Added off-line renderer that invokes dot.

doc/render.py

@@ -1,14 +1,32 @@
 #!/usr/bin/env python3
 
+import subprocess
 import sys
 
 if len(sys.argv) < 2:
     print("Must pass a filename argument")
     sys.exit(1)
 
-in_file = sys.argv[1]
-out_file = in_file.replace(".in.md", ".md")
+in_filename = sys.argv[1]
+out_filename = in_filename.replace(".in.md", ".md")
 
-if in_file == out_file:
+if in_filename == out_filename:
     print("File must end in .in.md")
     sys.exit(1)
+
+with open(out_filename, "wb") as out_file, open(in_filename, "rb") as in_file:
+    for line in in_file:
+        if line.startswith(b"```dot"):
+            dot_lines = []
+            while True:
+                dot_line = next(in_file)
+                if dot_line == b"```\n":
+                    break
+                dot_lines.append(dot_line)
+            dot_input = b"".join(dot_lines)
+            svg = subprocess.check_output(['dot', '-Tsvg'], input=dot_input)
+            out_file.write(b"<div align=center>")
+            out_file.write(svg)
+            out_file.write(b"</div>")
+        else:
+            out_file.write(line)