Replace May/Done/NotDone signal sets with one signal and extend

this treatment to anything that caused Player::setup_pieces.  This should
fix out-of-sequence Player emissions caused by setup_pieces being called
by one thread while the butler is calling pass().

27 files changed, 195 insertions, 237 deletions

diff --git a/src/lib/butler.cc b/src/lib/butler.cc
index f04b324cd..3a75e67d7 100644
--- a/src/lib/butler.cc
+++ b/src/lib/butler.cc
@@ -65,9 +65,7 @@ Butler::Butler (shared_ptr<Player> player, shared_ptr<Log> log, AudioMapping aud
 	_player_video_connection = _player->Video.connect (bind (&Butler::video, this, _1, _2));
 	_player_audio_connection = _player->Audio.connect (bind (&Butler::audio, this, _1, _2));
 	_player_text_connection = _player->Text.connect (bind (&Butler::text, this, _1, _2, _3));
-	_player_may_change_connection = _player->MayChange.connect (bind (&Butler::suspend, this));
-	_player_changed_connection = _player->Changed.connect (bind (&Butler::return_seek, this, _2));
-	_player_not_changed_connection = _player->NotChanged.connect (bind (&Butler::return_seek, this, false));
+	_player_change_connection = _player->Change.connect (bind (&Butler::player_change, this, _1, _3));
 	_thread = new boost::thread (bind (&Butler::thread, this));
 #ifdef DCPOMATIC_LINUX
 	pthread_setname_np (_thread->native_handle(), "butler");
@@ -107,10 +105,6 @@ Butler::~Butler ()
 bool
 Butler::should_run () const
 {
-	if (_suspended) {
-		return false;
-	}
-
 	if (_video.size() >= MAXIMUM_VIDEO_READAHEAD * 10) {
 		/* This is way too big */
 		throw ProgrammingError
@@ -131,7 +125,7 @@ Butler::should_run () const
 		LOG_WARNING ("Butler audio buffers reached %1 frames (video is %2)", _audio.size(), _video.size());
 	}
 
-	if (_stop_thread || _finished || _died) {
+	if (_stop_thread || _finished || _died || _suspended) {
 		/* Definitely do not run */
 		return false;
 	}
@@ -198,7 +192,7 @@ Butler::get_video ()
 	boost::mutex::scoped_lock lm (_mutex);
 
 	/* Wait for data if we have none */
-	while (_video.empty() && !_finished && !_died) {
+	while (_video.empty() && !_finished && !_died && !_suspended) {
 		_arrived.wait (lm);
 	}
 
@@ -316,27 +310,33 @@ Butler::memory_used () const
 }
 
 void
-Butler::return_seek (bool frequent)
+Butler::player_change (ChangeType type, bool frequent)
 {
 	boost::mutex::scoped_lock lm (_mutex);
-	if (_died || _pending_seek_position || frequent) {
-		return;
-	}
 
-	DCPTime seek_to;
-	DCPTime next = _video.get().second;
-	if (_awaiting && _awaiting > next) {
-		/* We have recently done a player_changed seek and our buffers haven't been refilled yet,
-		   so assume that we're seeking to the same place as last time.
-		*/
-		seek_to = *_awaiting;
-	} else {
-		seek_to = next;
-	}
+	if (type == CHANGE_TYPE_PENDING) {
+		_suspended = true;
+	} else if (type == CHANGE_TYPE_DONE) {
+
+		if (_died || _pending_seek_position || frequent) {
+			return;
+		}
+
+		DCPTime seek_to;
+		DCPTime next = _video.get().second;
+		if (_awaiting && _awaiting > next) {
+			/* We have recently done a player_changed seek and our buffers haven't been refilled yet,
+			   so assume that we're seeking to the same place as last time.
+			*/
+			seek_to = *_awaiting;
+		} else {
+			seek_to = next;
+		}
 
-	seek_unlocked (seek_to, true);
-	_suspended = false;
-	_awaiting = seek_to;
+		seek_unlocked (seek_to, true);
+		_suspended = false;
+		_awaiting = seek_to;
+	}
 }
 
 void
@@ -349,10 +349,3 @@ Butler::text (PlayerText pt, TextType type, DCPTimePeriod period)
 	boost::mutex::scoped_lock lm2 (_buffers_mutex);
 	_closed_caption.put (make_pair(pt, period));
 }
-
-void
-Butler::suspend ()
-{
-	boost::mutex::scoped_lock lm (_mutex);
-	_suspended = true;
-}
diff --git a/src/lib/butler.h b/src/lib/butler.h
index 6a13ed2d7..513176821 100644
--- a/src/lib/butler.h
+++ b/src/lib/butler.h
@@ -56,8 +56,7 @@ private:
 	void text (PlayerText pt, TextType type, DCPTimePeriod period);
 	bool should_run () const;
 	void prepare (boost::weak_ptr<PlayerVideo> video) const;
-	void suspend ();
-	void return_seek (bool frequent);
+	void player_change (ChangeType type, bool frequent);
 	void seek_unlocked (DCPTime position, bool accurate);
 
 	boost::shared_ptr<Player> _player;
@@ -102,7 +101,5 @@ private:
 	boost::signals2::scoped_connection _player_video_connection;
 	boost::signals2::scoped_connection _player_audio_connection;
 	boost::signals2::scoped_connection _player_text_connection;
-	boost::signals2::scoped_connection _player_may_change_connection;
-	boost::signals2::scoped_connection _player_changed_connection;
-	boost::signals2::scoped_connection _player_not_changed_connection;
+	boost::signals2::scoped_connection _player_change_connection;
 };
diff --git a/src/lib/content.cc b/src/lib/content.cc
index 8fd36a1d8..ae0b08dcc 100644
--- a/src/lib/content.cc
+++ b/src/lib/content.cc
@@ -179,10 +179,14 @@ Content::examine (shared_ptr<Job> job)
 }
 
