session.h

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/*
 * Copyright (C) 2000-2019 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2005-2009 Taybin Rutkin <taybin@taybin.com>
 * Copyright (C) 2006-2007 Jesse Chappell <jesse@essej.net>
 * Copyright (C) 2006-2009 Sampo Savolainen <v2@iki.fi>
 * Copyright (C) 2006-2015 David Robillard <d@drobilla.net>
 * Copyright (C) 2007-2012 Carl Hetherington <carl@carlh.net>
 * Copyright (C) 2007-2015 Tim Mayberry <mojofunk@gmail.com>
 * Copyright (C) 2008-2009 Hans Baier <hansfbaier@googlemail.com>
 * Copyright (C) 2008-2009 Sakari Bergen <sakari.bergen@beatwaves.net>
 * Copyright (C) 2012-2019 Robin Gareus <robin@gareus.org>
 * Copyright (C) 2013-2017 Nick Mainsbridge <mainsbridge@gmail.com>
 * Copyright (C) 2013-2018 John Emmas <john@creativepost.co.uk>
 * Copyright (C) 2014-2018 Ben Loftis <ben@harrisonconsoles.com>
 * Copyright (C) 2015-2018 Len Ovens <len@ovenwerks.net>
 *
 * 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
 
#ifdef WAF_BUILD
#include "libardour-config.h"
#endif
 
#include <atomic>
#include <exception>
#include <list>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <vector>
#include <queue>
#include <stdint.h>
 
#include <boost/dynamic_bitset.hpp>
#include <glibmm/threads.h>
 
#include <ltc.h>
 
#include "pbd/atomic.h"
#include "pbd/error.h"
#include "pbd/event_loop.h"
#include "pbd/file_archive.h"
#include "pbd/history_owner.h"
#include "pbd/rcu.h"
#include "pbd/statefuldestructible.h"
#include "pbd/signals.h"
#include "pbd/undo.h"
 
#ifdef USE_TLSF
#  include "pbd/tlsf.h"
#else
#  include "pbd/reallocpool.h"
#endif
#include "lua/luastate.h"
 
#include "temporal/range.h"
#include "temporal/domain_provider.h"
 
#include "midi++/types.h"
#include "midi++/mmc.h"
 
#include "temporal/time.h"
 
#include "ardour/ardour.h"
#include "ardour/chan_count.h"
#include "ardour/delivery.h"
#include "ardour/interthread_info.h"
#include "ardour/luascripting.h"
#include "ardour/location.h"
#include "ardour/monitor_processor.h"
#include "ardour/presentation_info.h"
#include "ardour/rc_configuration.h"
#include "ardour/session_configuration.h"
#include "ardour/session_event.h"
#include "ardour/plugin.h"
#include "ardour/presentation_info.h"
#include "ardour/route.h"
#include "ardour/graph_edges.h"
#include "ardour/transport_api.h"
#include "ardour/triggerbox.h"
 
class XMLTree;
class XMLNode;
struct _AEffect;
typedef struct _AEffect AEffect;
 
class PTFFormat;
 
namespace MIDI {
class Port;
class MachineControl;
class Parser;
}
 
namespace PBD {
class Controllable;
class Progress;
class Command;
}
 
namespace luabridge {
        class LuaRef;
}
 
namespace Evoral {
class Curve;
}
 
namespace Temporal {
class TempoMap;
}
 
namespace ARDOUR {
 
class Amp;
class AsyncMIDIPort;
class AudioEngine;
class AudioFileSource;
class AudioRegion;
class AudioSource;
class AudioTrack;
class Auditioner;
class AutomationList;
class AuxInput;
class BufferSet;
class Bundle;
class Butler;
class Click;
class CoreSelection;
class ExportHandler;
class ExportStatus;
class Graph;
struct GraphChain;
class IO;
class IOPlug;
class IOProcessor;
class IOTaskList;
class ImportStatus;
class MidiClockTicker;
class MidiControlUI;
class MidiPortManager;
class MidiPort;
class MidiRegion;
class MidiSource;
class MidiTrack;
class MixerScene;
class Playlist;
class PluginInsert;
class PluginInfo;
class Port;
class PortInsert;
class PortManager;
class ProcessThread;
class Processor;
class Region;
class Return;
class Route;
class RouteGroup;
class RTTaskList;
class SMFSource;
class Send;
class SceneChanger;
class SessionDirectory;
class SessionMetadata;
class SessionPlaylists;
class SoloMuteRelease;
class Source;
class Speakers;
class TransportMaster;
struct TransportFSM;
class Track;
class UI_TransportMaster;
class VCAManager;
class WindowsVSTPlugin;
 
extern void setup_enum_writer ();
 
class LIBARDOUR_API SessionException: public std::exception {
public:
        explicit SessionException(const std::string msg) : _message(msg) {}
        virtual ~SessionException() throw() {}
 
        virtual const char* what() const throw() { return _message.c_str(); }
 
private:
        std::string _message;
};
 
class LIBARDOUR_API Session : public PBD::HistoryOwner,
                              public PBD::StatefulDestructible,
                              public PBD::ScopedConnectionList,
                              public SessionEventManager,
                              public TransportAPI,
                              public Temporal::TimeDomainProvider
{
public:
        /* a new session might have non-empty mix_template, an existing session should always have an empty one.
           the bus profile can be null if no master out bus is required.
        */
 
        Session (AudioEngine&,
                 const std::string& fullpath,
                 const std::string& snapshot_name,
                 BusProfile const * bus_profile = 0,
                 std::string mix_template = "",
                 bool unnamed = false,
                 samplecnt_t samplerate = 0);
 
        virtual ~Session ();
 
        static int get_info_from_path (const std::string& xmlpath, float& sample_rate, SampleFormat& data_format, std::string& program_version, XMLNode* engine_hints = 0);
        static std::string get_snapshot_from_instant (const std::string& session_dir);
 
        static unsigned int next_name_id ();
 
        std::string path() const { return _path; }
        std::string name() const { return _name; }
        std::string snap_name() const { return _current_snapshot_name; }
        std::string raid_path () const;
        bool path_is_within_session (const std::string&);
 
        bool writable() const { return _writable; }
        void set_clean ();   // == Clean and emit DirtyChanged IFF session was Dirty
        void set_dirty ();   // |= Dirty and emit DirtyChanged (unless already dirty or Loading, Deletion)
        void unset_dirty (bool emit_dirty_changed = false); // &= ~Dirty
        void set_deletion_in_progress ();   // |= Deletion
        void clear_deletion_in_progress (); // &= ~Deletion
 
        bool reconnection_in_progress () const         { return _reconnecting_routes_in_progress; }
        bool routes_deletion_in_progress () const      { return _route_deletion_in_progress; }
        bool dirty () const                            { return _state_of_the_state & Dirty; }
        bool deletion_in_progress () const             { return _state_of_the_state & Deletion; }
        bool peaks_cleanup_in_progres () const         { return _state_of_the_state & PeakCleanup; }
        bool loading () const                          { return _state_of_the_state & Loading; }
        bool cannot_save () const                      { return _state_of_the_state & CannotSave; }
        bool in_cleanup () const                       { return _state_of_the_state & InCleanup; }
        bool inital_connect_or_deletion_in_progress () const { return _state_of_the_state & (InitialConnecting | Deletion); }
        bool have_external_connections_for_current_backend (bool tracks_only = true) const;
        bool unnamed() const;
 
        void end_unnamed_status () const;
 
        PBD::Signal<void()> DirtyChanged;
 
        const SessionDirectory& session_directory () const { return *(_session_dir.get()); }
 
        static PBD::Signal<void(std::string)> Dialog;
 
        PBD::Signal<void()> BatchUpdateStart;
        PBD::Signal<void()> BatchUpdateEnd;
 
        int ensure_subdirs ();
 
        std::string automation_dir () const;  
        std::string analysis_dir () const;    
        std::string plugins_dir () const;     
        std::string externals_dir () const;   
 
        std::string construct_peak_filepath (const std::string& audio_path, const bool in_session = false, const bool old_peak_name = false) const;
 
        bool audio_source_name_is_unique (const std::string& name);
        std::string format_audio_source_name (const std::string& legalized_base, uint32_t nchan, uint32_t chan, bool take_required, uint32_t cnt, bool related_exists);
        std::string new_audio_source_path_for_embedded (const std::string& existing_path);
        std::string new_audio_source_path (const std::string&, uint32_t nchans, uint32_t chan, bool take_required);
        std::string new_midi_source_path (const std::string&, bool need_source_lock = true);
 
        RouteList new_route_from_template (uint32_t how_many, PresentationInfo::order_t insert_at, const std::string& template_path, const std::string& name, PlaylistDisposition pd = NewPlaylist);
        RouteList new_route_from_template (uint32_t how_many, PresentationInfo::order_t insert_at, XMLNode&, const std::string& name, PlaylistDisposition pd = NewPlaylist);
        std::vector<std::string> get_paths_for_new_sources (bool allow_replacing, const std::string& import_file_path,
                                                            uint32_t channels, std::vector<std::string> const & smf_track_names, bool use_smf_file_names);
 
        int bring_all_sources_into_session (std::function<void(uint32_t,uint32_t,std::string)> callback);
 
        void process (pframes_t nframes);
 
        void send_ltc_for_cycle (samplepos_t, samplepos_t, pframes_t);
        void send_mclk_for_cycle (samplepos_t, samplepos_t, pframes_t, samplecnt_t);
 
        BufferSet& get_silent_buffers (ChanCount count = ChanCount::ZERO);
        BufferSet& get_noinplace_buffers (ChanCount count = ChanCount::ZERO);
        BufferSet& get_scratch_buffers (ChanCount count = ChanCount::ZERO, bool silence = true);
        BufferSet& get_route_buffers (ChanCount count = ChanCount::ZERO, bool silence = true);
        BufferSet& get_mix_buffers (ChanCount count = ChanCount::ZERO);
 
        void ensure_buffers_unlocked (ChanCount howmany);
 
        bool have_rec_enabled_track () const;
        bool have_rec_disabled_track () const;
 
        bool have_captured() const { return _have_captured; }
 
        samplecnt_t capture_duration () const { return _capture_duration; }
        unsigned int capture_xruns () const { return _capture_xruns; }
        unsigned int export_xruns () const { return _export_xruns; }
 
        void refill_all_track_buffers ();
        Butler* butler() { return _butler; }
        void butler_transport_work (bool have_process_lock = false);
 
        void refresh_disk_space ();
 
        int load_routes (const XMLNode&, int);
        std::shared_ptr<RouteList const> get_routes() const {
                return routes.reader ();
        }
 
        std::shared_ptr<RTTaskList> rt_tasklist () { return _rt_tasklist; }
        std::shared_ptr<IOTaskList> io_tasklist () { return _io_tasklist; }
 
