tablet-support "graphics tablets"
Touchpads are technically absolute devices but libinput converts the axis values
to directional motion and posts events as relative events. Touchpads do not count
@ -18,7 +18,10 @@ as absolute devices in libinput.
For all absolute devices in libinput, the default unit for x/y coordinates is
in mm off the top left corner on the device, or more specifically off the
device's sensor.
device's sensor. If the device is physically rotated from its natural
position and this rotation was communicated to libinput (e.g.
@ref libinput_device_config_left_handed_set "by setting the device left-handed"),
the coordinate origin is the top left corner of in the current rotation.
@section absolute_axes_handling Handling of absolute coordinates
@ -40,7 +43,7 @@ coordinate.
@section absolute_axes_nores Devices without x/y resolution
An absolute device that does not provide a valid resolution is considered
buggy and must be fixed in the kernel. Some touchpad devices that do not
buggy and must be fixed in the kernel. Some touchpad devices do not
provide resolution, those devices are correctly handled within libinput
(touchpads are not absolute devices, as mentioned above).
@ -107,11 +110,14 @@ The most common matrices are:
See Wikipedia's
<a href="http://en.wikipedia.org/wiki/Transformation_matrix">Transformation
Matrix article</a> for more information on the matrix maths.
See libinput_device_config_calibration_get_default_matrix() for how these
Matrix article</a> for more information on the matrix maths. See
libinput_device_config_calibration_get_default_matrix() for how these
matrices must be supplied to libinput.
Once applied, any x and y axis value has the calibration applied before it
is made available to the caller. libinput does not provide access to the
raw coordinates before the calibration is applied.
@section absolute_axes_nonorm Why x/y coordinates are not normalized
x/y are not given in @ref motion_normalization "normalized coordinates"