Is there a simple way to detect mouse or keyboard activity in Linux/Xorg/Qt4/Kde4?

typedef struct {
       Window window;                /∗ screen saver window */
       int state;                    /∗ ScreenSaver{Off,On,Disabled} */
       int kind;                     /∗ ScreenSaver{Blanked,Internal,External} */
       unsigned long til_or_since;   /∗ milliseconds */
       unsigned long idle;           /∗ milliseconds */
       unsigned long event_mask;     /∗ events */
   } XScreenSaverInfo;