[RFC evemu] Record active slots in syn report comments

[Benjamin Tissoires]

Hi Daniel,

On Tue, Sep 22, 2015 at 5:28 AM, Daniel Martin <consume.noise at gmail.com> wrote:
> Hi,
>
> I've hacked up a patch for evemu to print the active slots in addition
> to the syn report. I did this to see ghost reports much more easy.
> Scrolling through the report log was to error prone for me. It basicly
> looks like:
>     E: 12.345678 0000 0000 0000 # ------------ SYN_REPORT (0)
> ---------- 1234ms 0[12] 3[45]
> Here slot 0 (tracking id 12) and slot 3 (tracking id 45) are active.

I am not particularly a big fan of this. Especially because it feels
like opening a can of worms. People will also want to have a full
state of the buttons for instance. In addition, the syntax is not that
easy to follow and I feel like it will just confuse users.

For debugging multitouch devices (and stuck fingers), I just use
mtdiag-qt (https://github.com/bentiss/mtdiag-qt). If there is a ghost
dot, mtdiag-qt will show it (though you won't have the tracking id
here).

Also, for debugging your specific ghosts, I think a simple python
script with the python evemu interface should be enough.

>
> Atm. evemu is agnostic to any state, adding this would change this.
> But, imho it's a nice debugging feature. Would this be acceptable?
> Then I'll try to make the patch pretty and send it.
>

Sorry, but that's a NACK from me. I'd prefer having no state in evemu,
or we will end up in having a libinput like tool and the evemu-record
will not make any sense at all (I mean, we won't be able to trust it
as the output that is coming out of the kernel).
But if others really want it, I can always change my mind.

Cheers,
Benjamin