[Interest] Astropad and Tablet events
Alexei Gilchrist
te100 at runbox.com
Mon Mar 28 05:44:43 CEST 2016
Hi,
Got the qt.qpa.input.tablet events logging and got the results below. I
also compiled the tablet tester from
https://github.com/callaa/QTabletTest and get the same behaviour so
it’s not a PyQt problem.
I’ve included the events as seen at the application level in the
output stream for both a Wacom tablet and Astropad.
Wacom:
—
qt.qpa.input.tablet: proximity change on tablet 0: current tool 2 type 1
unique ID 70514773065729
<PyQt5.QtGui.QTabletEvent object at 0x10ab97168> 171
TabletEnterProximity
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 356.0, 399.0 root pos 698.0, 636.0 buttons 0x0
pressure 0.00 tilt 0, 0 rotation 0.00
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 357.0, 399.0 root pos 699.0, 636.0 buttons 0x0
pressure 0.00 tilt 0, 0 rotation 0.00
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 358.0, 400.0 root pos 700.0, 637.0 buttons 0x0
pressure 0.00 tilt 0, 0 rotation 0.00
: (lines suppressed)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 365.0, 433.0 root pos 707.0, 670.0 buttons 0x0
pressure 0.00 tilt 0, 0 rotation 0.00
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 365.0, 434.0 root pos 707.0, 671.0 buttons 0x1
pressure 0.00 tilt 0, 0 rotation 0.00
TabletPress: pointer=1 pressure=0.0 tilt=(0,0)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 365.0, 434.0 root pos 707.0, 671.0 buttons 0x1
pressure 0.65 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6470588445663452 tilt=(0,0)
MousePress
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 365.0, 436.0 root pos 707.0, 673.0 buttons 0x1
pressure 0.65 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6480811834335327 tilt=(0,0)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 365.0, 436.0 root pos 707.0, 673.0 buttons 0x1
pressure 0.65 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6451514363288879 tilt=(0,0)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 370.0, 445.0 root pos 712.0, 682.0 buttons 0x1
pressure 0.64 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6421911716461182 tilt=(0,0)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 381.0, 463.0 root pos 723.0, 700.0 buttons 0x1
pressure 0.64 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6421911716461182 tilt=(0,0)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 384.0, 469.0 root pos 726.0, 706.0 buttons 0x1
pressure 0.64 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6431372761726379 tilt=(0,0)
MouseMove
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 386.0, 474.0 root pos 728.0, 711.0 buttons 0x1
pressure 0.64 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6431372761726379 tilt=(0,0)
MouseMove
: (lines suppressed)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 388.0, 486.0 root pos 730.0, 723.0 buttons 0x1
pressure 0.61 tilt 0, 0 rotation 0.00
TabletMove: pointer=1 pressure=0.6117647290229797 tilt=(0,0)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 381.0, 478.0 root pos 723.0, 715.0 buttons 0x0
pressure 0.00 tilt 0, 0 rotation 0.00
TabletRelease: pointer=1 pressure=0.0 tilt=(0,0)
MouseMove
MouseRelease
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 381.0, 478.0 root pos 723.0, 715.0 buttons 0x0
pressure 0.00 tilt 0, 0 rotation 0.00
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
70514773065729 pos 381.0, 478.0 root pos 723.0, 715.0 buttons 0x0
pressure 0.00 tilt 0, 0 rotation 0.00
qt.qpa.input.tablet: proximity change on tablet 0: current tool 2 type 1
unique ID 70514773065729
<PyQt5.QtGui.QTabletEvent object at 0x10ab97168> 172
TabletLeaveProximity
—
So a bunch of events while the pen hovers, then the first event with
buttons 0x1 with pressure >0 gets reported as a TabletPress event and
the rest as TabletMove events. Mouse events get released for some of the
tablet events but not all.
Then the next event with buttons 0x0 and pressure=0 gets reported as a
TabletRelease.
