LXRandR is a simple monitor configuration tool utilizing X RandR extension.
It's a GUI frontend of the command line program xrandr and manages screen
resolution and external monitors. When you run LXRandR with an external
monitor or projector connected, its GUI will change and show you some options
to quickly configure the external device.
LXRandR is the standard screen manager of LXDE, the Lightweight X11 Desktop
Environment, but can be used in other desktop environments as well.