Support multiple readers for MIDI source/model

Fixes the multiple reader issue #6541 properly without resorting to a
linear search kludge.

All the read state has been pulled out into a MidiCursor which the
caller is required to pass.  The playlist keeps cursors for all the
regions it is reading, any number of cursors are allowed at a time.

MidiCursor should probably be made a smarter and more fool-proof
object (and/or possibly merged with some of the other tracker/fixer
stuff) but for now I wanted to keep it simple.

6 files changed, 75 insertions, 16 deletions

diff --git a/libs/ardour/ardour/midi_cursor.h b/libs/ardour/ardour/midi_cursor.h
new file mode 100644
index 0000000000..5cb89c87f5
--- /dev/null
+++ b/libs/ardour/ardour/midi_cursor.h
@@ -0,0 +1,56 @@
+/*
+    Copyright (C) 2016 Paul Davis
+    Author: David Robillard
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __ardour_midi_cursor_h__
+#define __ardour_midi_cursor_h__
+
+#include <set>
+
+#include <boost/utility.hpp>
+
+#include "ardour/types.h"
+#include "evoral/Beats.hpp"
+#include "evoral/Sequence.hpp"
+#include "pbd/signals.h"
+
+namespace ARDOUR {
+
+struct MidiCursor : public boost::noncopyable {
+	MidiCursor() : last_read_end(0) {}
+
+	void connect(PBD::Signal1<void, bool>& invalidated) {
+		connections.drop_connections();
+		invalidated.connect_same_thread(
+			connections, boost::bind(&MidiCursor::invalidate, this, _1));
+	}
+
+	void invalidate(bool preserve_notes) {
+		iter.invalidate(preserve_notes ? &active_notes : NULL);
+		last_read_end = 0;
+	}
+
+	Evoral::Sequence<Evoral::Beats>::const_iterator        iter;
+	std::set<Evoral::Sequence<Evoral::Beats>::WeakNotePtr> active_notes;
+	framepos_t                                             last_read_end;
+	PBD::ScopedConnectionList                              connections;
+};
+
+}
+
+#endif /* __ardour_midi_cursor_h__ */
diff --git a/libs/ardour/ardour/midi_model.h b/libs/ardour/ardour/midi_model.h
index c5467cc58d..cdf7b3fd3b 100644
--- a/libs/ardour/ardour/midi_model.h
+++ b/libs/ardour/ardour/midi_model.h
@@ -292,8 +292,6 @@ public:
 	void insert_silence_at_start (TimeType);
 	void transpose (NoteDiffCommand *, const NotePtr, int);
 
-	std::set<WeakNotePtr>& active_notes() { return _active_notes; }
-
 protected:
 	int resolve_overlaps_unlocked (const NotePtr, void* arg = 0);
 
@@ -327,8 +325,6 @@ private:
 	// We cannot use a boost::shared_ptr here to avoid a retain cycle
 	boost::weak_ptr<MidiSource> _midi_source;
 	InsertMergePolicy _insert_merge_policy;
-
-	std::set<WeakNotePtr> _active_notes;
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/midi_playlist.h b/libs/ardour/ardour/midi_playlist.h
index ad0a812cba..3c031a994f 100644
--- a/libs/ardour/ardour/midi_playlist.h
+++ b/libs/ardour/ardour/midi_playlist.h
@@ -26,6 +26,7 @@
 #include <boost/utility.hpp>
 
 #include "ardour/ardour.h"
+#include "ardour/midi_cursor.h"
 #include "ardour/midi_model.h"
 #include "ardour/midi_state_tracker.h"
 #include "ardour/note_fixer.h"
@@ -112,12 +113,14 @@ public:
 
 protected:
 	void remove_dependents (boost::shared_ptr<Region> region);
+	void region_going_away (boost::weak_ptr<Region> region);
 
 private:
 	typedef Evoral::Note<Evoral::Beats> Note;
 	typedef Evoral::Event<framepos_t>   Event;
 
 	struct RegionTracker : public boost::noncopyable {
+		MidiCursor       cursor;   ///< Cursor (iterator and read state)
 		MidiStateTracker tracker;  ///< Active note tracker
 		NoteFixer        fixer;    ///< Edit compensation
 	};
diff --git a/libs/ardour/ardour/midi_region.h b/libs/ardour/ardour/midi_region.h
index 0ad60a900c..d3a6cbbbb8 100644
--- a/libs/ardour/ardour/midi_region.h
+++ b/libs/ardour/ardour/midi_region.h
@@ -45,6 +45,7 @@ template<typename Time> class EventSink;
 namespace ARDOUR {
 
 class MidiChannelFilter;
+class MidiCursor;
 class MidiFilter;
 class MidiModel;
 class MidiSource;
@@ -77,6 +78,7 @@ class LIBARDOUR_API MidiRegion : public Region
 	                    framepos_t position,
 	                    framecnt_t dur,
 	                    Evoral::Range<framepos_t>* loop_range,
+	                    MidiCursor& cursor,
 	                    uint32_t  chan_n = 0,
 	                    NoteMode  mode = Sustained,
 	                    MidiStateTracker* tracker = 0,
@@ -86,6 +88,7 @@ class LIBARDOUR_API MidiRegion : public Region
 	                           framepos_t position,
 	                           framecnt_t dur,
 	                           Evoral::Range<framepos_t>* loop_range,
+	                           MidiCursor& cursor,
 	                           uint32_t  chan_n = 0,
 	                           NoteMode  mode = Sustained) const;
 