Astropad:
—
qt.qpa.input.tablet: proximity change on tablet 0: current tool 2 type 1
unique ID 4582773633348209
TabletEnterProximity
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 193.0, 302.5 root pos 535.0, 539.5 buttons 0x64
pressure 0.00 tilt 29, 9 rotation 0.00
TabletPress: pointer=1 pressure=0.0 tilt=(29,9)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 193.0, 302.5 root pos 535.0, 539.5 buttons 0x1
pressure 0.09 tilt 29, 9 rotation 0.00
TabletRelease: pointer=1 pressure=0.0941176488995552 tilt=(29,9)
MousePress
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 191.1, 302.3 root pos 533.1, 539.3 buttons 0x1
pressure 0.09 tilt 29, 9 rotation 0.00
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 189.0, 296.8 root pos 531.0, 533.8 buttons 0x1
pressure 0.09 tilt 29, 9 rotation 0.00
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 189.0, 296.8 root pos 531.0, 533.8 buttons 0x1
pressure 0.07 tilt 29, 9 rotation 0.00
MouseMove
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 187.8, 285.3 root pos 529.8, 522.3 buttons 0x1
pressure 0.15 tilt 29, 9 rotation 0.00
MouseMove
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 187.8, 286.7 root pos 529.8, 523.7 buttons 0x1
pressure 0.20 tilt 29, 9 rotation 0.00
MouseMove
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 199.9, 266.4 root pos 541.9, 503.4 buttons 0x1
pressure 0.22 tilt 29, 9 rotation 0.00
MouseMove
: (lines suppressed)
qt.qpa.input.tablet: event on tablet 0 with tool 2 type 1 unique ID
4582773633348209 pos 333.1, 336.1 root pos 675.1, 573.1 buttons 0x0
pressure 0.00 tilt 27, 4 rotation 0.00
MouseRelease
qt.qpa.input.tablet: proximity change on tablet 0: current tool 2 type 1
unique ID 4582773633348209
TabletLeaveProximity
—
No hover events obviously, but first event has buttons 0x64 pressure
0.00 which gets reported as a TabletPress but then the next event with
buttons 0x1 pressure 0.09 gets reported as a TabletRelease and
subsequent events are reported as Mouse despite continuing to receive
tablet events.
So it could be the change of buttons signature is getting interpreted as
lifting the pen. Seems like a bug in both Astropad and QT. Astropad
should send the first event as buttons 0x0 but QT could be made more
robust since it’s clearly still receiving tablet events (with
pressure, tilt etc) but just doesn’t interpret them properly.
Any idea what I’d need to patch in QT to fix this?
Alexei
On 23 Mar 2016, at 0:11, Alexei Gilchrist wrote:
> On 22 Mar 2016, at 20:18, Rutledge Shawn wrote:
>>> On 22 Mar 2016, at 02:30, Alexei Gilchrist <te100 at runbox.com> wrote:
>>>
>>> Hi all,
>>>
>>> I'm trying to use Astropad (app provides OsX tablet interface with
>>> an iPad) with an app I’ve written and I'm getting odd results with
>>> tablet events in QT. First of all, I've been in contact with the
>>> devs and they seem to think it's a QT bug rather than an Astropad
>>> bug, and in any case Astropad works with other graphics programs
>>> that I've tried.
>>
>> Why do they think it’s a Qt bug? Maybe they should tell us what we
>> are doing wrong if they know.
>>
>> I guess there must be a Mac daemon which tries to emulate a Wacom by
>> sending the same events? It’s not only for Qt applications, right?
>> But Qt applications work with a real Wacom but not Astropad, so they
>> must not be emulating the events exactly the same.
>
> It is running a daemon that handles communication with the
> corresponding app on an iPad. One reason to believe it’s a QT bug is
> that Astropad works fine with other applications such as Gimp,
> SketchbookEpress, InKist, Photoshop, all respond to pressure
> variations so multiple toolkits are able to interpret the synthesised
> events correctly.
>
>> You can enable the logging category qt.qpa.input.tablet to see how
>> the events come in (the code is in qnsview.mm).
>
> Cool. Didn’t know that. I Need to figure out how to display the
> logging events in pyqt as setting
>
> export QT_LOGGING_RULES='qt.qpa.input=true'
>
> or editing ~/.config/QtProject/qtlogging.ini is not reporting to the
> console, maybe the python logging module which I’m using is taking
> over stderr. Will play around and see if I can get some feedback.
>
>>
>>> I'm coding in python using pyqt and have Python 3.5.0 and QT 5.5.0
>>> installed.
>>>
>>> At the level of QWidget you get an initial TabletPress event with
>>> pressure=0 followed immediately by a TabletRelease event with
>>> pressure>0 at which point the rest of the stroke is only reported as
>>> mouse events, with are low frequency and don’t contain pressure
>>> info.
