[solved] two pdf-presentations - switching slides simultaneously

saciel · 2008-03-16 03:25:32

[note: I changed the subject to better suit the solution we found. (orig: dual head: two WMs, one keyboard -> I want simultaneous input!)]

Apart from my Xinerama setup I configured Xorg to run separte WMs on both screens. By default only one of them has the mouse and/or keyboard focus.

But I would like to have simultaneous input, especially for the keyboard!

It's for a talk at a conference for which I have created a (pdf) presentation. What I'm trying to do is running two versions of my presentation, each on one of the heads. The beamer VGA-ouput shall show the plain presentation, while my laptop ought to give me additional notes. However, both heads should change slides simultaneously with one single click.

Any ideas on how to get simultaneous input on both screens? Or might there be another goal to achive this. All I want is two instances of xpdf that both change slides on hitting space-key. I don't really care how it is done, two heads sharing the same input was just my first idea.

Last edited by saciel (2008-03-17 03:57:41)

retsaw · 2008-03-17 00:52:25

From reading the Xpdf man page, Xpdf has an option to run a remote instance of Xpdf which can also be sent commands remotely. You might be able to take advantage of this by running the "remote" instance on your VGA output and set a keybinding for Xpdf in your .xpdfrc which both switches to the next page and sends a command to the remote instance of Xpdf to do the same. I haven't tried this myself (and don't currently have a dual head setup to test it with), but it seems like it should work.

saciel · 2008-03-17 01:50:17

Thanks a lot. This is even better than the option I thought about and it works, at least with some little work-arounds. It obviously isn't possible to have one xpdf server connected to two remote instances. So I start one remote session with

xpdf -remote myNotes presentation.with.notes.pdf

Now I can advance pages with the shell command

xpdf -remote myNotes -exec nextPage

Then I'm going for the keybinding and start a conventional session of xpdf with

xpdf presentation.beamer.pdf

Here is where the workaround is needed as I try to bind space to advance pages in both, current and remote session:

nextPage run(xpdf -remote myNotes -exec nextPage)

However, bound commands in the xpdfrc are seperated only by spaces, so the parser thinks the run-part are several commands. Quoting the string or \-ing the spaces doesn't help. I tried to alias it in .bashrc but run invokes sh, not bash. So for now - I couldn't come up with a better idea I have a shellscript that executes the remote-page-advance command to get rid of the spaces in xpdfrc. Also, I always have to uncomment this bind line if not running a two screen presentation because otherwise clicking space will always invoke an empty xpdf session which gets annoying pretty soon. Probably I'm going to write a shell script (which I will then post here) that automatically does the keybinding invokes two sessions on the appropriate screens and so on...

Anyway, it's wokring fine with about half a second of delay in the remote session but that's ok if my notes don't pop up instantly. I just wouldn't start the beamer presentation as the remote session.

Sigi · 2008-03-17 03:47:03

saciel wrote:

Anyway, it's wokring fine with about half a second of delay in the remote session but that's ok if my notes don't pop up instantly.

This even gives you a little more time to think what you're going to say before the audience can see the slide

saciel · 2008-03-17 03:54:02

Sigi wrote:

This even gives you a little more time to think what you're going to say before the audience can see the slide

It's not a bug... it's a feature At conference presentations one uses to talk too fast anyway. So the delay forces the lecturer to slow down a little bit and give the audience some breathing time between the slides.

However, I quess I'd rather have the delay on my notes, not on the beamer, anyway.

saciel · 2008-03-17 04:09:00

So here is what I call SI(E)Mple PREsentation -- siempre -- for now. A very rudimental shell script solution. Siempre can open two pdf-files and manages the creation and deletion of the required keybindings. The two instances have to be arranged on the screen(s) manually after. Maybe I'll add some more options later.

#!/bin/bash

#SI(E)Mple PREsentation - start two instances of xpdf with simultaneous page
# turning enabled;

if test \( -z $2 \); then echo "Usage: siempre <file.for.audience> <file.with.notes>"; exit; fi


# commandline-parameters are kept simple for now; you can just pass the name
# of two pdf-files; spaces in file names are NOT SUPPORTED;
BEAMER=$1;
NOTES=$2;


# path to your standard xpdfrc file:
CONFIG="~/.xpdfrc"; #/etc/xpdfrc


# create a temporary xpdfrc (based on existing configuration), adding
# keybindings for simultaneous page-turning; any previous bindings for 'space'
# and 'backspace' are overwritten;
mkdir /tmp/siempre;
if test \( -n "$CONFIG" \); then cp $CONFIG /tmp/siempre/xpdfrc; fi
echo "bind     space any nextPage run(/tmp/siempre/xpdf_next)" | cat - >> /tmp/siempre/xpdfrc;
echo "bind backspace any prevPage run(/tmp/siempre/xpdf_prev)" | cat - >> /tmp/siempre/xpdfrc;


# create temporary scripts for page-turning in the remote session; this is
# necessary as the "run" command in the keybindings cannot handle spaces;
echo -e "#!/bin/bash\nxpdf -remote 2ndInstance -exec nextPage" > /tmp/siempre/xpdf_next;
echo -e "#!/bin/bash\nxpdf -remote 2ndInstance -exec prevPage" > /tmp/siempre/xpdf_prev;
chmod 744 /tmp/siempre/xpdf_{next,prev};


# invoke both instances of xpdf; first one is the beamer presentation, second
# one is for additonal notes; kill the note-instance when the main presentation
# is closed;
xpdf -remote 2ndInstance $NOTES & xpdf -cfg /tmp/siempre/xpdfrc $BEAMER;
xpdf -remote 2ndInstance -quit;


# delete temporary files;
rm -r /tmp/siempre/;

Last edited by saciel (2008-03-17 13:38:05)

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#1 2008-03-16 03:25:32

[solved] two pdf-presentations - switching slides simultaneously

#2 2008-03-17 00:52:25

Re: [solved] two pdf-presentations - switching slides simultaneously

#3 2008-03-17 01:50:17

Re: [solved] two pdf-presentations - switching slides simultaneously

#4 2008-03-17 03:47:03

Re: [solved] two pdf-presentations - switching slides simultaneously

#5 2008-03-17 03:54:02

Re: [solved] two pdf-presentations - switching slides simultaneously

#6 2008-03-17 04:09:00

Re: [solved] two pdf-presentations - switching slides simultaneously

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