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/*
* DNN - Data News Network
*
* by Stephane Chatty
*
* Copyright 1993-1994
* Centre d'Etudes de la Navigation Aerienne (CENA)
*
* Event triggers.
*
* $Id$
* $CurLog$
*/
#include "Trigger.h"
#include "Reaction.h"
/*?class DnnTrigger
\typ{DnnTrigger}s are the core of event detection and emission. The presence of a trigger
(generally in a sensor) determines whether a certain situation, or the reception
of an event from the underlying window system, should provoke the emission of an event.
Each trigger holds a list of reactions (of type \typ{DnnBaseReaction}). These reactions will
receive all the events whose creation and emission was caused by the presence of
the trigger.
?*/
/*?
Create a trigger with an empty list of associated reaction.
?*/
DnnTrigger :: DnnTrigger ()
: Subscribers (),
Grabs ()
{
}
/*?nodoc?*/
DnnTrigger :: ~DnnTrigger ()
{
}
/*?nextdoc?*/
void
DnnTrigger :: Subscribe (DnnBaseReaction& a)
{
Subscribers.Append (&a);
}
/*?
Add (resp. Remove) a reaction to (resp. from) the list of reactions that should receive
events caused by this trigger.
?*/
void
DnnTrigger :: Unsubscribe (DnnBaseReaction& a)
{
Subscribers.Remove (&a);
Grabs.Remove (&a);
}
/*?nextdoc?*/
void
DnnTrigger :: Grab (DnnBaseReaction& a)
{
Grabs.Prepend (&a);
}
/*?
Add (resp. Remove) a reaction onto (resp. from) the stack of reactions that preempt
events caused by this trigger.
?*/
void
DnnTrigger :: Release (DnnBaseReaction& a)
{
Subscribers.Remove (&a);
}
/*?
Have a trigger dispatch the event \var{ev} to its associated reactions.
?*/
void
DnnTrigger :: Dispatch (DnnEvent& ev)
{
DnnBaseReaction* r = Grabs.First ();
if (r) {
r->Manage (ev);
} else {
CcuListOf <DnnBaseReaction> subscribers = Subscribers;
CcuListIterOf <DnnBaseReaction> ai = subscribers;
while (++ai)
(*ai)->Manage (ev);
}
}
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