Allow signals to be blocked and resumed, and so make sure that a set

of content changes taken from an examiner are handled at the same
time.

Should fix DoM #2523.

6 files changed, 125 insertions, 15 deletions

diff --git a/src/lib/change_signaller.cc b/src/lib/change_signaller.cc
new file mode 100644
index 000000000..a1f093d14
--- /dev/null
+++ b/src/lib/change_signaller.cc
@@ -0,0 +1,24 @@
+/*
+    Copyright (C) 2018-2021 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic 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.
+
+    DCP-o-matic 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 DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+#include "change_signaller.h"
+
+
diff --git a/src/lib/change_signaller.h b/src/lib/change_signaller.h
index 8612cf426..1d7d482df 100644
--- a/src/lib/change_signaller.h
+++ b/src/lib/change_signaller.h
@@ -23,6 +23,10 @@
 #define DCPOMATIC_CHANGE_SIGNALLER_H
 
 
+#include <boost/thread.hpp>
+#include <vector>
+
+
 enum class ChangeType
 {
 	PENDING,
@@ -32,29 +36,103 @@ enum class ChangeType
 
 
 template <class T, class P>
+class ChangeSignal
+{
+public:
+	ChangeSignal(T* thing_, P property_, ChangeType type_)
+		: thing(thing_)
+		, property(property_)
+		, type(type_)
+	{}
+
+	T* thing;
+	P property;
+	ChangeType type;
+};
+
+
+class ChangeSignalDespatcherBase
+{
+protected:
+	static boost::mutex _instance_mutex;
+};
+
+
+template <class T, class P>
+class ChangeSignalDespatcher : public ChangeSignalDespatcherBase
+{
+public:
+	ChangeSignalDespatcher() = default;
+
+	ChangeSignalDespatcher(ChangeSignalDespatcher const&) = delete;
+	ChangeSignalDespatcher& operator=(ChangeSignalDespatcher const&) = delete;
+
+	void signal_change(ChangeSignal<T, P> const& signal)
+	{
+		if (_suspended) {
+			boost::mutex::scoped_lock lm(_mutex);
+			_pending.push_back(signal);
+		} else {
+			signal.thing->signal_change(signal.type, signal.property);
+		}
+	}
+
+	void suspend()
+	{
+		boost::mutex::scoped_lock lm(_mutex);
+		_suspended = true;
+	}
+
+	void resume()
+	{
+		boost::mutex::scoped_lock lm(_mutex);
+		auto pending = _pending;
+		lm.unlock();
+
+		for (auto signal: pending) {
+			signal.thing->signal_change(signal.type, signal.property);
+		}
+
+		lm.lock();
+		_pending.clear();
+		_suspended = false;
+	}
+
+	static ChangeSignalDespatcher* instance()
+	{
+		static boost::mutex _instance_mutex;
+		static boost::mutex::scoped_lock lm(_instance_mutex);
+		static ChangeSignalDespatcher<T, P>* _instance;
+		if (!_instance) {
+			_instance = new ChangeSignalDespatcher<T, P>();
+		}
+		return _instance;
+	}
+
+private:
+	std::vector<ChangeSignal<T, P>> _pending;
+	bool _suspended = false;
+	boost::mutex _mutex;
+};
+
+
+template <class T, class P>
 class ChangeSignaller
 {
 public:
 	ChangeSignaller (T* t, P p)
-		: _thing (t)
-		, _property (p)
-		, _done (true)
+		: _thing(t)
+		, _property(p)
+		, _done(true)
 	{
-		_thing->signal_change (ChangeType::PENDING, _property);
+		ChangeSignalDespatcher<T, P>::instance()->signal_change({_thing, _property, ChangeType::PENDING});
 	}
 
 	~ChangeSignaller ()
 	{
-		if (_done) {
-			_thing->signal_change (ChangeType::DONE, _property);
-		} else {
-			_thing->signal_change (ChangeType::CANCELLED, _property);
-		}
+		ChangeSignalDespatcher<T, P>::instance()->signal_change({_thing, _property, _done ? ChangeType::DONE : ChangeType::CANCELLED});
 	}
 
-	ChangeSignaller (ChangeSignaller const&) = delete;
-	ChangeSignaller& operator= (ChangeSignaller const&) = delete;
-
 	void abort ()
 	{
 		_done = false;
diff --git a/src/lib/content.h b/src/lib/content.h
index 0ce87ed9b..f2fecddf0 100644
--- a/src/lib/content.h
+++ b/src/lib/content.h
@@ -234,7 +234,7 @@ private:
 	friend struct best_dcp_frame_rate_test_double;
 	friend struct audio_sampling_rate_test;
 	friend struct subtitle_font_id_change_test2;
-	template<class, class> friend class ChangeSignaller;
+	template<class, class> friend class ChangeSignalDespatcher;
 
 	void signal_change (ChangeType, int);
 
@@ -256,6 +256,7 @@ private:
 
 
 typedef ChangeSignaller<Content, int> ContentChangeSignaller;
+typedef ChangeSignalDespatcher<Content, int> ContentChangeSignalDespatcher;
 
 
 #endif
diff --git a/src/lib/dcp_content.cc b/src/lib/dcp_content.cc
index 231a93bd0..cad775b24 100644
--- a/src/lib/dcp_content.cc
+++ b/src/lib/dcp_content.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2014-2022 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2014-2023 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -31,6 +31,7 @@
 #include "job.h"
 #include "log.h"
 #include "overlaps.h"
+#include "scope_guard.h"
 #include "text_content.h"
 #include "video_content.h"
 #include <dcp/dcp.h>
@@ -213,6 +214,11 @@ DCPContent::examine (shared_ptr<const Film> film, shared_ptr<Job> job)
 	bool const needed_kdm = needs_kdm ();
 	string const old_name = name ();
 
+	ContentChangeSignalDespatcher::instance()->suspend();
+	ScopeGuard sg = []() {
+		ContentChangeSignalDespatcher::instance()->resume();
+	};
+
 	ContentChangeSignaller cc_texts (this, DCPContentProperty::TEXTS);
 	ContentChangeSignaller cc_assets (this, DCPContentProperty::NEEDS_ASSETS);
 	ContentChangeSignaller cc_kdm (this, DCPContentProperty::NEEDS_KDM);
diff --git a/src/lib/film.h b/src/lib/film.h
index b7a9f94ac..958c388b3 100644
--- a/src/lib/film.h
+++ b/src/lib/film.h
@@ -492,7 +492,7 @@ private:
 	friend struct ::isdcf_name_with_atmos;
 	friend struct ::recover_test_2d_encrypted;
 	friend struct ::atmos_encrypted_passthrough_test;
-	template <class, class> friend class ChangeSignaller;
+	template <class, class> friend class ChangeSignalDespatcher;
 
 	boost::filesystem::path info_file (dcpomatic::DCPTimePeriod p) const;
 
diff --git a/src/lib/wscript b/src/lib/wscript
index f8c2d5dc2..de7b947c2 100644
--- a/src/lib/wscript
+++ b/src/lib/wscript
@@ -51,6 +51,7 @@ sources = """
           check_content_job.cc
           cinema.cc
           cinema_sound_processor.cc
+          change_signaller.cc
           collator.cc
           colour_conversion.cc
           config.cc