        RouteList get_routelist (bool mixer_order = false, PresentationInfo::Flag fl = PresentationInfo::MixerRoutes) const;
 
        CoreSelection& selection () const { return *_selection; }
 
        /* because the set of Stripables consists of objects managed
         * independently, in multiple containers within the Session (or objects
         * owned by the session), we fill out a list in-place rather than
         * return a pointer to a copy of the (RCU) managed list, as happens
         * with get_routes()
         */
 
        void get_stripables (StripableList&, PresentationInfo::Flag fl = PresentationInfo::MixerStripables) const;
        StripableList get_stripables () const;
        std::shared_ptr<RouteList> get_tracks() const;
        std::shared_ptr<RouteList> get_routes_with_internal_returns() const;
        std::shared_ptr<RouteList> get_routes_with_regions_at (timepos_t const &) const;
 
        uint32_t nstripables (bool with_monitor = false) const;
        uint32_t nroutes() const { return routes.reader()->size(); }
        uint32_t ntracks () const;
        uint32_t naudiotracks () const;
        uint32_t nbusses () const;
 
        bool plot_process_graph (std::string const& file_name) const;
 
        std::shared_ptr<BundleList const> bundles () {
                return _bundles.reader ();
        }
 
        void notify_presentation_info_change (PBD::PropertyChange const&);
 
        template<class T> void foreach_route (T *obj, void (T::*func)(Route&), bool sort = true);
        template<class T> void foreach_route (T *obj, void (T::*func)(std::shared_ptr<Route>), bool sort = true);
        template<class T, class A> void foreach_route (T *obj, void (T::*func)(Route&, A), A arg, bool sort = true);
 
        template<class A>            void foreach_track (void (Track::*method)(A), A arg);
        template<class A1, class A2> void foreach_track (void (Track::*method)(A1, A2), A1 arg1, A2 arg2);
 
        void foreach_route (void (Route::*method)());
        template<class A>            void foreach_route (void (Route::*method)(A), A arg);
        template<class A1, class A2> void foreach_route (void (Route::*method)(A1, A2), A1 arg1, A2 arg2);
 
        static const std::string session_name_is_legal (const std::string&);
 
        bool io_name_is_legal (const std::string&) const;
        std::shared_ptr<Route> route_by_name (std::string) const;
        std::shared_ptr<Route> route_by_id (PBD::ID) const;
        std::shared_ptr<Stripable> stripable_by_id (PBD::ID) const;
        std::shared_ptr<Stripable> get_remote_nth_stripable (PresentationInfo::order_t n, PresentationInfo::Flag) const;
        std::shared_ptr<Route> get_remote_nth_route (PresentationInfo::order_t n) const;
        std::shared_ptr<Route> route_by_selected_count (uint32_t cnt) const;
        void routes_using_input_from (const std::string& str, RouteList& rl);
 
        bool route_name_unique (std::string) const;
        bool route_name_internal (std::string) const;
 
        uint32_t track_number_decimals () const {
                return _track_number_decimals;
        }
 
        bool get_record_enabled() const {
                return (record_status () >= Enabled);
        }
 
        RecordState record_status() const {
                return _record_status.load();
        }
 
        bool actively_recording () const {
                return record_status() == Recording;
        }
 
        bool record_enabling_legal () const;
        void maybe_enable_record (bool rt_context = false);
        void disable_record (bool rt_context, bool force = false);
        void step_back_from_record ();
 
        void set_all_tracks_record_enabled(bool);
 
        void maybe_write_autosave ();
 
        PBD::Signal<void(int)> SurroundObjectCountChanged;
 
        /* Emitted when all i/o connections are complete */
 
        PBD::Signal<void()> IOConnectionsComplete;
 
        /* Record status signals */
 
        PBD::Signal<void()> RecordStateChanged; /* signals changes in recording state (i.e. are we recording) */
        /* XXX may 2015: paul says: it isn't clear to me that this has semantics that cannot be inferrred
           from the previous signal and session state.
        */
        PBD::Signal<void()> RecordArmStateChanged; /* signals changes in recording arming */
 
        PBD::Signal<void()> UpdateRouteRecordState; /* signals potential change in route recording arming */
 
        /* Emited when session is loaded */
        PBD::Signal<void()> SessionLoaded;
 
        /* Transport mechanism signals */
 
        PBD::Signal<void()> TransportStateChange;
 
        PBD::Signal<void(samplepos_t)> PositionChanged; /* sent after any non-sequential motion */
        PBD::Signal<void(samplepos_t)> Xrun;
        PBD::Signal<void()> TransportLooped;
 
        PBD::Signal<void()> Located;
 
        PBD::Signal<void(RouteList&)> RouteAdded;
        PBD::Signal<void(RouteGroup *)> RouteGroupPropertyChanged;
        PBD::Signal<void(RouteGroup *, std::weak_ptr<Route> )> RouteAddedToRouteGroup;
        PBD::Signal<void(RouteGroup *, std::weak_ptr<Route> )> RouteRemovedFromRouteGroup;
 
        PBD::Signal<void()> FBSendsChanged;
 
        /* Step Editing status changed */
        PBD::Signal<void(bool)> StepEditStatusChange;
 
        /* Timecode state signals */
        PBD::Signal<void()> MtcOrLtcInputPortChanged;
 
        void queue_event (SessionEvent*);
 
        void request_roll_at_and_return (samplepos_t start, samplepos_t return_to);
        void request_bounded_roll (samplepos_t start, samplepos_t end);
        void request_roll (TransportRequestSource origin = TRS_UI);
        void request_stop (bool abort = false, bool clear_state = false, TransportRequestSource origin = TRS_UI);
        void request_locate (samplepos_t sample, bool force = false, LocateTransportDisposition ltd = RollIfAppropriate, TransportRequestSource origin = TRS_UI);
 
        void request_play_loop (bool yn, bool leave_rolling = false);
        bool get_play_loop () const { return play_loop; }
 
        samplepos_t last_transport_start () const { return _last_roll_location; }
        void goto_end ();
        void goto_start (bool and_roll = false);
        void use_rf_shuttle_speed ();
        void allow_auto_play (bool yn);
 
        double default_play_speed ();
        void reset_transport_speed (TransportRequestSource origin = TRS_UI);
 
        void trigger_stop_all (bool now = true);
 
        void request_transport_speed (double speed, TransportRequestSource origin = TRS_UI);
        void request_default_play_speed (double speed, TransportRequestSource origin = TRS_UI);
        void request_transport_speed_nonzero (double, TransportRequestSource origin = TRS_UI);
        void request_overwrite_buffer (std::shared_ptr<Track>, OverwriteReason);
        void adjust_playback_buffering();
        void adjust_capture_buffering();
 
        bool global_locate_pending() const { return _global_locate_pending; }
        bool locate_pending() const;
        bool locate_initiated() const;
        bool declick_in_progress () const;
        bool transport_locked () const;
 
        bool had_destructive_tracks () const;
        void set_had_destructive_tracks (bool yn);
 
        int wipe ();
 
        timepos_t current_end () const;
        timepos_t current_start () const;
        samplepos_t current_end_sample () const;
        samplepos_t current_start_sample () const;
        samplecnt_t sample_rate () const { return _current_sample_rate; }
        samplecnt_t nominal_sample_rate () const { return _base_sample_rate; }
        samplecnt_t frames_per_hour () const { return _frames_per_hour; }
 
        double samples_per_timecode_frame() const { return _samples_per_timecode_frame; }
        samplecnt_t timecode_frames_per_hour() const { return _timecode_frames_per_hour; }
 
        MIDI::byte get_mtc_timecode_bits() const {
                return mtc_timecode_bits;   /* encoding of SMTPE type for MTC */
        }
 
        double timecode_frames_per_second() const;
        bool timecode_drop_frames() const;
 
        /* Locations */
 
        Locations *locations() { return _locations; }
 
        PBD::Signal<void(Location*)>    auto_loop_location_changed;
        PBD::Signal<void(Location*)>    auto_punch_location_changed;
        PBD::Signal<void()>              locations_modified;
 
        void set_auto_punch_location (Location *);
        void set_auto_loop_location (Location *);
        void set_session_extents (timepos_t const & start, timepos_t const & end);
        bool session_range_is_free () const { return _session_range_is_free; }
        void set_session_range_is_free (bool);
 
        pframes_t get_block_size () const         { return current_block_size; }
        samplecnt_t worst_output_latency () const { return _worst_output_latency; }
        samplecnt_t worst_input_latency () const  { return _worst_input_latency; }
        samplecnt_t worst_route_latency () const  { return _worst_route_latency; }
        samplecnt_t io_latency () const           { return _io_latency; }
        samplecnt_t worst_latency_preroll () const;
        samplecnt_t worst_latency_preroll_buffer_size_ceil () const;
 
        PBD::Signal<void(bool)> LatencyUpdated;
 
        struct SaveAs {
                std::string new_parent_folder;  /* parent folder where new session folder will be created */
                std::string new_name;           /* name of newly saved session */
                bool        switch_to;     /* true if we should be working on newly saved session after save-as; false otherwise */
                bool        include_media; /* true if the newly saved session should contain references to media */
                bool        copy_media;    /* true if media files (audio, media, etc) should be copied into newly saved session; false otherwise */
                bool        copy_external; /* true if external media should be consolidated into the newly saved session; false otherwise */
 
                std::string final_session_folder_name; /* filled in by * Session::save_as(), provides full path to newly saved session */
 
                /* emitted as we make progress. 3 arguments passed to signal
                 * handler:
                 *
                 *  1: percentage complete measured as a fraction (0-1.0) of
                 *     total data copying done.
                 *  2: number of files copied so far
                 *  3: total number of files to copy
                 *
                 * Handler should return true for save-as to continue, or false
                 * to stop (and remove all evidence of partial save-as).
                 */
                PBD::Signal<bool(float,int64_t,int64_t)> Progress;
 
