I have two Ubuntu 10.4 machines (and Ubuntu continues to hide more and more xorg.conf config such that I no longer know where to find it). One is a laptop running dual headed - DP1 is the internal screen, and VGA1 is an external monitor; both are running at 1600x900. The other machine is a desktop running both VGA1 and HDMI1 (which is actually a display port with a DVI adapter) at 1600x900. So in both instances my desktop is 3200x900. I run a VNC server on the laptop and connect to it (via SSH tunnel) from the desktop - when I press the full screen hot key, I get a 1600x900 view of the remote machine on one monitor, and half of my local desktop on the other monitor - the "full screen" only expands to fill one local monitor.
Normally this is exactly what you want when you full screen a web browser, email client, or other application. I'm sure there's some X magic to make it clear what a full screen actually entails, and the vnc client application is just dutifully accepting what it's told. While I would like to keep the normal full screen behavior for regular applications, but when I'm VNCing to another 3200x900 machine, I'd really like full screen to stretch across both local displays. Resizing the window to be "close" isn't quite good enough since I still have local panels at the top and bottom of one display (though I can set them to autohide), plus the VNC client application window border (since it doesn't appear to respect -notitle).
Is there any good way to have X lie to a single application about the "full screen" size? Can I get it to lie to all applications? xrandr --noprimary appears to have no effect.