I've got a Raspberry Pi running Debian/Raspbian (thus X server) that I'd like to drive two screens with. I'm programming something that will have a public-facing screen and an operator-facing screen. To give an example of the things I'm trying to do, say the operator will have a GUI where he or she can press 'cat' and a fullscreen cat will appear on the other monitor.
The problem is that the Pi only has one HDMI output, making driving two monitors difficult unless you resort to SSH/remote desktop sessions with a second computer (eg a laptop). Now, I've done remote desktop on headless Pis before with very little difficulty. The issue that is brickwalling me right now is that when I remote desktop in, I get a completely independent second desktop than the one that's driving the primary monitor, ergo the monitor is inaccessible to me. How do I make it so that when I remote in, I get control over that monitor, but also screen area for a GUI that will only go on the remote computer? Also, how do I make it so when the program starts up, the public facing display goes fullscreen and the operator gui pops up on the other?
I'd like to keep as much as possible on the Pi so that the only requirement of the remote computer be that it can do remote desktop. In other words, I don't want to divide my software into remote and local executables.