                /* if save_as() returns non-zero, this string will indicate the reason why.
                 */
                std::string failure_message;
        };
 
        int save_as (SaveAs&);
 
        int save_state (std::string snapshot_name = "",
                        bool pending = false,
                        bool switch_to_snapshot = false,
                        bool template_only = false,
                        bool for_archive = false,
                        bool only_used_assets = false);
 
        enum ArchiveEncode {
                NO_ENCODE,
                FLAC_16BIT,
                FLAC_24BIT
        };
 
        int archive_session (const std::string&, const std::string&,
                             ArchiveEncode compress_audio = FLAC_16BIT,
                             PBD::FileArchive::CompressionLevel compression_level = PBD::FileArchive::CompressGood,
                             bool only_used_sources = false,
                             PBD::Progress* p = 0);
 
        int restore_state (std::string snapshot_name);
        int save_template (const std::string& template_name, const std::string& description = "", bool replace_existing = false);
        int save_history (std::string snapshot_name = "");
        int restore_history (std::string snapshot_name);
        void remove_state (std::string snapshot_name);
        void rename_state (std::string old_name, std::string new_name);
        void remove_pending_capture_state ();
        int rename (const std::string&);
        bool get_nsm_state () const { return _under_nsm_control; }
        void set_nsm_state (bool state) { _under_nsm_control = state; }
        bool save_default_options ();
 
        PBD::Signal<void(std::string)> StateSaved;
        PBD::Signal<void()> StateReady;
 
        /* emitted when session needs to be saved due to some internal
         * event or condition (i.e. not in response to a user request).
         *
         * Only one object should
         * connect to this signal and take responsibility.
         *
         * Argument is the snapshot name to use when saving.
         */
        PBD::Signal<void(std::string)> SaveSessionRequested;
 
        /* emitted during a session save to allow other entities to add state, via
         * extra XML, to the session state
         */
        PBD::Signal<void()> SessionSaveUnderway;
 
        std::vector<std::string> possible_states() const;
        static std::vector<std::string> possible_states (std::string path);
 
        bool export_track_state (std::shared_ptr<RouteList> rl, const std::string& path);
 
        void add_instant_xml (XMLNode&, bool write_to_config = true);
        XMLNode* instant_xml (const std::string& str);
 
        enum StateOfTheState {
                Clean = 0x0,
                Dirty = 0x1,
                CannotSave = 0x2,
                Deletion = 0x4,
                InitialConnecting = 0x8,
                Loading = 0x10,
                InCleanup = 0x20,
                PeakCleanup = 0x40
        };
 
        class StateProtector {
                public:
                        StateProtector (Session* s) : _session (s) {
                                PBD::atomic_inc (s->_suspend_save);
                        }
                        ~StateProtector () {
                                if (PBD::atomic_dec_and_test (_session->_suspend_save)) {
                                        while (_session->_save_queued) {
                                                _session->_save_queued = false;
                                                _session->save_state ("");
                                        }
                                        while (_session->_save_queued_pending) {
                                                _session->_save_queued_pending = false;
                                                _session->save_state ("", true);
                                        }
                                }
                        }
                private:
                        Session * _session;
        };
 
        class LIBARDOUR_API ProcessorChangeBlocker {
        public:
                ProcessorChangeBlocker (Session* s, bool rc = true);
                ~ProcessorChangeBlocker ();
 
        private:
                Session* _session;
                bool _reconfigure_on_delete;
        };
 
        RouteGroup* new_route_group (const std::string&);
        void add_route_group (RouteGroup *);
        void remove_route_group (RouteGroup* rg) { if (rg) remove_route_group (*rg); }
        void remove_route_group (RouteGroup&);
        void reorder_route_groups (std::list<RouteGroup*>);
 
        RouteGroup* route_group_by_name (std::string);
        RouteGroup& all_route_group() const;
 
        PBD::Signal<void(RouteGroup*)> route_group_added;
        PBD::Signal<void()>             route_group_removed;
        PBD::Signal<void()>             route_groups_reordered;
 
        void foreach_route_group (std::function<void(RouteGroup*)> f) {
                for (std::list<RouteGroup *>::iterator i = _route_groups.begin(); i != _route_groups.end(); ++i) {
                        f (*i);
                }
        }
 
        std::list<RouteGroup*> const & route_groups () const {
                return _route_groups;
        }
 
        /* fundamental operations. duh. */
 
        std::list<std::shared_ptr<AudioTrack> > new_audio_track (
                int input_channels,
                int output_channels,
                RouteGroup* route_group,
                uint32_t how_many,
                std::string name_template,
                PresentationInfo::order_t order,
                TrackMode mode = Normal,
                bool input_auto_connect = true,
                bool trigger_visibility = false
                );
 
        std::list<std::shared_ptr<MidiTrack> > new_midi_track (
                const ChanCount& input, const ChanCount& output, bool strict_io,
                std::shared_ptr<PluginInfo> instrument,
                Plugin::PresetRecord* pset,
                RouteGroup* route_group, uint32_t how_many, std::string name_template,
                PresentationInfo::order_t,
                TrackMode mode,
                bool input_auto_connect,
                bool trigger_visibility = false
                );
 
        RouteList new_audio_route (int input_channels, int output_channels, RouteGroup* route_group, uint32_t how_many, std::string name_template, PresentationInfo::Flag, PresentationInfo::order_t);
        RouteList new_midi_route (RouteGroup* route_group, uint32_t how_many, std::string name_template, bool strict_io, std::shared_ptr<PluginInfo> instrument, Plugin::PresetRecord*, PresentationInfo::Flag, PresentationInfo::order_t);
 
        void remove_routes (std::shared_ptr<RouteList>);
        void remove_route (std::shared_ptr<Route>);
 
        void resort_routes ();
 
        AudioEngine & engine() { return _engine; }
        AudioEngine const & engine () const { return _engine; }
 
        static std::string default_track_name_pattern (DataType);
 
        /* Time */
 
        samplepos_t transport_sample () const { return _transport_sample; }
        samplepos_t record_location () const { return _last_record_location; }
        samplepos_t audible_sample (bool* latent_locate = NULL) const;
        samplepos_t requested_return_sample() const { return _requested_return_sample; }
        void set_requested_return_sample(samplepos_t return_to);
        std::optional<samplepos_t> const & nominal_jack_transport_sample() { return _nominal_jack_transport_sample; }
 
        bool compute_audible_delta (samplepos_t& pos_and_delta) const;
        samplecnt_t remaining_latency_preroll () const { return _remaining_latency_preroll; }
 
        enum PullupFormat {
                pullup_Plus4Plus1,
                pullup_Plus4,
                pullup_Plus4Minus1,
                pullup_Plus1,
                pullup_None,
                pullup_Minus1,
                pullup_Minus4Plus1,
                pullup_Minus4,
                pullup_Minus4Minus1
        };
 
        void sync_time_vars();
 
        void timecode_to_sample(Timecode::Time& timecode, samplepos_t& sample, bool use_offset, bool use_subframes) const;
        void sample_to_timecode(samplepos_t sample, Timecode::Time& timecode, bool use_offset, bool use_subframes) const;
        void timecode_time (Timecode::Time &);
        void timecode_time (samplepos_t when, Timecode::Time&);
        void timecode_time_subframes (samplepos_t when, Timecode::Time&);
 
        void timecode_duration (samplecnt_t, Timecode::Time&) const;
        void timecode_duration_string (char *, size_t len, samplecnt_t) const;
 
        samplecnt_t convert_to_samples (AnyTime const & position);
        samplecnt_t any_duration_to_samples (samplepos_t position, AnyTime const & duration);
 
        static PBD::Signal<void(samplepos_t)> StartTimeChanged;
        static PBD::Signal<void(samplepos_t)> EndTimeChanged;
 
        void   request_sync_source (std::shared_ptr<TransportMaster>);
        bool   synced_to_engine() const;
 
        double engine_speed() const { return _engine_speed; }
        double actual_speed() const;
        double transport_speed (bool incl_preroll = false) const;
        bool   transport_stopped() const;
        bool   transport_stopped_or_stopping() const;
        bool   transport_state_rolling() const;
        bool transport_rolling() const;
        bool transport_will_roll_forwards() const;
        bool transport_locating() const;
 
        bool silent () { return _silent; }
 
        bool punch_is_possible () const;
        bool loop_is_possible () const;
        PBD::Signal<void()> PunchLoopConstraintChange;
 
        void maybe_update_tempo_from_midiclock_tempo (float bpm);
 
        unsigned int    get_xrun_count () const {return _xrun_count; }
        void            reset_xrun_count ();
 
        /* region info  */
 
        std::shared_ptr<Region> find_whole_file_parent (std::shared_ptr<Region const>) const;
 
        std::shared_ptr<Region>      XMLRegionFactory (const XMLNode&, bool full);
        std::shared_ptr<AudioRegion> XMLAudioRegionFactory (const XMLNode&, bool full);
        std::shared_ptr<MidiRegion>  XMLMidiRegionFactory (const XMLNode&, bool full);
 
        void deinterlace_midi_region ( std::shared_ptr<MidiRegion> mr );
 
        /* source management */
 
        void import_files (ImportStatus&);
        bool sample_rate_convert (ImportStatus&, std::string infile, std::string& outfile);
        std::string build_tmp_convert_name (std::string file);
 
        std::shared_ptr<ExportHandler> get_export_handler ();
        std::shared_ptr<ExportStatus> get_export_status ();
 
        int start_audio_export (samplepos_t position, bool realtime = false, bool region_export = false);
 
        PBD::Signal<int(samplecnt_t)> ProcessExport;
        static PBD::Signal<void(std::string, std::string, bool, samplepos_t)> Exported;
 
        void add_source (std::shared_ptr<Source>);
        void remove_source (std::weak_ptr<Source>, bool drop_references = true);
 
        void cleanup_regions();
        bool can_cleanup_peakfiles () const;
        int  cleanup_peakfiles ();
        int  cleanup_sources (CleanupReport&);
        int  cleanup_trash_sources (CleanupReport&);
 
        int destroy_sources (std::list<std::shared_ptr<Source> > const&);
 
        int remove_last_capture ();
        void get_last_capture_sources (std::list<std::shared_ptr<Source> >&);
 
        static PBD::Signal<int(std::shared_ptr<Playlist> )>  AskAboutPlaylistDeletion;
 
        static PBD::Signal<int(samplecnt_t, samplecnt_t)> AskAboutSampleRateMismatch;
 
        static PBD::Signal<void(samplecnt_t, samplecnt_t)> NotifyAboutSampleRateMismatch;
 
        static PBD::Signal<int()> AskAboutPendingState;
 
        static PBD::Signal<void()> AfterConnect;
 
        std::shared_ptr<AudioFileSource> create_audio_source_for_session (
                size_t, std::string const &, uint32_t);
 
        std::shared_ptr<MidiSource> create_midi_source_for_session (std::string const &);
        std::shared_ptr<MidiSource> create_midi_source_by_stealing_name (std::shared_ptr<Track>);
 
        std::shared_ptr<Source> source_by_id (const PBD::ID&);
        std::shared_ptr<AudioFileSource> audio_source_by_path_and_channel (const std::string&, uint16_t) const;
        std::shared_ptr<MidiSource> midi_source_by_path (const std::string&, bool need_source_lock) const;
        uint32_t count_sources_by_origin (const std::string&);
 
        void add_playlist (std::shared_ptr<Playlist>);
 
