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/*
Copyright (C) 2015-2021 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/>.
*/
#ifndef DCPOMATIC_SIGNALLER_H
#define DCPOMATIC_SIGNALLER_H
#include "signal_manager.h"
#include <boost/thread/mutex.hpp>
class WrapperBase
{
public:
virtual ~WrapperBase () {}
/* Can be called from any thread */
void invalidate ()
{
boost::mutex::scoped_lock lm (_mutex);
_valid = false;
}
bool finished () const {
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 = 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.
*/
template <class T>
class Wrapper : public WrapperBase
{
public:
explicit Wrapper (T signal)
: _signal (signal)
{
}
/* Called by the UI thread only */
void signal ()
{
boost::mutex::scoped_lock lm (_mutex);
if (_valid) {
_signal ();
}
_finished = true;
}
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));
*/
class Signaller
{
public:
/* Can be called from any thread */
virtual ~Signaller () {
boost::mutex::scoped_lock lm (_signaller_mutex);
for (auto i: _wrappers) {
i->invalidate();
}
}
/* Can be called from any thread */
template <class T>
void emit (T signal)
{
auto w = new Wrapper<T> (signal);
if (signal_manager) {
signal_manager->emit (boost::bind(&Wrapper<T>::signal, w));
}
boost::mutex::scoped_lock lm (_signaller_mutex);
/* Clean up finished Wrappers */
auto i = _wrappers.begin ();
while (i != _wrappers.end ()) {
auto tmp = i;
++tmp;
if ((*i)->finished ()) {
delete *i;
_wrappers.erase (i);
}
i = tmp;
}
/* Add the new one */
_wrappers.push_back (w);
}
private:
/* Protect _wrappers */
boost::mutex _signaller_mutex;
std::list<WrapperBase*> _wrappers;
};
#endif
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