Port FluidSim core and scenarios to C++20

include/FluidSim/SoundEngine.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include "FluidSim/AudioOutputStream.hpp"
+
+namespace fluidsim::port {
+
+// Lifecycle wrapper matching the C# Audio.SoundEngine. The output stream owns
+// the device callback, while this class gives the application one explicit
+// start/stop and playback-control surface.
+class SoundEngine {
+public:
+    explicit SoundEngine(SimulationRingBuffer& source_buffer);
+    ~SoundEngine();
+
+    SoundEngine(const SoundEngine&) = delete;
+    SoundEngine& operator=(const SoundEngine&) = delete;
+
+    void start();
+    void stop();
+    void set_speed(double speed);
+    double speed() const;
+    void set_volume(float volume);
+    float volume() const;
+    bool is_playing() const { return is_playing_; }
+
+private:
+    AudioOutputStream stream_;
+    bool is_playing_{};
+};
+
+} // namespace fluidsim::port