god let's actually put this in source control

graphgif.scm

@@ -0,0 +1,74 @@
+#!/usr/bin/guile -s
+!#
+(use-modules (cairo))
+
+;;;;;;;;;;;;;;;;;;;
+;; Basic Drawing ;;
+;;;;;;;;;;;;;;;;;;;
+
+(define pi 3.14159)
+(define tau (* 2 pi))
+
+(define black (cairo-pattern-create-rgb 0 0 0))
+(define white (cairo-pattern-create-rgb 1 1 1))
+(define red   (cairo-pattern-create-rgb 1 0 0))
+
+(define my-graph
+  `(((10 . 10) (1) ,white)
+    ((30 . 20) ()  ,red)))
+
+(define more-complex-graph
+  `(((10 . 10) () ,white) 
+    ((40 . 10) (0) ,white)
+    ((25 . 25) (0 1) ,white)
+    ((10 . 40) (0 2 4) ,white)
+    ((40 . 40) (1 2 3) ,white)))
+
+(define (edge-painter cr graph)
+  (lambda (node)
+    (cairo-set-source cr black)
+    (let ([x (caar node)]
+	  [y (cdar node)]
+	  [edges (cadr node)])
+      (for-each
+       (lambda (edge)
+	 (let* ([other (list-ref graph edge)]
+		[ox (caar other)]
+		[oy (cdar other)])
+	   (cairo-move-to cr x y)
+	   (cairo-line-to cr ox oy)
+	   (cairo-stroke cr)))
+       edges))))
+
+(define (node-painter cr)
+  (lambda (node)
+    (let ([x (caar node)]
+	  [y (cdar node)]
+	  [color (caddr node)])
+      (cairo-arc cr x y 4. 0. tau)
+      (cairo-set-source cr color)
+      (cairo-fill-preserve cr)
+      (cairo-set-source cr black)
+      (cairo-stroke cr))))
+
+(define (draw-abstract-graph graph)
+  (let* ([surface (cairo-image-surface-create 'argb32 400 400)]
+	 [cr (cairo-create surface)])
+    (define paint-edges (edge-painter cr graph))
+    (define paint-nodes (node-painter cr))
+    ;; White background
+    (cairo-rectangle cr 0 0 400 400)
+    (cairo-set-source cr white)
+    (cairo-fill cr)
+    (for-each paint-edges graph)
+    (for-each paint-nodes graph)
+    (cairo-destroy cr)
+    surface))
+
+(define my-surface (draw-abstract-graph more-complex-graph))
+(cairo-surface-write-to-png my-surface "graph.png")
+(cairo-surface-destroy my-surface)
+
+;; Local Variables:
+;; geiser-scheme-implementation: guile
+;; End: