Initial commit

Event.h

@@ -0,0 +1,55 @@
+
+//
+// An event/listener system.
+//
+
+#ifndef EVENT_H
+#define EVENT_H
+
+#include <functional>
+#include <unordered_map>
+
+class Event;
+
+class CallbackHandle {
+  public:
+    CallbackHandle(Event *evt, int id) : m_evt(evt), m_id(id) {
+    }
+    ~CallbackHandle();
+
+  private:
+    Event *m_evt;
+    int m_id;
+};
+
+class Event {
+  public:
+    using Callback = std::function<void()>;
+
+    CallbackHandle addListener(Callback cb) {
+        int id = m_nextId++;
+        m_callbacks[id] = std::move(cb);
+        return CallbackHandle(this, id);
+    }
+
+    void remove(int id) {
+        m_callbacks.erase(id);
+    }
+
+    void fire() {
+        for (auto &kv : m_callbacks)
+            kv.second();
+    }
+
+  private:
+    friend class CallbackHandle;
+    std::unordered_map<int, Callback> m_callbacks;
+    int m_nextId = 0;
+};
+
+CallbackHandle::~CallbackHandle() {
+    if (m_evt)
+        m_evt->remove(m_id);
+}
+
+#endif // EVENT_H