        /* Curves and AutomationLists (TODO when they go away) */
        void add_automation_list(AutomationList*);
 
        /* auditioning */
 
        std::shared_ptr<Auditioner> the_auditioner() { return auditioner; }
        void audition_playlist ();
        void audition_region (std::shared_ptr<Region>);
        void cancel_audition ();
        bool is_auditioning () const;
 
        PBD::Signal<void(bool)> AuditionActive;
 
        /* session script */
        void register_lua_function (const std::string&, const std::string&, const LuaScriptParamList&);
        void unregister_lua_function (const std::string& name);
        std::vector<std::string> registered_lua_functions ();
        uint32_t registered_lua_function_count () const { return _n_lua_scripts; }
        void scripts_changed (); // called from lua, updates _n_lua_scripts
 
        PBD::Signal<void()> LuaScriptsChanged;
 
        /* I/O Plugin */
        PBD::Signal<void()> IOPluginsChanged;
 
        void load_io_plugin (std::shared_ptr<IOPlug>);
        bool unload_io_plugin (std::shared_ptr<IOPlug>);
 
        std::shared_ptr<IOPlug> nth_io_plug (uint32_t n) {
                std::shared_ptr<IOPlugList const> iop (_io_plugins.reader ());
                if (n < iop->size ()) {
                        return (*iop)[n];
                }
                return std::shared_ptr<IOPlug> ();
        }
 
        std::shared_ptr<IOPlugList const> io_plugs () const {
                return _io_plugins.reader ();
        }
 
        /* flattening stuff */
 
        std::shared_ptr<Region> write_one_track (Track&, samplepos_t start, samplepos_t end,
                                                 bool overwrite, std::vector<std::shared_ptr<Source> >&, InterThreadInfo& wot,
                                                 std::shared_ptr<Processor> endpoint,
                                                 bool include_endpoint, bool for_export, bool for_freeze,
                                                 std::string const& source_name = "", std::string const& region_name = "");
        int freeze_all (InterThreadInfo&);
 
        /* session-wide solo/mute/rec-enable */
 
        bool muted () const;
        std::vector<std::weak_ptr<AutomationControl> > cancel_all_mute ();
 
        bool soloing () const { return _non_soloed_outs_muted; }
        bool listening () const;
        bool solo_isolated () const { return _solo_isolated_cnt > 0; }
        void cancel_all_solo ();
 
        bool solo_selection_active ();
        void solo_selection (StripableList&, bool);
 
        void clear_all_solo_state (std::shared_ptr<RouteList const>);
        void prepare_momentary_solo (SoloMuteRelease* smr = NULL, bool exclusive = false, std::shared_ptr<Route> route = std::shared_ptr<Route> ());
 
        static const SessionEvent::RTeventCallback rt_cleanup;
 
        /* Control-based methods */
 
        void set_controls (std::shared_ptr<AutomationControlList>, double val, PBD::Controllable::GroupControlDisposition);
        void set_control (std::shared_ptr<AutomationControl>, double val, PBD::Controllable::GroupControlDisposition);
 
        void set_exclusive_input_active (std::shared_ptr<RouteList> rt, bool onoff, bool flip_others = false);
 
        PBD::Signal<void(bool)> SoloActive;
        PBD::Signal<void()> SoloChanged;
        PBD::Signal<void()> MuteChanged;
        PBD::Signal<void()> IsolatedChanged;
        PBD::Signal<void()> MonitorChanged;
        PBD::Signal<void()> MonitorBusAddedOrRemoved;
        PBD::Signal<void()> SurroundMasterAddedOrRemoved;
 
        PBD::Signal<void()> session_routes_reconnected;
 
        /* monitor/master out */
        int add_master_bus (ChanCount const&);
 
        void reset_monitor_section ();
        bool monitor_active() const { return (_monitor_out && _monitor_out->monitor_control () && _monitor_out->monitor_control ()->monitor_active()); }
 
        std::shared_ptr<Route> monitor_out() const { return _monitor_out; }
        std::shared_ptr<Route> master_out() const { return _master_out; }
        std::shared_ptr<GainControl>  master_volume () const;
        std::shared_ptr<Route> surround_master() const { return _surround_master; }
 
        PresentationInfo::order_t master_order_key () const { return _master_out ? _master_out->presentation_info ().order () : -1; }
        bool ensure_stripable_sort_order ();
 
        void globally_add_internal_sends (std::shared_ptr<Route> dest, Placement p, bool);
        void globally_set_send_gains_from_track (std::shared_ptr<Route> dest);
        void globally_set_send_gains_to_zero (std::shared_ptr<Route> dest);
        void globally_set_send_gains_to_unity (std::shared_ptr<Route> dest);
        void add_internal_sends (std::shared_ptr<Route> dest, Placement p, std::shared_ptr<RouteList> senders);
        void add_internal_send (std::shared_ptr<Route>, int, std::shared_ptr<Route>);
        void add_internal_send (std::shared_ptr<Route>, std::shared_ptr<Processor>, std::shared_ptr<Route>);
 
        static void set_disable_all_loaded_plugins (bool yn) {
                _disable_all_loaded_plugins = yn;
        }
        static bool get_disable_all_loaded_plugins() {
                return _disable_all_loaded_plugins;
        }
        static void set_bypass_all_loaded_plugins (bool yn) {
                _bypass_all_loaded_plugins = yn;
        }
        static bool get_bypass_all_loaded_plugins() {
                return _bypass_all_loaded_plugins;
        }
 
        uint32_t next_send_id();
        uint32_t next_surround_send_id();
        uint32_t next_aux_send_id();
        uint32_t next_return_id();
        uint32_t next_insert_id();
        void mark_send_id (uint32_t);
        void mark_surround_send_id (uint32_t);
        void mark_aux_send_id (uint32_t);
        void mark_return_id (uint32_t);
        void mark_insert_id (uint32_t);
        void unmark_send_id (uint32_t);
        void unmark_surround_send_id (uint32_t);
        void unmark_aux_send_id (uint32_t);
        void unmark_return_id (uint32_t);
        void unmark_insert_id (uint32_t);
 
        bool vapor_barrier ();
        bool vapor_export_barrier ();
 
        /* s/w "RAID" management */
 
        std::optional<samplecnt_t> available_capture_duration();
 
        /* I/O bundles */
 
        void add_bundle (std::shared_ptr<Bundle>, bool emit_signal = true);
        void remove_bundle (std::shared_ptr<Bundle>);
        std::shared_ptr<Bundle> bundle_by_name (std::string) const;
 
        PBD::Signal<void()> BundleAddedOrRemoved;
 
        void midi_panic ();
 
        /* History (for editors, mixers, UIs etc.) */
 
        void undo (uint32_t n);
        void redo (uint32_t n);
 
        PBD::UndoHistory& history() { return _history; }
 
        uint32_t undo_depth() const { return _history.undo_depth(); }
        uint32_t redo_depth() const { return _history.redo_depth(); }
        std::string next_undo() const { return _history.next_undo(); }
        std::string next_redo() const { return _history.next_redo(); }
 
 
        std::map<PBD::ID,PBD::StatefulDestructible*> registry;
 
        // these commands are implemented in libs/ardour/session_command.cc
        PBD::Command* memento_command_factory(XMLNode* n);
        PBD::Command* stateful_diff_command_factory (XMLNode *);
        void register_with_memento_command_factory(PBD::ID, PBD::StatefulDestructible*);
 
        /* clicking */
 
        std::shared_ptr<IO> click_io() { return _click_io; }
        std::shared_ptr<Amp> click_gain() { return _click_gain; }
 
        /* disk, buffer loads */
 
        uint32_t playback_load ();
        uint32_t capture_load ();
 
        /* ranges */
 
        void request_play_range (std::list<TimelineRange>*, bool leave_rolling = false);
        void request_cancel_play_range ();
        bool get_play_range () const { return _play_range; }
 
        void maybe_update_session_range (timepos_t const &, timepos_t const &);
 
        /* preroll */
        samplecnt_t preroll_samples (samplepos_t) const;
 
        void request_preroll_record_trim (samplepos_t start, samplecnt_t preroll);
        void request_count_in_record ();
 
        samplecnt_t preroll_record_trim_len () const { return _preroll_record_trim_len; }
 
        /* temporary hacks to allow selection to be pushed from GUI into backend.
           Whenever we move the selection object into libardour, these will go away.
         */
        void set_range_selection (Temporal::timepos_t const & start, Temporal::timepos_t const & end);
        void set_object_selection (Temporal::timepos_t const & start, Temporal::timepos_t const & end);
        void clear_range_selection ();
        void clear_object_selection ();
 
        void cut_copy_section (Temporal::timepos_t const& start, Temporal::timepos_t const& end, Temporal::timepos_t const& to, SectionOperation const op);
 
        /* buffers for gain and pan */
 
        gain_t* gain_automation_buffer () const;
        gain_t* trim_automation_buffer () const;
        gain_t* send_gain_automation_buffer () const;
        gain_t* scratch_automation_buffer () const;
        pan_t** pan_automation_buffer () const;
 
        /* VST support */
 
        static int  vst_current_loading_id;
        static const char* vst_can_do_strings[];
        static const int vst_can_do_string_count;
 
        static intptr_t vst_callback (
                AEffect* effect,
                int32_t opcode,
                int32_t index,
                intptr_t value,
                void* ptr,
                float opt
                );
 
        static PBD::Signal<void()> SendFeedback;
 
        /* Speakers */
 
        std::shared_ptr<Speakers> get_speakers ();
 
        /* Controllables */
 
        std::shared_ptr<ARDOUR::Trigger> trigger_by_id (PBD::ID) const;
 
        std::shared_ptr<Processor> processor_by_id (PBD::ID) const;
 
        std::shared_ptr<PBD::Controllable> controllable_by_id (const PBD::ID&);
        std::shared_ptr<AutomationControl> automation_control_by_id (const PBD::ID&);
 
        void add_controllable (std::shared_ptr<PBD::Controllable>);
 
        std::shared_ptr<PBD::Controllable> solo_cut_control() const;
        std::shared_ptr<PBD::Controllable> recently_touched_controllable () const;
 
        bool apply_nth_mixer_scene (size_t);
        bool apply_nth_mixer_scene (size_t, RouteList const&);
        void store_nth_mixer_scene (size_t);
        bool nth_mixer_scene_valid (size_t) const;
        size_t last_touched_mixer_scene_idx () {return _last_touched_mixer_scene_idx;}
 
        std::shared_ptr<MixerScene>              nth_mixer_scene (size_t, bool create_if_missing = false);
        std::vector<std::shared_ptr<MixerScene>> mixer_scenes () const;
 
