X-Git-Url: https://git.carlh.net/gitweb/?a=blobdiff_plain;f=src%2Flib%2Fsignaller.h;h=44650de871cbbd4109aa403d6e465ce7899c7b6b;hb=323b8cbb0b95297fbd027ffdc4ea5003b59ef25f;hp=13474ee91baa3eac4e9c7d98042e29f17f68f0aa;hpb=dd8a7d1bbb8f2afb1b98d2be856ff0a9920e180d;p=dcpomatic.git

diff --git a/src/lib/signaller.h b/src/lib/signaller.h
index 13474ee91..44650de87 100644
--- a/src/lib/signaller.h
+++ b/src/lib/signaller.h
@@ -1,36 +1,35 @@
 /*
-    Copyright (C) 2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2015-2021 Carl Hetherington <cth@carlh.net>
 
-    This program is free software; you can redistribute it and/or modify
+    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.
 
-    This program is distributed in the hope that it will be useful,
+    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 this program; if not, write to the Free Software
-    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
 
 */
 
+
 #ifndef DCPOMATIC_SIGNALLER_H
 #define DCPOMATIC_SIGNALLER_H
 
+
 #include "signal_manager.h"
 #include <boost/thread/mutex.hpp>
 
+
 class WrapperBase
 {
 public:
-	WrapperBase ()
-		: _valid (true)
-		, _finished (false)
-	{}
-
 	virtual ~WrapperBase () {}
 
 	/* Can be called from any thread */
@@ -41,17 +40,28 @@ public:
 	}
 
 	bool finished () const {
-		boost::mutex::scoped_lock lm (_mutex);
+		boost::mutex::scoped_lock lm (_mutex, boost::try_to_lock);
+		if (!lm) {
+			/* It's possible that emission of this
+			   wrapper's signal causes another signal to
+			   be emitted, which causes finished() on this
+			   wrapper to be called (by Signaller::emit).
+			   In this case, just say that the wrapper is
+			   not yet finished.
+			*/
+			return false;
+		}
 		return _finished;
 	}
 
 protected:
 	/* Protect _valid and _finished */
 	mutable boost::mutex _mutex;
-	bool _valid;
-	bool _finished;
+	bool _valid = true;
+	bool _finished = false;
 };
 
+
 /** Helper class to manage lifetime of signals, specifically to address
  *  the problem where an object containing a signal is deleted before
  *  its signal is emitted.
@@ -60,7 +70,7 @@ template <class T>
 class Wrapper : public WrapperBase
 {
 public:
-	Wrapper (T signal)
+	explicit Wrapper (T signal)
 		: _signal (signal)
 	{
 
@@ -80,6 +90,7 @@ private:
 	T _signal;
 };
 
+
 /** Parent for any class which needs to raise cross-thread signals (from non-UI
  *  to UI).  Subclasses should call, e.g. emit (boost::bind (boost::ref (MySignal), foo, bar));
  */
@@ -89,8 +100,8 @@ public:
 	/* Can be called from any thread */
 	virtual ~Signaller () {
 		boost::mutex::scoped_lock lm (_signaller_mutex);
-		for (std::list<WrapperBase*>::iterator i = _wrappers.begin(); i != _wrappers.end(); ++i) {
-			(*i)->invalidate ();
+		for (auto i: _wrappers) {
+			i->invalidate();
 		}
 	}
 
@@ -98,17 +109,17 @@ public:
 	template <class T>
 	void emit (T signal)
 	{
-		Wrapper<T>* w = new Wrapper<T> (signal);
+		auto w = new Wrapper<T> (signal);
 		if (signal_manager) {
-			signal_manager->emit (boost::bind (&Wrapper<T>::signal, w));
+			signal_manager->emit (boost::bind(&Wrapper<T>::signal, w));
 		}
 
 		boost::mutex::scoped_lock lm (_signaller_mutex);
 
 		/* Clean up finished Wrappers */
-		std::list<WrapperBase*>::iterator i = _wrappers.begin ();
+		auto i = _wrappers.begin ();
 		while (i != _wrappers.end ()) {
-			std::list<WrapperBase*>::iterator tmp = i;
+			auto tmp = i;
 			++tmp;
 			if ((*i)->finished ()) {
 				delete *i;
@@ -127,4 +138,5 @@ private:
 	std::list<WrapperBase*> _wrappers;
 };
 
+
 #endif