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.Dd December 21, 2022
.Dt AG_CUSTOMEVENTLOOP 3
.Os Agar 1.7
.Sh NAME
.Nm AG_CustomEventLoop
.Nd agar GUI custom event loop example
.Sh SYNOPSIS
.Bd -literal
#include <agar/core.h>
#include <agar/gui.h>
.Ed
.Sh DESCRIPTION
In general, most Agar GUI applications will use the standard Agar-Core
event loop,
.Xr AG_EventLoop 3 ,
since it uses the most efficient event-notification mechanism available for
the target platform (e.g.,
.Xr kqueue 2 ,
.Xr select 2 ,
etc.)
.Pp
However, Agar-GUI applications are not required to use
.Fn AG_EventLoop
at all, and may use an application-specific event loop routine.
To simplify writing of custom event loops, Agar provides the
.Xr AG_GetNextEvent 3 ,
.Xr AG_ProcessEvent 3
and
.Xr AG_ProcessTimeouts 3
functions.
Low-level driver events are represented by the transparent, driver-independent
.Ft AG_DriverEvent
structure (see
.Xr AG_Driver 3
for details and examples).
.Sh CUSTOM EVENT LOOP EXAMPLE
The following event loop redraws Agar windows whenever needed (the redraw
frequency being limited to some nomimal frame rate), processes input events,
and executes timer callbacks (using an inefficient delay loop):
.Bd -literal
.\" SYNTAX(c)
void
MY_GenericEventLoop(void *obj)
{
	AG_Window *win;
	Uint32 t1, t2;

	t1 = AG_GetTicks();
	for (;;) {
		t2 = AG_GetTicks();
		if (t2 - t1 >= rNom) {
			AG_WindowDrawQueued();

			t1 = AG_GetTicks();
			rCur = rNom - (t1-t2);
			if (rCur < 1) { rCur = 1; }
		} else if (AG_PendingEvents(NULL)) {
			AG_DriverEvent dev;

			if (AG_GetNextEvent(NULL, &dev) == 1)
				AG_ProcessEvent(NULL, &dev);
		} else {
			AG_ProcessTimeouts(t2);
			AG_Delay(1);
		}
		AG_WindowProcessQueued();
	}
}
.Ed
.Sh SEE ALSO
.Xr AG_Delay 3 ,
.Xr AG_Driver 3 ,
.Xr AG_Event 3 ,
.Xr AG_EventLoop 3 ,
.Xr AG_Timer 3 ,
.Xr AG_Window 3
.Sh HISTORY
The
.Nm
routine first appeared in Agar 1.0.
The
.Fn AG_GetNextEvent
interface appeared in Agar 1.4.0.