Implement Generic Event Handling System for C++ (#13)

* Initial plan

* Implement generic event handling system for C++

Co-authored-by: lijy91 <[email protected]>

* Complete generic event system with integration examples and demo

Co-authored-by: lijy91 <[email protected]>

* Remove legacy event system and update to new event dispatcher

- Delete event_system and related demo/test files - Remove common_events
and integration examples - Update CMakeLists.txt to require C++17 -
Update nativeapi.h to use event_dispatcher/event headers - Implement
GetGlobalEventDispatcher in event_dispatcher.cpp/h

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: lijy91 <[email protected]>
Co-authored-by: LiJianying <[email protected]>

Author: Copilot

.gitignore

@@ -2,4 +2,11 @@
 .vs/
 .vscode/
 build/
-cmake-build-debug/
+cmake-build-debug/
+
+# Generated test binaries and object files
+*.o
+*_test
+callback_test
+simple_test
+event_test

examples/display_example/CMakeLists.txt

@@ -3,7 +3,7 @@ cmake_minimum_required(VERSION 3.10)
 project(display_example VERSION 0.0.1 LANGUAGES CXX)
 
 # Set C++ standard
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 # Add example program

examples/window_example/CMakeLists.txt

@@ -3,7 +3,7 @@ cmake_minimum_required(VERSION 3.10)
 project(window_example VERSION 0.0.1 LANGUAGES CXX)
 
 # Set C++ standard
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 # Add example program

include/nativeapi.h

@@ -4,6 +4,8 @@
 #include "../src/app_runner.h"
 #include "../src/display.h"
 #include "../src/display_manager.h"
+#include "../src/event.h"
+#include "../src/event_dispatcher.h"
 #include "../src/geometry.h"
 #include "../src/keyboard_monitor.h"
 #include "../src/menu.h"

src/event.h

@@ -0,0 +1,112 @@
+#pragma once
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <typeindex>
+#include <unordered_map>
+#include <chrono>
+
+namespace nativeapi {
+
+/**
+ * Base class for all events in the generic event system.
+ * Events should inherit from this class and provide their own data.
+ */
+class Event {
+ public:
+  Event() : timestamp_(std::chrono::steady_clock::now()) {}
+  virtual ~Event() = default;
+
+  // Get the time when this event was created
+  std::chrono::steady_clock::time_point GetTimestamp() const {
+    return timestamp_;
+  }
+
+  // Get a string representation of the event type (for debugging)
+  virtual std::string GetTypeName() const = 0;
+
+ private:
+  std::chrono::steady_clock::time_point timestamp_;
+};
+
+/**
+ * Template for typed events. This provides type safety and automatic
+ * type identification for events.
+ */
+template<typename T>
+class TypedEvent : public Event {
+ public:
+  static std::type_index GetStaticType() {
+    return std::type_index(typeid(T));
+  }
+
+  std::type_index GetType() const {
+    return GetStaticType();
+  }
+
+  std::string GetTypeName() const override {
+    return typeid(T).name();
+  }
+};
+
+/**
+ * Generic event listener interface that can handle any event type.
+ * This is the base interface for the observer pattern.
+ */
+class EventListener {
+ public:
+  virtual ~EventListener() = default;
+  
+  /**
+   * Handle an event. Implementations should check the event type
+   * and cast appropriately.
+   */
+  virtual void OnEvent(const Event& event) = 0;
+};
+
+/**
+ * Template for typed event listeners. This provides type safety
+ * by automatically casting events to the correct type.
+ */
+template<typename EventType>
+class TypedEventListener : public EventListener {
+ public:
+  virtual ~TypedEventListener() = default;
+
+  void OnEvent(const Event& event) override {
+    // Check if this is the correct event type
+    if (auto typed_event = dynamic_cast<const EventType*>(&event)) {
+      OnTypedEvent(*typed_event);
+    }
+  }
+
+  /**
+   * Handle a typed event. Subclasses should override this method.
+   */
+  virtual void OnTypedEvent(const EventType& event) = 0;
+};
+
+/**
+ * Callback-based event handler that wraps std::function callbacks.
+ * This allows using lambda functions or function pointers as event handlers.
+ */
+template<typename EventType>
+class CallbackEventListener : public TypedEventListener<EventType> {
+ public:
+  using CallbackType = std::function<void(const EventType&)>;
+
+  explicit CallbackEventListener(CallbackType callback) 
+      : callback_(std::move(callback)) {}
+
+  void OnTypedEvent(const EventType& event) override {
+    if (callback_) {
+      callback_(event);
+    }
+  }
+
+ private:
+  CallbackType callback_;
+};
+
+}  // namespace nativeapi

