latent.h

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/*
 * Copyright (C) 2007-2017 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2009 David Robillard <d@drobilla.net>
 * Copyright (C) 2010-2011 Carl Hetherington <carl@carlh.net>
 * Copyright (C) 2019 Robin Gareus <robin@gareus.org>
 *
 * 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
#pragma once
 
#include "pbd/signals.h"
 
#include "ardour/libardour_visibility.h"
#include "ardour/types.h"
 
namespace ARDOUR {
 
class LIBARDOUR_API HasLatency {
public:
        virtual ~HasLatency() {}
        virtual samplecnt_t signal_latency() const = 0;
};
 
class LIBARDOUR_API Latent : public HasLatency {
public:
        Latent ();
        Latent (Latent const&);
        virtual ~Latent() {}
 
 
        /* effective latency to be used while processing */
        samplecnt_t effective_latency() const {
                if (_zero_latency) {
                        return 0;
                } else if (_use_user_latency) {
                        return _user_latency;
                } else {
                        return signal_latency ();
                }
        }
 
        /* custom user-set latency, if any */
        samplecnt_t user_latency () const {
                if (_use_user_latency) {
                        return _user_latency;
                } else {
                        return 0;
                }
        }
 
        void unset_user_latency () {
                _use_user_latency = false;
                _user_latency = 0;
        }
 
        virtual void set_user_latency (samplecnt_t val) {
                _use_user_latency = true;
                _user_latency = val;
        }
 
        static void force_zero_latency (bool en) {
                if (_zero_latency == en) {
                        return;
                }
                _zero_latency = en;
                DisableSwitchChanged (); /* EMIT SIGNAL */
        }
 
        static bool zero_latency () {
                return _zero_latency;
        }
 
        static PBD::Signal<void()> DisableSwitchChanged;
        PBD::Signal<void()> LatencyChanged;
 
protected:
        int  set_state (const XMLNode& node, int version);
        void add_state (XMLNode*) const;
 
private:
        samplecnt_t _use_user_latency;
        samplecnt_t _user_latency;
 
        static bool _zero_latency;
};
 
} /* namespace */