Haxel Engine learning 4 -- Event System

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博客介绍了Event系统代码的创建，在Event文件夹中包含4个.h文件，定义了EventCategory枚举，说明了不同事件类别之间的所属关系。还提到可以用宏来代替部分代码，最后给出了四个event文件的完整代码，并提及在Appication.cpp里添加事件及运行操作。

完整代码：https://github.com/DXT00/Hazel_study/tree/master/Event%20System

创建Event文件夹，包含4个.h文件

Event.h

#pragma once

#include "Hazel/Core.h"

#include<string>
#include<functional>

namespace Hazel {
	//Events in Hazel is blocking,when an event happen 
	//,the whole APP stop and process that event.


	enum class EventType {
		None = 0,
		WindowClose, WindowResize, WindowFocus, WindowsLostFocus, WindowMoved,
		AppTick, AppUpdate, AppRender,
		KeyPressed, KeyReleased,
		MouseButtonPressed,MouseButtonRelease,MouseMoved,MouseScrolled

	};
	enum EventCategory {
		None = 0,
		EventCategoryApplication  = BIT(0),
		EventCategoryInput        = BIT(1),
		EventCategoryKeyBoard     = BIT(2),
		EventCategoryMouse        = BIT(3),
		EventCategoryMouseButton  = BIT(4)

	};

	class HAZEL_API Event {
		friend class EventDispatcher;
	public:
		virtual EventType GetEventype() const = 0;
		virtual const char* GetName() const = 0;
		virtual int GetCategoryFlags() const = 0;
		virtual std::string ToString()const { return GetName(); }

		inline bool IsInCategory(EventCategory category) {
			return GetCategoryFlags() & category;
		}
	protected:
		bool m_Handled = false; //Event是否被处理了
	};
}

Core.h

#define BIT(x) (1<<x)

包含EventType 和 EventCategory

注意EventCategory使用bit field

   enum EventCategory {
       None = 0,
       EventCategoryApplication = BIT(0), //0000 0000
       EventCategoryInput = BIT(1), //0000 0001
       EventCategoryKeyBoard = BIT(2), //0000 0010
       EventCategoryMouse = BIT(3), //0000 0100
       EventCategoryMouseButton = BIT(4) //0000 1000

   };

也即是：

EventCategoryMouseButton，EventCategoryMouse， EventCategoryKeyBoard，EventCategoryInput 属于 EventCategoryApplication

EventCategoryMouseButton，EventCategoryMouse， EventCategoryKeyBoard 属于 EventCategoryInput

EventCategoryMouseButton 属于 EventCategoryMouse

比如 flags = 0000 0111时 ,

flags&EventCategoryMouse>0

flags&EventCategoryKeyBoard>0

flags&EventCategoryInput>0

所以flags属于EventCategoryMouse，EventCategoryKeyBoard，EventCategoryInput 3种Events

KeyEvent.h

class HAZEL_API KeyPressedEvent : public KeyEvent {
	public:
		KeyPressedEvent(int keycode,int repeatCount): //keep track the amount of time that the key has repeated
			KeyEvent(keycode), m_RepeatCount(repeatCount){}

		inline int GetRepeatCount() const { return m_RepeatCount; }
		
		std::string ToString()const override{
			std::stringstream ss;
			ss << "KeyPressedEvent: " << m_KeyCode << " (" << m_RepeatCount << "repeats)";
			return ss.str();
		}

		static EventType GetStaticType() { return EventType::MouseScrolled; }
		virtual EventType GetEventype()const override { return GetStaticType(); }
		virtual const char* GetName() const override { return "MouseScrolled"; }
		virtual int GetCategoryFlags() const override { return EventCategoryInput| EventCategoryMouse; }

	private:
		int m_RepeatCount;
	};

这4行可以用宏来代替：

       static EventType GetStaticType() { return EventType::MouseScrolled; }
       virtual EventType GetEventype()const override { return GetStaticType(); }
       virtual const char* GetName() const override { return "MouseScrolled"; }
       virtual int GetCategoryFlags() const override { return EventCategoryInput| EventCategoryMouse; }

#define EVENT_CLASS_TYPE(type) static EventType GetStaticType() { return EventType::##type; }\
virtual EventType GetEventype()const override { return GetStaticType(); }\
virtual const char* GetName() const override { return #type; }

#define EVENT_CLASS_CATEGORY(category) virtual int GetCategoryFlags() const override{ return category;}

四个event文件完整代码：

Event.h

#pragma once

#include "Hazel/Core.h"

#include<string>
#include<functional>

namespace Hazel {
	//Events in Hazel is blocking,when an event happen 
	//,the whole APP stop and process that event.


	enum class EventType {
		None = 0,
		WindowClose, WindowResize, WindowFocus, WindowsLostFocus, WindowMoved,
		AppTick, AppUpdate, AppRender,
		KeyPressed, KeyReleased,
		MouseButtonPressed,MouseButtonReleased,MouseMoved,MouseScrolled