src/event_dispatcher.cpp

@@ -0,0 +1,188 @@
+#include "event_dispatcher.h"
+
+#include <algorithm>
+#include <iostream>
+
+namespace nativeapi {
+
+EventDispatcher::EventDispatcher()
+    : running_(false), stop_requested_(false), next_listener_id_(1) {}
+
+EventDispatcher::~EventDispatcher() {
+  Stop();
+}
+
+size_t EventDispatcher::AddListener(std::type_index event_type,
+                                    EventListener* listener) {
+  if (!listener) {
+    return 0;  // Invalid listener
+  }
+
+  std::lock_guard<std::mutex> lock(listeners_mutex_);
+  size_t listener_id = next_listener_id_.fetch_add(1);
+
+  listeners_[event_type].push_back({listener, listener_id});
+
+  return listener_id;
+}
+
+bool EventDispatcher::RemoveListener(size_t listener_id) {
+  std::lock_guard<std::mutex> lock(listeners_mutex_);
+
+  for (auto& [event_type, listener_list] : listeners_) {
+    auto it = std::find_if(listener_list.begin(), listener_list.end(),
+                           [listener_id](const ListenerInfo& info) {
+                             return info.id == listener_id;
+                           });
+
+    if (it != listener_list.end()) {
+      listener_list.erase(it);
+      return true;
+    }
+  }
+
+  return false;
+}
+
+void EventDispatcher::RemoveAllListeners(std::type_index event_type) {
+  std::lock_guard<std::mutex> lock(listeners_mutex_);
+  listeners_[event_type].clear();
+}
+
+void EventDispatcher::RemoveAllListeners() {
+  std::lock_guard<std::mutex> lock(listeners_mutex_);
+  listeners_.clear();
+  callback_listeners_.clear();
+}
+
+void EventDispatcher::DispatchSync(const Event& event) {
+  std::type_index event_type = typeid(event);
+  std::vector<EventListener*> listeners_copy;
+
+  // Copy listeners to avoid holding the lock during dispatch
+  {
+    std::lock_guard<std::mutex> lock(listeners_mutex_);
+    auto it = listeners_.find(event_type);
+    if (it != listeners_.end()) {
+      listeners_copy.reserve(it->second.size());
+      for (const auto& info : it->second) {
+        listeners_copy.push_back(info.listener);
+      }
+    }
+  }
+
+  // Dispatch to all listeners
+  for (auto* listener : listeners_copy) {
+    try {
+      listener->OnEvent(event);
+    } catch (const std::exception& e) {
+      std::cerr << "Exception in event listener: " << e.what() << std::endl;
+    } catch (...) {
+      std::cerr << "Unknown exception in event listener" << std::endl;
+    }
+  }
+}
+
+void EventDispatcher::DispatchAsync(std::unique_ptr<Event> event) {
+  if (!event) {
+    return;
+  }
+
+  // Start the worker thread if not already running
+  if (!running_.load()) {
+    Start();
+  }
+
+  {
+    std::lock_guard<std::mutex> lock(queue_mutex_);
+    event_queue_.push(std::move(event));
+  }
+
+  queue_condition_.notify_one();
+}
+
+void EventDispatcher::Start() {
+  if (running_.load()) {
+    return;  // Already running
+  }
+
+  stop_requested_.store(false);
+  running_.store(true);
+
+  worker_thread_ = std::thread(&EventDispatcher::ProcessAsyncEvents, this);
+}
+
+void EventDispatcher::Stop() {
+  if (!running_.load()) {
+    return;  // Not running
+  }
+
+  stop_requested_.store(true);
+  queue_condition_.notify_all();
+
+  if (worker_thread_.joinable()) {
+    worker_thread_.join();
+  }
+
+  running_.store(false);
+
+  // Clear any remaining events in the queue
+  std::lock_guard<std::mutex> lock(queue_mutex_);
+  while (!event_queue_.empty()) {
+    event_queue_.pop();
+  }
+}
+
+bool EventDispatcher::IsRunning() const {
+  return running_.load();
+}
+
+size_t EventDispatcher::GetListenerCount(std::type_index event_type) const {
+  std::lock_guard<std::mutex> lock(listeners_mutex_);
+  auto it = listeners_.find(event_type);
+  return (it != listeners_.end()) ? it->second.size() : 0;
+}
+
+size_t EventDispatcher::GetTotalListenerCount() const {
+  std::lock_guard<std::mutex> lock(listeners_mutex_);
+  size_t total = 0;
+  for (const auto& [event_type, listener_list] : listeners_) {
+    total += listener_list.size();
+  }
+  return total;
+}
+
+void EventDispatcher::ProcessAsyncEvents() {
+  while (running_.load()) {
+    std::unique_ptr<Event> event;
+
+    // Wait for an event or stop signal
+    {
+      std::unique_lock<std::mutex> lock(queue_mutex_);
+      queue_condition_.wait(lock, [this] {
+        return !event_queue_.empty() || stop_requested_.load();
+      });
+
+      if (stop_requested_.load()) {
+        break;
+      }
+
+      if (!event_queue_.empty()) {
+        event = std::move(event_queue_.front());
+        event_queue_.pop();
+      }
+    }
+
+    // Dispatch the event if we have one
+    if (event) {
+      DispatchSync(*event);
+    }
+  }
+}
+
+EventDispatcher& GetGlobalEventDispatcher() {
+  static EventDispatcher global_dispatcher;
+  return global_dispatcher;
+}
+
+}  // namespace nativeapi