Getting all avaliable space


I’m building a game that I developed only the interpreted gui until now… and then the question comes: "what resolution I will use? support all? fullscreen?"
And then I thinked that, better then supporting 640x480, 800x600 and 1024x768 (the more commons), I wanted to use the space in the user desktop that is avaliable, that is, the space that is not used by task bar, etc, etc, etc…
Becose it’s too ill to have to occult the taskbar to run railroad tyccon II (loki games) under any window managers… (guess that wm don’t have this problem, but I prefer using icewm…) and I hate that taskbar hidding all the time, but I have to do it, or run it in another x session. If don’t, I won’t see how much money I have, the status bar, exit buttons hehe.
Is there a way to get the space not used by the window manager and the call SDL_SetVideoMode or I should always use that fixed resolutions?

Thanks for helping,–
Marcelo R Leitner
ICQ #: 29966851