        SessionConfiguration config;
 
        SessionConfiguration* cfg () { return &config; }
 
        bool exporting () const {
                return _exporting;
        }
 
        bool realtime_export() const {
                return _realtime_export;
        }
 
        bool bounce_processing() const {
                return _bounce_processing_active;
        }
 
        /* this is a private enum, but setup_enum_writer() needs it,
           and i can't find a way to give that function
           friend access. sigh.
        */
 
        enum PostTransportWork {
                PostTransportStop               = 0x1,
                PostTransportLocate             = 0x2,
                PostTransportAbort              = 0x8,
                PostTransportOverWrite          = 0x10,
                PostTransportAudition           = 0x20,
                PostTransportReverse            = 0x40,
                PostTransportClearSubstate      = 0x80,
                PostTransportAdjustPlaybackBuffering  = 0x100,
                PostTransportAdjustCaptureBuffering   = 0x200,
                PostTransportLoopChanged        = 0x400
        };
 
        std::shared_ptr<SessionPlaylists> playlists () const { return _playlists; }
 
        void send_mmc_locate (samplepos_t);
        void queue_full_time_code () { _send_timecode_update = true; }
        void queue_song_position_pointer () { /* currently does nothing */ }
 
        bool step_editing() const { return (_step_editors > 0); }
 
        void request_suspend_timecode_transmission ();
        void request_resume_timecode_transmission ();
        bool timecode_transmission_suspended () const;
 
        std::vector<std::string> source_search_path(DataType) const;
        void ensure_search_path_includes (const std::string& path, DataType type);
        void remove_dir_from_search_path (const std::string& path, DataType type);
 
        std::list<std::string> unknown_processors () const;
 
        std::list<std::string> missing_filesources (DataType) const;
 
        static PBD::Signal<void()> FeedbackDetected;
 
        static PBD::Signal<void()> SuccessfulGraphSort;
 
        /* handlers can return an integer value:
           0: config.set_audio_search_path() or config.set_midi_search_path() was used
           to modify the search path and we should try to find it again.
           1: quit entire session load
           2: as 0, but don't ask about other missing files
           3: don't ask about other missing files, and just mark this one missing
           -1: just mark this one missing
           any other value: as -1
        */
        static PBD::Signal<int(Session*,std::string,DataType)> MissingFile;
 
        void set_missing_file_replacement (const std::string& mfr) {
                _missing_file_replacement = mfr;
        }
 
        static PBD::Signal<void()> Quit;
 
        static PBD::Signal<void(std::string,std::string)> VersionMismatch;
 
        SceneChanger* scene_changer() const { return _scene_changer; }
 
        /* asynchronous MIDI control ports */
 
        std::shared_ptr<Port> mmc_output_port () const;
        std::shared_ptr<Port> mmc_input_port () const;
        std::shared_ptr<Port> trigger_input_port () const;
        std::shared_ptr<Port> scene_input_port () const;
        std::shared_ptr<Port> scene_output_port () const;
 
        std::shared_ptr<AsyncMIDIPort> vkbd_output_port () const;
 
        /* synchronous MIDI ports used for synchronization */
 
        std::shared_ptr<MidiPort> midi_clock_output_port () const;
        std::shared_ptr<MidiPort> mtc_output_port () const;
        std::shared_ptr<Port> ltc_output_port() const { return _ltc_output_port; }
 
        MIDI::MachineControl& mmc() { return *_mmc; }
 
        void reconnect_midi_scene_ports (bool);
        void reconnect_mmc_ports (bool);
 
        void reconnect_ltc_output ();
 
        VCAManager& vca_manager() { return *_vca_manager; }
        VCAManager* vca_manager_ptr() { return _vca_manager; }
 
        void auto_connect_thread_wakeup ();
 
        double compute_speed_from_master (pframes_t nframes);
        bool   transport_master_is_external() const;
        bool   transport_master_no_external_or_using_engine() const;
        std::shared_ptr<TransportMaster> transport_master() const;
 
        void import_pt_sources (PTFFormat& ptf, ImportStatus& status);
        void import_pt_rest (PTFFormat& ptf);
        bool import_sndfile_as_region (std::string path, SrcQuality quality, timepos_t& pos, SourceList& sources, ImportStatus& status, uint32_t current, uint32_t total);
 
        struct ptflookup {
                uint16_t index1;
                uint16_t index2;
                PBD::ID  id;
 
                bool operator ==(const struct ptflookup& other) {
                        return (this->index1 == other.index1);
                }
        };
        std::vector<struct ptflookup> ptfwavpair;
        SourceList pt_imported_sources;
 
        enum TimingTypes {
                OverallProcess = 0,
                ProcessFunction = 1,
                NoRoll = 2,
                Roll = 3,
                /* end */
                NTT = 4
        };
 
        PBD::TimingStats dsp_stats[NTT];
 
        int32_t first_cue_within (samplepos_t s, samplepos_t e, bool& was_recorded);
        void trigger_cue_row (int32_t);
        CueEvents const & cue_events() const { return _cue_events; }
 
        int num_triggerboxes () const;
        std::shared_ptr<TriggerBox> triggerbox_at (int32_t route_index) const;
        TriggerPtr trigger_at (int32_t route_index, int32_t row_index) const;
        bool bang_trigger_at(int32_t route_index, int32_t row_index, float velocity = 1.0);
        bool unbang_trigger_at(int32_t route_index, int32_t row_index);
        void clear_cue (int row_index);
 
        void start_domain_bounce (Temporal::DomainBounceInfo&);
        void finish_domain_bounce (Temporal::DomainBounceInfo&);
 
        AnyTime global_quantization() const { return _global_quantization; }
        void set_global_quantization (AnyTime const &);
        PBD::Signal<void()> QuantizationChanged;
 
protected:
        friend class AudioEngine;
        void set_block_size (pframes_t nframes);
        void set_sample_rate (samplecnt_t nframes);
 
        friend class Route;
        void update_latency_compensation (bool force, bool called_from_backend);
 
        /* transport API */
 
        void locate (samplepos_t, bool for_loop_end=false, bool force=false, bool with_mmc=true);
        void stop_transport (bool abort = false, bool clear_state = false);
        void start_transport (bool after_loop);
        void butler_completed_transport_work ();
        void post_locate ();
        void schedule_butler_for_transport_work ();
        bool should_roll_after_locate () const;
        bool user_roll_after_locate () const;
        bool should_stop_before_locate () const;
        samplepos_t position() const { return _transport_sample; }
        void set_transport_speed (double speed);
        void set_default_play_speed (double spd);
        bool need_declick_before_locate () const;
        void tempo_map_changed ();
 
private:
        int  create (const std::string& mix_template, BusProfile const *, bool unnamed);
        void destroy ();
 
        static std::atomic<unsigned int> _name_id_counter;
        static void init_name_id_counter (unsigned int n);
        static unsigned int name_id_counter ();
 
        std::shared_ptr<SessionPlaylists> _playlists;
 
        /* stuff used in process() should be close together to
           maximise cache hits
        */
 
        typedef void (Session::*process_function_type)(pframes_t);
 
        AudioEngine&            _engine;
        process_function_type    process_function;
        process_function_type    last_process_function;
        bool                    _bounce_processing_active;
        bool                     waiting_for_sync_offset;
        samplecnt_t             _base_sample_rate;     // sample-rate of the session at creation time, "native" SR
        samplecnt_t             _current_sample_rate;  // this includes video pullup offset
        samplepos_t             _transport_sample;
        std::atomic<int>       _seek_counter;
        std::atomic<int>       _butler_seek_counter;
        Location*               _session_range_location; 
        bool                    _session_range_is_free;
        bool                    _silent;
        samplecnt_t             _remaining_latency_preroll;
        size_t                  _last_touched_mixer_scene_idx;
 
        // varispeed playback -- TODO: move out of session to backend.
        double                  _engine_speed;
        double                  _signalled_varispeed;
 
        bool                     auto_play_legal;
        samplepos_t             _requested_return_sample;
        pframes_t                current_block_size;
        samplecnt_t             _worst_output_latency;
        samplecnt_t             _worst_input_latency;
        samplecnt_t             _worst_route_latency;
        samplecnt_t             _io_latency;
        uint32_t                _send_latency_changes;
        bool                    _update_send_delaylines;
        bool                    _have_captured;
        samplecnt_t             _capture_duration;
        unsigned int            _capture_xruns;
        unsigned int            _export_xruns;
        bool                    _non_soloed_outs_muted;
        bool                    _listening;
        uint32_t                _listen_cnt;
        uint32_t                _solo_isolated_cnt;
        bool                    _writable;
        bool                    _was_seamless;
        bool                    _under_nsm_control;
        unsigned int            _xrun_count;
 
        std::string             _missing_file_replacement;
 
        mutable std::atomic<int> _processing_prohibited;
        mutable std::atomic<RecordState> _record_status;
 
        void add_monitor_section ();
        void remove_monitor_section ();
 
        void add_surround_master ();
        void remove_surround_master ();
 
        std::optional<bool> _vapor_available;
        std::optional<bool> _vapor_exportable;
 
        void update_latency (bool playback);
        void set_owned_port_public_latency (bool playback);
        bool update_route_latency (bool reverse, bool apply_to_delayline, bool* delayline_update_needed);
        void initialize_latencies ();
        void set_worst_output_latency ();
        void set_worst_input_latency ();
 
        void send_latency_compensation_change ();
        void update_send_delaylines ();
 
        void setup_engine_resampling ();
 
        void ensure_buffers (ChanCount howmany = ChanCount::ZERO);
        ChanCount _required_thread_buffers;
        size_t    _required_thread_buffersize;
 
        void process_without_events (pframes_t);
        void process_with_events    (pframes_t);
        void process_audition       (pframes_t);
        void process_export         (pframes_t);
        void process_export_fw      (pframes_t);
 
        samplecnt_t calc_preroll_subcycle (samplecnt_t) const;
 
        void block_processing();
        void unblock_processing() { _processing_prohibited.store (0); }
        bool processing_blocked() const { return _processing_prohibited.load (); }
 
        static const samplecnt_t bounce_chunk_size;
 
