I'm running Fedora 20 on a small Openbox setup that I'm fond of. I sometimes want to send things through a second display, e.g. plugging into a projector or a television. Given the pretty spartan nature of an Openbox session, just plugging in the HDMI cable (and turning on the display at the other end) gives me nothing; there's no obvious sign that the machine has found another display.
My problem isn't terribly technical; I can get things to work: the current workaround is to stop my session, dropping myself back to the GDM greeter, whereupon the screen blacks out for an instant and the laptop recognizes the display, allowing me to work across the two screens concurrently. I can then log back into Openbox and continue as cleared. This has obvious drawbacks, like requiring I drop all my work and re-login every time I want to watch something on a bigger screen.
My goal is to be able to "hotplug" a display and have my Openbox session adapt immediately to the two-screen setup, whether by some magical GNOME daemon or other trickery unknown to me. How should I approach this?