Optimization: grid processing array

synth_engine.h

@@ -2,6 +2,8 @@
 #define SYNTH_ENGINE_H
 
 #include <stdint.h>
+#include <vector>
+#include <utility>
 
 #if defined(ARDUINO_ARCH_RP2040)
 #include <pico/mutex.h>
@@ -103,6 +105,7 @@ public:
         float param = 0.5f; // 0.0 to 1.0
         int rotation = 0;   // 0:N, 1:E, 2:S, 3:W (Output direction)
         float value = 0.0f; // Current output sample
+        float next_value = 0.0f; // For double-buffering in processGridStep
         float phase = 0.0f; // For Oscillator, Noise state
     };
 
@@ -113,6 +116,7 @@ public:
     void exportGrid(uint8_t* buffer);
     void importGrid(const uint8_t* buffer);
     void loadPreset(int preset);
+    void rebuildProcessingOrder();
     void clearGrid();
 
     GridCell grid[GRID_W][GRID_H];
@@ -129,6 +133,8 @@ private:
     Waveform _waveform;
     bool _isGateOpen;
     uint32_t _rngState;
+    std::vector<std::pair<int, int>> _processing_order;
+    void rebuildProcessingOrder_locked();
 
     // Internal random number generator
     float _random();