Specifies the connection to the X server.
Specifies the event mask.
Specifies the window whose events you are interested in.
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.