 void
-Content::signal_changed (int p)
+Content::signal_change (ChangeType c, int p)
 {
 	try {
-		emit (boost::bind (boost::ref(Changed), shared_from_this(), p, _change_signals_frequent));
+		if (c == CHANGE_TYPE_PENDING || c == CHANGE_TYPE_CANCELLED) {
+			Change (c, shared_from_this(), p, _change_signals_frequent);
+		} else {
+			emit (boost::bind (boost::ref(Change), c, shared_from_this(), p, _change_signals_frequent));
+		}
 	} catch (boost::bad_weak_ptr) {
 		/* This must be during construction; never mind */
 	}
diff --git a/src/lib/content.h b/src/lib/content.h
index c9edf6e22..e8710ccb7 100644
--- a/src/lib/content.h
+++ b/src/lib/content.h
@@ -178,14 +178,8 @@ public:
 
 	std::list<UserProperty> user_properties () const;
 
-	/* May be emitted from any thread */
-	boost::signals2::signal<void ()> MayChange;
-
-	/* Emitted from the GUI thread */
-	boost::signals2::signal<void (boost::weak_ptr<Content>, int, bool)> Changed;
-
-	/* May be emitted from any thread */
-	boost::signals2::signal<void ()> NotChanged;
+	/* CHANGE_PENDING and CHANGE_CANCELLED may be emitted from any thread; CHANGE_DONE always from GUI thread */
+	boost::signals2::signal<void (ChangeType, boost::weak_ptr<Content>, int, bool)> Change;
 
 	boost::shared_ptr<VideoContent> video;
 	boost::shared_ptr<AudioContent> audio;
@@ -215,7 +209,7 @@ private:
 	friend struct audio_sampling_rate_test;
 	friend class ContentChange;
 
-	void signal_changed (int);
+	void signal_change (ChangeType, int);
 
 	std::string _digest;
 	DCPTime _position;
diff --git a/src/lib/content_change.cc b/src/lib/content_change.cc
index c286f80eb..6e390dc76 100644
--- a/src/lib/content_change.cc
+++ b/src/lib/content_change.cc
@@ -26,16 +26,16 @@ ContentChange::ContentChange (Content* c, int p)
 	, _property (p)
 	, _done (true)
 {
-	_content->MayChange ();
+	_content->signal_change (CHANGE_TYPE_PENDING, _property);
 }
 
 
 ContentChange::~ContentChange ()
 {
 	if (_done) {
-		_content->signal_changed (_property);
+		_content->signal_change (CHANGE_TYPE_DONE, _property);
 	} else {
-		_content->NotChanged ();
+		_content->signal_change (CHANGE_TYPE_CANCELLED, _property);
 	}
 }
 
diff --git a/src/lib/film.cc b/src/lib/film.cc
index ba97f833e..846e8ac51 100644
--- a/src/lib/film.cc
+++ b/src/lib/film.cc
@@ -160,9 +160,9 @@ Film::Film (optional<boost::filesystem::path> dir)
 {
 	set_isdcf_date_today ();
 
-	_playlist_changed_connection = _playlist->Changed.connect (bind (&Film::playlist_changed, this));
+	_playlist_change_connection = _playlist->Change.connect (bind (&Film::playlist_change, this, _1));
 	_playlist_order_changed_connection = _playlist->OrderChanged.connect (bind (&Film::playlist_order_changed, this));
-	_playlist_content_changed_connection = _playlist->ContentChanged.connect (bind (&Film::playlist_content_changed, this, _1, _2, _3));
+	_playlist_content_change_connection = _playlist->ContentChange.connect (bind (&Film::playlist_content_change, this, _1, _2, _3, _4));
 
 	if (dir) {
 		/* Make state.directory a complete path without ..s (where possible)
@@ -1154,8 +1154,12 @@ Film::active_frame_rate_change (DCPTime t) const
 }
 
 void
-Film::playlist_content_changed (weak_ptr<Content> c, int p, bool frequent)
+Film::playlist_content_change (ChangeType type, weak_ptr<Content> c, int p, bool frequent)
 {
+	if (type != CHANGE_TYPE_DONE) {
+		return;
+	}
+
 	_dirty = true;
 
 	if (p == ContentProperty::VIDEO_FRAME_RATE) {
@@ -1164,14 +1168,16 @@ Film::playlist_content_changed (weak_ptr<Content> c, int p, bool frequent)
 		signal_changed (NAME);
 	}
 
-	emit (boost::bind (boost::ref (ContentChanged), c, p, frequent));
+	emit (boost::bind (boost::ref (ContentChange), type, c, p, frequent));
 }
 
 void
-Film::playlist_changed ()
+Film::playlist_change (ChangeType type)
 {
-	signal_changed (CONTENT);
-	signal_changed (NAME);
+	if (type == CHANGE_TYPE_DONE) {
+		signal_changed (CONTENT);
+		signal_changed (NAME);
+	}
 }
 
 void
diff --git a/src/lib/film.h b/src/lib/film.h
index 20a1e2ca6..c6c8403cb 100644
--- a/src/lib/film.h
+++ b/src/lib/film.h
@@ -327,7 +327,7 @@ public:
 	mutable boost::signals2::signal<void (Property)> Changed;
 