        /* Transport master DLL */
 
        enum TransportMasterState {
                Stopped, /* no incoming or invalid signal/data for master to run with */
                Waiting, /* waiting to get full lock on incoming signal/data */
                Running  /* lock achieved, master is generating meaningful speed & position */
        };
 
        samplepos_t master_wait_end;
 
        enum TransportMasterAction {
                TransportMasterRelax,
                TransportMasterNoRoll,
                TransportMasterLocate,
                TransportMasterStart,
                TransportMasterStop,
                TransportMasterWait,
        };
 
        struct TransportMasterStrategy {
                TransportMasterAction action;
                samplepos_t target;
                LocateTransportDisposition roll_disposition;
                double catch_speed;
 
                TransportMasterStrategy ()
                        : action (TransportMasterRelax)
                        , target (0)
                        , roll_disposition (MustStop)
                        , catch_speed (0.) {}
        };
 
        TransportMasterStrategy transport_master_strategy;
        double plan_master_strategy (pframes_t nframes, double master_speed, samplepos_t master_transport_sample, double catch_speed);
        double plan_master_strategy_engine (pframes_t nframes, double master_speed, samplepos_t master_transport_sample, double catch_speed);
        bool implement_master_strategy ();
 
        bool follow_transport_master (pframes_t nframes);
 
        void sync_source_changed (SyncSource, samplepos_t pos, pframes_t cycle_nframes);
 
        bool post_export_sync;
        samplepos_t post_export_position;
 
        bool _exporting;
        bool _export_rolling;
        bool _realtime_export;
        bool _region_export;
        samplepos_t _export_preroll;
 
        std::shared_ptr<ExportHandler> export_handler;
        std::shared_ptr<ExportStatus>  export_status;
 
        int  pre_export ();
        int  stop_audio_export ();
        void finalize_audio_export (TransportRequestSource trs);
        void finalize_export_internal (bool stop_freewheel);
        bool _pre_export_mmc_enabled;
 
        PBD::ScopedConnection export_freewheel_connection;
 
        void get_track_statistics ();
        int  process_routes (pframes_t, bool& need_butler);
        int  silent_process_routes (pframes_t, bool& need_butler);
 
        bool maybe_stop (samplepos_t limit);
        bool maybe_sync_start (pframes_t &);
 
        std::string             _path;
        std::string             _name;
        bool                    _is_new;
        bool                    _send_qf_mtc;
        pframes_t               _pframes_since_last_mtc;
        bool                     play_loop;
        bool                     loop_changing;
        samplepos_t              last_loopend;
 
        const std::unique_ptr<SessionDirectory> _session_dir;
 
        void hookup_io ();
        void graph_reordered (bool called_from_backend);
 
        void set_snapshot_name (const std::string &);
        void save_snapshot_name (const std::string &);
        std::string _current_snapshot_name;
 
        XMLTree*         state_tree;
        StateOfTheState _state_of_the_state;
 
        friend class     StateProtector;
        std::atomic<int> _suspend_save;
        volatile bool    _save_queued;
        volatile bool    _save_queued_pending;
        bool             _no_save_signal;
 
        Glib::Threads::Mutex save_state_lock;
        Glib::Threads::Mutex save_source_lock;
        Glib::Threads::Mutex peak_cleanup_lock;
 
        int        load_options (const XMLNode&);
        int        load_state (std::string snapshot_name, bool from_template = false);
        static int parse_stateful_loading_version (const std::string&);
 
        samplepos_t _last_roll_location;
        samplepos_t _last_roll_or_reversal_location;
        samplepos_t _last_record_location;
 
        bool              pending_abort;
        bool              pending_auto_loop;
 
#ifdef USE_TLSF
        PBD::TLSF _mempool;
#else
        PBD::ReallocPool _mempool;
#endif
        LuaState lua;
        mutable Glib::Threads::Mutex lua_lock;
        luabridge::LuaRef * _lua_run;
        luabridge::LuaRef * _lua_add;
        luabridge::LuaRef * _lua_del;
        luabridge::LuaRef * _lua_list;
        luabridge::LuaRef * _lua_load;
        luabridge::LuaRef * _lua_save;
        luabridge::LuaRef * _lua_cleanup;
        uint32_t            _n_lua_scripts;
 
        void setup_lua ();
        void luabindings_session_rt (lua_State*);
        void try_run_lua (pframes_t);
 
        SerializedRCUManager<IOPlugList> _io_plugins;
 
        std::vector<std::shared_ptr<MixerScene>> _mixer_scenes;
        mutable Glib::Threads::RWLock              _mixer_scenes_lock;
 
        Butler* _butler;
 
        TransportFSM* _transport_fsm;
 
        static const PostTransportWork ProcessCannotProceedMask = PostTransportWork (PostTransportAudition);
 
        std::atomic<PostTransportWork> _post_transport_work; /* accessed only atomic ops */
        PostTransportWork post_transport_work() const        { return _post_transport_work.load(); }
        void set_post_transport_work (PostTransportWork ptw) { _post_transport_work.store (ptw); }
        void add_post_transport_work (PostTransportWork ptw);
 
        void schedule_playback_buffering_adjustment ();
        void schedule_capture_buffering_adjustment ();
 
        Locations*       _locations;
        void location_added (Location*);
        void location_removed (Location*);
        void locations_changed ();
        void _locations_changed (const Locations::LocationList&);
 
        void update_skips (Location*, bool consolidate);
        void update_marks (Location* loc);
        void consolidate_skips (Location*);
        void sync_locations_to_skips ();
        void _sync_locations_to_skips ();
 
        PBD::ScopedConnectionList skip_update_connections;
        bool _ignore_skips_updates;
 
        PBD::ScopedConnectionList punch_connections;
        void             auto_punch_start_changed (Location *);
        void             auto_punch_end_changed (Location *);
        void             auto_punch_changed (Location *);
 
        PBD::ScopedConnectionList loop_connections;
        void             auto_loop_changed (Location *);
 
        void pre_engine_init (std::string path);
        int  post_engine_init ();
        int  immediately_post_engine ();
        void remove_empty_sounds ();
 
        void session_loaded ();
 
        void setup_midi_control ();
        int  midi_read (MIDI::Port *);
 
        void enable_record ();
 
        void increment_transport_position (samplecnt_t val) {
                if (max_samplepos - val < _transport_sample) {
                        _transport_sample = max_samplepos;
                } else {
                        _transport_sample += val;
                }
        }
 
        void decrement_transport_position (samplecnt_t val) {
                if (val < _transport_sample) {
                        _transport_sample -= val;
                } else {
                        _transport_sample = 0;
                }
        }
 
        void post_transport_motion ();
        static void *session_loader_thread (void *arg);
 
        void *do_work();
 
        /* Signal Forwarding */
        void emit_route_signals ();
        void emit_thread_run ();
        static void *emit_thread (void *);
        void emit_thread_start ();
        void emit_thread_terminate ();
 
        pthread_t       _rt_emit_thread;
        bool            _rt_thread_active;
 
        pthread_mutex_t _rt_emit_mutex;
        pthread_cond_t  _rt_emit_cond;
        bool            _rt_emit_pending;
 
        /* Auto Connect Thread */
        static void *auto_connect_thread (void *);
        void auto_connect_thread_run ();
        void auto_connect_thread_start ();
        void auto_connect_thread_terminate ();
 
        pthread_t        _auto_connect_thread;
        std::atomic<int> _ac_thread_active;
        pthread_mutex_t  _auto_connect_mutex;
        pthread_cond_t   _auto_connect_cond;
 
        struct AutoConnectRequest {
                public:
                AutoConnectRequest (std::shared_ptr <Route> r,
                                bool ci, bool co,
                                const ChanCount& is,
                                const ChanCount& os,
                                const ChanCount& io,
                                const ChanCount& oo)
                        : route (std::weak_ptr<Route> (r))
                        , connect_inputs (ci)
                        , connect_outputs (co)
                        , input_start (is)
                        , output_start (os)
                        , input_offset (io)
                        , output_offset (oo)
                {}
 
                std::weak_ptr <Route> route;
                bool connect_inputs;
                bool connect_outputs;
                ChanCount input_start;
                ChanCount output_start;
                ChanCount input_offset;
                ChanCount output_offset;
        };
 
        Glib::Threads::Mutex  _update_latency_lock;
 
        typedef std::queue<AutoConnectRequest> AutoConnectQueue;
        Glib::Threads::Mutex _auto_connect_queue_lock;
        AutoConnectQueue     _auto_connect_queue;
        std::atomic<unsigned int>   _latency_recompute_pending;
 
        void get_physical_ports (std::vector<std::string>& inputs, std::vector<std::string>& outputs, DataType type,
                                 MidiPortFlags include = MidiPortFlags (0),
                                 MidiPortFlags exclude = MidiPortFlags (0));
 
        void auto_connect (const AutoConnectRequest&);
        void queue_latency_recompute ();
 
        /* SessionEventManager interface */
 
        void process_event (SessionEvent*);
        void set_next_event ();
        void cleanup_event (SessionEvent*,int);
 
        /* MIDI Machine Control */
 
        void spp_start ();
        void spp_continue ();
        void spp_stop ();
 
        void mmc_deferred_play (MIDI::MachineControl &);
        void mmc_stop (MIDI::MachineControl &);
        void mmc_step (MIDI::MachineControl &, int);
        void mmc_pause (MIDI::MachineControl &);
        void mmc_record_pause (MIDI::MachineControl &);
        void mmc_record_strobe (MIDI::MachineControl &);
        void mmc_record_exit (MIDI::MachineControl &);
        void mmc_track_record_status (MIDI::MachineControl &, uint32_t track, bool enabled);
        void mmc_fast_forward (MIDI::MachineControl &);
        void mmc_rewind (MIDI::MachineControl &);
        void mmc_locate (MIDI::MachineControl &, const MIDI::byte *);
        void mmc_shuttle (MIDI::MachineControl &mmc, float speed, bool forw);
        void mmc_record_enable (MIDI::MachineControl &mmc, size_t track, bool enabled);
 
        int64_t _last_mmc_step;
        double  step_speed;
 
        typedef std::function<bool()> MidiTimeoutCallback;
        typedef std::list<MidiTimeoutCallback> MidiTimeoutList;
 
        MidiTimeoutList midi_timeouts;
        bool mmc_step_timeout ();
        void send_immediate_mmc (MIDI::MachineControlCommand);
 
