Ensure that NotePlayHandles get processed before the InstrumentPlayHandle on instruments that use both NotePlayHandles and InstrumentPlayHandle, such as LB302 and SF2-Player

Issue: Currently, we use threads to process all PlayHandles, so there's no guarantee of the order they are processed in. This causes timing inaccuracy and jitter: notes of instruments that use both NPH's and IPH's can get randomly delayed by one entire period.
The issue is solved thusly:
- When processing an IPH, we check if the instrument is midi-based. If yes, we just process it normally (no NPH's to worry about).
- If it's not, then it also uses NPH's, so we'll have the IPH wait until all NPH's belonging to same instrument have been processed. There's some similar code in the new FX mixer, I pretty much just copied how we do it there.

include/Instrument.h

@@ -119,13 +119,13 @@ public:
 
 	virtual bool isFromTrack( const track * _track ) const;
 
-
-protected:
 	inline InstrumentTrack * instrumentTrack() const
 	{
 		return m_instrumentTrack;
 	}
 
+
+protected:
 	// instruments may use this to apply a soft fade out at the end of
 	// notes - method does this only if really less or equal
 	// desiredReleaseFrames() frames are left

include/InstrumentPlayHandle.h

@@ -22,11 +22,12 @@
  *
  */
 
-#ifndef _INSTRUMENT_PLAY_HANDLE_H
-#define _INSTRUMENT_PLAY_HANDLE_H
+#ifndef INSTRUMENT_PLAY_HANDLE_H
+#define INSTRUMENT_PLAY_HANDLE_H
 
 #include "PlayHandle.h"
 #include "Instrument.h"
+#include "NotePlayHandle.h"
 
 
 class InstrumentPlayHandle : public PlayHandle
@@ -45,6 +46,25 @@ public:
 
 	virtual void play( sampleFrame * _working_buffer )
 	{
+		// if the instrument is midi-based, we can safely render right away
+		if( m_instrument->flags() & Instrument::IsMidiBased )
+		{
+			m_instrument->play( _working_buffer );
+			return;
+		}
+		
+		// if not, we need to ensure that all our nph's have been processed first
+		ConstNotePlayHandleList nphv = NotePlayHandle::nphsOfInstrumentTrack( m_instrument->instrumentTrack(), true );
+		
+		foreach( const NotePlayHandle * cnph, nphv )
+		{
+			NotePlayHandle * nph = const_cast<NotePlayHandle *>( cnph );
+			while( nph->state() != ThreadableJob::Done )
+			{
+				nph->process();
+			}
+		}
+		
 		m_instrument->play( _working_buffer );
 	}
 

plugins/sf2_player/sf2_player.h

@@ -79,7 +79,7 @@ public:
 
 	virtual Flags flags() const
 	{
-		return IsSingleStreamed | IsMidiBased;
+		return IsSingleStreamed;
 	}
 
 	virtual PluginView * instantiateView( QWidget * _parent );