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cbd4f35442
This is a large commit because it's difficult to split this up and we don't care about bisecting here anyway. doxygen is going to produce the API documentation only sphinx is going to produce the prose user (and a bit of developer) documentation. The source split is doc/api and doc/user. Steps performed: - run the doxygen-to-sphinx.sh script to convert all .dox sources to .rst - manually fixed the .rst to render correctly - add a few extra .rst documents to generate the right hierarchy - hook up sphinx-build in meson - add a new @mainpage for doxygen more aimed at developers For the build directory: - sphinx produces /Documentation - doxygen now produces /api/ These need to be manually combined in the wayland-web repo, meson doesn't support subdirectories as output paths within the build dir and the documentation doesn't need to be installed anywhere. Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
105 lines
4 KiB
ReStructuredText
105 lines
4 KiB
ReStructuredText
.. _touchpad_jitter:
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==============================================================================
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Touchpad jitter
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==============================================================================
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Touchpad jitter describes random movement by a few pixels even when the
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user's finger is unmoving.
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libinput has a mechanism called a **hysteresis** to avoid that jitter. When
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active, movement with in the **hysteresis margin** is discarded. If the
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movement delta is larger than the margin, the movement is passed on as
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pointer movement. This is a simplified summary, developers should
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read the implementation of the hysteresis in ``src/evdev.c``.
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libinput uses the kernel ``fuzz`` value to determine the size of the
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hysteresis. Users should override this with a udev hwdb entry where the
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device itself does not provide the correct value.
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.. _touchpad_jitter_fuzz_override:
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------------------------------------------------------------------------------
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Overriding the hysteresis margins
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------------------------------------------------------------------------------
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libinput provides the debugging tool ``libinput measure fuzz`` to help edit or
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test a fuzz value. This tool is interactive and provides a udev hwdb entry
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that matches the device. To check if a fuzz is currently present, simply run
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without arguments or with the touchpad's device node:
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::
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$ sudo libinput measure fuzz
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Using Synaptics TM2668-002: /dev/input/event17
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Checking udev property... not set
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Checking axes... x=16 y=16
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In the above output, the axis fuzz is set to 16. To set a specific fuzz, run
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with the ``--fuzz=<value>`` argument.
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::
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$ sudo libinput measure fuzz --fuzz=8
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The tool will attempt to construct a hwdb file that matches your touchpad
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device. Follow the printed prompts.
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In the ideal case, the tool will provide you with a file that can be
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submitted to the systemd repo for inclusion.
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However, hwdb entry creation is difficult to automate and it's likely
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that the tools fails in doing so, especially if an existing entry is already
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present.
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Below is the outline of what a user needs to do to override a device's fuzz
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value in case the ``libinput measure fuzz`` tool fails.
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Check with ``udevadm info /sys/class/input/eventX`` (replace your device node
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number) whether an existing hwdb override exists. If the ``EVDEV_ABS_``
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properties are present, the hwdb overried exists. Find the file that
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contains that entry, most likely in ``/etc/udev/hwdb.d`` or
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``/usr/lib/udev/hwdb.d``.
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The content of the property is a set of values in the format
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``EVDEV_ABS_00=min:max:resolution:fuzz``. You need to set the ``fuzz`` part,
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leaving the remainder of the property as-is. Values may be empty, e.g. a
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property that only sets resolution and fuzz reads as ``EVDEV_ABS_00=::32:8``.
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If no properties exist, your hwdb.entry should look approximately like this:
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::
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evdev:name:Synaptics TM2668-002:dmi:*:svnLENOVO*:pvrThinkPadT440s*:
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EVDEV_ABS_00=:::8
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EVDEV_ABS_01=:::8
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EVDEV_ABS_35=:::8
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EVDEV_ABS_36=:::8
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Substitute the ``name`` field with the device name (see the output of
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``libinput measure fuzz`` and the DMI match content with your hardware. See
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:ref:`hwdb_modifying` for details.
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Once the hwdb entry has been modified, added, or created,
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:ref:`reload the hwdb <hwdb_reloading>`. Once reloaded, :ref:`libinput-record`
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"libinput record" should show the new fuzz value for the axes.
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Restart the host and libinput should pick up the revised fuzz values.
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.. _kernel_fuzz:
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------------------------------------------------------------------------------
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Kernel fuzz
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------------------------------------------------------------------------------
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A fuzz set on an absolute axis in the kernel causes the kernel to apply
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hysteresis-like behavior to the axis. Unfortunately, this behavior leads to
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inconsistent deltas. To avoid this, libinput sets the kernel fuzz on the
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device to 0 to disable this kernel behavior but remembers what the fuzz was
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on startup. The fuzz is stored in the ``LIBINPUT_FUZZ_XX`` udev property, on
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startup libinput will check that property as well as the axis itself.
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