 	/** Emitted when some property of our content has changed */
-	mutable boost::signals2::signal<void (boost::weak_ptr<Content>, int, bool)> ContentChanged;
+	mutable boost::signals2::signal<void (ChangeType, boost::weak_ptr<Content>, int, bool)> ContentChange;
 
 	/** Current version number of the state file */
 	static int const current_state_version;
@@ -338,9 +338,9 @@ private:
 
 	void signal_changed (Property);
 	std::string video_identifier () const;
-	void playlist_changed ();
+	void playlist_change (ChangeType);
 	void playlist_order_changed ();
-	void playlist_content_changed (boost::weak_ptr<Content>, int, bool frequent);
+	void playlist_content_change (ChangeType type, boost::weak_ptr<Content>, int, bool frequent);
 	void maybe_add_content (boost::weak_ptr<Job>, boost::weak_ptr<Content>, bool disable_audio_analysis);
 	void audio_analysis_finished ();
 
@@ -401,9 +401,9 @@ private:
 	/** film being used as a template, or 0 */
 	boost::shared_ptr<Film> _template_film;
 
-	boost::signals2::scoped_connection _playlist_changed_connection;
+	boost::signals2::scoped_connection _playlist_change_connection;
 	boost::signals2::scoped_connection _playlist_order_changed_connection;
-	boost::signals2::scoped_connection _playlist_content_changed_connection;
+	boost::signals2::scoped_connection _playlist_content_change_connection;
 	std::list<boost::signals2::connection> _job_connections;
 	std::list<boost::signals2::connection> _audio_analysis_connections;
 
diff --git a/src/lib/player.cc b/src/lib/player.cc
index df8c47cf9..0c3aea028 100644
--- a/src/lib/player.cc
+++ b/src/lib/player.cc
@@ -98,10 +98,8 @@ Player::Player (shared_ptr<const Film> film, shared_ptr<const Playlist> playlist
 	, _shuffler (0)
 {
 	_film_changed_connection = _film->Changed.connect (bind (&Player::film_changed, this, _1));
-	_playlist_changed_connection = _playlist->Changed.connect (bind (&Player::playlist_changed, this));
-	_playlist_content_may_change_connection = _playlist->ContentMayChange.connect (bind(&Player::playlist_content_may_change, this));
-	_playlist_content_changed_connection = _playlist->ContentChanged.connect (bind(&Player::playlist_content_changed, this, _1, _2, _3));
-	_playlist_content_not_changed_connection = _playlist->ContentNotChanged.connect (bind(&Player::playlist_content_not_changed, this));
+	_playlist_change_connection = _playlist->Change.connect (bind (&Player::playlist_change, this, _1));
+	_playlist_content_change_connection = _playlist->ContentChange.connect (bind(&Player::playlist_content_change, this, _1, _3, _4));
 	set_video_container_size (_film->frame_size ());
 
 	film_changed (Film::AUDIO_PROCESSOR);
@@ -224,78 +222,21 @@ Player::setup_pieces_unlocked ()
 }
 
 void
-Player::playlist_content_may_change ()
+Player::playlist_content_change (ChangeType type, int property, bool frequent)
 {
-	{
+	if (type == CHANGE_TYPE_PENDING) {
 		boost::mutex::scoped_lock lm (_mutex);
 		/* The player content is probably about to change, so we can't carry on
 		   until that has happened and we've rebuilt our pieces.  Stop pass()
 		   and seek() from working until then.
 		*/
 		_suspended = true;
+	} else if (type == CHANGE_TYPE_DONE) {
+		/* A change in our content has gone through.  Re-build our pieces. */
+		setup_pieces ();
 	}
 
-	MayChange ();
-}
-
-void
-Player::playlist_content_changed (weak_ptr<Content> w, int property, bool frequent)
-{
-	/* A change in our content has gone through.  Re-build our pieces and signal
-	   it to anybody that is interested.
-	*/
-
-	shared_ptr<Content> c = w.lock ();
-	if (!c) {
-		return;
-	}
-
-	setup_pieces ();
-
-	if (
-		property == ContentProperty::POSITION ||
-		property == ContentProperty::LENGTH ||
-		property == ContentProperty::TRIM_START ||
-		property == ContentProperty::TRIM_END ||
-		property == ContentProperty::PATH ||
-		property == VideoContentProperty::FRAME_TYPE ||
-		property == VideoContentProperty::COLOUR_CONVERSION ||
-		property == AudioContentProperty::STREAMS ||
-		property == DCPContentProperty::NEEDS_ASSETS ||
-		property == DCPContentProperty::NEEDS_KDM ||
-		property == DCPContentProperty::CPL ||
-		property == TextContentProperty::COLOUR ||
-		property == TextContentProperty::EFFECT ||
-		property == TextContentProperty::EFFECT_COLOUR ||
-		property == FFmpegContentProperty::SUBTITLE_STREAM ||
-		property == FFmpegContentProperty::FILTERS ||
-		property == TextContentProperty::LINE_SPACING ||
-		property == TextContentProperty::OUTLINE_WIDTH ||
-		property == TextContentProperty::Y_SCALE ||
-		property == TextContentProperty::FADE_IN ||
-		property == TextContentProperty::FADE_OUT ||
-		property == ContentProperty::VIDEO_FRAME_RATE ||
-		property == TextContentProperty::USE ||
-		property == TextContentProperty::X_OFFSET ||
-		property == TextContentProperty::Y_OFFSET ||
-		property == TextContentProperty::X_SCALE ||
-		property == TextContentProperty::FONTS ||
-		property == TextContentProperty::TYPE ||
-		property == VideoContentProperty::CROP ||
-		property == VideoContentProperty::SCALE ||
-		property == VideoContentProperty::FADE_IN ||
-		property == VideoContentProperty::FADE_OUT
-		) {
-
-		Changed (property, frequent);
-	}
-}
-
-void
-Player::playlist_content_not_changed ()
-{
-	/* A possible content change did end up happening for some reason */
-	NotChanged ();
+	Change (type, property, frequent);
 }
 
 void
@@ -314,14 +255,16 @@ Player::set_video_container_size (dcp::Size s)
 		_black_image->make_black ();
 	}
 
