[PATCH weston 4/5] evdev: Improve touchpad support and add motion filters

[Chase Douglas]

On 05/09/2012 02:31 PM, Jonas Ådahl wrote:
> Touchpad related code has been rewritten and moved to its own file
> accessed by evdev via the dispatch interface.
> 
> The various functionality implemented are anti-flicker (don't jumping
> around), smoother motions, touch detection, pointer acceleration and
> some more.
> 
> Pointer acceleration is implemented as one generic part, and one touch
> specific part (a profile).
> 
> Some ideas and magic numbers comes from xserver and
> xf86-input-synaptics.

Can we move the acceleration code to a library? The reason I ask is that
we will want acceleration to feel the same whether the display server or
a client wants to move objects.

In Unity, we have a three finger gesture to move a window around.
Unfortunately, we can't really replicate the X server's motion because
of how it is completely intertwined in the X server implementation.
Thus, our window motion feels completely different to the X server's
cursor motion. Benjamin Otte has had similar frustrations as he has been
trying to implement gestures in GTK+.

My suggestion would be to create a separate library that implements the
pointer acceleration. It would be configurable by querying settings from
a system location. The user of the library would merely pass in raw
motion locations and timestamps, and maybe other data like pressure if
needed, and the library would spit out accelerated locations.

-- Chase