Re-add Controllable registry

To facilitate a central registry with weak/shared pointer lookup,
  enable_shared_from_this<ARDOUR::AutomationControl>
was migrated to
  enable_shared_from_this<PBD::Controllable>

The main (and only) user is generic-midi surface's state interface :(

libs/ardour/ardour/automation_control.h

@@ -26,7 +26,6 @@
 #include <glibmm/threads.h>
 
 #include <boost/shared_ptr.hpp>
-#include <boost/enable_shared_from_this.hpp>
 
 #include "pbd/controllable.h"
 
@@ -51,7 +50,6 @@ class ControlGroup;
 class LIBARDOUR_API AutomationControl
 	: public PBD::Controllable
 	, public Evoral::Control
-	, public boost::enable_shared_from_this<AutomationControl>
 	, public ControlGroupMember
 	, public SessionHandleRef
 {

libs/ardour/automation_control.cc

@@ -141,7 +141,7 @@ AutomationControl::set_value (double val, PBD::Controllable::GroupControlDisposi
 	}
 
 	if (_group && _group->use_me (gcd)) {
-		_group->set_group_value (shared_from_this(), val);
+		_group->set_group_value (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()), val);
 	} else {
 		actually_set_value (val, gcd);
 	}
@@ -252,7 +252,7 @@ AutomationControl::set_automation_state (AutoState as)
 		}
 
 		if (as == Write) {
-			AutomationWatch::instance().add_automation_watch (shared_from_this());
+			AutomationWatch::instance().add_automation_watch (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()));
 		} else if (as & (Touch | Latch)) {
 			if (alist()->empty()) {
 				Control::set_double (val, _session.current_start_sample (), true);
@@ -260,17 +260,17 @@ AutomationControl::set_automation_state (AutoState as)
 				Changed (true, Controllable::NoGroup);
 			}
 			if (!touching()) {
-				AutomationWatch::instance().remove_automation_watch (shared_from_this());
+				AutomationWatch::instance().remove_automation_watch (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()));
 			} else {
 				/* this seems unlikely, but the combination of
 				 * a control surface and the mouse could make
 				 * it possible to put the control into Touch
 				 * mode *while* touching it.
 				 */
-				AutomationWatch::instance().add_automation_watch (shared_from_this());
+				AutomationWatch::instance().add_automation_watch (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()));
 			}
 		} else {
-			AutomationWatch::instance().remove_automation_watch (shared_from_this());
+			AutomationWatch::instance().remove_automation_watch (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()));
 			Changed (false, Controllable::NoGroup);
 		}
 	}
@@ -293,7 +293,7 @@ AutomationControl::start_touch (double when)
 		AutomationControl::actually_set_value (get_value (), Controllable::NoGroup);
 		alist()->start_touch (when);
 		if (!_desc.toggled) {
-			AutomationWatch::instance().add_automation_watch (shared_from_this());
+			AutomationWatch::instance().add_automation_watch (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()));
 		}
 		set_touching (true);
 	}
@@ -315,7 +315,7 @@ AutomationControl::stop_touch (double when)
 	if (alist()->automation_state() & (Touch | Latch)) {
 		alist()->stop_touch (when);
 		if (!_desc.toggled) {
-			AutomationWatch::instance().remove_automation_watch (shared_from_this());
+			AutomationWatch::instance().remove_automation_watch (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()));
 		}
 	}
 }
@@ -378,7 +378,7 @@ AutomationControl::check_rt (double val, Controllable::GroupControlDisposition g
 {
 	if (!_session.loading() && (flags() & Controllable::RealTime) && !AudioEngine::instance()->in_process_thread()) {
 		/* queue change in RT context */
-		_session.set_control (shared_from_this(), val, gcd);
+		_session.set_control (boost::dynamic_pointer_cast<AutomationControl>(shared_from_this()), val, gcd);
 		return true;
 	}
 

