Add 'midiCC' hint to Parameter, use in as DSSI code already

This provides the initial work for #12.
We need to export this info for LV2s as well.

distrho/DistrhoPlugin.hpp

@@ -289,6 +289,14 @@ struct Parameter {
     */
     ParameterRanges ranges;
 
+   /**
+      MIDI CC to use by default on this parameter.@n
+      A value of 0 or 32 (bank change) is considered invalid.@n
+      Must also be less or equal to 120.
+      @note This value is only a hint! Hosts might map it automatically or completely ignore it.
+    */
+    uint8_t midiCC;
+
    /**
       Default constructor for a null parameter.
     */
@@ -297,7 +305,8 @@ struct Parameter {
           name(),
           symbol(),
           unit(),
-          ranges() {}
+          ranges(),
+          midiCC(0) {}
 
    /**
       Constructor using custom values.
@@ -307,7 +316,8 @@ struct Parameter {
           name(n),
           symbol(s),
           unit(u),
-          ranges(def, min, max) {}
+          ranges(def, min, max),
+          midiCC(0) {}
 };
 
 /**

distrho/src/DistrhoPluginInternal.hpp

@@ -323,6 +323,13 @@ public:
         return fData->parameters[index].ranges;
     }
 
+    uint8_t getParameterMidiCC(const uint32_t index) const noexcept
+    {
+        DISTRHO_SAFE_ASSERT_RETURN(fData != nullptr && index < fData->parameterCount, 0);
+
+        return fData->parameters[index].midiCC;
+    }
+
     float getParameterValue(const uint32_t index) const
     {
         DISTRHO_SAFE_ASSERT_RETURN(fPlugin != nullptr, 0.0f);

distrho/src/DistrhoPluginLADSPA+DSSI.cpp

@@ -328,6 +328,16 @@ public:
         }
     }
 # endif
+
+    int dssi_get_midi_controller_for_port(const ulong port) noexcept
+    {
+        const uint8_t midiCC = fPlugin.getParameterMidiCC(port);
+
+        if (midiCC == 0 || midiCC == 32 || midiCC >= 0x78)
+            return DSSI_NONE;
+
+        return DSSI_CC(midiCC);
+    }
 #endif
 
     // -------------------------------------------------------------------
@@ -434,6 +444,11 @@ static void dssi_select_program(LADSPA_Handle instance, ulong bank, ulong progra
 }
 # endif
 
+static int dssi_get_midi_controller_for_port(LADSPA_Handle instance, ulong port)
+{
+    return instancePtr->dssi_get_midi_controller_for_port(port);
+}
+
 # if DISTRHO_PLUGIN_WANT_MIDI_INPUT
 static void dssi_run_synth(LADSPA_Handle instance, ulong sampleCount, snd_seq_event_t* events, ulong eventCount)
 {
@@ -488,7 +503,7 @@ static DSSI_Descriptor sDssiDescriptor = {
     /* get_program                  */ nullptr,
     /* select_program               */ nullptr,
 # endif
-    /* get_midi_controller_for_port */ nullptr,
+    dssi_get_midi_controller_for_port,
 # if DISTRHO_PLUGIN_WANT_MIDI_INPUT
     dssi_run_synth,
 # else