This looked good on paper but clearly no-one (including myself) ever tested this
in a real-life situation or they would've noticed that the constant factor is
missing, causing a segfault on the first two-finger scroll event, touchpad
gesture or button scrolling.
Adding the constant factor makes the API much worse and the benefit is
unclear, so out of the window it goes. We can revisit this for libinput 1.12
but this isn't going to make the next release.
This reverts commit d8bd650540.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
This adds a third profile to the available profiles to map device-specific
speed to an acceleration factor, fully defined by the caller.
There has been a consistent call for different acceleration profiles in
libinput, but very little specifics in what actually needs to be changed.
"faster horses" and whatnot (some notable exceptions in e.g. bug 101139).
Attempts to change the actual acceleration function will likely break things
for others.
This approach opens up the profile itself to a user-specific acceleration
curve. A caller can set an acceleration curve by defining a number of points
on that curve to map input speed to an output factor. That factor is applied
to the input delta.
libinput does relatively little besides mapping the deltas to the
device-specific speed, querying the curve for that speed and applying that
factor. The curve is device-specific, the input speed is in device units/ms.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Switch to a pure factor with a max scaled after a function. The offset is just
0 now (will be removed eventually). Both are determined with a function based
on a linear/exponential regression of a sample set of data pairs.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
The quartett of new config functions is:
libinput_device_config_accel_get_profiles
libinput_device_config_accel_get_profile
libinput_device_config_accel_set_profile
libinput_device_config_accel_get_default_profile
The profile defines how the pointer acceleration works, from a very high-level
perspective. Two profiles are on offer, "adaptive", the standard one we have
used so far and "flat" which is a simple multiplier of input deltas and
provides 1:1 mapping of device movement vs pointer movement.
The speed setting is on top of the profile, a speed of 0 (default) is the
equivalent to "no pointer acceleration". This is popular among gamers and
users of switchable-dpi mice.
The flat profile unnormalizes the deltas, i.e. you get what the device does
and any device below 800dpi will feel excruciatingly slow. The speed range
[-1, 1] maps into 0-200% of the speed. At 200%, a delta of 1 is translated
into a 2 pixel movement, anything higher makes it rather pointless.
The flat profile is currently available for all pointer devices but touchpads.
https://bugs.freedesktop.org/show_bug.cgi?id=89485
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
