[PATCH libinput v9 0/2] add orientation, size and pressure of touch

[Andreas Pokorny]

Hi,
The scale of major minor is still an open problem. As you know none of the
reported absinfos contains resolution information. The reported size range
is somewhat similar acress various devices, but needs different scaling
factors.
I have tested the patch with meizu mx4, nexus4, aquaris e4.5, nexus10.
Apart from the already known driver issues, and sometimes astonishing lack
of accuracy it works fine.

So to get to the right values I measured the size of my fingerprints with
different amount of pressure and tried to reproduce the same amount of
pressure on the touch screen and looked at the result.
I am still gathering numbers but for example on mx4 to get to convincing
diameter sizes multiplying the mm value with 2.0 gives good results. On
Nexus 4 I found something between 2.1 and 2.2 to be reasonable. The
measured values on the e4.5 jumped a lot further. I need a more accurate
method for that. In the second round I will probably try to verify the
result with a finger-paint application.


On Mon, Nov 23, 2015 at 5:19 AM, Peter Hutterer <peter.hutterer at who-t.net>
wrote:

> On Fri, Nov 13, 2015 at 08:46:42AM +0100, Andreas Pokorny wrote:
> > Hi,
> > This version contains several rewordings and documentation additions
> from Peter
> > that I missed in the last update, within the first patch of the series,
> while
> > the second patch contains no changes compared to v8.
>
> two high-level questions:
> - do you have a list of devices you've tested on so far that provide useful
>   data?
>   we need to figure out how to handle devices that have invalid ranges,
> such
>   as the T440s on my desk. Range claims 0..255, the max I can trigger with
> a
>   finger is ~10 which atm translates to 0.20mm or so. I can get up to
>   about 20 if I put my whole palm down.
>   either way, we need some strategy in place to deal with those devices and
>   figure out how widespread those are.
>

I havent figured out how to identify the type of touch screen. The device
names / vendor ids .. are rather inconclusive. But yes I think we need some
way to configure a scaling factor.


> - do you have client-side code that makes use of these properties yet? I'd
>   like to have a look at it.
>

We do use that information in the mirclient backend of qt. Not sure if qt
uses the information for anytihing internally - but it is available to
applications.
I mainly test with a plain-mir demo application called
mir_client_fingerpaint .

regards
Andreas
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