-	Changed (PlayerProperty::VIDEO_CONTAINER_SIZE, false);
+	Change (CHANGE_TYPE_DONE, PlayerProperty::VIDEO_CONTAINER_SIZE, false);
 }
 
 void
-Player::playlist_changed ()
+Player::playlist_change (ChangeType type)
 {
-	setup_pieces ();
-	Changed (PlayerProperty::PLAYLIST, false);
+	if (type == CHANGE_TYPE_DONE) {
+		setup_pieces ();
+	}
+	Change (type, PlayerProperty::PLAYLIST, false);
 }
 
 void
@@ -333,13 +276,14 @@ Player::film_changed (Film::Property p)
 	*/
 
 	if (p == Film::CONTAINER) {
-		Changed (PlayerProperty::FILM_CONTAINER, false);
+		Change (CHANGE_TYPE_PENDING, PlayerProperty::FILM_CONTAINER, false);
 	} else if (p == Film::VIDEO_FRAME_RATE) {
 		/* Pieces contain a FrameRateChange which contains the DCP frame rate,
 		   so we need new pieces here.
 		*/
+		/* XXX: missing PENDING! */
 		setup_pieces ();
-		Changed (PlayerProperty::FILM_VIDEO_FRAME_RATE, false);
+		Change (CHANGE_TYPE_DONE, PlayerProperty::FILM_VIDEO_FRAME_RATE, false);
 	} else if (p == Film::AUDIO_PROCESSOR) {
 		if (_film->audio_processor ()) {
 			boost::mutex::scoped_lock lm (_mutex);
@@ -1187,10 +1131,14 @@ Player::discard_audio (shared_ptr<const AudioBuffers> audio, DCPTime time, DCPTi
 void
 Player::set_dcp_decode_reduction (optional<int> reduction)
 {
+	Change (CHANGE_TYPE_PENDING, PlayerProperty::DCP_DECODE_REDUCTION, false);
+
 	{
 		boost::mutex::scoped_lock lm (_mutex);
 
 		if (reduction == _dcp_decode_reduction) {
+			lm.unlock ();
+			Change (CHANGE_TYPE_CANCELLED, PlayerProperty::DCP_DECODE_REDUCTION, false);
 			return;
 		}
 
@@ -1198,7 +1146,7 @@ Player::set_dcp_decode_reduction (optional<int> reduction)
 		setup_pieces_unlocked ();
 	}
 
-	Changed (PlayerProperty::DCP_DECODE_REDUCTION, false);
+	Change (CHANGE_TYPE_DONE, PlayerProperty::DCP_DECODE_REDUCTION, false);
 }
 
 optional<DCPTime>
diff --git a/src/lib/player.h b/src/lib/player.h
index f7ab1000d..165820799 100644
--- a/src/lib/player.h
+++ b/src/lib/player.h
@@ -88,19 +88,7 @@ public:
 
 	boost::optional<DCPTime> content_time_to_dcp (boost::shared_ptr<Content> content, ContentTime t);
 
-	/* The player's internal state may be about to change such so
-	   that its emissions from Video and Audio will suddenly be
-	   from an undefined position.  Listeners should prepare
-	   themselves for this possibility.
-	*/
-	boost::signals2::signal<void ()> MayChange;
-
-	/** The player's internal state has now changed.
-	 *
-	 *  The first parameter is what changed.
-	 *  The second parameter is true if these signals are currently likely to be frequent.
-	 */
-	boost::signals2::signal<void (int, bool)> Changed;
+	boost::signals2::signal<void (ChangeType, int, bool)> Change;
 
 	/** The change suggested by a MayChange did not happen */
 	boost::signals2::signal<void ()> NotChanged;
@@ -125,10 +113,8 @@ private:
 	void setup_pieces_unlocked ();
 	void flush ();
 	void film_changed (Film::Property);
-	void playlist_changed ();
-	void playlist_content_may_change ();
-	void playlist_content_changed (boost::weak_ptr<Content>, int, bool);
-	void playlist_content_not_changed ();
+	void playlist_change (ChangeType);
+	void playlist_content_change (ChangeType, int, bool);
 	std::list<PositionImage> transform_bitmap_texts (std::list<BitmapText>) const;
 	Frame dcp_to_content_video (boost::shared_ptr<const Piece> piece, DCPTime t) const;
 	DCPTime content_video_to_dcp (boost::shared_ptr<const Piece> piece, Frame f) const;
@@ -217,10 +203,8 @@ private:
 	boost::shared_ptr<AudioProcessor> _audio_processor;
 
 	boost::signals2::scoped_connection _film_changed_connection;
-	boost::signals2::scoped_connection _playlist_changed_connection;
-	boost::signals2::scoped_connection _playlist_content_may_change_connection;
-	boost::signals2::scoped_connection _playlist_content_changed_connection;
-	boost::signals2::scoped_connection _playlist_content_not_changed_connection;
+	boost::signals2::scoped_connection _playlist_change_connection;
+	boost::signals2::scoped_connection _playlist_content_change_connection;
 };
 