        MIDI::byte mtc_msg[16];
        MIDI::byte mtc_timecode_bits;   /* encoding of SMTPE type for MTC */
        MIDI::byte midi_msg[16];
        double outbound_mtc_timecode_frame;
        Timecode::Time transmitting_timecode_time;
        int next_quarter_frame_to_send;
 
        double _samples_per_timecode_frame; /* has to be floating point because of drop sample */
        samplecnt_t _frames_per_hour;
        samplecnt_t _timecode_frames_per_hour;
 
        /* cache the most-recently requested time conversions. This helps when we
         * have multiple clocks showing the same time (e.g. the transport sample) */
        bool last_timecode_valid;
        samplepos_t last_timecode_when;
        Timecode::Time last_timecode;
 
        bool _send_timecode_update; 
 
        int send_midi_time_code_for_cycle (samplepos_t, samplepos_t, pframes_t nframes);
 
        LTCEncoder*       ltc_encoder;
        ltcsnd_sample_t*  ltc_enc_buf;
 
        Timecode::TimecodeFormat ltc_enc_tcformat;
        int32_t           ltc_buf_off;
        int32_t           ltc_buf_len;
 
        double            ltc_speed;
        int32_t           ltc_enc_byte;
        samplepos_t       ltc_enc_pos;
        double            ltc_enc_cnt;
        samplepos_t       ltc_enc_off;
        bool              restarting;
        samplepos_t       ltc_prev_cycle;
 
        samplepos_t       ltc_timecode_offset;
        bool              ltc_timecode_negative_offset;
 
        LatencyRange      ltc_out_latency;
        LatencyRange      mtc_out_latency;
 
        void ltc_tx_initialize();
        void ltc_tx_cleanup();
        void ltc_tx_reset();
        void ltc_tx_resync_latency (bool);
        void ltc_tx_recalculate_position();
        void ltc_tx_parse_offset();
        PBD::ScopedConnectionList ltc_tx_connections;
 
        void reset_record_status ();
 
        int no_roll (pframes_t nframes);
        int fail_roll (pframes_t nframes);
 
        bool non_realtime_work_pending() const { return static_cast<bool>(post_transport_work()); }
        bool process_can_proceed() const { return !(post_transport_work() & ProcessCannotProceedMask); }
 
        MidiControlUI* midi_control_ui;
 
        int           start_midi_thread ();
 
        bool should_ignore_transport_request (TransportRequestSource, TransportRequestType);
 
        void set_play_loop (bool yn, bool change_transport_state);
        void unset_play_loop (bool change_transport_state = false);
        void overwrite_some_buffers (std::shared_ptr<Route>, OverwriteReason);
        void flush_all_inserts ();
        int  micro_locate (samplecnt_t distance);
 
        enum PunchLoopLock {
                NoConstraint,
                OnlyPunch,
                OnlyLoop,
        };
 
        std::atomic<PunchLoopLock> _punch_or_loop;
        std::atomic<int> _current_usecs_per_track;
 
        bool punch_active () const;
        void unset_punch ();
        void reset_punch_loop_constraint ();
        bool maybe_allow_only_loop (bool play_loop = false);
        bool maybe_allow_only_punch ();
 
        void force_locate (samplepos_t sample, LocateTransportDisposition);
        void realtime_stop (bool abort, bool clear_state);
        void realtime_locate (bool);
        void non_realtime_set_speed ();
        void non_realtime_locate ();
        void non_realtime_stop (bool abort, int entry_request_count, bool& finished, bool will_locate);
        void non_realtime_overwrite (int entry_request_count, bool& finished, bool reset_loop_declicks);
        void engine_halted ();
        void engine_running ();
        void xrun_recovery ();
        void set_track_loop (bool);
        bool select_playhead_priority_target (samplepos_t&);
        void follow_playhead_priority ();
        void flush_cue_recording ();
 
        /* These are synchronous and so can only be called from within the process
         * cycle
         */
 
        void mtc_tx_resync_latency (bool);
        int  send_full_time_code (samplepos_t, pframes_t nframes);
        void send_song_position_pointer (samplepos_t);
 
        /* edit/mix groups */
 
        int load_route_groups (const XMLNode&, int);
 
        std::list<RouteGroup *> _route_groups;
        RouteGroup*             _all_route_group;
 
        /* routes stuff */
 
        SerializedRCUManager<RouteList>  routes;
 
        void add_routes (RouteList&, bool input_auto_connect, bool output_auto_connect, PresentationInfo::order_t);
        void add_routes_inner (RouteList&, bool input_auto_connect, bool output_auto_connect, PresentationInfo::order_t);
        bool _adding_routes_in_progress;
        bool _reconnecting_routes_in_progress;
        bool _route_deletion_in_progress;
        bool _route_reorder_in_progress;
 
        void load_and_connect_instruments (RouteList&,
                        bool strict_io,
                        std::shared_ptr<PluginInfo> instrument,
                        Plugin::PresetRecord* pset,
                        ChanCount& existing_outputs
                        );
 
        std::shared_ptr<Route> XMLRouteFactory (const XMLNode&, int);
        std::shared_ptr<Route> XMLRouteFactory_2X (const XMLNode&, int);
        std::shared_ptr<Route> XMLRouteFactory_3X (const XMLNode&, int);
 
        void route_processors_changed (RouteProcessorChange);
 
        bool find_route_name (std::string const &, uint32_t& id, std::string& name, bool);
        void count_existing_track_channels (ChanCount& in, ChanCount& out);
        void auto_connect_route (std::shared_ptr<Route>, bool, bool, const ChanCount&, const ChanCount&, const ChanCount& io = ChanCount(), const ChanCount& oo = ChanCount());
        void midi_output_change_handler (IOChange change, void* /*src*/, std::weak_ptr<Route> midi_track);
 
        /* track numbering */
 
        void reassign_track_numbers ();
        uint32_t _track_number_decimals;
 
        /* solo/mute/notifications */
 
        void route_listen_changed (PBD::Controllable::GroupControlDisposition, std::weak_ptr<Route>);
        void route_mute_changed ();
        void route_solo_changed (bool self_solo_change, PBD::Controllable::GroupControlDisposition group_override, std::weak_ptr<Route>);
        void route_solo_isolated_changed (std::weak_ptr<Route>);
 
        void update_route_solo_state (std::shared_ptr<RouteList const> r = std::shared_ptr<RouteList const>());
 
        void listen_position_changed ();
        void solo_control_mode_changed ();
 
        /* REGION MANAGEMENT */
 
        mutable Glib::Threads::Mutex region_lock;
 
        int load_regions (const XMLNode& node);
        int load_compounds (const XMLNode& node);
 
        void route_added_to_route_group (RouteGroup *, std::weak_ptr<Route>);
        void route_removed_from_route_group (RouteGroup *, std::weak_ptr<Route>);
        void route_group_property_changed (RouteGroup *);
 
        /* SOURCES */
 
        mutable Glib::Threads::Mutex source_lock;
 
public:
 
        /* Emited when a new source is added to the session */
        PBD::Signal< void(std::weak_ptr<Source> )> SourceAdded;
        PBD::Signal< void(std::weak_ptr<Source> )> SourceRemoved;
 
        typedef std::map<PBD::ID,std::shared_ptr<Source> > SourceMap;
 
        void foreach_source (std::function<void( std::shared_ptr<Source> )> f) {
                Glib::Threads::Mutex::Lock ls (source_lock);
                for (SourceMap::iterator i = sources.begin(); i != sources.end(); ++i) {
                        f ( (*i).second );
                }
        }
 
        bool playlist_is_active( std::shared_ptr<Playlist>);
        ARDOUR::CueMarkers pending_source_markers; // source markers created while recording
 
private:
        void reset_write_sources (bool mark_write_complete);
        SourceMap sources;
 
        int load_sources (const XMLNode& node);
        XMLNode& get_sources_as_xml ();
 
        std::shared_ptr<Source> XMLSourceFactory (const XMLNode&);
 
        /* PLAYLISTS */
 
        void remove_playlist (std::weak_ptr<Playlist>);
        void track_playlist_changed (std::weak_ptr<Track>);
        void playlist_region_added (std::weak_ptr<Region>);
        void playlist_ranges_moved (std::list<Temporal::RangeMove> const &);
        void playlist_regions_extended (std::list<Temporal::Range> const &);
 
        /* CURVES and AUTOMATION LISTS */
        std::map<PBD::ID, AutomationList*> automation_lists;
 
        std::map<PBD::ID, std::string> _diskstreams_2X;
 
        /* DEFAULT FADE CURVES */
 
        float default_fade_steepness;
        float default_fade_msecs;
 
        /* AUDITIONING */
 
        std::shared_ptr<Auditioner> auditioner;
        void set_audition (std::shared_ptr<Region>);
        void non_realtime_set_audition ();
        std::shared_ptr<Region> pending_audition_region;
 
        /* EXPORT */
 
        /* FLATTEN */
 
        int flatten_one_track (AudioTrack&, samplepos_t start, samplecnt_t cnt);
 
        /* INSERT AND SEND MANAGEMENT */
 
        boost::dynamic_bitset<uint32_t> send_bitset;
        boost::dynamic_bitset<uint32_t> surround_send_bitset;
        boost::dynamic_bitset<uint32_t> aux_send_bitset;
        boost::dynamic_bitset<uint32_t> return_bitset;
        boost::dynamic_bitset<uint32_t> insert_bitset;
 
        /* S/W RAID */
 
        struct space_and_path {
                uint32_t blocks;     
                bool blocks_unknown; 
                std::string path;
 
                space_and_path ()
                        : blocks (0)
                        , blocks_unknown (true)
                {}
        };
 
        struct space_and_path_ascending_cmp {
                bool operator() (space_and_path a, space_and_path b) {
                        if (a.blocks_unknown != b.blocks_unknown) {
                                return !a.blocks_unknown;
                        }
                        return a.blocks > b.blocks;
                }
        };
 
        void setup_raid_path (std::string path);
 
        std::vector<space_and_path> session_dirs;
        std::vector<space_and_path>::iterator last_rr_session_dir;
        uint64_t _total_free_4k_blocks;
        bool _total_free_4k_blocks_uncertain;
        Glib::Threads::Mutex space_lock;
 
        bool no_questions_about_missing_files;
 
        std::string get_best_session_directory_for_new_audio ();
 
        mutable std::atomic<int> _playback_load;
        mutable std::atomic<int> _capture_load;
 
        /* I/O bundles */
 
        SerializedRCUManager<BundleList> _bundles;
        XMLNode* _bundle_xml_node;
        int load_bundles (XMLNode const &);
 
        int  backend_sync_callback (TransportState, samplepos_t);
 
        void process_rtop (SessionEvent*);
 
        enum snapshot_t {
                NormalSave,
                SnapshotKeep,
                SwitchToSnapshot
        };
 
