From 6d32f3eda675ac0c36d835e69054eba2b1a777c8 Mon Sep 17 00:00:00 2001
From: chatty
Date: Tue, 10 May 1994 08:50:04 +0000
Subject: Added Grab/Release

---
 dnn/Reaction.cc | 27 ++++++++++++++++++++++++++-
 dnn/Trigger.cc  | 34 +++++++++++++++++++++++++++++-----
 2 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/dnn/Reaction.cc b/dnn/Reaction.cc
index 62a6849..845d689 100644
--- a/dnn/Reaction.cc
+++ b/dnn/Reaction.cc
@@ -25,13 +25,19 @@ and can be associated to one or more triggers, generally located in a sensor.
 Create a reaction.
 ?*/
 DnnBaseReaction :: DnnBaseReaction ()
+: Triggers (),
+  Grabbed ()
 {
 }
 
 /*?nodoc?*/
 DnnBaseReaction :: ~DnnBaseReaction ()
 {
-	CcuListIterOf <DnnTrigger> ti (Triggers);
+	CcuListIterOf <DnnTrigger> ti = Grabbed;
+	while (++ti)
+		(*ti)->Release (*this);
+
+	ti = Triggers;
 	while (++ti)
 		(*ti)->Unsubscribe (*this);
 }
@@ -55,6 +61,25 @@ DnnBaseReaction :: UnsubscribeTo (DnnTrigger& t)
 	t.Unsubscribe (*this);
 }
 
+/*?nextdoc?*/
+void
+DnnBaseReaction :: Grab (DnnTrigger& t)
+{
+	Grabbed.Append (&t);
+	t.Grab (*this);
+}
+
+/*?
+Tell that a reaction should (resp. should no more) be the only one
+activated when the trigger \var{t} causes the emission of an event.
+?*/
+void
+DnnBaseReaction :: Release (DnnTrigger& t)
+{
+	Grabbed.Remove (&t);
+	t.Release (*this);
+}
+
 /*?
 This virtual function is called when an event is emitted because of a trigger to which
 this reaction was attached. It should be redefined in derived classes to implement
diff --git a/dnn/Trigger.cc b/dnn/Trigger.cc
index 59a3b33..9b6db60 100644
--- a/dnn/Trigger.cc
+++ b/dnn/Trigger.cc
@@ -28,7 +28,8 @@ the trigger.
 Create a trigger with an empty list of associated reaction.
 ?*/
 DnnTrigger :: DnnTrigger ()
-: Subscribers ()
+: Subscribers (),
+  Grabs ()
 {
 }
 
@@ -52,6 +53,24 @@ 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);
 }
 
 /*?
@@ -60,8 +79,13 @@ Have a trigger dispatch the event \var{ev} to its associated reactions.
 void
 DnnTrigger :: Dispatch (DnnEvent& ev)
 {
-	CcuListOf <DnnBaseReaction> subscribers = Subscribers;
-	CcuListIterOf <DnnBaseReaction> ai (subscribers);
-	while (++ai)
-		(*ai)->Manage (ev);
+	DnnBaseReaction* r = Grabs.First ();
+	if (r) {
+		r->Manage (ev);
+	} else {
+		CcuListOf <DnnBaseReaction> subscribers = Subscribers;
+		CcuListIterOf <DnnBaseReaction> ai = subscribers;
+		while (++ai)
+			(*ai)->Manage (ev);
+	}
 }
-- 
cgit v1.1