Watcher callbacks

All watchers can be active(waiting for events) or inactive(paused). Only active watchers will have their callbacks invoked. All callbacks will be called with at least two arguments: watcher - the watcher, and revents a bitmask of received events.

Watcher callbacks are passed to the watcher constructors (the classes derived from EvWatcher - EvCheck::__construct() , EvChild::__construct() etc.). A watcher callback should match the following prototype:

watcher

The watcher instance(of a class extending EvWatcher ).

revents

Watcher received events .

Each watcher type has its associated bit in revents , so one can use the same callback for multiple watchers. The event mask is named after the type, i.e. EvChild (or EvLoop::child() ) sets EV::CHILD , EvPrepare (or EvLoop::prepare() ) sets Ev::PREPARE , EvPeriodic (or EvLoop::periodic() ) sets Ev::PERIODIC and so on, with the exception of I/O events (which can set both Ev::READ and Ev::WRITE bits).