Quickly render a 'dot' (Graphviz) graph

On Linux and OSX the command:

dot -Txlib mygraph.gv

will quickly launch a lightweight window containing a dot rendering of the graph in mygraph.gv.

The rendering should automatically refresh when mygraph.gv is updated. (I've occasionally run into small glitches with this that force me to re-launch the window, but they are rare and obvious.)

The same -Txlib parameter works for the other Graphviz rendering engines, including neato, twopi, fdp, sfdp, circo, and patchwork.