import os
def check(cmd, mf):
    m = mf.findNode('matplotlib')
    if m is None or m.filename is None:
        return None

    if cmd.matplotlib_backends:
        backends = {}
        for backend in cmd.matplotlib_backends:
            if backend == '-':
                pass

            elif backend == '*':
                mf.import_hook('matplotlib.backends', m, ['*'])

            else:
                mf.import_hook('matplotlib.backends.backend_%s'%(backend,), m)

    else:
        backends = {'packages': ['matplotlib']}


    return dict(
        prescripts=['py2app.recipes.matplotlib_prescript'],
        resources=[os.path.join(os.path.dirname(m.filename), 'mpl-data')],
        **backends
    )