I've been playing Nexuiz for a couple of months now in its native full-screen mode, and never was able to minimize it or use any other windows without closing the game completely. Finally, I decided to find a way to at least minimize it somehow. So here's what I've come up with.
The idea is to *disable* the native fullscreen mode, so Nexuiz will run in its own window, and make use of the fullscreen mode that is built into your window manager (Metacity for Gnome, kwin for KDE, etc). I have only tried this in KDE, but it should also work for Gnome and, perhaps, other environments (someone said it also worked in openbox). The steps are:
1. Open Nexuiz, go to Settings -> Video, uncheck "Full screen", click "Apply"
2. In the configuration dialog for your window manager, assign a keyboard shortcut to expand the current window to full-screen.
In KDE/Ubuntu: System Settings -> Keyboard & Mouse -> Keyboard Shortcuts, in the Global Shortcuts tab, line "Make Window Fullscreen".
In Gnome: follow this explanation: http://infinity-unbound.blogspot.com/20 ... in_15.html
3. A catch (at least with kwin, but probably also with other environments): kwin is only able to make a window full-screen, if it's a "normal window". The problem is -- Nexuiz presents itself as a non-normal window (dialog, perhaps).
To change this, in KDE:
a) run Nexuiz in windowed mode
b) press shift-esc. This will display a text console and also allow your mouse to escape from the Nexuiz' window.
c) right-click the window title, Advanced -> Special Application Settings
d) Window tab -> click Detect button
e) in the dialog that appears, choose "Use window class (whole application)", click OK
f) Workarounds tab -> turn on the "Window type" checkbox, choose "Force" from the drop-down next to it and "Normal window" from the second drop-down
g) click OK
I have no idea how to do this in Gnome (or is it even required), but it should also be possible this way or another (perhaps through a small external program).
4. If you'd like Nexuiz to always start in this full-screen mode, you can do this from the same Special Application Settings dialog, Geometry tab. Check the "Fullscreen" checkbox and choose "Apply Initially" from the drop-down.
5. In order to minimize Nexuiz or switch to other windows, you must always open its command prompt first (only when the prompt is open, Nexuiz will allow you to move your mouse outside the Nexuiz' window or trigger WM-specific keyboard shortcuts). You can do this with the tilde (~) button in-game or with shift-esc in the game's menus.
After opening the command prompt, if you want to minimize Nexuiz, you can either use you WM's minimization keyboard shortcut or press the shortcut to make it non-fullscreen again and then minimize it with the mouse. If you want to switch to other windows, you can just use alt-tab (or whatever is configured for this in your WM).
EDIT:
6. A limitation: you won't be able to run Nexuiz at resolutions other than the resolution of your desktop. If you want that, native full-screen is probably your only way.
That's all, have fun =)