You will need to provide additional information.
Gnome's global functionality is dependent on the window manager. Metacity has customizable global shortcuts, like Compiz and Sawfish, and they are all configured differently. Xhotkeys can also be used for the same functionality. However, they are all limited to startup applications only.
KDE KAction , . kded ( ), KDE.
KDE, X11, API xlib XGrabKey .
, X, , root ( ) 2.6, /dev/input/event* .