Pen tilt y is being replaced with tilt x since 0.36

[daniel-ferguson]

xf86-input-wacom: 0.36
OS: Arch linux
Tablet: Intuos 5 PTH-650/K

I noticed issues with tilt direction being broken in Krita and did some digging...

Is my tablet broken?

Probably not, I plugged the tablet into my laptop running an older version of xf86-input-wacom (0.35.x) and tilt works fine.

Where is the issue occurring

I took a dig into events being emitted by the kernel driver for my wacom pen with:

evtest | grep TILT

ABS_TILT_X and ABS_TILT_Y events are being emitted separately, with values corresponding to the angle I'm holding the pen.

On the other hand, looking at xorg events with:

xinput test $pen_id

Gave me rows like:

motion ... a[3]=39 a[4]=39 ...

Where a[3] and a[4] are always equal, and respond to changes in x tilt. Looking at the source for this project indicates they represent x and y tilt, respectively.

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I took a dig through source changes which have occurred since xf86-input-wacom 0.35 and spotted this line, which looks like it'd explain the issue I'm seeing: https://github.com/linuxwacom/xf86-input-wacom/blob/master/src/wcmFilter.c#L317

ds->tilty = wcmFilterAverage(state->tiltx, common->wcmRawSample);

It appears there's a typo here, tiltx is being averaged, then being assigned to tilty - I think the line should read:

ds->tilty = wcmFilterAverage(state->tilty, common->wcmRawSample);

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Let me know if there's anything I can do to help with this, and thank you for your efforts maintaining this great project 👍

edit: added a little more info to line of source code

[daniel-ferguson]

Just a quick follow-up - I've rebuilt 0.36 with the change illustrated above and, after a reboot, seem to be getting correct tiltys showing up when inspecting events with xinput test $pen_id.

Brushes in krita are behaving well too.

[jigpu]

Ouch, good find. Looks like I authored the offending commit (527fa95) and was bit by the classic last-line effect...

Would you mind providing a copy of your fix? You can either send a git patch directly to the linuxwacom-devel mailinglist, attach a git patch to this bug, or make a pull request with the fix. In any case, please be sure to include the following three lines at the end of your commit message for tracking purposes:

Ref: https://github.com/linuxwacom/xf86-input-wacom/issues/11
Fixes: 527fa95c29 ("Refactor coordinate averaging to seperate function")
Signed-off-by: $YOUR_NAME <$YOUR_EMAIL>

[daniel-ferguson]

^ Sorry for the noise, github's commit message link formatting surprised me a few times.

[jigpu]

Fix has been included with the 0.36.1 release.