>>>
>>> Astropad:
>>>
>>> TabletPress: pointer=1 pressure=0.0 tilt=(27,12)
>>> TabletRelease: pointer=1 pressure=0.13333334028720856 tilt=(27,12)
>>> MousePress
>>> MouseMove
>>> MouseMove
>>> ...[ many MouseMove ]...
>>> MouseRelease
>>>
>>> Works as you'd expect with Wacom tablet, though accepting the tablet
>>> events does't stop the mouse events being fired (minor niggle):
>>
>> That’s https://bugreports.qt.io/browse/QTBUG-47007 It’s probably
>> always been that way, at least in Qt 5, because the platform plugins
>> are doing this mouse emulation when necessary. (In some cases the
>> window system will send a synthesized mouse event itself, in which
>> case we don’t need to.) Plugins don’t pay attention to whether
>> the tablet event was accepted or not, because sending events from the
>> platform plugin into the application is asynchronous, going through a
>> queue. We assume the tablet event is rejected because that’s the
>> default policy (outside of QtQuick where we assume an event is
>> accepted), so the default is that the application does nothing, and
>> then it gets a mouse event (so that you can use the stylus to
>> interact with widgets etc.) AFAIK there isn’t a nice mechanism to
>> wait and see whether the app accepted the tablet event or not; we’d
>> have to wait until the asynchronous delivery is done, somehow.
>>
>> In older Qt versions, you needed the mouse event (which means you
>> should reject the tablet event, according to the docs) in order to
>> find out what buttons on the stylus were pressed. But if you reject
>> the tablet press event, you don’t get movement updates as tablet
>> events, and the mouse events are compressed (as you noticed). Now,
>> QTabletEvent has buttons too, so you no longer need to do that, but
>> there may still be some legacy applications that are already written
>> to work that way. So I’m not sure whether we should fix that now,
>> or will it be seen as a behavior change which breaks applications? I
>> guess fixing it in 5.7 or later ought to be OK at least. But it’s
>> nontrivial to fix.
>
> This is not much of a problem as a TabletPress is delivered before a
> MousePress so it’s easy to toggle a pen_down variable and ignore
> mouse events.
>
>>
>> QTBUG-51617 is about labelling the mouse events as synthesized so
>> that you can at least easily know which mouse events to reject. It
>> should be fixed now on X11 (for 5.6.1), we just need to make sure the
>> other platforms work consistently. So you can have a mouse handler
>> which ignores such events.
>
> Will take a look at those, it would be a more robust solution in case
> the ordering of events should change.
>
>>
>>> TabletPress: pointer=1 pressure=0.4313725531101227 tilt=(0,0)
>>> MousePress
>>> TabletMove: pointer=1 pressure=0.45098039507865906 tilt=(0,0)
>>> MouseMove
>>> TabletMove: pointer=1 pressure=0.45098039507865906 tilt=(0,0)
>>> TabletMove: pointer=1 pressure=0.4470588266849518 tilt=(0,0)
>>> ...[ many MouseMove and many more TableMove ] ...
>>> TabletRelease: pointer=1 pressure=0.0 tilt=(0,0)
>>> MouseMove
>>> MouseRelease
>>>
>>> At the level of QApplication I'm seeing TabletEnterProximity and
>>> TabletLeaveProximity events as you'd expect.
>>
>> Cool. Are you using an iPad Pro? Otherwise it can’t detect
>> proximity, but maybe it synthesizes those events when you press?
>
> Yes, using an iPad pro. Astropad mirrors the mac screen to the iPad
> pro and captures pencil and finger events synthesising corresponding
> events on the mac. Effectively creating a Cintiq like tablet. I’m
> guessing they add the proximity events for compatibility with apps
> that are coded for a wacom tablet and looking for the hover (iPad pro
> does’t detect pencil proximity).
>
> When I first contacted the Astropad devs you could trick their code
> into sending some sequence that QT transmitted with TabletMove events
> for one stroke after doing a stroke on a wacom tablet. I pointed out
> the problem and sent then a test app and got back:
>
>> I wanted to let you know that we found a workaround for this. It does
>> appear to be a bug in QT, but we figured out what event from Astropad
>> was confusing it. By removing this event (which doesn’t appear to
>> be necessary) QT once again works with Astropad.
>
> Since then, they’ve updated their code and no TabletMove events are
> generated at all. Not sure why they concluded that they’d created a
> workaround, but they’re no longer responding to me pestering them :P
>
> Alexei
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