[Development] QTabletEvent in QML

Dean Floyd dean.floyd.lkml at gmail.com
Fri Jul 11 14:57:52 CEST 2014

On Fri, Jul 11, 2014 at 11:58 AM, Rutledge Shawn <Shawn.Rutledge at digia.com>

> On 11 Jul 2014, at 10:34 AM, Dean Floyd wrote:
> > I have been using the Wacom Cintiq HD 24 Touch for some of my research
> efforts, and I have tried to use MultiPointTouchArea to handle the touch
> events, however, this has not lead to a great deal of success. To remedy
> the situation, I decided to use the Wacom SDK to intercept these events and
> create my own QML component to do what MultiPointTouchArea usually does,
> which isn't awfully fast with the signal emitting and all, but sufficiently
> smooth - I use touch events to control a camera in a 3D scene graph.
> Yeah there is QTBUG-39572 for Linux, but if you are using the Wacom SDK I
> suppose you must be on Windows.  We plan to get touch working with Wacom
> touch devices.  I guess your Cintiq is different than the Bamboo
> relative-touch device (more like a touchpad) which I test with sometimes.

I'm actually on a Macintosh, and some of the boys here are on Windows. By
Wacom SDK, I meant the Feel Multi Touch API. MultiPointTouchArea receives
touch events generated by the Magic TrackPad on iMac, but not from Cintiq.
Do you think this is still related to QTBUG-39572?

 > Now, I would like to draw using the Wacom Pen, and, although I can do
> this through QWidget::tabletEvent(), I was not able to find a suitable QML
> component which offers the same tabletEvent() functionality. I see some
> examples using MouseArea to draw with a pen, but I would like to be able to
> distinguish between a mouse and a pen device. In other words, I would like
> to intercept QTabletEvent events within QML. Is there a way to do this? If
> not, could somebody confirm that this is not possible? I would highly
> appreciate any help. Thank you.
> No there is no support for QTabletEvents in QtQuick 2 yet.  I experimented
> with it during a hackathon last year; the patch which adds support for them
> is
> https://codereview.qt-project.org/#/c/74202/
Splendid! I will surely take a look at it. If I manage to further your
efforts on this account, I will most certainly send you patches.

> But after you've got the events in QtQuick, what next?  We are also
> missing public API for creating and manipulating polylines and "ink"
> objects.  You could take the events individually and then try to use Canvas
> in QML, or implement your own means of using QPainterPath in C++, or use
> Qt.labs.shapes from
> https://codereview.qt-project.org/#/admin/projects/playground/scenegraph

I only need the x, y, pressure, and tilt information from the pen. Then I
intend to go back to C++, and use our own rendering libraries. There are
various reasons why we must use QtQuick, in lieu of QtWidgets. Now I gather
this is not possible with QtQuick. Thanks for confirming this.

I looked at Krita, and it appears they are using Wintab for Windows, and
the linux-related drivers and libraries for Linux to intercept pen events.
I did not find anything suitable for Macintosh there. Does Krita handle pen
events in Macintosh? Alternatively, I could use the Cocoa framework to
handle the pen events, but I do not wish to enter a world of pain by trying
to mix QtQuick and Cocoa. Ideally, we would like to have a QML component
that intercepts tabletEvents() akin to QtWidgets.

Thank you for your elaborate answer, and help!

Dean Floyd

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