lazydot
=======

I really love Graphviz to make drawings using keyboard only - much easier than
fiddling around with the mouse to move everything in its position. And moving
it all again when inserting or removing items.

I even use it on the fly to draw graphs during presentations or when explaining
more complicated things to colleagues. Because it's true: "A picture is worth a
thousand words."

But I had to encounter some weaknesses of the DOT language in this concrete use
case. This lead me to cobble together the simplified lazydot minilanguage, a
preprocessor for Graphviz.

Its main (and only) features are:

- Use '.' and '$' instead of repeating the ID of the first or last edge in the
  last sequence of nodes. This makes it much easier to change a node's ID and
  means less typing.

- Set attributes right after nodes, edges or subgraphs are defined. Especially
  useful when you want to tweak an edge: Just write the attributes after the
  arrow. You don't have to put a separate node-arraw-node-attributes sequence
  to modify a single edge.

- Apply attributes on individual nodes and edges only, but not on other items
  that follow. Allows you to reorder things without changing colors and shapes
  unintentionally.

- Define a set of attributes as template and apply it to multiple items.
  Something like "redbox" is easier to read and faster to write than two
  attributes.

- Clusters don't need a fixed prefix and no numerical id. The syntax is
  similiar to that of nodes: You label it and put attributes in square-brackets
  if you need any.

- You don't have to put IDs in quotes if it contains a dash or other special
  characters - only whitespaces and equal signs require you to use quotes.

Most of that is used in the following example:

    graph [ rankdir=LR labelloc=t fontsize=18
            label="Objective Social Situation and Right-Wing Populism"
            URL=https://pub.uni-bielefeld.de/record/2564817 ]
             
    template dimension [ color="#008891" fontcolor="#008891" fontsize=14 ]

    cluster "Desintegration\n(socio-structural dimension)" [ =dimension ] {
            "Social situation"
    }

    cluster "Desintegration\n(institutional dimension)" [ =dimension ] {
            . -> [ label=.27 ] "Political\nalientation"
            . -> [ label=.26 ] "Distrust of\npolitical elites"
    }

    cluster "Endangering\ndemocratic attitudes" [ =dimension ] {
            $ -> [ label=.24 ] "Right-wing\npopulist orientation\n.42"
            "Political\nalientation" -> [ label=.35 ] $
            "Social situation" -> [ label=.28  ] $
    }

Usage
-----

As lazydot outputs DOT code, just use it with a pipe:

    lazydot example.lazydot | dot -Tsvg -oexample.svg

My setup for presentations is quite simple: On the presentation screen I open
an image viewer which redraws when the file changes (e.g. GNOME Image Viewer).
On another screen I edit the input file. A bash loop calls the above command
whenever inotifywait notices a change to the input:

    while inotifywait -e modify example.lazydot; do
        lazydot example.lazydot | dot -Tsvg -oexample.svg
    done

Bugs and Limitations
--------------------

- Sub-clusters inherit attributes from their parents. But stopping that
  counterintuitive behavior is rather complicated: Each attribute set in the
  parent cluster but not in its children must be reset by outputing the
  attribute's default value in the children.

- This program will leak memory, if a parser or lexer error occurs. The memory
  strdup'ed in the lexer will only be freed, if the token is processed
  successfully. Some kind of bookkeeping of each allocated string would be
  required to free all memory at all events. But as lazydot terminates on
  errors, that won't be a real problem.

- Good code doesn't store its state in a global variable and would rather
  use a reentrant lexer/parser. But this code will never be used as library or
  by a multi-threaded program...

Build
-----

You need g++ (with C++11 support), flex and bison. Then it's nothing more than:

    make

Install the result (as root):

   cp lazydot /usr/local/bin/lazydot

License
-------

License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>