matplotlib OS-X binary

I'd vote for Agg. Postscript is not the native format on

    > OS-X that it is on other unices.

    > Is there a way to make the default back-end system
    > dependent on install?

For a src distribution, you could write a postinstall script that does
try/except on various GUIs and writes an rc file based on what it
finds. This is basically what does in trying to figure out
which backend to build, but doesn't transmit that information to rc --
perhaps it should. Although this would be fairly easy in a src
distro, it would be fairly hard in the binary installer which you are
trying to build.

Alternatively, the backend importer could be a little smarter, and
first try the default rc param and then loop over available backends
trying to find a match, and issue a verbose report saying "dear
newbie, I cannot import your default backend, please see http://blah."
but still go ahead and launch something. I have mixed feelings about
this -- the more magic we do the more complex it is to debug
problems. Also, you have to be careful not to swallow tracebacks, eg
pygtk import can fail even if pygtk has been installed on the system,
and the user needs to know about this. But I am not totally opposed
to it.

In fact, I would definitely include it if it was an rc option. Eg,
binary package makers like yourself could turn it on since you don't
know the user configuration, and src distributors like me could turn
it off, assuming people who build their own code can configure it like
they like it.

Power users want as little magic going on as possible -- new users
usually want maximal magic.

The function to look at is in the main matplotlib tree.
Currently we do

def get_backend():
    return rcParams['backend']

you would want to add an rc param, something like

backend : ['TkAgg']
# try these if default fails
backend.try = ['GTKAgg, 'WXAgg', 'Agg', 'PS]

and then modify get_backend to iterate over these backends, trying to
import something to test if it is available, issuing reports if the
default backend fails.

In the src distro, I always have the option of making backend.try the
empty list, which would be the same as the current behavior.