 #endif
diff --git a/src/lib/playlist.cc b/src/lib/playlist.cc
index 1bb0ad0d6..e4fc0f072 100644
--- a/src/lib/playlist.cc
+++ b/src/lib/playlist.cc
@@ -65,48 +65,38 @@ Playlist::~Playlist ()
 }
 
 void
-Playlist::content_may_change ()
+Playlist::content_change (ChangeType type, weak_ptr<Content> content, int property, bool frequent)
 {
-	ContentMayChange ();
-}
+	if (type == CHANGE_TYPE_DONE) {
+		if (
+			property == ContentProperty::TRIM_START ||
+			property == ContentProperty::TRIM_END ||
+			property == ContentProperty::LENGTH ||
+			property == VideoContentProperty::FRAME_TYPE
+			) {
+			/* Don't respond to position changes here, as:
+			   - sequencing after earlier/later changes is handled by move_earlier/move_later
+			   - any other position changes will be timeline drags which should not result in content
+			   being sequenced.
+			*/
+			maybe_sequence ();
+		}
 
-void
-Playlist::content_not_changed ()
-{
-	ContentNotChanged ();
-}
+		if (
+			property == ContentProperty::POSITION ||
+			property == ContentProperty::LENGTH ||
+			property == ContentProperty::TRIM_START ||
+			property == ContentProperty::TRIM_END) {
 
-void
-Playlist::content_changed (weak_ptr<Content> content, int property, bool frequent)
-{
-	if (
-		property == ContentProperty::TRIM_START ||
-		property == ContentProperty::TRIM_END ||
-		property == ContentProperty::LENGTH ||
-		property == VideoContentProperty::FRAME_TYPE
-		) {
-		/* Don't respond to position changes here, as:
-		   - sequencing after earlier/later changes is handled by move_earlier/move_later
-		   - any other position changes will be timeline drags which should not result in content
-		   being sequenced.
-		*/
-		maybe_sequence ();
-	}
-
-	if (
-		property == ContentProperty::POSITION ||
-		property == ContentProperty::LENGTH ||
-		property == ContentProperty::TRIM_START ||
-		property == ContentProperty::TRIM_END) {
-
-		ContentList old = _content;
-		sort (_content.begin(), _content.end(), ContentSorter ());
-		if (_content != old) {
-			OrderChanged ();
+			ContentList old = _content;
+			sort (_content.begin(), _content.end(), ContentSorter ());
+			if (_content != old) {
+				OrderChanged ();
+			}
 		}
 	}
 
-	ContentChanged (content, property, frequent);
+	ContentChange (type, content, property, frequent);
 }
 
 void
@@ -215,15 +205,18 @@ Playlist::as_xml (xmlpp::Node* node, bool with_content_paths)
 void
 Playlist::add (shared_ptr<Content> c)
 {
+	Change (CHANGE_TYPE_PENDING);
 	_content.push_back (c);
 	sort (_content.begin(), _content.end(), ContentSorter ());
 	reconnect ();
-	Changed ();
+	Change (CHANGE_TYPE_DONE);
 }
 
 void
 Playlist::remove (shared_ptr<Content> c)
 {
+	Change (CHANGE_TYPE_PENDING);
+
 	ContentList::iterator i = _content.begin ();
 	while (i != _content.end() && *i != c) {
 		++i;
@@ -231,7 +224,9 @@ Playlist::remove (shared_ptr<Content> c)
 
 	if (i != _content.end ()) {
 		_content.erase (i);
-		Changed ();
+		Change (CHANGE_TYPE_DONE);
+	} else {
+		Change (CHANGE_TYPE_CANCELLED);
 	}
 
 	/* This won't change order, so it does not need a sort */
@@ -240,6 +235,8 @@ Playlist::remove (shared_ptr<Content> c)
 void
 Playlist::remove (ContentList c)
 {
+	Change (CHANGE_TYPE_PENDING);
+
 	BOOST_FOREACH (shared_ptr<Content> i, c) {
 		ContentList::iterator j = _content.begin ();
 		while (j != _content.end() && *j != i) {
@@ -253,7 +250,7 @@ Playlist::remove (ContentList c)
 
 	/* This won't change order, so it does not need a sort */
 
-	Changed ();
+	Change (CHANGE_TYPE_DONE);
 }
 
 class FrameRateCandidate
@@ -362,9 +359,7 @@ Playlist::reconnect ()
 	_content_connections.clear ();
 
 	BOOST_FOREACH (shared_ptr<Content> i, _content) {
-		_content_connections.push_back (i->MayChange.connect(boost::bind(&Playlist::content_may_change, this)));
-		_content_connections.push_back (i->Changed.connect(boost::bind(&Playlist::content_changed, this, _1, _2, _3)));
-		_content_connections.push_back (i->NotChanged.connect(boost::bind(&Playlist::content_not_changed, this)));
+		_content_connections.push_back (i->Change.connect(boost::bind(&Playlist::content_change, this, _1, _2, _3, _4)));
 	}
 }
 
@@ -461,6 +456,8 @@ Playlist::repeat (ContentList c, int n)
 		range.second = max (range.second, i->end ());
 	}
 
+	Change (CHANGE_TYPE_PENDING);
+
 	DCPTime pos = range.second;
 	for (int i = 0; i < n; ++i) {
 		BOOST_FOREACH (shared_ptr<Content> j, c) {
@@ -474,7 +471,7 @@ Playlist::repeat (ContentList c, int n)
 	sort (_content.begin(), _content.end(), ContentSorter ());
 
 	reconnect ();
-	Changed ();
+	Change (CHANGE_TYPE_DONE);
 }
 
 void
diff --git a/src/lib/playlist.h b/src/lib/playlist.h
index 649887f72..d55232dad 100644
--- a/src/lib/playlist.h
+++ b/src/lib/playlist.h
@@ -75,21 +75,13 @@ public:
 	void repeat (ContentList, int);
 
