== graphviz

Some Graphviz abstractions
[[toc:]]
=== {{default-width}}
<parameter>default-width → 1600</parameter>
Default width for graphs
<enscript highlight="scheme">(define default-width (make-parameter 1600))
</enscript>
=== {{default-height}}
<parameter>default-height → 900</parameter>
Default width for graphs
<enscript highlight="scheme">(define default-height (make-parameter 900))
</enscript>
=== {{default-font-size}}
<parameter>default-font-size → 48.0</parameter>
Default font-size for graphs
<enscript highlight="scheme">(define default-font-size (make-parameter 48.0))
</enscript>
=== {{default-node-attributes}}
<parameter>default-node-attributes → (quote ())</parameter>
Default node attributes
<enscript highlight="scheme">(define default-node-attributes (make-parameter '()))
</enscript>
==== Examples
Creating default node attributes
 (default-node-attributes '((font . monospace)))
=== {{default-edge-attributes}}
<parameter>default-edge-attributes → (quote ())</parameter>
Default edge attributes
<enscript highlight="scheme">(define default-edge-attributes (make-parameter '()))
</enscript>
==== Examples
Creating default edge attributes
 (default-edge-attributes '((dir . none)))
=== {{default-graph-attributes}}
<parameter>default-graph-attributes → (quote ())</parameter>
Default graph attributes
<enscript highlight="scheme">(define default-graph-attributes (make-parameter '()))
</enscript>
==== Examples
Creating default graph attributes
 (default-graph-attributes '((splines . true)))
=== {{write-graph-preamble}}
<procedure>(write-graph-preamble) → unspecified</procedure>
<procedure>(write-graph-preamble graph-attributes) → unspecified</procedure>
<procedure>(write-graph-preamble graph-attributes width height font-size) → unspecified</procedure>
Write a graph preamble.
; {{graph-attributes}} : Attributes of the graph
; {{width}} : Width in pixels
; {{height}} : Height in pixels
; {{font-size}} : Font-size in pt
<enscript highlight="scheme">(define write-graph-preamble
  (case-lambda
    (() (write-graph-preamble '()))
    ((graph-attributes)
     (write-graph-preamble
       graph-attributes
       (default-width)
       (default-height)
       (default-font-size)))
    ((graph-attributes width height font-size)
     (display "digraph G {")
     (unless
       (null? graph-attributes)
       (format #t "graph [~a];" (attributes->string graph-attributes)))
     (unless
       (null? (default-graph-attributes))
       (format
         #t
         "graph [~a];"
         (attributes->string (default-graph-attributes))))
     (unless
       (null? (default-node-attributes))
       (format #t "node [~a];" (attributes->string (default-node-attributes))))
     (unless
       (null? (default-edge-attributes))
       (format #t "edge [~a];" (attributes->string (default-edge-attributes))))
     (if (and width height)
       (begin
         (format #t "graph [fontsize=~a, ratio=fill];" font-size)
         (let ((width-in-inches (px->in width))
               (height-in-inches (px->in height)))
           (format
             #t
             "graph [viewport=\"~a,~a\", size=\"~a,~a!\"];"
             (in->dot width-in-inches)
             (in->dot height-in-inches)
             width-in-inches
             height-in-inches)))))))
</enscript>
==== Examples
A trivial graph
 (write-graph-preamble '((splines . true)))
 (write-node a '((label . "Big bang")))
 (write-node b '((label . "Today")))
 (write-edge a b '((label . "Entropy gradient")))
 (write-graph-postamble)
=== {{write-graph-postamble}}
<procedure>(write-graph-postamble) → unspecified</procedure>
Write the graph postamble.

<enscript highlight="scheme">(define (write-graph-postamble) (display "}"))
</enscript>
=== {{pos}}
<procedure>(pos x y) → unspecified</procedure>
For placing nodes at specific positions in a unit graph using the {{pos}}
 attribute, apply a linear scaling.
; {{x}} : The x position
; {{y}} : The y position
<enscript highlight="scheme">(define (pos x y) (format "~a,~a" (* x (linear-scale)) (* y (linear-scale))))
</enscript>
=== {{write-node}}
<procedure>(write-node label) → unspecified</procedure>
<procedure>(write-node label attributes) → unspecified</procedure>
Write a node
; {{label}} : The node's label
; {{attributes}} : Attributes of the node
<enscript highlight="scheme">(define write-node
  (case-lambda
    ((label) (write-node label '()))
    ((label attributes)
     (format #t "~a [~a];" label (attributes->string attributes)))))
</enscript>
=== {{write-edge}}
<procedure>(write-edge whence whither) → unspecified</procedure>
<procedure>(write-edge whence whither attributes) → unspecified</procedure>
Write an edge
; {{whence}} : The label whence
; {{whither}} : The lable whither
; {{attributes}} : Attributes of the edge
<enscript highlight="scheme">(define write-edge
  (case-lambda
    ((whence whither) (write-edge whence whither '()))
    ((whence whither attributes)
     (format
       #t
       "~a -> ~a [~a];"
       whence
       whither
       (attributes->string attributes)))))
</enscript>
=== About this egg

==== Author

[[/users/klutometis|Peter Danenberg]]
==== Repository
[[https://github.com/klutometis/graphviz]]
==== License
BSD
==== Dependencies
* [[(hahn 0.9.3)]]
* [[matchable]]
* [[setup-helper]]


==== Colophon

Documented by [[/egg/hahn|hahn]].