	};
	enum EventCategory {
		None = 0,
		EventCategoryApplication  = BIT(0),
		EventCategoryInput        = BIT(1),
		EventCategoryKeyBoard     = BIT(2),
		EventCategoryMouse        = BIT(3),
		EventCategoryMouseButton  = BIT(4)


	};

#define EVENT_CLASS_TYPE(type) static EventType GetStaticType() { return EventType::##type; }\
								virtual EventType GetEventype()const override { return GetStaticType(); }\
								virtual const char* GetName() const override { return #type; }

#define EVENT_CLASS_CATEGORY(category) virtual int GetCategoryFlags() const override{ return category;}


	/*-----------------------------------------------------------------------*/
	class HAZEL_API Event {
		friend class EventDispatcher;
	public:
		virtual EventType GetEventype() const = 0;
		virtual const char * GetName() const = 0;
		virtual int GetCategoryFlags() const = 0;
		virtual std::string ToString()const { return GetName(); }

		inline bool IsInCategory(EventCategory category) {
			return GetCategoryFlags() & category;
		}
	protected:
		bool m_Handled = false; //Event是否被处理了
	};
	/*-----------------------------------------------------------------------*/
	class EventDispatcher
	{
		template<typename T>
		using EventFn = std::function<bool(T&)>; //输入参数类型 (T&),返回参数类型 bool
	public:
		EventDispatcher(Event& event)
			:m_Event(event){}

		template<typename T>
		bool Dispatch(EventFn<T> func) {
			if (m_Event.GetEventype() == T::GetStaticType()) {
				m_Event.m_Handled = func(*(T*)&m_Event);
				return true;
			}
			return false;
		}

	private:
		Event &m_Event;
	};

	inline std::ostream& operator<<(std::ostream& os, const Event&e) {
		return os << e.ToString();
	}


}

event调度类：

class EventDispatcher
	{
		template<typename T>
		using EventFn = std::function<bool(T&)>; //输入参数类型 (T&),返回参数类型 bool
	public:
		EventDispatcher(Event& event)
			:m_Event(event){}

		template<typename T>
		bool Dispatch(EventFn<T> func) {
			if (m_Event.GetEventype() == T::GetStaticType()) {
				m_Event.m_Handled = func(*(T*)&m_Event);
				return true;
			}
			return false;
		}

	private:
		Event &m_Event;
	};

Application.h

#pragma once
#include"Event.h"
#include <sstream>

namespace Hazel {

	class HAZEL_API WindowResizeEvent :public Event
	{
	public:
		WindowResizeEvent(unsigned int width, unsigned int height)
			:m_Width(width), m_Height(height){}

		inline unsigned int GetWidth() const{ return m_Width; }
		inline unsigned int GetHeight() const { return m_Height; }

		std::string ToString() const override {
			std::stringstream ss;
			ss << "WindowResizeEvent: " << GetWidth() << ", " << GetHeight();
			return ss.str();
		}
		EVENT_CLASS_TYPE(WindowResize)
		EVENT_CLASS_CATEGORY(EventCategoryApplication)


	private:
		unsigned int m_Width, m_Height;
	};

	class HAZEL_API WindowCloseEvent :public Event
	{
	public:
		WindowCloseEvent() {}

		EVENT_CLASS_TYPE(WindowClose)
		EVENT_CLASS_CATEGORY(EventCategoryApplication)

	};

	class HAZEL_API AppTickEvent :public Event
	{
	public:
		AppTickEvent() {}

		EVENT_CLASS_TYPE(AppTick)
		EVENT_CLASS_CATEGORY(EventCategoryApplication)

	};
	class HAZEL_API AppUpdateEvent :public Event
	{
	public:
		AppUpdateEvent() {}

		EVENT_CLASS_TYPE(AppUpdate)
		EVENT_CLASS_CATEGORY(EventCategoryApplication)

	};
	class HAZEL_API AppRenderEvent :public Event
	{
	public:
		AppRenderEvent() {}

		EVENT_CLASS_TYPE(AppRender)
		EVENT_CLASS_CATEGORY(EventCategoryApplication)

	};
}

KeyEvent.h

#pragma once

#include "Event.h"
#include <sstream>

namespace Hazel {


	class HAZEL_API KeyEvent:public Event //abstact 
	{
	public:
		inline int GetKeyCode()const { return m_KeyCode; }
		EVENT_CLASS_CATEGORY(EventCategoryInput | EventCategoryKeyBoard)
		
	protected:
		KeyEvent(int keycode):m_KeyCode(keycode){} //you won't be able to make a KeyEvent
		int m_KeyCode;
	};


