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- .. _trackpoints:
- ==============================================================================
- Trackpoints and Pointing Sticks
- ==============================================================================
- This page provides an overview of trackpoint handling in libinput, also
- referred to as Pointing Stick or Trackstick. The device itself is usually a
- round plastic stick between the G, H and B keys with a set of buttons below
- the space bar.
- .. figure:: button-scrolling.svg
- :align: center
- A trackpoint
- libinput always treats the buttons below the space bar as the buttons that
- belong to the trackpoint even on the few laptops where the buttons are not
- physically wired to the trackpoint device anyway, see :ref:`t440_support`.
- .. _trackpoint_buttonscroll:
- ------------------------------------------------------------------------------
- Button scrolling on trackpoints
- ------------------------------------------------------------------------------
- Trackpoint devices have :ref:`button_scrolling` enabled by default. This may
- interfere with middle-button dragging, if middle-button dragging is required
- by a user then button scrolling must be disabled.
- .. _trackpoint_range:
- ------------------------------------------------------------------------------
- Motion range on trackpoints
- ------------------------------------------------------------------------------
- It is difficult to associate motion on a trackpoint with a physical
- reference. Unlike mice or touchpads where the motion can be
- measured in mm, the trackpoint only responds to pressure. Without special
- equipment it is impossible to measure identical pressure values across
- multiple laptops.
- The values provided by a trackpoint are motion deltas, usually corresponding
- to the pressure applied to the trackstick. For example, pressure towards the
- screen on a laptop provides negative y deltas. The reporting rate increases
- as the pressure increases and once events are reported at the maximum rate,
- the delta values increase. The figure below shows a rough illustration of
- this concept. As the pressure
- decreases, the delta decrease first, then the reporting rate until the
- trackpoint is in a neutral state and no events are reported. Trackpoint data
- is hard to generalize, see
- `Observations on trackpoint input data
- <https://who-t.blogspot.com/2018/06/observations-on-trackpoint-input-data.html>`_
- for more details.
- .. figure:: trackpoint-delta-illustration.svg
- :align: center
- Illustration of the relationship between reporting rate and delta values on a trackpoint
- The delta range itself can vary greatly between laptops, some devices send a
- maximum delta value of 30, others can go beyond 100. However, the useful
- delta range is a fraction of the maximum range. It is uncomfortable to exert
- sufficient pressure to even get close to the maximum ranges.
- libinput provides a :ref:`Magic Trackpoint Multiplier
- <trackpoint_multiplier>` to normalize the trackpoint input data.
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