Move and conslolidate voice count to a Storage atomic

Make the vcoice=0->1 swap for display only in formula modulator
Add a comment to why we did this micro-cheat

Closes #7742

src/common/SurgeStorage.h

@@ -1364,9 +1364,11 @@ class alignas(16) SurgeStorage
     bool oscReceiving{false};
     bool oscSending{false};
 
-    int voiceCount; // TODO: use SurgeSynthesizer class to fetch synth->polydisplay directly from
-                    // valueAt() in FormulaModulationHelper.cpp where it's needed and remove
-                    // this and its assignment in SurgeSynthesizer.cpp
+    /*
+     * A bit of a cheat - this isn't really the storage, but is updated by the synth at render time.
+     * We put it here so LFOS can get it, which formula needs
+     */
+    std::atomic<int> activeVoiceCount{0};
 
     bool getOverrideDataHome(std::string &value);
     void createUserDirectory();

src/common/SurgeSynthesizer.cpp

@@ -222,7 +222,7 @@ SurgeSynthesizer::SurgeSynthesizer(PluginLayer *parent, const std::string &suppl
         send[i][1].set_blocksize(BLOCK_SIZE);
     }
 
-    polydisplay = 0;
+    storage.activeVoiceCount = 0;
     refresh_editor = false;
     patch_loaded = false;
     storage.getPatch().category = "Init";
@@ -4822,8 +4822,7 @@ void SurgeSynthesizer::process()
     }
 
     storage.modRoutingMutex.unlock();
-    polydisplay = vcount;
-    storage.voiceCount = vcount;
+    storage.activeVoiceCount = vcount;
 
     // TODO: FIX SCENE ASSUMPTION
     if (play_scene[0])

src/common/SurgeSynthesizer.h

@@ -487,7 +487,6 @@ class alignas(16) SurgeSynthesizer
     std::atomic<int> patchid_queue;
 
     // updated in audio thread, read from UI, so have assignments be atomic
-    std::atomic<int> polydisplay;
     std::atomic<int> hasUpdatedMidiCC;
     std::atomic<int> modwheelCC, pitchbendMIDIVal, sustainpedalCC;
     std::atomic<bool> midiSoftTakeover;

src/common/dsp/modulators/FormulaModulationHelper.cpp

@@ -505,8 +505,8 @@ void valueAt(int phaseIntPart, float phaseFracPart, SurgeStorage *storage,
     addi("cycle", phaseIntPart); // Alias cycle for intphase
 
     // Fake a voice count of one for display calls
-    int voiceCount = storage->voiceCount;
-    if (voiceCount == 0)
+    int voiceCount = storage->activeVoiceCount;
+    if (voiceCount == 0 && s->is_display)
         voiceCount = 1;
     addi("voice_count", voiceCount);
 

src/surge-xt/gui/SurgeGUIEditor.cpp

@@ -800,9 +800,9 @@ void SurgeGUIEditor::idle()
         {
             int prior = polydisp->getPlayingVoiceCount();
 
-            if (prior != synth->polydisplay)
+            if (prior != synth->storage.activeVoiceCount)
             {
-                polydisp->setPlayingVoiceCount(synth->polydisplay);
+                polydisp->setPlayingVoiceCount(synth->storage.activeVoiceCount);
                 polydisp->repaint();
             }
         }