 	/** Emitted when content has been added to or removed from the playlist; implies OrderChanged */
-	mutable boost::signals2::signal<void ()> Changed;
+	mutable boost::signals2::signal<void (ChangeType)> Change;
 	mutable boost::signals2::signal<void ()> OrderChanged;
 
-	mutable boost::signals2::signal<void ()> ContentMayChange;
-	/** Emitted when something about a piece of our content has changed;
-	 *  these emissions include when the position of the content changes.
-	 *  Third parameter is true if signals are currently being emitted frequently.
-	 */
-	mutable boost::signals2::signal<void (boost::weak_ptr<Content>, int, bool)> ContentChanged;
-	mutable boost::signals2::signal<void ()> ContentNotChanged;
+	mutable boost::signals2::signal<void (ChangeType, boost::weak_ptr<Content>, int, bool)> ContentChange;
 
 private:
-	void content_may_change ();
-	void content_changed (boost::weak_ptr<Content>, int, bool);
-	void content_not_changed ();
+	void content_change (ChangeType, boost::weak_ptr<Content>, int, bool);
 	void reconnect ();
 
 	/** List of content.  Kept sorted in position order. */
diff --git a/src/lib/types.h b/src/lib/types.h
index 42e2e3eec..22d652b3f 100644
--- a/src/lib/types.h
+++ b/src/lib/types.h
@@ -129,6 +129,13 @@ enum ReelType
 	REELTYPE_BY_LENGTH
 };
 
+enum ChangeType
+{
+	CHANGE_TYPE_PENDING,
+	CHANGE_TYPE_DONE,
+	CHANGE_TYPE_CANCELLED
+};
+
 /** Type of captions.
  *
  *  The generally accepted definitions seem to be:
diff --git a/src/wx/audio_dialog.cc b/src/wx/audio_dialog.cc
index 8c015ab68..e1f7c15a6 100644
--- a/src/wx/audio_dialog.cc
+++ b/src/wx/audio_dialog.cc
@@ -150,7 +150,7 @@ AudioDialog::AudioDialog (wxWindow* parent, shared_ptr<Film> film, shared_ptr<Co
 	overall_sizer->Layout ();
 	overall_sizer->SetSizeHints (this);
 
-	_film_connection = film->ContentChanged.connect (boost::bind (&AudioDialog::content_changed, this, _2));
+	_film_connection = film->ContentChange.connect (boost::bind (&AudioDialog::content_change, this, _1, _3));
 	DCPOMATIC_ASSERT (film->directory());
 	SetTitle(wxString::Format(_("DCP-o-matic audio - %s"), std_to_wx(film->directory().get().string())));
 
@@ -282,8 +282,12 @@ AudioDialog::channel_clicked (wxCommandEvent& ev)
 }
 
 void
-AudioDialog::content_changed (int p)
+AudioDialog::content_change (ChangeType type, int p)
 {
+	if (type != CHANGE_TYPE_DONE) {
+		return;
+	}
+
 	if (p == AudioContentProperty::STREAMS) {
 		try_to_load_analysis ();
 	} else if (p == AudioContentProperty::GAIN) {
diff --git a/src/wx/audio_dialog.h b/src/wx/audio_dialog.h
index 6d4428546..2c077c9d1 100644
--- a/src/wx/audio_dialog.h
+++ b/src/wx/audio_dialog.h
@@ -38,7 +38,7 @@ public:
 	void set_cursor (boost::optional<DCPTime> time, boost::optional<float> db);
 
 private:
-	void content_changed (int);
+	void content_change (ChangeType, int);
 	void channel_clicked (wxCommandEvent &);
 	void type_clicked (wxCommandEvent &);
 	void smoothing_changed ();
diff --git a/src/wx/content_widget.h b/src/wx/content_widget.h
index e162aca49..e5125680b 100644
--- a/src/wx/content_widget.h
+++ b/src/wx/content_widget.h
@@ -105,7 +105,7 @@ public:
 		update_from_model ();
 
 		for (typename List::iterator i = _content.begin(); i != _content.end(); ++i) {
-			_connections.push_back ((*i)->Changed.connect (boost::bind (&ContentWidget::model_changed, this, _2)));
+			_connections.push_back ((*i)->Change.connect (boost::bind (&ContentWidget::model_changed, this, _1, _3)));
 		}
 	}
 
@@ -185,9 +185,9 @@ private:
 		}
 	}
 
-	void model_changed (int property)
+	void model_changed (ChangeType type, int property)
 	{
-		if (property == _property && !_ignore_model_changes) {
+		if (type == CHANGE_TYPE_DONE && property == _property && !_ignore_model_changes) {
 			update_from_model ();
 		}
 	}
diff --git a/src/wx/film_editor.cc b/src/wx/film_editor.cc
index 5380cbd9b..1c1c02f5b 100644
--- a/src/wx/film_editor.cc
+++ b/src/wx/film_editor.cc
@@ -86,8 +86,12 @@ FilmEditor::film_changed (Film::Property p)
 }
 
 void
-FilmEditor::film_content_changed (int property)
+FilmEditor::film_content_change (ChangeType type, int property)
 {
+	if (type != CHANGE_TYPE_DONE) {
+		return;
+	}
+
 	ensure_ui_thread ();
 
 	if (!_film) {
@@ -118,7 +122,7 @@ FilmEditor::set_film (shared_ptr<Film> film)
 
 	if (_film) {
 		_film->Changed.connect (bind (&FilmEditor::film_changed, this, _1));
-		_film->ContentChanged.connect (bind (&FilmEditor::film_content_changed, this, _2));
+		_film->ContentChange.connect (bind (&FilmEditor::film_content_change, this, _1, _3));
 	}
 
 	if (_film && _film->directory()) {
diff --git a/src/wx/film_editor.h b/src/wx/film_editor.h
index 576cd5ba1..cd2180b3c 100644
--- a/src/wx/film_editor.h
+++ b/src/wx/film_editor.h
@@ -57,7 +57,7 @@ public:
 
