[Xournal-devel] xournal touchscreen updates / windows to-do

[Denis A. <au...@ma...>]

Dear all,

I finally have a laptop with dual pen+touch input (a Thinkpad Yoga), so 
some updates have been happening to how xournal handles input events.

1. Touch device options and tweaks:

You'll see from the last few commits (in the git and cvs repositories at 
sourceforge.net) that there's now a bunch of new options and menu 
entries related to touch devices -- one is the "touchscreen as hand 
tool" option to map a touch device to the hand tool, another is a "pen 
disables touchscreen" option to disable the touch device in xournal when 
the pen is near the screen, and there are other tweaks to the event 
processing code. Note in particular, if you find that the interface 
becomes non-responsive and the pen won't stop drawing, the option 
ignore_btn_reported_up in the config file -- no menu entry for that one; 
the new default is true, the old default behavior was false. The old 
behavior is safer in terms of restoring sanity if xournal somehow fails 
to receive a button-release event, but it doesn't work at all with the 
Thinkpad Yoga's touchscreen.

This is almost exclusively for Linux since in Windows the touch device 
is not recognized as a separate xinput device. (one could still use "pen 
disables touchscreen" to disable the Core Pointer when the pen is in 
range in windows as well, except the Core Pointer seems to already 
disable itself too much in Windows -- see below).

It would be great if some of you with various touch/pen devices can test 
in the coming days and confirm that the new behavior doesn't cause any 
annoying regressions, and that the various new options do make life with 
a touchscreen somewhat better.

2. Windows:

After installing MinGW more or less successfully, I'm again able to 
build xournal for windows. I got immediately hit with the issue of 
xournal crashing when done editing a text box, which has been reported 
here. Unfortunately, as soon as I tried to install gdb and add debug 
output to the code, the problem disappeared. I'll try to reproduce it 
again another day... however, if you have a working MinGW development 
environment, basic expertise in debugging, and do encounter this bug and 
can figure out where exactly things get stuck at the end of a text box 
editing action, that would be extremely useful. (Most likely, you want 
to attach gdb to a running instance of xournal and interrupt the 
execution when it gets stuck to get a backtrace.) Also, if some of you 
experience this bug intermittently, ideas about what causes it to happen 
or disappear would be helpful.

Another bug I'd like to figure out is the drawing area being 
unresponsive to touch/mouse/... after drawing with the pen with xinput 
enabled (and the wacom driver), until one clicks somewhere outside of 
the drawing area. (There seem to be other variants of this issue). 
Debugging the event code suggests that GTK+ never passes the button 
press and pointer motion events to us -- presumably using the wacom pen 
puts GTK+ in a mode where Core Pointer events don't get passed along 
anymore.  If this is a GTK+ bug, a custom GTK+ DLL might need to be 
packaged with the 'semi-official' Xournal win32 build. This one should 
be within my abilities -- I understand the GTK+ xinput code reasonably 
well, though I've never looked at the win32 side of it.

Yet another issue is the general trouble with fonts and text and export 
/ printing. I am not sure I am competent to do anything here, but I'll 
take a look. Ditto for the bug that causes copy-paste to go "numb" 
sometimes (the clipboard starts giving xournal the wrong data at some 
point, and when this happens xournal just rejects the copy-paste 
attempts instead of crashing).

Any other bugs of a similar severity level (things that crash, don't 
work at all, or are generally major annoyances to using xournal in 
windows) ?

Ah, another note: those of you who report that the beginning of pen 
strokes is sloppy / missing / slow to appear:
in Windows 8.1 at least, I solved this by going to Control Panel -> Pen 
and Touch -> disable Flicks


Thanks in advance for any feedback you can provide, either on touch 
device behavior in linux or on the main windows issues to be sorted out.

Best,
Denis








-- 
Denis Auroux                             au...@ma...
University of California, Berkeley       Tel: 510-642-4367
Department of Mathematics                Fax: 510-642-8204
817 Evans Hall # 3840
Berkeley, CA 94720-3840