[PATCH libinput 3/3] Add support for relative device rotation (trackball only)

[Hans de Goede]

Hi,

On 04-05-16 11:20, Peter Hutterer wrote:
> On Wed, May 04, 2016 at 07:13:43AM +1000, Peter Hutterer wrote:
>> Trackballs are effectively stationary devices and can be positioned at any
>> rotation. They are also employed by users with impaired dexterity which
>> sometimes implies that they are positioned at an non-default angle to make the
>> buttons easier to reach.
>>
>> Add a config option for rotation for trackball devices. Currently only
>> supported for 90-degree angles, if there is a need we can add more angles
>> later.
>>
>> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
>> ---
>> I'm not 100% sure yet that this is the feature we should have. Rotation
>> itself is important for trackpoints, no doubt, but I'm contemplating whether
>> to make this a more generic form like a matrix. It makes decisions of
>> precedence a lot easier, especially if we need to add other options later
>> that may overlap or conflict with rotation (admittedly, it just shifts that
>> decision to the caller). but a matrix can also be misused easier and makes
>> it harder for libinput to detect what the caller wants to do. while this
>> doesn't have a use-case yet for this feature, sometimes knowing what the
>> caller wants to do allows us to modify other features.
>
> a few notes from my meeting with Benjamin today:
> if we expose the matrix, what would we gain: immediate support for
> translation, shearing, scaling and reflection. translation and shearing make
> no sense for relative devices. scaling is effectively only a way to work
> around/against pointer acceleration and we don't want to enable that.
> reflection *could* be interesting but we failed to come up with a reasonable
> use-case where it is needed on relative devices.
>
> so it looks like this API is indeed the best approach.

Given the above (and with Yong Bakos' comment fixed) this series is:

Reviewed-by: Hans de Goede <hdegoede at redhat.com>

Regards,

Hans