SYNOPSIS

#include <agar/core.h>

DESCRIPTION

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:

Activity on a socket or file descriptor.
Expiration of a timer.
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).

MAIN INTERFACE

int AG_EventLoop (void)

void AG_Terminate (int exitCode)

void AG_TerminateEv (AG_Event *event)

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.

EVENT SINKS

AG_EventSink * AG_AddEventSink (enum ag_event_sink_type type, int ident, Uint flags, AG_EventSinkFn fn, const char *fnArgs)

void AG_DelEventSink (AG_EventSink *sink)

void AG_DelEventsSinkByIdent (enum ag_event_sink_type type, int ident, Uint flags)

AG_EventSink * AG_AddEventPrologue (AG_EventSinkFn fn, const char *fnArgs, ...)

AG_EventSink * AG_AddEventEpilogue (AG_EventSinkFn fn, const char *fnArgs, ...)

AG_EventSink * AG_AddEventSpinner (AG_EventSinkFn fn, const char *fnArgs, ...)

void AG_DelEventPrologue (AG_EventSink *sink)

void AG_DelEventEpilogue (AG_EventSink *sink)

void AG_DelEventSpinner (AG_EventSink *sink)

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.

FILESYSTEM EVENTS

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.

PROCESS EVENTS

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).

EXAMPLES

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:

Display *display;

static int
EventSink(AG_EventSink *es, AG_Event *event)
{
	Display *dpy = AG_PTR(1);

	while (XPending(dpy)) { /* Process event */ }
}

AG_AddEventSink(AG_SINK_READ,
    XConnectionNumber(display), 0,
    EventSink, "%p", display);

HISTORY

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