Presentations with mdp

It feels like work is just a constant stream of preparing, travelling for and giving presentations. Brief words and pictures is an excellent for conveying information between small groups of humans. All of these presentations I write in keynote, keynote manages to be light weight, powerful and not horrific to use. As a bonus, my boss feels at home in keynote and is happy to make edits there.

The keynote workflow does not match well to how I think. When dreaming up a presentation I want to shit of a stream of conciousness and have it magically become slides in the right shape.

I might write a series of headings like:

# intro
# who
# meat 
# details
# questions?

I will iterate on these to add bodies, details and more slides.

For quite a while I have wanted a system where I could write plain text and have it become slides. I [wrote][3] about the [sent][4] tool from suckless, but in the end I found it wanting. I have also considered just showing screens of text, but a nightmare DEFCON wireess village talk by Hak5 scared me away. They attempted to just present using just a plain text file and less, but the window size got out of whack and it all fell apart.

Enter mdp

mdp is a terminal presentation program, it takes slides it approximately markdown and takes over the entire terminal as its presentation surface.

Intrigued I used an opportunity to speak at a [local tech event][5] to try out mdp. [The slides][6] from that presentation can be found on [my talks page][7] and overall I thought mdp worked quite well.

I was able to draft in the stream of conciousness style I want, getting the bulk of the slides written very quickly. Adding diagrams required resorting to ASCII art which isn't so bad, I like [ascii][10] [art][11]. mdp worked great in practice, I had to find readable dimensions for the text by trial and error, but overall it went well.

Plain text as a format does have some major downsides, mdp has a way to encode builds for text (see below), but I couldn't use it with my tools. ASCII art diagrams also meant that the builds I did use were eggregious to maintain, any modification required manual propigation through the build chain.

mdp does not support a portable output format. You may say the source markdown is an excellent format for portability, but I find it lacks the crispness of having a single slide in view at once.

I wanted to be able to point at a viewable copy of my slides and so I hacked together some tools to export the mdp presentation to html, but for this I had to sacrifice the built in build mechanism of mdp

Finally there was no way to include images in the mdp presentation let alone the sacride gif format required to correctly convey nyan cat. I played with some terminal graphics viewers, but none of them worked well and after a while I started to think 'what is the point of reinventing everything'.

Drafting the presentation in markdown fit very well with my work flow, but the difficulties in getting a complete presentation with mdp meant that I didn't want to use it for future presentations.

Exporting to html

Getting html of the mdp presentation hinged on a complete hack. There is a tool I had seen in the past that can output a html dump of a tmux session unsurprisingly called [tmux2html][12]. With some playing around I was able to automate a tmux session to work through the slides and use tmux2html to grab each slide as a frame.

Finding the number of slides in the deck required splitting on the slide seperator from the markdown, this ruled out using the built in build mechanism as I would end up with the wrong number of slides.

The output script runs through the markdown to find the number of slides then uses tmux send-keys to control moving through the deck.

#!/bin/sh

set -e 

command -v tmux >/dev/null 2>&1 || { echo >&2 "I require tmux but it's not installed.  Aborting."; exit 1; }
command -v tmux2html >/dev/null 2>&1 || { echo >&2 "I require tmux2html but it's not installed.  Aborting."; exit 1; }
command -v mdp >/dev/null 2>&1 || { echo >&2 "I require mdp but it's not installed.  Aborting."; exit 1; }

if [ -z "$1" ]
  then
    echo "tohtml presentatin.md [outfile.html]"
    exit
fi

file=$1
outfile=outfile.html

if [ ! -z "$2" ]
  then
  outfile=$2
fi

javascript="<script>function page(){var e=!1,n=document.getElementsByClassName('tmux-html'),l=0; document.onkeydown=function(t){if(t=t||window.event,key=t.keyCode,e)if(13==key){e=!1,l=0;for(var i=0;i<n.length;i++)n[i].style.display='inline'}else{37==key&&--l<0&&(l=0),39==key&&++l>=n.length&&(l=n.length-1);for(i=0;i<n.length;i++)n[i].style.display='none';n[l].style.display='inline'}else if(13==key){e=!0,n[0].style.display='inline',l=0;for(i=1;i<n.length;i++)n[i].style.display='none'}}}window.onload=function(){page()};</script>"

tmpfile=tmpfilenamefilething
tmux='mdptohtmlconverstionsession'

slides=`grep -e "^---" $file | wc -l`

tmux new-session -s $tmux -d -x 96 -y 25

tmux send-keys -t $tmux "mdp $file"
tmux send-keys -t $tmux "Enter"

tmux send-keys -t $tmux 'g'
tmux2html -o $tmpfile $tmux 1>/dev/null

# insert javascript
lines=`cat $tmpfile | wc -l`
styleend=`cat -n $tmpfile | grep -e "</style>" | awk '{print \$1}'`
head -n $styleend $tmpfile > $outfile
echo $javascript >> $outfile
tail -n $((lines-styleend)) $tmpfile >> $outfile
mv $outfile $tmpfile

# remove closing tag
lines=`cat $tmpfile | wc -l `
end=`tail -n 1 $tmpfile`
head -n $((lines-1)) $tmpfile > $outfile

echo turning $file into $((slides+1)) slides 

i=1
while [ $i -lt $((slides+1)) ]
do
    printf "\rSlide $i"
    tmux send-keys -t $tmux 'j'

    tmux2html -o $tmpfile $tmux 1>/dev/null 
    grep -e "^<div" $tmpfile >> $outfile
    (( i++ ))
done

echo $end >> $outfile
tmux kill-session -t $tmux 
rm $tmpfile
printf "\rwritten to $outfile \n"

[If you view the presentation page][6] you will see the entire slide deck, this was the first output I got from this script. All the slides in a nice order. After a little pondering I wrote up some javascript to give controls, if you hit enter it will go from all slides to single slide. Arrow keys in single slide mode will allow you to move through the slide deck. The unminified javascript for this is below.

function page() 
{
    var presenting = false
    var elements = document.getElementsByClassName('tmux-html');
    var current = 0;

    document.onkeydown = function(evt) {
        evt = evt || window.event;
        key = evt.keyCode 

        if (presenting) {
            if (key == 13) {
                presenting = false;
                current = 0;
                for (var i = 0; i < elements.length;i++)
                    elements[i].style.display='inline'
            } else {
                if (key == 37) {    //left
                    current--;
                    if (current < 0)
                        current = 0;
                }
                if (key == 39) {    //right
                    current++;
                    if (current >= elements.length)
                        current = elements.length-1;
                }
                for (var i = 0; i < elements.length;i++)
                    elements[i].style.display='none'
                elements[current].style.display='inline'
            }
        } else {
            if (key == 13) {
                presenting = true;
                elements[0].style.display='inline'

                current = 0;
                for (var i = 1; i < elements.length;i++)
                    elements[i].style.display='none'
            }
        }
    };
}

window.onload = function () {
   page();
}

[3]: sent blog post [4]: sent link [5]: techmeetup aberdeen [6]: mdp slides [7]: talks page

[10]: ietf ascii art guidelines [11]: draft cco [12]: tmux to html