	/*-----------------------------------------------------------------------*/
	class HAZEL_API KeyPressedEvent : public KeyEvent {
	public:
		KeyPressedEvent(int keycode,int repeatCount): //keep track the amount of time that the key has repeated
			KeyEvent(keycode), m_RepeatCount(repeatCount){}

		inline int GetRepeatCount() const { return m_RepeatCount; }
		
		std::string ToString()const override{
			std::stringstream ss;
			ss << "KeyPressedEvent: " << m_KeyCode << " (" << m_RepeatCount << "repeats)";
			return ss.str();
		}

	
		EVENT_CLASS_TYPE(KeyPressed)
		EVENT_CLASS_CATEGORY( EventCategoryInput | EventCategoryKeyBoard)
	private:
		int m_RepeatCount;
	};



	/*-----------------------------------------------------------------------*/
	class HAZEL_API KeyReleasedEvent : public KeyEvent {
	public:
		KeyReleasedEvent(int keycode) : //keep track the amount of time that the key has repeated
			KeyEvent(keycode) {}

		

		std::string ToString()const override {
			std::stringstream ss;
			ss << "KeyReleasedEvent: " << m_KeyCode ;
			return ss.str();
		}


		EVENT_CLASS_TYPE(KeyReleased)
		EVENT_CLASS_CATEGORY(EventCategoryInput | EventCategoryKeyBoard)
	};
}

MouseEvent.h

#pragma once

#include "Event.h"
#include <sstream>

namespace Hazel {
	class HAZEL_API MouseMovedEvent : public Event 
	{
	public:
		MouseMovedEvent(float x,float y) : //keep track the amount of time that the key has repeated
			m_MouseX(x), m_MouseY(y) {}

		inline float GetX() const { return m_MouseX; }
		inline float GetY() const { return m_MouseY; }

		std::string ToString()const override {
			std::stringstream ss;
			ss << "MouseMovedEvent: " << GetX() << " , " << GetY();
			return ss.str();
		}

		
		EVENT_CLASS_TYPE(MouseMoved);
		EVENT_CLASS_CATEGORY(EventCategoryInput | EventCategoryMouse);

	private:
		int m_MouseX,m_MouseY;
	};


	class HAZEL_API MouseScrolledEvent : public Event
	{
	public:
		MouseScrolledEvent(float xOffset, float yOffset) : //keep track the amount of time that the key has repeated
			m_XOffset(xOffset), m_YOffset(yOffset) {}

		inline float GetXOffset() const { return m_XOffset; }
		inline float GetYOffset() const { return m_YOffset; }

		std::string ToString()const override {
			std::stringstream ss;
			ss << "MouseScrolledEvent: " << GetXOffset() << " , " << GetYOffset();
			return ss.str();
		}

		EVENT_CLASS_TYPE(MouseScrolled);
		EVENT_CLASS_CATEGORY(EventCategoryInput | EventCategoryMouse);

	/*	static EventType GetStaticType() { return EventType::MouseScrolled; }
		virtual EventType GetEventype()const override { return GetStaticType(); }
		virtual const char* GetName() const override { return "MouseScrolled"; }
		virtual int GetCategoryFlags() const override { return EventCategoryInput| EventCategoryMouse; }*/


	private:
		int m_XOffset, m_YOffset;
	};


	class HAZEL_API MouseButtonEvent : public Event 
	{
	public:
		inline int GetMouseButton() const { return m_Button; }
		EVENT_CLASS_CATEGORY(EventCategoryInput | EventCategoryMouse);

	protected:
		MouseButtonEvent(int button)
					:m_Button(button) {};

		int m_Button;
	};


	class HAZEL_API MouseButtonPressedEvent : public MouseButtonEvent 
	{
	public:
		MouseButtonPressedEvent(int button)
			:MouseButtonEvent(button) {};

		std::string ToString()const override {
			std::stringstream ss;
			ss << "MouseButtonPressedEvent: " << m_Button;
			return ss.str();
		}
		EVENT_CLASS_TYPE(MouseButtonPressed);

	};

	class HAZEL_API MouseButtonReleaseEvent : public MouseButtonEvent
	{
	public:
		MouseButtonReleaseEvent(int button)
			:MouseButtonEvent(button) {};

		std::string ToString()const override {
			std::stringstream ss;
			ss << "MouseButtonReleaseEvent: " << m_Button;
			return ss.str();
		}
		EVENT_CLASS_TYPE(MouseButtonReleased);

	};
}

Appication.cpp里添加一个event:

#include "Application.h"
#include "Hazel/Event/ApplicationEvent.h"
#include "Hazel/Log.h"
namespace Hazel {

	Application::Application()
	{
	}
	
	
	Application::~Application()
	{
	}

	
	
	
	void Application:: Run() {
		WindowResizeEvent e(1280, 720);
		HZ_TRACE(e);
		while (true);
	}
}

F5 run: