Dear developers,

let me first introduce you to Ipe, which is a multi platform drawing
application mainly aimed at academic publication drawings with LaTex and
has been made Pen-ready lately. Unfortunately it does not work with the
latest drivers and kernels because the Qt-Interface seems to introduce
coordinate jumps; seemingly because the Qt-interface has not been
upgraded yet to work with the latest driver.

The developer of Ipe, Otfried Cheong, does not have a Tablet for testing
himself. I would like to make you aware of the situation and ask you to
file the appropriate Qt-Bug report (details of the bug as it appears to
me below), so that the issue can be handled at top level directly
without taking any more circles. I would also like you to have a close
look at Ipe, to make sure that it works well with the driver and if
necessary provide some support to the developer.

---

Ipe:

Ipe is working well with older pen-drivers. Native output formats are
ipe_xml, eps and pdf. It supports layers and can also import and export
most common graphic formats reasonably well. It has a very efficient
user interface, with emphasis on consistent appearance (style sheets),
excellent snapping functions and is extensible through c or lua scripts.
It can also very well be used for general drawings on Tablet-PCs.
Together with Xournal I consider Ipe to be the best Linux Pen-ready
application for practical use now. Except for me there seem to be no
other Ipe pen-users yet.

Ipe homepage:

http://ipe7.sourceforge.net/

Ipe source:

http://sourceforge.net/projects/ipe7/files/ipe/7.1.0/

Please take the latest Ipe 7.1.1 from there, decompress and just follow
the step by step compiling instructions in the install.txt there. For
import of common formats (pdf, svg, fig) you also need to install the
tools (not necessary for testing):

http://sourceforge.net/projects/ipe7/files/tools/

The Ipe pen-handling code is in Canvas::tabletEvent(QTabletEvent *ev)
starting on Line 234 in:

ipe-7.1.1/src/ipecanvas/ipecanvas_qt.cpp

Please have a look at this function and test with any tablet yourself as
confirmation. The function uses the Qt-interface only.

---

Coordinate jumps:

The latest standard Ubuntu kernel driver is working fine for me with
most applications (Xournal, etc.) on Ubuntu 11.04, 32bit (Motion
Computing Tablet-PC LE1600 and LE1700). Ipe is also working well with an
older self compiled driver with Ubuntu 10.04 LTS on a hp2710p. The
working applications seem to either interface to the pen-driver directly
or simply use the mouse mode of the driver.

The pen functions of Krita and Ipe are broken here with the latest
kernel and driver, both are interfacing through Qt. The same bug appears
on the Tablet-PCs as well as on my Desktop-PC with a Wacom-Bamboo. My
conclusion in the Ipe-Bug Report:

"I strongly suspect that the underlying cause of all the screw ups is
the change of the coordinate scaling in the driver interface, which has
not been properly changed in the Qt interface. It seems that by not
regarding the new scale factor in Qt the pen is now mapped to a tiny
area of the screen in the upper left corner, then Qt gets further
screwed up, reverts to mouse mode and the coordinate buffer overflows."

For details please see the full Ipe bug report here:

http://sourceforge.net/apps/mantisbt/ipe7/view.php?id=62&nbn=6#bugnotes

Please check for the correctness of my educated guesses there. Some
might be wrong; I have not programmed seriously anymore for almost 2
decades, don't know much about Linux and Qt, but have some solid
embedded hardware background. Please take the appropriate steps to get
the issue solved.

Thanks in advance for your help and the driver,
regards,
Gerhard Mesenich


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