[PATCH xf86-input-synaptics 00/12] Clickpad support

[Daniel Stone]

Hi,

On 11 February 2012 15:42, Chase Douglas <chase.douglas at canonical.com> wrote:
> On 02/11/2012 11:51 AM, Daniel Stone wrote:
>> On 11 February 2012 01:25, Chase Douglas <chase.douglas at canonical.com> wrote:
>>> This means we also can't emit touch events while moving the cursor. I
>>> added a patch that ensures the cursor is only ever moved when one touch
>>> is on the device so we can emit touch events when two touches are on the
>>> device.
>>
>> The click case in particular is a difficult one to solve correctly.  I
>> guess you ultimately don't want to crush any movement which is a
>> direct continuation of what came previously, but only new movement.
>> You do need to stop at least some movement though, since otherwise it
>> becomes near-impossible to click something accurately, as your finger
>> will invariably wiggle a bit while doing the physical click.
>
> I believe you are getting at a different issue. I will admit that I
> don't attempt to solve the issue of pointer motion while trying to click
> on a button pad in this patch series. It's a problem that should be
> addressed, I'm just not sure how yet.
>
> What Bryce was saying is when you go from one touch on the touchpad to
> two, but before the button is pressed, the cursor freezes. As soon as
> the button is pressed, the cursor unfreezes so you can click and drag
> with two fingers. On irc, Bryce told me that he tends to leave one
> finger on the buttonpad, move the pointer with another, and press the
> button when he's got the cursor in the right location. That's not
> possible anymore because we inhibit pointer motion when more than one
> touch is on the touchpad.

Right - separate but all related - we hit this too during our clickpad
work.  When the second finger lands, it could be for a scroll, for a
click, or for some other gesture.  So perhaps one approach could be to
not change state until we've definitively established what's going on
- so if you've got pointer motion on going and a second finger lands,
continue tracking the same finger for pointer motion until you've
worked out whether it's a scroll, or a click, or a pure touch gesture.
 We did this to some extent with the scroll stuff, to make sure we
were avoiding unwanted pointer motion when doing two-finger scrolling.

Some of this stuff gets pretty worrying though; people expect to be
able to do two-finger scrolling with one finger, so distinguishing
between that case, and the case with one finger down for clicks and
another for motion, becomes basically impossible.

Cheers,
Daniel