 	/* Handle changes to the model */
 	void film_changed (Film::Property);
-	void film_content_changed (int);
+	void film_content_change (ChangeType type, int);
 
 	void set_general_sensitivity (bool);
 	void active_jobs_changed (boost::optional<std::string>);
diff --git a/src/wx/film_viewer.cc b/src/wx/film_viewer.cc
index 0e0fc4315..463854992 100644
--- a/src/wx/film_viewer.cc
+++ b/src/wx/film_viewer.cc
@@ -225,7 +225,7 @@ FilmViewer::set_film (shared_ptr<Film> film)
 	_player->set_play_referenced ();
 
 	_film->Changed.connect (boost::bind (&FilmViewer::film_changed, this, _1));
-	_player->Changed.connect (boost::bind (&FilmViewer::player_changed, this, _1, _2));
+	_player->Change.connect (boost::bind (&FilmViewer::player_change, this, _1, _2, _3));
 
 	/* Keep about 1 second's worth of history samples */
 	_latency_history_count = _film->audio_frame_rate() / _audio_block_size;
@@ -665,9 +665,9 @@ FilmViewer::forward_clicked (wxKeyboardState& ev)
 }
 
 void
-FilmViewer::player_changed (int property, bool frequent)
+FilmViewer::player_change (ChangeType type, int property, bool frequent)
 {
-	if (frequent) {
+	if (type != CHANGE_TYPE_DONE || frequent) {
 		return;
 	}
 
@@ -780,7 +780,7 @@ FilmViewer::set_coalesce_player_changes (bool c)
 
 	if (!c) {
 		BOOST_FOREACH (int i, _pending_player_changes) {
-			player_changed (i, false);
+			player_change (CHANGE_TYPE_DONE, i, false);
 		}
 		_pending_player_changes.clear ();
 	}
diff --git a/src/wx/film_viewer.h b/src/wx/film_viewer.h
index a41500ace..d6d9a99a8 100644
--- a/src/wx/film_viewer.h
+++ b/src/wx/film_viewer.h
@@ -97,7 +97,7 @@ private:
 	void rewind_clicked (wxMouseEvent &);
 	void back_clicked (wxKeyboardState& s);
 	void forward_clicked (wxKeyboardState &);
-	void player_changed (int, bool);
+	void player_change (ChangeType type, int, bool);
 	void update_position_label ();
 	void update_position_slider ();
 	void get ();
diff --git a/src/wx/hints_dialog.cc b/src/wx/hints_dialog.cc
index 2c02a4f72..3872ea8ae 100644
--- a/src/wx/hints_dialog.cc
+++ b/src/wx/hints_dialog.cc
@@ -76,7 +76,7 @@ HintsDialog::HintsDialog (wxWindow* parent, boost::weak_ptr<Film> film, bool ok)
 	boost::shared_ptr<Film> locked_film = _film.lock ();
 	if (locked_film) {
 		_film_changed_connection = locked_film->Changed.connect (boost::bind (&HintsDialog::film_changed, this));
-		_film_content_changed_connection = locked_film->ContentChanged.connect (boost::bind (&HintsDialog::film_changed, this));
+		_film_content_changed_connection = locked_film->ContentChange.connect (boost::bind (&HintsDialog::film_content_change, this, _1));
 	}
 
 	_hints->Hint.connect (bind (&HintsDialog::hint, this, _1));
@@ -107,6 +107,14 @@ HintsDialog::film_changed ()
 }
 
 void
+HintsDialog::film_content_change (ChangeType type)
+{
+	if (type == CHANGE_TYPE_DONE) {
+		film_changed ();
+	}
+}
+
+void
 HintsDialog::update ()
 {
 	_text->Clear ();
diff --git a/src/wx/hints_dialog.h b/src/wx/hints_dialog.h
index 06f979a74..83510643a 100644
--- a/src/wx/hints_dialog.h
+++ b/src/wx/hints_dialog.h
@@ -18,6 +18,7 @@
 
 */
 
+#include "lib/types.h"
 #include <wx/wx.h>
 #include <boost/weak_ptr.hpp>
 #include <boost/signals2.hpp>
@@ -33,6 +34,7 @@ public:
 
 private:
 	void film_changed ();
+	void film_content_change (ChangeType type);
 	void shut_up (wxCommandEvent& ev);
 	void update ();
 	void hint (std::string text);
diff --git a/src/wx/subtitle_appearance_dialog.cc b/src/wx/subtitle_appearance_dialog.cc
index cab473c18..6473cd68b 100644
--- a/src/wx/subtitle_appearance_dialog.cc
+++ b/src/wx/subtitle_appearance_dialog.cc
@@ -185,11 +185,19 @@ SubtitleAppearanceDialog::SubtitleAppearanceDialog (wxWindow* parent, shared_ptr
 	_force_fade_in->Bind (wxEVT_CHECKBOX, bind (&SubtitleAppearanceDialog::setup_sensitivity, this));
 	_force_fade_out->Bind (wxEVT_CHECKBOX, bind (&SubtitleAppearanceDialog::setup_sensitivity, this));
 	_effect->Bind (wxEVT_CHOICE, bind (&SubtitleAppearanceDialog::setup_sensitivity, this));
-	_content_connection = _content->Changed.connect (bind (&SubtitleAppearanceDialog::setup_sensitivity, this));
+	_content_connection = _content->Change.connect (bind (&SubtitleAppearanceDialog::content_change, this, _1));
 
