[PATCH weston v2 2/2] evdev: Improve touchpad support and add motion filters

Chase Douglas chase.douglas at canonical.com
Thu May 17 08:07:37 PDT 2012

On 05/17/2012 07:39 AM, Jonas Ådahl wrote:
> On Thu, May 17, 2012 at 4:20 PM, Chase Douglas
> <chase.douglas at canonical.com> wrote:
>> On 05/17/2012 03:18 AM, 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-jitter (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.
>>> Signed-off-by: Jonas Ådahl <jadahl at gmail.com>
>> I know I don't have much (any?) clout in wayland, but I feel strongly
>> enough about moving this logic to a separate library that I'm going to
>> NACK this. We need to resolve this problem from the beginning, or else
>> we will end up in some of the same messes we have in the X server.
> Have you experimented with having pointer acceleration completely
> server side defining a versatile enough input protocol so that the
> features you wish to implement will still be possible? What would be
> needed?

The configuration of parameters isn't the main reason for having this
code in a library. The real reason is that many compositors and clients
will need to implement the same algorithm. There's no point in
reinventing the wheel every time.

I'm also afraid that if this is merged into weston it will become an
opaque implementation detail that no other client can replicate, which
is the biggest issue with the X pointer acceleration mechanism.

-- Chase

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