        XMLNode& state (bool save_template,
                        snapshot_t snapshot_type = NormalSave,
                        bool for_archive = false,
                        bool only_used_assets = false) const;
 
        XMLNode& get_state () const;
        int      set_state (const XMLNode& node, int version); // not idempotent
        XMLNode& get_template ();
 
        bool maybe_copy_midifile (snapshot_t, std::shared_ptr<Source> src, XMLNode*);
 
        void collect_sources_of_this_snapshot (std::set<std::shared_ptr<Source>>&, bool incl_unused = true) const;
 
        /* click track */
        typedef std::list<Click*>     Clicks;
        Clicks                        clicks;
        bool                         _clicking;
        bool                         _click_rec_only;
        std::shared_ptr<IO>          _click_io;
        std::shared_ptr<Amp>         _click_gain;
        Sample*                       click_data;
        Sample*                       click_emphasis_data;
        samplecnt_t                   click_length;
        samplecnt_t                   click_emphasis_length;
        mutable Glib::Threads::RWLock click_lock;
        samplecnt_t                  _click_io_latency;
        PBD::ScopedConnection        _click_io_connection;
        Temporal::GridIterator       _click_iterator;
 
        static const Sample     default_click[];
        static const samplecnt_t default_click_length;
        static const Sample     default_click_emphasis[];
        static const samplecnt_t default_click_emphasis_length;
 
        Click* get_click();
        samplepos_t _clicks_cleared;
        samplecnt_t _count_in_samples;
        void setup_click_sounds (int which);
        void setup_click_sounds (Sample**, Sample const *, samplecnt_t*, samplecnt_t, std::string const &);
        void clear_clicks ();
        void click (samplepos_t start, samplecnt_t nframes);
        void run_click (samplepos_t start, samplecnt_t nframes);
        void add_click (samplepos_t pos, bool emphasis);
        void click_io_resync_latency (bool);
 
        /* range playback */
 
        std::list<TimelineRange> current_audio_range;
        bool _play_range;
        void set_play_range (std::list<TimelineRange>&, bool leave_rolling);
        void unset_play_range ();
 
        /* temporary hacks to allow selection to be pushed from GUI into backend
           Whenever we move the selection object into libardour, these will go away.
        */
        Temporal::Range _range_selection;
        Temporal::Range _object_selection;
 
        void unset_preroll_record_trim ();
 
        samplecnt_t _preroll_record_trim_len;
        bool _count_in_once;
 
        /* main outs */
        uint32_t main_outs;
 
        std::shared_ptr<Route> _master_out;
        std::shared_ptr<Route> _monitor_out;
        std::shared_ptr<Route> _surround_master;
 
        friend class PortManager;
        void auto_connect_master_bus ();
        void auto_connect_monitor_bus ();
        void auto_connect_surround_master ();
        void auto_connect_io (std::shared_ptr<IO>);
 
        void setup_route_monitor_sends (bool enable, bool need_process_lock);
        void setup_route_surround_sends (bool enable, bool need_process_lock);
 
        int find_all_sources (std::string path, std::set<std::string>& result);
        int find_all_sources_across_snapshots (std::set<std::string>& result, bool exclude_this_snapshot);
 
        typedef std::set<std::shared_ptr<PBD::Controllable> > Controllables;
        Glib::Threads::Mutex controllables_lock;
        Controllables controllables;
 
        std::shared_ptr<PBD::Controllable> _solo_cut_control;
 
        void controllable_touched (std::weak_ptr<PBD::Controllable>);
        std::weak_ptr<PBD::Controllable> _recently_touched_controllable;
 
        void reset_native_file_format();
        bool first_file_data_format_reset;
        bool first_file_header_format_reset;
 
        void config_changed (std::string, bool);
 
        XMLNode& get_control_protocol_state () const;
 
        void set_history_depth (uint32_t depth);
 
        static bool _disable_all_loaded_plugins;
        static bool _bypass_all_loaded_plugins;
 
        mutable bool have_looped; 
 
        void update_route_record_state ();
        std::atomic<int> _have_rec_enabled_track;
        std::atomic<int> _have_rec_disabled_track;
 
        static int ask_about_playlist_deletion (std::shared_ptr<Playlist>);
 
        /* realtime "apply to set of routes" operations */
        template<typename T> SessionEvent*
                get_rt_event (std::shared_ptr<RouteList const> rl, T targ, SessionEvent::RTeventCallback after, PBD::Controllable::GroupControlDisposition group_override,
                              void (Session::*method) (std::shared_ptr<RouteList const>, T, PBD::Controllable::GroupControlDisposition)) {
                SessionEvent* ev = new SessionEvent (SessionEvent::RealTimeOperation, SessionEvent::Add, SessionEvent::Immediate, 0, 0.0);
                ev->rt_slot = std::bind (method, this, rl, targ, group_override);
                ev->rt_return = after;
                ev->event_loop = PBD::EventLoop::get_event_loop_for_thread ();
 
                return ev;
        }
 
        /* specialized version realtime "apply to set of routes" operations */
        template<typename T1, typename T2> SessionEvent*
                get_rt_event (std::shared_ptr<RouteList const> rl, T1 t1arg, T2 t2arg, SessionEvent::RTeventCallback after, PBD::Controllable::GroupControlDisposition group_override,
                              void (Session::*method) (std::shared_ptr<RouteList const>, T1, T2, PBD::Controllable::GroupControlDisposition)) {
                SessionEvent* ev = new SessionEvent (SessionEvent::RealTimeOperation, SessionEvent::Add, SessionEvent::Immediate, 0, 0.0);
                ev->rt_slot = std::bind (method, this, rl, t1arg, t2arg, group_override);
                ev->rt_return = after;
                ev->event_loop = PBD::EventLoop::get_event_loop_for_thread ();
 
                return ev;
        }
 
        /* specialized version realtime "apply to set of controls" operations */
        SessionEvent* get_rt_event (std::shared_ptr<WeakAutomationControlList> cl, double arg, PBD::Controllable::GroupControlDisposition group_override) {
                SessionEvent* ev = new SessionEvent (SessionEvent::RealTimeOperation, SessionEvent::Add, SessionEvent::Immediate, 0, 0.0);
                ev->rt_slot = std::bind (&Session::rt_set_controls, this, cl, arg, group_override);
                ev->rt_return = Session::rt_cleanup;
                ev->event_loop = PBD::EventLoop::get_event_loop_for_thread ();
 
                return ev;
        }
 
        void rt_set_controls (std::shared_ptr<WeakAutomationControlList>, double val, PBD::Controllable::GroupControlDisposition group_override);
        void rt_clear_all_solo_state (std::shared_ptr<RouteList const>, bool yn, PBD::Controllable::GroupControlDisposition group_override);
 
        void setup_midi_machine_control ();
 
        void step_edit_status_change (bool);
        uint32_t _step_editors;
 
        mutable std::atomic<int> _suspend_timecode_transmission;
 
        void start_time_changed (samplepos_t);
        void end_time_changed (samplepos_t);
 
        void set_track_monitor_input_status (bool);
        samplepos_t compute_stop_limit () const;
 
        std::shared_ptr<Speakers> _speakers;
        void load_nested_sources (const XMLNode& node);
 
        GraphEdges _current_route_graph;
 
        friend class IOPlug;
        std::shared_ptr<Graph>      _process_graph;
        std::shared_ptr<GraphChain> _graph_chain;
        std::shared_ptr<GraphChain> _io_graph_chain[2];
 
        void resort_routes_using (std::shared_ptr<RouteList>);
        void resort_io_plugs ();
 
        bool rechain_process_graph (GraphNodeList&);
        bool rechain_ioplug_graph (bool);
 
        void ensure_route_presentation_info_gap (PresentationInfo::order_t, uint32_t gap_size);
 
        friend class ProcessorChangeBlocker;
        std::atomic<int> _ignore_route_processor_changes;
        std::atomic<int> _ignored_a_processor_change;
 
        MidiClockTicker* midi_clock;
 
        std::shared_ptr<Port>  _ltc_output_port;
 
        std::shared_ptr<RTTaskList> _rt_tasklist;
        std::shared_ptr<IOTaskList> _io_tasklist;
 
        /* Scene Changing */
        SceneChanger* _scene_changer;
 
        /* persistent, non-track related MIDI ports */
        MidiPortManager* _midi_ports;
        MIDI::MachineControl* _mmc;
 
        void setup_ltc ();
        void setup_click ();
        void setup_click_state (const XMLNode*);
        void setup_bundles ();
 
        void port_registry_changed ();
        void probe_ctrl_surfaces ();
 
        void save_as_bring_callback (uint32_t, uint32_t, std::string);
 
        static const uint32_t session_end_shift;
 
        std::string _template_state_dir;
 
        VCAManager* _vca_manager;
 
        std::shared_ptr<Route> get_midi_nth_route_by_id (PresentationInfo::order_t n) const;
 
        std::string created_with;
        mutable std::string modified_with;
 
        void midi_track_presentation_info_changed (PBD::PropertyChange const &, std::weak_ptr<MidiTrack>);
        void rewire_selected_midi (std::shared_ptr<MidiTrack>);
        void rewire_midi_selection_ports ();
        void disconnect_port_for_rewire (std::string const& port) const;
        std::weak_ptr<MidiTrack> current_midi_target;
 
        StripableList _soloSelection;  //the items that are soloe'd during a solo-selection operation; need to unsolo after the roll
 
        CoreSelection* _selection;
 
        bool _global_locate_pending;
        std::optional<samplepos_t> _nominal_jack_transport_sample;
 
        bool _had_destructive_tracks;
 
        std::string unnamed_file_name () const;
 
        std::atomic<int> _update_pretty_names;
 
        void setup_thread_local_variables ();
        void cue_marker_change (Location*);
 
        struct CueEventTimeComparator {
                bool operator() (CueEvent const & c, samplepos_t s) {
                        return c.time < s;
                }
        };
 
        CueEvents _cue_events;
        void sync_cues ();
        void sync_cues_from_list (Locations::LocationList const &);
 
        std::atomic<int32_t> _pending_cue;
        std::atomic<int32_t> _active_cue;
        void maybe_find_pending_cue ();
        void clear_active_cue ();
 
        int tb_with_filled_slots;
        void handle_slots_empty_status (std::weak_ptr<Route> const &);
 
        void time_domain_changed ();
 
        AnyTime _global_quantization;
};
 
 
} // namespace ARDOUR