 	setup_sensitivity ();
 }
 
+void
+SubtitleAppearanceDialog::content_change (ChangeType type)
+{
+	if (type == CHANGE_TYPE_DONE) {
+		setup_sensitivity ();
+	}
+}
+
 wxCheckBox*
 SubtitleAppearanceDialog::set_to (wxWindow* w, int& r)
 {
diff --git a/src/wx/subtitle_appearance_dialog.h b/src/wx/subtitle_appearance_dialog.h
index 6cced717b..80ef58470 100644
--- a/src/wx/subtitle_appearance_dialog.h
+++ b/src/wx/subtitle_appearance_dialog.h
@@ -44,6 +44,7 @@ private:
 	void setup_sensitivity ();
 	void restore ();
 	wxCheckBox* set_to (wxWindow* w, int& r);
+	void content_change (ChangeType type);
 
 	wxCheckBox* _force_colour;
 	wxColourPickerCtrl* _colour;
diff --git a/src/wx/timeline.cc b/src/wx/timeline.cc
index 02f8be059..7353baf82 100644
--- a/src/wx/timeline.cc
+++ b/src/wx/timeline.cc
@@ -110,7 +110,7 @@ Timeline::Timeline (wxWindow* parent, ContentPanel* cp, shared_ptr<Film> film)
 	SetMinSize (wxSize (640, 4 * pixels_per_track() + 96));
 
 	_film_changed_connection = film->Changed.connect (bind (&Timeline::film_changed, this, _1));
-	_film_content_changed_connection = film->ContentChanged.connect (bind (&Timeline::film_content_changed, this, _2, _3));
+	_film_content_change_connection = film->ContentChange.connect (bind (&Timeline::film_content_change, this, _1, _3, _4));
 
 	setup_scrollbars ();
 	_labels_canvas->ShowScrollbars (wxSHOW_SB_NEVER, wxSHOW_SB_NEVER);
@@ -243,8 +243,12 @@ Timeline::recreate_views ()
 }
 
 void
-Timeline::film_content_changed (int property, bool frequent)
+Timeline::film_content_change (ChangeType type, int property, bool frequent)
 {
+	if (type != CHANGE_TYPE_DONE) {
+		return;
+	}
+
 	ensure_ui_thread ();
 
 	if (property == AudioContentProperty::STREAMS) {
diff --git a/src/wx/timeline.h b/src/wx/timeline.h
index 2214ee13f..9f3a4a47b 100644
--- a/src/wx/timeline.h
+++ b/src/wx/timeline.h
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2013-2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2013-2018 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -92,7 +92,7 @@ private:
 	void mouse_moved_select (wxMouseEvent &);
 	void mouse_moved_zoom (wxMouseEvent &);
 	void film_changed (Film::Property);
-	void film_content_changed (int, bool frequent);
+	void film_content_change (ChangeType type, int, bool frequent);
 	void resized ();
 	void assign_tracks ();
 	void set_position_from_event (wxMouseEvent &);
@@ -139,5 +139,5 @@ private:
 	static int const _minimum_pixels_per_track;
 
 	boost::signals2::scoped_connection _film_changed_connection;
-	boost::signals2::scoped_connection _film_content_changed_connection;
+	boost::signals2::scoped_connection _film_content_change_connection;
 };
diff --git a/src/wx/timeline_content_view.cc b/src/wx/timeline_content_view.cc
index bf22e0156..12691f661 100644
--- a/src/wx/timeline_content_view.cc
+++ b/src/wx/timeline_content_view.cc
@@ -33,7 +33,7 @@ TimelineContentView::TimelineContentView (Timeline& tl, shared_ptr<Content> c)
 	, _content (c)
 	, _selected (false)
 {
-	_content_connection = c->Changed.connect (bind (&TimelineContentView::content_changed, this, _2));
+	_content_connection = c->Change.connect (bind (&TimelineContentView::content_change, this, _1, _3));
 }
 
 dcpomatic::Rect<int>
@@ -160,8 +160,12 @@ TimelineContentView::y_pos (int t) const
 }
 
 void
-TimelineContentView::content_changed (int p)
+TimelineContentView::content_change (ChangeType type, int p)
 {
+	if (type != CHANGE_TYPE_DONE) {
+		return;
+	}
+
 	ensure_ui_thread ();
 
 	if (p == ContentProperty::POSITION || p == ContentProperty::LENGTH) {
diff --git a/src/wx/timeline_content_view.h b/src/wx/timeline_content_view.h
index b5b000bdb..27cfed53e 100644
--- a/src/wx/timeline_content_view.h
+++ b/src/wx/timeline_content_view.h
@@ -21,6 +21,7 @@
 #ifndef DCPOMATIC_TIMELINE_CONTENT_VIEW_H
 #define DCPOMATIC_TIMELINE_CONTENT_VIEW_H
 
+#include "lib/types.h"
 #include "timeline_view.h"
 #include <wx/wx.h>
 #include <boost/signals2.hpp>
@@ -57,7 +58,7 @@ private:
 
 	void do_paint (wxGraphicsContext* gc, std::list<dcpomatic::Rect<int> > overlaps);
 	int y_pos (int t) const;
-	void content_changed (int p);
+	void content_change (ChangeType type, int p);
 
 	boost::optional<int> _track;
 	bool _selected;