libs/ardour/pan_controllable.cc

@@ -57,5 +57,5 @@ PanControllable::actually_set_value (double v, Controllable::GroupControlDisposi
 std::string
 PanControllable::get_user_string () const
 {
-	return owner->value_as_string (shared_from_this());
+	return owner->value_as_string (boost::dynamic_pointer_cast<const AutomationControl>(shared_from_this()));
 }

libs/pbd/controllable.cc

@@ -34,13 +34,19 @@ PBD::Signal1<bool, boost::weak_ptr<PBD::Controllable> > Controllable::StartLearn
 PBD::Signal1<void, boost::weak_ptr<PBD::Controllable> > Controllable::StopLearning;
 PBD::Signal1<void, boost::weak_ptr<PBD::Controllable> > Controllable::GUIFocusChanged;
 
+Glib::Threads::RWLock Controllable::registry_lock;
+Controllable::Controllables Controllable::registry;
+PBD::ScopedConnectionList Controllable::registry_connections;
+
 const std::string Controllable::xml_node_name = X_("Controllable");
 
 Controllable::Controllable (const string& name, Flag f)
 	: _name (name)
 	, _flags (f)
 	, _touching (false)
-{}
+{
+	add (*this);
+}
 
 XMLNode&
 Controllable::get_state ()
@@ -91,3 +97,34 @@ Controllable::set_flags (Flag f)
 {
 	_flags = f;
 }
+
+void
+Controllable::add (Controllable& ctl)
+{
+	Glib::Threads::RWLock::WriterLock lm (registry_lock);
+	registry.insert (&ctl);
+	ctl.DropReferences.connect_same_thread (registry_connections, boost::bind (&Controllable::remove, &ctl));
+}
+
+void
+Controllable::remove (Controllable* ctl)
+{
+	Glib::Threads::RWLock::WriterLock lm (registry_lock);
+	Controllables::iterator i = std::find (registry.begin(), registry.end(), ctl);
+	if (i != registry.end()) {
+		registry.erase (i);
+	}
+}
+
+boost::shared_ptr<Controllable>
+Controllable::by_id (const ID& id)
+{
+	Glib::Threads::RWLock::ReaderLock lm (registry_lock);
+
+	for (Controllables::iterator i = registry.begin(); i != registry.end(); ++i) {
+		if ((*i)->id() == id) {
+			return (*i)->shared_from_this ();
+		}
+	}
+	return boost::shared_ptr<Controllable>();
+}

libs/pbd/pbd/controllable.h

@@ -28,6 +28,8 @@
 #include "pbd/signals.h"
 #include <glibmm/threads.h>
 
+#include <boost/enable_shared_from_this.hpp>
+
 #include "pbd/statefuldestructible.h"
 
 using std::min;
@@ -49,7 +51,8 @@ namespace PBD {
  * as a control whose value can range between 0 and 1.0.
  *
  */
-class LIBPBD_API Controllable : public PBD::StatefulDestructible {
+class LIBPBD_API Controllable : public PBD::StatefulDestructible, public boost::enable_shared_from_this<Controllable>
+{
 public:
 	enum Flag {
 		Toggle = 0x1,
@@ -150,6 +153,8 @@ public:
 	Flag flags() const { return _flags; }
 	void set_flags (Flag f);
 
+	static boost::shared_ptr<Controllable> by_id (const PBD::ID&);
+
 	static const std::string xml_node_name;
 
 protected:
@@ -160,11 +165,20 @@ protected:
 	}
 
 private:
-
 	std::string _name;
 	std::string _units;
 	Flag        _flags;
 	bool        _touching;
+
+	typedef std::set<PBD::Controllable*> Controllables;
+
+	static ScopedConnectionList registry_connections;
+	static Glib::Threads::RWLock registry_lock;
+	static Controllables registry;
+
+	static void add (Controllable&);
+	static void remove (Controllable*);
+
 };
 
 /* a utility class for the occasions when you need but do not have