Reveal: Graphviz Viewer

Graphviz is a well-known data visualization software. You can create graphs using a simple text language, for example:

digraph { a -> b }

With Reveal, you can view such graphs by selecting a graphviz action on strings that start with "graph" or "digraph":

Additionally, graphviz action can watch refs (such as vars) so you can incrementally build the graph description with live feedback: