Refactor arpdirdown, arpdirdownup

Fix issue with wrong pattern when going down and cycle is over 0.

src/core/InstrumentFunctions.cpp

@@ -433,16 +433,11 @@ void InstrumentFunctionArpeggio::processNote( NotePlayHandle * _n )
 
 		int cur_arp_idx = 0;
 		// process according to arpeggio-direction...
-		if( dir == ArpDirection::Up )
+		if (dir == ArpDirection::Up || dir == ArpDirection::Down)
 		{
 			cur_arp_idx = ( cur_frame / arp_frames ) % range;
 		}
-		else if( dir == ArpDirection::Down )
-		{
-			cur_arp_idx = range - ( cur_frame / arp_frames ) %
-								range - 1;
-		}
-		else if( dir == ArpDirection::UpAndDown && range > 1 )
+		else if ((dir == ArpDirection::UpAndDown || dir == ArpDirection::DownAndUp) && range > 1)
 		{
 			// imagine, we had to play the arp once up and then
 			// once down -> makes 2 * range possible notes...
@@ -456,19 +451,6 @@ void InstrumentFunctionArpeggio::processNote( NotePlayHandle * _n )
 				cur_arp_idx = range - cur_arp_idx % ( range - 1 ) - 1;
 			}
 		}
-		else if( dir == ArpDirection::DownAndUp && range > 1 )
-		{
-			// copied from ArpDirection::UpAndDown above
-			cur_arp_idx = ( cur_frame / arp_frames ) % ( range * 2 - 2 );
-			// if greater than range, we have to play down...
-			// looks like the code for arp_dir==DOWN... :)
-			if( cur_arp_idx >= range )
-			{
-				cur_arp_idx = range - cur_arp_idx % ( range - 1 ) - 1;
-			}
-			// inverts direction
-			cur_arp_idx = range - cur_arp_idx - 1;
-		}
 		else if( dir == ArpDirection::Random )
 		{
 			// just pick a random chord-index
@@ -485,6 +467,12 @@ void InstrumentFunctionArpeggio::processNote( NotePlayHandle * _n )
 			cur_arp_idx %= static_cast<int>( range / m_arpRepeatsModel.value() );
 		}
 
+		// If ArpDirection::Down or ArpDirection::DownAndUp, invert the final range.
+		if (dir == ArpDirection::Down || dir == ArpDirection::DownAndUp)
+		{
+			cur_arp_idx = static_cast<int>(range) - cur_arp_idx - 1;
+		}
+
 		// now calculate final key for our arp-note
 		const int sub_note_key = base_note_key + (cur_arp_idx / cur_chord_size ) *
 							KeysPerOctave + chord_table.chords()[selected_arp][cur_arp_idx % cur_chord_size];