Most mice have a wheel click angle of 15 degrees, i.e. 24 clicks per full
wheel rotation. Some mice, like the Logitech M325 have a larger angle. To
allow userspace to make use of that knowledge, add a property to the hwdb.
This allows for better predictive scrolling. e.g. a mouse that has a smaller
click angle will scroll faster, with this value you can accommodate this
where needed. Likewise, using "half turn of the wheel" or "full turn of the
wheel" as a UI element becomes possible.
This addition is mainly driven by libinput 0.8, having the angle enables
libinput to provide an API that distinguishes between a physical distance
(like touchpad scrolling does) and discrete steps (wheel clicks).
Callers can choose what they prefer based on the device.
Error, DATA expected but got 'mouse:usb:v046dpc24c:name:Logitech G400s Optical
Gaming Mouse:' in '/etc/udev/hwdb.d/70-mouse.hwdb':
Error, MATCH expected but got ' MOUSE_DPI=400@1000 *800@1000 2000@1000
4000@1000' in '/etc/udev/hwdb.d/70-mouse.hwdb':
Introduced in 6366e349
Reporter says he incorrectly measured the data but the device is not available
anymore to correct it. We'll have to wait for someone else to submit the data.
https://bugs.freedesktop.org/show_bug.cgi?id=87343
Note that the MS receivers likely work like the Logitech ones, i.e. all
devices connected show up with the same vid/pid/name. Full evidence remains to
be gathered.
This way entries from the same brand with the same dpi and frequency
can be coalesced. It is also visually easier to find the right DPI
than order hexadecimal identifiers.
Pointer acceleration for relative input devices (mice, trackballs, etc.)
applies to the deltas of the device. Alas, those deltas have no physical
reference point - a delta of 10 may be caused by a large movement of a
low-dpi mouse or by a minute movement of a high-dpi mouse.
Which makes pointer acceleration a bit useless and high-dpi devices
essentially unusable.
In an ideal world, we could read the DPI from the device directly and work
with that. In the world we actually live in, we need to compile this list
manually. This patch introduces the database, with the usual match formats
and a single property to be set on a device: MOUSE_DPI
That is either a single value for most mice, or a list of values for mice
that can change resolution at runtime. The exact format is detailed in the
hwdb file.
Note that we're explicitly overshooting the requirements we have for
libinput atm. Frequency could be detected in software and we don't
actually use the list of multiple resolutions (because we can't detect
when they change anyway). However, we might as well collect those values
from the get-go, adding/modifying what will eventually amount to hundreds
of entries is a bit cumbersome.
Note: we rely on the input_id builtin to tag us as mouse first, ordering
of the rules is important.
(David: fixed up typos and moved hwdb file into ./hwdb/)
