Prepare files for public release

include/util/Event.h

@@ -0,0 +1,50 @@
+
+#ifndef CONTROL_EVENT_H
+#define CONTROL_EVENT_H
+
+#include <functional>
+
+class Event;
+
+class CallbackHandle {
+  public:
+    CallbackHandle(Event *evt, int id) : evt(evt), id(id) {
+    }
+    ~CallbackHandle();
+
+  private:
+    Event *evt;
+    int id;
+};
+
+class Event {
+  public:
+    using Callback = std::function<void()>;
+
+    CallbackHandle addListener(Callback cb) {
+        int id = nextId++;
+        callbacks[id] = std::move(cb);
+        return CallbackHandle(this, id);
+    }
+
+    void remove(int id) {
+        callbacks.erase(id);
+    }
+
+    void fire() {
+        for (auto &kv : callbacks)
+            kv.second();
+    }
+
+  private:
+    friend class CallbackHandle;
+    std::unordered_map<int, Callback> callbacks;
+    int nextId = 0;
+};
+
+CallbackHandle::~CallbackHandle() {
+    if (evt)
+        evt->remove(id);
+}
+
+#endif // CONTROL_EVENT_H