From edcfa23e14d968605bd5f07ae6b0793229f11f2c Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sun, 30 Jul 2017 02:40:45 +0200
Subject: [PATCH] Binding Proxy: Drop references as requested.

---
 libs/widgets/binding_proxy.cc        | 15 +++++++++++++++
 libs/widgets/widgets/binding_proxy.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/libs/widgets/binding_proxy.cc b/libs/widgets/binding_proxy.cc
index 666797a0eb..85119ab1c0 100644
--- a/libs/widgets/binding_proxy.cc
+++ b/libs/widgets/binding_proxy.cc
@@ -20,6 +20,7 @@
 #include <iostream>
 
 #include "pbd/controllable.h"
+#include "gtkmm2ext/gui_thread.h"
 #include "gtkmm2ext/keyboard.h"
 #include "widgets/binding_proxy.h"
 #include "widgets/popup.h"
@@ -38,6 +39,12 @@ BindingProxy::BindingProxy (boost::shared_ptr<Controllable> c)
 	: prompter (0),
 	  controllable (c)
 {
+	if (c) {
+		c->DropReferences.connect (
+				_controllable_going_away_connection, invalidator (*this),
+				boost::bind (&BindingProxy::set_controllable, this, boost::shared_ptr<Controllable> ()),
+				gui_context());
+	}
 }
 
 BindingProxy::BindingProxy ()
@@ -57,6 +64,14 @@ BindingProxy::set_controllable (boost::shared_ptr<Controllable> c)
 {
 	learning_finished ();
 	controllable = c;
+
+	_controllable_going_away_connection.disconnect ();
+	if (c) {
+		c->DropReferences.connect (
+				_controllable_going_away_connection, invalidator (*this),
+				boost::bind (&BindingProxy::set_controllable, this, boost::shared_ptr<Controllable> ()),
+				gui_context());
+	}
 }
 
 void
diff --git a/libs/widgets/widgets/binding_proxy.h b/libs/widgets/widgets/binding_proxy.h
index 8ac49edb9f..4d5051382d 100644
--- a/libs/widgets/widgets/binding_proxy.h
+++ b/libs/widgets/widgets/binding_proxy.h
@@ -59,6 +59,7 @@ protected:
 	static guint bind_statemask;
 
 	PBD::ScopedConnection learning_connection;
+	PBD::ScopedConnection _controllable_going_away_connection;
 	void learning_finished ();
 	bool prompter_hiding (GdkEventAny *);
 };