The AG_EventLoop routine loops, continually checking for low-level events and processing them. Its operation is governed by a registered set of Event Sinks which determine the type of low-level events to monitor, and the procedures to invoke in order to handle them.

The most common type of low-level events are:

1. Activity on a socket or file descriptor.
2. Expiration of a timer.
3. Kernel-event notifications (e.g., kqueue(2) events). This includes filesystem events and process monitoring.

Concurrent instances of AG_EventLoop() are allowed in multithreaded builds. In threaded builds, event sinks are associated with running thread at the time of creation (in thread-local storage).

AG_EventLoop() blocks the current thread, waiting for low-level events, and processing them until termination is requested. Its operation is governed by the registered set of event sinks.

The AG_Terminate() function requests termination of the event loop associated with the current thread. If the current thread is the main thread, AG_Terminate() will terminate the application with exitCode as return code. The AG_TerminateEv() variant accepts an AG_Event style argument instead of an int for the exit code.

The AG_AddEventSink() routine creates a new event sink under the current thread, and returns a pointer to a newly-allocated AG_EventSink structure. The type argument may be one of:

AG_SINK_READ	Data is available for reading on file referenced by ident.
AG_SINK_WRITE	Data is available for writing on file referenced by ident.
AG_SINK_FSEVENT	A filesystem event has occurred on the file/directory referenced by ident. The type of event is specified in flags (see FILESYSTEM EVENTS for the accepted flags).
AG_SINK_PROCEVENT	An event has occurred on the monitored process ident. The type of event is specified in flags (see PROCESS EVENTS below).

The AG_DelEventSink() function destroys the specified event sink. The AG_DelEventSinksByIdent() function destroys all event sinks with matching ident and flags.

The AG_AddEventPrologue() function registers a callback routine to be invoked once at the start of AG_EventLoop(). AG_AddEventEpilogue() registers a callback routine to be invoked on exit, before AG_EventLoop() returns. AG_DelEventEpilogue() and AG_DelEventPrologue() destroy the specified epilogue/prologue routine.

The AG_AddEventSpinner() routine registers a "spinner" callback routine. Spinner routines are invoked repeatedly and unconditionally by AG_EventLoop(), until the event loop terminates, or AG_DelEventSpinner() is invoked.

Acceptable flags for the AG_SINK_FSEVENT event sink include:

AG_FSEVENT_DELETE	The file has been deleted.
AG_FSEVENT_WRITE	The file was written to.
AG_FSEVENT_EXTEND	The file was extended in size.
AG_FSEVENT_ATTRIB	File attributes have been changed.
AG_FSEVENT_LINK	The link count on the file has changed.
AG_FSEVENT_RENAME	The referenced file has been renamed.
AG_FSEVENT_REVOKE	Filesystem has unmount, or revoke(2) called.

Acceptable flags for the AG_SINK_PROCEVENT event sink include:

AG_PROCEVENT_EXIT	Monitored process has exited.
AG_PROCEVENT_FORK	Monitored process has called fork(2).
AG_PROCEVENT_EXEC	Monitored process has called exec(3).

The AG_FileDlg(3) widget uses AG_SINK_FSEVENT to auto-refresh directory listings on platforms that offer filesystem monitoring capabilitie

The AG_ConsoleOpenFile(3) feature of AG_Console(3) sets up an event sink of type AG_SINK_READ to monitor changes on a file or stream.

The agardb(1) debugger uses AG_SINK_PROCEVENT to monitor events related to processes being debugged.

Agar's X11 driver AG_DriverGLX(3) sets up an event sink of type AG_SINK_READ in order to receive events from the X file descriptor:

AG_CustomEventLoop(3), AG_Event(3), AG_Intro(3), poll(2), select(2), kqueue(2)

The AG_EventLoop call first appeared in Agar 1.0. Event sinks first appeared in Agar 1.5.0.