rootpy/rootpy — pull request #55 by pwaller (2012-11-07 16:45:28+00:00)
Title: State preserving context managers, invisible canvas and TEfficieny.xaxis

This pull request adds what #54 failed to add.

This introduces a `painted_graph` property to the `Efficiency` class, which causes the `TEfficiency` to be drawn to a temporary invisible canvas, if it isn't available. `xaxis` and `yaxis` are then defined in terms of `painted_graph`.

In addition, this introduces a few context managers useful for preserving state.