Upon doing:
    $ gm display foo.jpg
    ^C
or
    $ gm display foo.jpg
    ^Z
    $ kill %1
    $ fg
gm does not exit. In fact, neither signal 2 or 15, sent from 'top'
in another window, for example, cause the process to exit.

It often appears to have exited, as it removes its window, but the
process still hangs around.