@@ -130,6 +133,7 @@ class LIBARDOUR_API MidiRegion : public Region
 	                     framepos_t position,
 	                     framecnt_t dur,
 	                     Evoral::Range<framepos_t>* loop_range,
+	                     MidiCursor& cursor,
 	                     uint32_t chan_n = 0,
 	                     NoteMode mode = Sustained,
 	                     MidiStateTracker* tracker = 0,
diff --git a/libs/ardour/ardour/midi_source.h b/libs/ardour/ardour/midi_source.h
index 4815263739..1ff0a08f71 100644
--- a/libs/ardour/ardour/midi_source.h
+++ b/libs/ardour/ardour/midi_source.h
@@ -36,8 +36,9 @@
 namespace ARDOUR {
 
 class MidiChannelFilter;
-class MidiStateTracker;
+class MidiCursor;
 class MidiModel;
+class MidiStateTracker;
 
 template<typename T> class MidiRingBuffer;
 
@@ -87,18 +88,18 @@ class LIBARDOUR_API MidiSource : virtual public Source, public boost::enable_sha
 	 * \param tracker an optional pointer to MidiStateTracker object, for note on/off tracking.
 	 * \param filtered Parameters whose MIDI messages will not be returned.
 	 */
-
 	virtual framecnt_t midi_read (const Lock&                        lock,
 	                              Evoral::EventSink<framepos_t>&     dst,
 	                              framepos_t                         source_start,
 	                              framepos_t                         start,
 	                              framecnt_t                         cnt,
 	                              Evoral::Range<framepos_t>*         loop_range,
+	                              MidiCursor&                        cursor,
 	                              MidiStateTracker*                  tracker,
 	                              MidiChannelFilter*                 filter,
 	                              const std::set<Evoral::Parameter>& filtered,
-				      const double                       pulse,
-				      const double                       start_beats) const;
+	                              const double                       pulse,
+	                              const double                       start_beats) const;
 
 	/** Write data from a MidiRingBuffer to this source.
 	 *  @param source Source to read from.
@@ -175,10 +176,11 @@ class LIBARDOUR_API MidiSource : virtual public Source, public boost::enable_sha
 
 	/** Reset cached information (like iterators) when things have changed.
 	 * @param lock Source lock, which must be held by caller.
-	 * @param notes If non-NULL, currently active notes are added to this set.
 	 */
-	void invalidate(const Glib::Threads::Mutex::Lock&                       lock,
-	                std::set<Evoral::Sequence<Evoral::Beats>::WeakNotePtr>* notes=NULL);
+	void invalidate(const Glib::Threads::Mutex::Lock& lock);
+
+	/** Thou shalt not emit this directly, use invalidate() instead. */
+	mutable PBD::Signal1<void, bool> Invalidated;
 
 	void set_note_mode(const Glib::Threads::Mutex::Lock& lock, NoteMode mode);
 
@@ -230,11 +232,7 @@ class LIBARDOUR_API MidiSource : virtual public Source, public boost::enable_sha
 	boost::shared_ptr<MidiModel> _model;
 	bool                         _writing;
 
-	mutable Evoral::Sequence<Evoral::Beats>::const_iterator _model_iter;
-	mutable bool                                            _model_iter_valid;
-
-	mutable Evoral::Beats _length_beats;
-	mutable framepos_t    _last_read_end;
+	Evoral::Beats _length_beats;
 
 	/** The total duration of the current capture. */
 	framepos_t _capture_length;
diff --git a/libs/ardour/ardour/playlist.h b/libs/ardour/ardour/playlist.h
index 04615acb26..1530eede9f 100644
--- a/libs/ardour/ardour/playlist.h
+++ b/libs/ardour/ardour/playlist.h
@@ -276,6 +276,7 @@ public:
 	RegionListProperty   regions;  /* the current list of regions in the playlist */
 	std::set<boost::shared_ptr<Region> > all_regions; /* all regions ever added to this playlist */
 	PBD::ScopedConnectionList region_state_changed_connections;
+	PBD::ScopedConnectionList region_drop_references_connections;
 	DataType        _type;
 	int             _sort_id;
 	mutable gint    block_notifications;
@@ -359,6 +360,7 @@ public:
 
 
 	virtual void remove_dependents (boost::shared_ptr<Region> /*region*/) {}
+	virtual void region_going_away (boost::weak_ptr<Region> /*region*/) {}
 
 	virtual XMLNode& state (bool);