Re: [Xournal-devel] Win32 Version

[Felix B. <fe...@fb...>]

Hi Denis,

thank you for your detailed reply!

1) What I mean by "choppy" is that pen strokes look exactly like mouse
strokes. (That is the rate at which the stylus position is sampled is
much lower than is expected from a pen.) I do not experience the
symptom of the first 0.2 seconds of each stroke being lost.

2) Enabling or disabling "XInput" in Xournal does not make any difference.

3) As far as I can tell, using Xournal's DLLs or Gimp's DLLs with
Xournal does not make any difference.

4) In Gimp both the sample rate is high (strokes are not choppy) and
pressure sensitivity works.

5) To get XInput events (in Gimp or Xournal) I had to install Wacom's
Tablet PC drivers. The tablet drivers coming with Windows 7 did not
suffice. In fact, this is strange as all Windows apps that use pen
input work perfectly without Wacom's drivers.

6) IIRC, when using XInput, you have to specify the "name" of the
pointer you want to receive extended input events for. However I
cannot find any option in Xournal where you can specify which pointer
to use. How is this handled in Xournal? Maybe on my system Xournal
simply selects the wrong "pointer"?

7) I might actually try to recompile Xournal for Windows, however I
have no idea how to do this. You mentioned that Dirk Gerrits provided
instructions on how to do so. Are these instructions available
somewhere?

Thanks a lot!

Felix

2009/11/25 Denis Auroux <au...@ma...>:
> Hello, and thanks for your report! I am not sure that I'll be very helpful
> -- I am the main developer of Xournal, but I am completely ignorant of
> everything that regards Windows since I don't use it...
> in particular I don't really understand the specifics of how Windows
> processes input events and how GDK-Win32 converts them into GDK events,
> which is a shame because I'm sure it's at the heart of the choppiness issue.
>
> So, if anyone on this list feels competent to look into issues with the
> port, I'm happy to delegate! That being said:
>
>> Pen input does not work properly on my system:
>> * The strokes are choppy.
>
> I think I have that problem too on my system (XP) -- or perhaps your strokes
> are even choppier than mine! I'd say on my systems (an Acer C310 and a
> Lenovo X200, both using Windows XP Tablet) the first 0.2 seconds or so of
> each stroke are lost or replaced by a single line segment, and then things
> work fine; but this only happens if drawing with the pen, not when using a
> mouse. So if I draw a long curve, it looks pretty good, but if I write
> quickly in my chicken-scratch handwriting that involves lots of short
> strokes, it's completely garbled. Is your issue kind of similar, or is it
> worse ? It is my understanding that Dirk Gerrits (who kindly provided the
> instructions on how to get xournal to compile under windows) does not have
> this problem.
>
> This is obviously a major issue, and I'm planning to look into it with my
> modest abilities when I find time (= probably not immediately since I'm busy
> with real work at the moment, but hopefully in finite time).
> It helps that I'm experiencing the issue, so I can at least see what happens
> if I tinker with the source code in the hope of making it better.
>
> Generally speaking, recompiling with the "#define INPUT_DEBUG" line in
> src/xournal.h uncommented will produce lots of debug output about device
> input, which might or might not be of any use. [Note: don't send raw debug
> output, it's pretty useless unless annotated with a description of what
> you're doing at the same time, for example "Now I'm about to draw a stroke
> with the pen, with xinput enabled"].
> Because one of the issues is speed / processing time, modifying the debug
> code in src/xo-callbacks.c to also output the event's timestamp and the
> system time when the event is processed would presumably be useful.
>
>> * Pressure sensitity does not work.
>> * Nonetheless: XInput is available and selected in the Options menus.
>> (Pressure sensitivity is selected as well.)
>
> Interesting! For me XInput is not available at all (and hence there's no
> pressure sensitivity either). Are you using the DLLs that came with the
> xournal package (in particular libgdk-win32-2.0-0.dll), or did you already
> have them installed on your system (perhaps from GIMP)?
>
> If anyone can check: it may be that the version of libgdk-win32 packaged
> with xournal (which is the "official" build from
> http://www.gtk.org/download-windows.html) does not have XInput emulation
> enabled, while Gimp's version has it? Or it may be that gdk-win32 only
> supports XInput with more recent versions of windows (I only have XP
> Tablet)?
>
> (Perhaps you can test: try using either the DLLs that came with xournal or
> those you already had on your system, and see if it makes a difference for
> xournal, and if it makes a difference for gimp. My understanding is that
> windows looks for the DLLs both in the executable's runtime directory and in
> the windows directories; try moving the DLLs around to force xournal to use
> one set of DLLs or the other).
>
> Also, another important note: in principle, there's a lot more processing of
> strokes to do with XInput enabled, so it might accentuate the choppiness. Do
> you notice a difference in responsiveness when you turn XInput on or off in
> the Options menu?
>
> Pressure sensitivity is probably a secondary issue (or maybe not implemented
> in GDK-win32 at all), so I'm not going to worry about it -- once XInput
> works properly (if it can be made to work), pressure sensitivity should also
> start working.
>
>> * Also: The pen works fine in Gimp.
>
> By that I assume you mean: strokes are not choppy, and pressure sensitivity
> works?
>
> When I have time (again, probably not soon), I'll try to look into the Gimp
> source code and see if their Windows port does anything special to handle
> pen input or if it just relies on GDK.
>
>> If there is anything else I can try, to help resolve this issue,
>> please let me know.
>
> If you have time and inclination, checking a few of the things mentioned
> above would be helpful, namely:
>
> 1) whether responsiveness is affected by selecting / deselecting "Use
> XInput" in the Options menu.
>
> 2) whether responsiveness is also an issue when you try to draw with a mouse
> or touchpad instead of a pen. (This is a bit hard to compare, because the
> pen typically sends a lot more input data).
>
> 3) checking whether you have other versions of the GDK/GTK DLLs in your
> windows directory, perhaps coming from Gimp, whether Xournal would work
> better with Gimp's DLLs, and whether Gimp would work worse with Xournal's
> DLLs.
>
> Your feedback is highly appreciated. I'm sorry that I can't promise any
> concrete improvements in return...
>
> Thanks,
> Denis
>
> --
> Denis Auroux                    au...@ma...
> MIT Department of Mathematics   ON LEAVE AT UC BERKELEY
> 77 Massachusetts Ave. 2-236
> Cambridge MA 02139
>