Prepare API for per disk-reader de-click

libs/ardour/ardour/disk_reader.h

@@ -93,6 +93,10 @@ public:
 	void playlist_modified ();
 	void reset_tracker ();
 
+	bool declick_in_progress () const {
+		return _declick_gain != 0; // declick-out
+	}
+
 	static void set_midi_readahead_samples (samplecnt_t samples_ahead) { midi_readahead = samples_ahead; }
 
 	static void set_no_disk_output (bool yn);
@@ -132,6 +136,8 @@ private:
 	IOChange      input_change_pending;
 	samplepos_t   file_sample[DataType::num_types];
 
+	gain_t        _declick_gain;
+
 	int _do_refill_with_alloc (bool partial_fill);
 
 	static samplecnt_t _chunk_samples;

libs/ardour/ardour/track.h

@@ -64,7 +64,8 @@ public:
 
 	bool set_processor_state (XMLNode const & node, XMLProperty const* prop, ProcessorList& new_order, bool& must_configure);
 
-	bool needs_butler() const { return _needs_butler; }
+	bool needs_butler () const { return _needs_butler; }
+	bool declick_in_progress () const;
 
 	bool can_record();
 

libs/ardour/disk_reader.cc

@@ -56,6 +56,7 @@ DiskReader::DiskReader (Session& s, string const & str, DiskIOProcessor::Flag f)
 	, overwrite_offset (0)
 	, _pending_overwrite (false)
 	, overwrite_queued (false)
+	, _declick_gain (0)
 {
 	file_sample[DataType::AUDIO] = 0;
 	file_sample[DataType::MIDI] = 0;

libs/ardour/track.cc

@@ -250,6 +250,12 @@ Track::freeze_state() const
 	return _freeze_record.state;
 }
 
+bool
+Track::declick_in_progress () const
+{
+	return _disk_reader->declick_in_progress ();
+}
+
 bool
 Track::can_record()
 {