diff options
| -rw-r--r-- | doc/pointer-acceleration.dox | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/doc/pointer-acceleration.dox b/doc/pointer-acceleration.dox index 2fbb4cc..502bc7b 100644 --- a/doc/pointer-acceleration.dox +++ b/doc/pointer-acceleration.dox @@ -108,14 +108,33 @@ The image above shows the touchpad acceleration profile in comparison to the @section ptraccel-trackpoint Pointer acceleration on trackpoints +Trackpoint hardware is quite varied in how it reacts to user pressure and +unlike other devices it cannot easily be normalized for physical properties. +Measuring pressure objectively across a variety of hardware is nontrivial. +libinput relies on some sytem-wide configured properties, specifically the +@ref udev_config. The two properties that influence trackpoint acceleration +````POINTINGSTICK_CONST_ACCEL```` which is a constant factor applied to the +trackpoint's motion data. For example, a factor of 3 will see all input data +multipled by 3. This multiplication is done by libinput. + +Additionally, some trackpoints provide the ability to adjust the sensitivity in +hardware by modifying a sysfs file on the serio node. The udev property +````POINTINGSTICK_SENSITIVITY```` indicates the desired value, a udev +builtin is expected to apply this to the device, i.e. libinput does not +handle this property. Once applied, the sensitivity adjusts the deltas +coming out of the hardware. + Trackpoint pointer acceleration uses the @ref ptraccel-low-dpi profile, with a -constant deceleration factor taking the place of the DPI settings. +constant acceleration factor taking the place of the DPI settings. @image html ptraccel-trackpoint.svg "Pointer acceleration curves for trackpoints" The image above shows the trackpoint acceleration profile in comparison to the -@ref ptraccel-linear. The constant acceleration factor, usually applied by -udev, shapes the acceleration profile. +@ref ptraccel-linear. + +The constant acceleration factor, usually applied in +@ref udev_config, shapes the acceleration profile and is pre-applied before +any user-specific acceleration adjustments. @section ptraccel-profile-flat The flat pointer acceleration profile |