mirror of
https://gitlab.freedesktop.org/libinput/libinput.git
synced 2025-12-20 06:50:05 +01:00
3320c6df90
The GitLab migrations means that bugs should now be reported there
rather than Bugzilla. Though the repository is still available via
anongit, cloning through GitLab allows use of HTTPS.
All freedesktop.org URLs are also preferentially served over HTTPS
rather than unsecured HTTP.
Signed-off-by: Daniel Stone <daniels@collabora.com>
(cherry picked from commit 94dba68f96)
84 lines
3.3 KiB
Text
84 lines
3.3 KiB
Text
/**
|
|
@page motion_normalization Normalization of relative motion
|
|
|
|
Most relative input devices generate input in so-called "mickeys". A
|
|
mickey is in device-specific units that depend on the resolution
|
|
of the sensor. Most optical mice use sensors with 1000dpi resolution, but
|
|
some devices range from 100dpi to well above 8000dpi.
|
|
|
|
Without a physical reference point, a relative coordinate cannot be
|
|
interpreted correctly. A delta of 10 mickeys may be a millimeter of
|
|
physical movement or 10 millimeters, depending on the sensor. This
|
|
affects pointer acceleration in libinput and interpretation of relative
|
|
coordinates in callers.
|
|
|
|
libinput does partial normalization of relative input. For devices with a
|
|
resolution of 1000dpi and higher, motion events are normalized to a default
|
|
of 1000dpi before pointer acceleration is applied. As a result, devices with
|
|
1000dpi and above feel the same.
|
|
|
|
Devices below 1000dpi are not normalized (normalization of a 1-device unit
|
|
movement on a 400dpi mouse would cause a 2.5 pixel movement). Instead,
|
|
libinput applies a dpi-dependent acceleration function. At low speeds, a
|
|
1-device unit movement usually translates into a 1-pixel movements. As the
|
|
movement speed increases, acceleration is applied - at high speeds a low-dpi
|
|
device will roughly feel the same as a higher-dpi mouse.
|
|
|
|
This normalization only applies to accelerated coordinates, unaccelerated
|
|
coordinates are left in device-units. It is up to the caller to interpret
|
|
those coordinates correctly.
|
|
|
|
@section motion_normalization_touchpad Normalization of touchpad coordinates
|
|
|
|
Touchpads may have a different resolution for the horizontal and vertical
|
|
axis. Interpreting coordinates from the touchpad without taking resolution
|
|
into account results in uneven motion.
|
|
|
|
libinput scales unaccelerated touchpad motion to the resolution of the
|
|
touchpad's x axis, i.e. the unaccelerated value for the y axis is:
|
|
y = (x / resolution_x) * resolution_y
|
|
|
|
@section motion_normalization_tablet Normalization of tablet coordinates
|
|
|
|
See @ref tablet-relative-motion
|
|
|
|
@section motion_normalization_customization Setting custom DPI settings
|
|
|
|
Devices usually do not advertise their resolution and libinput relies on
|
|
the udev property <b>MOUSE_DPI</b> for this information. This property is usually
|
|
set via the <a
|
|
href="http://cgit.freedesktop.org/systemd/systemd/tree/hwdb/70-mouse.hwdb">udev hwdb</a>.
|
|
The "mouse-dpi-tool" utility provided by <a
|
|
href="https://freedesktop.org/wiki/Software/libevdev/">libevdev</a> should be
|
|
used to measure a device's resolution.
|
|
|
|
The format of the property for single-resolution mice is:
|
|
@code
|
|
MOUSE_DPI=resolution@frequency
|
|
@endcode
|
|
|
|
The resolution is in dots per inch, the frequency in Hz.
|
|
The format of the property for multi-resolution mice may list multiple
|
|
resolutions and frequencies:
|
|
@code
|
|
MOUSE_DPI=r1@f1 *r2@f2 r3@f3
|
|
@endcode
|
|
|
|
The default frequency must be pre-fixed with an asterisk.
|
|
|
|
For example, these two properties are valid:
|
|
@code
|
|
MOUSE_DPI=800@125
|
|
MOUSE_DPI=400@125 800@125 *1000@500 5500@500
|
|
@endcode
|
|
|
|
The behavior for a malformed property is undefined.
|
|
|
|
If the property is unset, libinput assumes the resolution is 1000dpi.
|
|
|
|
Note that HW does not usually provide information about run-time
|
|
resolution changes, libinput will thus not detect when a resolution
|
|
changes to the non-default value.
|
|
|
|
*/
|
|
|