XSelectInput 3X11 __xorgversion__ XLIB FUNCTIONS XSelectInput select input events int XSelectInput ( Display *display , Window w , long event_mask ); display Specifies the connection to the X server. event_mask Specifies the event mask. w Specifies the window whose events you are interested in. The  XSelectInput  function requests that the X server report the events associated with the specified event mask. Initially, X will not report any of these events. Events are reported relative to a window. If a window is not interested in a device event, it usually propagates to the closest ancestor that is interested, unless the do_not_propagate mask prohibits it. Setting the event-mask attribute of a window overrides any previous call for the same window but not for other clients. Multiple clients can select for the same events on the same window with the following restrictions: Multiple clients can select events on the same window because their event masks are disjoint. When the X server generates an event, it reports it to all interested clients. Only one client at a time can select  CirculateRequest ,  ConfigureRequest , or  MapRequest  events, which are associated with the event mask  SubstructureRedirectMask . Only one client at a time can select a  ResizeRequest  event, which is associated with the event mask  ResizeRedirectMask . Only one client at a time can select a  ButtonPress  event, which is associated with the event mask  ButtonPressMask . The server reports the event to all interested clients.  XSelectInput  can generate a  BadWindow  error.  BadWindow  A value for a Window argument does not name a defined Window. Xlib - C Language X Interface