More generic structure for responding to MIDI controller messages

This is preparation for continuing work on issue jamulussoftware#95.  While it does
not yet introduce functional differences, MIDI controller information
is organised in a manner where reacting to more than just fader
control messages becomes easy.

The preparation right now is for controllers of type fader, pan, solo,
mute but can be easily extended for other messages arriving on a
single channel.

src/soundbase.cpp

@@ -36,7 +36,7 @@ CSoundBase::CSoundBase ( const QString& strNewSystemDriverTechniqueName,
     bCallbackEntered             ( false ),
     strSystemDriverTechniqueName ( strNewSystemDriverTechniqueName ),
     iCtrlMIDIChannel             ( INVALID_MIDI_CH ),
-    iMIDIOffsetFader             ( 70 ) // Behringer X-TOUCH: offset of 0x46
+    aMidiCtls                    ( 128 )
 {
     // parse the MIDI setup command line argument string
     ParseCommandLineArgument ( strMIDISetup );
@@ -234,7 +234,12 @@ QVector<QString> CSoundBase::LoadAndInitializeFirstValidDriver ( const bool bOpe
 \******************************************************************************/
 void CSoundBase::ParseCommandLineArgument ( const QString& strMIDISetup )
 {
-    // parse the server info string according to definition:
+    int iMIDIOffsetFader = 70; // Behringer X-TOUCH: offset of 0x46
+
+    // parse the server info string according to definition: there is
+    // the legacy definition with just one or two numbers that only
+    // provides a definition for the controller offset of the level
+    // controllers (default 70 for the sake of Behringer X-Touch)
     // [MIDI channel];[offset for level]
     if ( !strMIDISetup.isEmpty() )
     {
@@ -252,6 +257,13 @@ void CSoundBase::ParseCommandLineArgument ( const QString& strMIDISetup )
         {
             iMIDIOffsetFader = slMIDIParams[1].toUInt();
         }
+
+        for ( int i = 0; i < MAX_NUM_CHANNELS; i++ )
+        {
+            if ( i + iMIDIOffsetFader > 127 )
+                break;
+            aMidiCtls[i + iMIDIOffsetFader] = { EMidiCtlType::Fader, i };
+        }
     }
 }
 
@@ -287,15 +299,26 @@ printf ( "\n" );
                     // make sure packet is long enough
                     if ( vMIDIPaketBytes.Size() > 2 )
                     {
-                        // we are assuming that the controller number is the same
-                        // as the audio fader index and the range is 0-127
-                        const int iFaderLevel = static_cast<int> ( static_cast<double> (
-                            qMin ( vMIDIPaketBytes[2], uint8_t ( 127 ) ) ) / 127 * AUD_MIX_FADER_MAX );
-
-                        // consider offset for the faders
-                        const int iChID = vMIDIPaketBytes[1] - iMIDIOffsetFader;
-
-                        emit ControllerInFaderLevel ( iChID, iFaderLevel );
+                        const auto &cCtrl = aMidiCtls[qMin ( vMIDIPaketBytes[1], uint8_t ( 127 ) )];
+                        const int iValue = qMin ( vMIDIPaketBytes[2], uint8_t ( 127 ) );
+                        switch ( cCtrl.eType )
+                        {
+                        case Fader:
+                            {
+                                // we are assuming that the controller number is the same
+                                // as the audio fader index and the range is 0-127
+                                const int iFaderLevel = static_cast<int> (
+                                    static_cast<double> ( iValue ) / 127 * AUD_MIX_FADER_MAX );
+
+                                // consider offset for the faders
+
+                                emit ControllerInFaderLevel ( cCtrl.iChannel, iFaderLevel );
+                            }
+                            break;
+
+                        default:
+                            break;
+                        }
                     }
                 }
             }

src/soundbase.h

@@ -43,6 +43,23 @@ enum ESndCrdResetType
     RS_RELOAD_RESTART_AND_INIT
 };
 
+enum EMidiCtlType
+{
+    Fader = 0,
+    Pan,
+    Solo,
+    Mute,
+    None
+};
+
+class CMidiCtlEntry {
+public:
+    CMidiCtlEntry ( EMidiCtlType eT = EMidiCtlType::None, int iC = 0 )
+        : eType ( eT ), iChannel ( iC )
+        { }
+    EMidiCtlType eType;
+    int iChannel;
+};
 
 /* Classes ********************************************************************/
 class CSoundBase : public QThread
@@ -138,7 +155,7 @@ class CSoundBase : public QThread
 
     QString strSystemDriverTechniqueName;
     int     iCtrlMIDIChannel;
-    int     iMIDIOffsetFader;
+    QVector<CMidiCtlEntry> aMidiCtls;
 
     long    lNumDevs;
     QString strCurDevName;