From: Peter Hutterer Date: Thu, 3 Nov 2016 04:01:17 +0000 (+1000) Subject: doc: expand trackpoint pointer acceleration documentation a bit X-Git-Tag: 1.5.1~3 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=e0ccfc87f047ff3c5595e268869c071c0b48428d;p=platform%2Fupstream%2Flibinput.git doc: expand trackpoint pointer acceleration documentation a bit Signed-off-by: Peter Hutterer --- diff --git a/doc/pointer-acceleration.dox b/doc/pointer-acceleration.dox index 2fbb4cc2..502bc7b5 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