Modulation Index Support (#4870)

Addresses #4868

1. Add a source index to modrouting and stream it
2. Use that modrouting to lookup values in processing (but not in all the 'is' or 'get' apis)
3. Const up a bunch of stuff along the way (workign on #3808)
4. Plumbing through vector value to formula mod
5. Modify the UI so that by menus you can map formula modulators but not
   by click-to-arm yet.

src/common/ModulationSource.h

@@ -262,6 +262,7 @@ struct ModulationRouting
     int destination_id;
     float depth;
     bool muted = false;
+    int source_index{0};
 };
 
 class ModulationSource
@@ -275,13 +276,15 @@ class ModulationSource
     virtual void attack(){};
     virtual void release(){};
     virtual void reset(){};
+    // override these if you support indices
+    virtual int get_active_outputs() { return 1; }
     virtual float get_output(int which) { return output; }
     virtual float get_output01(int which) { return output; }
     virtual void set_output(int which, float f) { output = f; }
+
     virtual bool per_voice() { return false; }
     virtual bool is_bipolar() { return false; }
     virtual void set_bipolar(bool b) {}
-    virtual int get_num_outputs() { return 1; }
 
   protected:
     float output;

src/common/SurgePatch.cpp

@@ -1358,6 +1358,12 @@ void SurgePatch::load_xml(const void *data, int datasize, bool is_preset)
                     else
                         t.muted = false;
 
+                    int source_index = 0;
+                    if (mr->QueryIntAttribute("source_index", &source_index) == TIXML_SUCCESS)
+                        t.source_index = source_index;
+                    else
+                        t.source_index = 0;
+
                     if (sceneId != 0)
                         t.destination_id = paramIdInScene;
                     else
@@ -2219,6 +2225,7 @@ unsigned int SurgePatch::save_xml(void **data) // allocates mem, must be freed b
                             mr.SetAttribute("source", r->at(b).source_id);
                             mr.SetAttribute("depth", float_to_str(r->at(b).depth, tempstr));
                             mr.SetAttribute("muted", r->at(b).muted);
+                            mr.SetAttribute("source_index", r->at(b).source_index);
                             p.InsertEndChild(mr);
                         }
                     }

src/common/SurgeStorage.cpp

@@ -727,7 +727,7 @@ void SurgeStorage::initializePatchDb()
     }
 }
 
-SurgePatch &SurgeStorage::getPatch() { return *_patch.get(); }
+SurgePatch &SurgeStorage::getPatch() const { return *_patch.get(); }
 
 struct PEComparer
 {
@@ -1384,6 +1384,7 @@ void SurgeStorage::clipboard_copy(int type, int scene, int entry)
             {
                 ModulationRouting m;
                 m.source_id = getPatch().scene[scene].modulation_voice[i].source_id;
+                m.source_index = getPatch().scene[scene].modulation_voice[i].source_index;
                 m.depth = getPatch().scene[scene].modulation_voice[i].depth;
                 m.destination_id =
                     getPatch().scene[scene].modulation_voice[i].destination_id + idoffset;
@@ -1395,6 +1396,7 @@ void SurgeStorage::clipboard_copy(int type, int scene, int entry)
             {
                 ModulationRouting m;
                 m.source_id = getPatch().scene[scene].modulation_scene[i].source_id;
+                m.source_index = getPatch().scene[scene].modulation_scene[i].source_index;
                 m.depth = getPatch().scene[scene].modulation_scene[i].depth;
                 m.destination_id =
                     getPatch().scene[scene].modulation_scene[i].destination_id + idoffset;
@@ -1502,6 +1504,7 @@ void SurgeStorage::clipboard_paste(int type, int scene, int entry)
             {
                 ModulationRouting m;
                 m.source_id = clipboard_modulation_voice[i].source_id;
+                m.source_index = clipboard_modulation_voice[i].source_index;
                 m.depth = clipboard_modulation_voice[i].depth;
                 m.destination_id =
                     clipboard_modulation_voice[i].destination_id + id - n_global_params;
@@ -1512,6 +1515,7 @@ void SurgeStorage::clipboard_paste(int type, int scene, int entry)
             {
                 ModulationRouting m;
                 m.source_id = clipboard_modulation_scene[i].source_id;
+                m.source_index = clipboard_modulation_scene[i].source_index;
                 m.depth = clipboard_modulation_scene[i].depth;
                 m.destination_id =
                     clipboard_modulation_scene[i].destination_id + id - n_global_params;
@@ -1540,6 +1544,7 @@ void SurgeStorage::clipboard_paste(int type, int scene, int entry)
             {
                 ModulationRouting m;
                 m.source_id = clipboard_modulation_voice[i].source_id;
+                m.source_index = clipboard_modulation_voice[i].source_index;
                 m.depth = clipboard_modulation_voice[i].depth;
                 m.destination_id = clipboard_modulation_voice[i].destination_id;
                 getPatch().scene[scene].modulation_voice.push_back(m);
@@ -1549,6 +1554,7 @@ void SurgeStorage::clipboard_paste(int type, int scene, int entry)
             {
                 ModulationRouting m;
                 m.source_id = clipboard_modulation_scene[i].source_id;
+                m.source_index = clipboard_modulation_scene[i].source_index;
                 m.depth = clipboard_modulation_scene[i].depth;
                 m.destination_id = clipboard_modulation_scene[i].destination_id;
                 getPatch().scene[scene].modulation_scene.push_back(m);

src/common/SurgeStorage.h

@@ -949,7 +949,8 @@ class alignas(16) SurgeStorage
 
     std::unique_ptr<SurgePatch> _patch;
 
-    SurgePatch &getPatch();
+    // SurgePatch &getPatch();
+    SurgePatch &getPatch() const;
 
     float pitch_bend;