XSelectInput() - select input events
XSelectInput (Display *display, Window w, long event_mask)
The XSelectInput(3) 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:
The server reports the event to all interested clients.
XSelectInput(3) can generate a BadWindow error.
Xlib