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本文介绍: 游戏引擎，cherno，c++，opengl，contex，上下文，第一个三角形

渲染上下文：

目的：修改WindowsWindow的结构，把glad抽离出来

WindowsWindow.h:新建m_Context

#pragma once
#include "YOTO/Window.h"
#include <YOTO/Renderer/GraphicsContext.h>
#include<GLFW/glfw3.h>
#include"YOTO/Log.h"


struct GLFWwindow;
namespace YOTO {
	class WindowsWindow :public Window
	{
	public :
		WindowsWindow(const WindowProps& props);
		virtual ~WindowsWindow();
		void OnUpdate() override;
		
		inline unsigned int GetWidth() const override { return m_Data.Width; };
		inline unsigned int GetHeight() const override { return m_Data.Height; };

		inline void SetEventCallback(const EventCallbackFn& callback)override
		{ m_Data.EventCallback = callback; };
		void SetVSync(bool enable) ;
		bool IsVSync()const;
		//返回window
		inline virtual void* GetNativeWindow() const { return m_Window; }
	private: 
		virtual void Init(const WindowProps& props);
		virtual void ShutDown();
	private:
		GLFWwindow* m_Window;
		GraphicsContext* m_Context;
		struct WindowData {
			std::string Title;
			unsigned int Width, Height;
			bool VSync;
			EventCallbackFn EventCallback;
		};
		WindowData m_Data;
	};
}

WindowsWindow.cpp:把glad的API全部替换成m_Context的方法：

#include "ytpch.h"
#include "WindowsWindow.h"

#include"YOTO/Event/ApplicationEvent.h"
#include"YOTO/Event/MouseEvent.h"
#include"YOTO/Event/KeyEvent.h"

#include"Platform/OpenGL/OpenGLContext.h"
namespace YOTO {

	static bool s_GLFWInitialized = false;

	Window* Window::Creat(const WindowProps& props) {
		return new WindowsWindow(props);
	}
	WindowsWindow::WindowsWindow(const WindowProps& props) {
		Init(props);
	}
	WindowsWindow::~WindowsWindow() {
		ShutDown();
	}

	void WindowsWindow::Init(const WindowProps& props) {
		m_Data.Title = props.Title;
		m_Data.Width = props.Width;
		m_Data.Height = props.Height;
		YT_CORE_INFO("WindowsWindow：创建了{0},{1},{2}", props.Title, props.Width, props.Height);



		if (!s_GLFWInitialized) {
			int success = glfwInit();
			YT_CLIENT_ASSERT("WindowsWindow：不能创建新的glfw,{0}",success );
			glfwSetErrorCallback([](int error_code, const char* description) {
				YT_CORE_ERROR("WindowsWindow：GLFW错误:错误码({0})：{1} ", error_code, description);
				});
			s_GLFWInitialized = true;

		}
		m_Window = glfwCreateWindow((int)props.Width, (int)props.Height, m_Data.Title.c_str(), nullptr, nullptr);
		m_Context = new OpenGLContext(m_Window);
		m_Context->Init();

		
		glfwSetWindowUserPointer(m_Window, &m_Data);
		SetVSync(true);


		//GLFW回调，每次改变调用lambda里的部分
		//窗口大小回调
		glfwSetWindowSizeCallback(m_Window, [](GLFWwindow* window, int width, int height) {
			WindowData& data=*(WindowData*)glfwGetWindowUserPointer(window);
			data.Width = width;
			data.Height = height;
			WindowResizeEvent event(width, height);
			//调用回调函数
			data.EventCallback(event);
			});
		//窗口关闭回调
		glfwSetWindowCloseCallback(m_Window, [](GLFWwindow* window) {
			WindowData& data = *(WindowData*)glfwGetWindowUserPointer(window);
			WindowCloseEvent event;
			data.EventCallback(event);
			});
		//键盘按键回调
		glfwSetKeyCallback(m_Window, [](GLFWwindow* window, int key, int scancode, int action, int mods) {
			WindowData& data = *(WindowData*)glfwGetWindowUserPointer(window);
			switch (action) {
				case GLFW_PRESS:
				{
					KeyPressedEvent event(key, 0);
					data.EventCallback(event);
					break;
				}
				case GLFW_RELEASE:
				{
					KeyReleasedEvent event(key);
					data.EventCallback(event);
					break;
				}
				case GLFW_REPEAT:
				{
					KeyPressedEvent event(key, 1);
					data.EventCallback(event);
					break;
				}
				}
			});
		//鼠标按键回调
		glfwSetMouseButtonCallback(m_Window, [](GLFWwindow* window, int button, int action, int mods) {
			WindowData& data = *(WindowData*)glfwGetWindowUserPointer(window);
			switch (action)
			{
				case GLFW_PRESS:
				{
					MouseButtonPressedEvent event(button);
					data.EventCallback(event);
					break;
				}

				case GLFW_RELEASE:
				{
					MouseButtonReleasedEvent event(button);
					data.EventCallback(event);
					break;
				}
			}
			});
		//滚轮回调
		glfwSetScrollCallback(m_Window, [](GLFWwindow* window, double xoffset, double yoffset) {
			WindowData& data = *(WindowData*)glfwGetWindowUserPointer(window);
			MouseScrolledEvent event((float)xoffset, (float)yoffset);
			data.EventCallback(event);
			});
		//鼠标位置回调
		glfwSetCursorPosCallback(m_Window, [](GLFWwindow* window, double xpos, double ypos) {
			WindowData& data = *(WindowData*)glfwGetWindowUserPointer(window);
			MouseMovedEvent event((float)xpos, (float)ypos);
			data.EventCallback(event);
			});
		//字符回调
		glfwSetCharCallback(m_Window, [](GLFWwindow* window, unsigned int codepoint) {
			WindowData& data = *(WindowData*)glfwGetWindowUserPointer(window);
			KeyTypedEvent event(codepoint);
			data.EventCallback(event);
			});
	}
	void WindowsWindow::ShutDown() {
		glfwDestroyWindow(m_Window);
	}
	void WindowsWindow::OnUpdate()
	{
		//轮询事件
		glfwPollEvents();

		//交换缓冲区
		m_Context->SwapBuffers();



	}
	void WindowsWindow::SetVSync(bool enable) {
		if (enable)
			glfwSwapInterval(1);
		else
			glfwSwapInterval(0);
		m_Data.VSync = enable;
		}
	bool WindowsWindow::IsVSync() const {
		return m_Data.VSync;
		}
}

新建类：OpenGLContext和GraphicsContext文件如下结构：

 

GraphicsContext.h:作为基类

#pragma once

namespace YOTO {
	class GraphicsContext
	{
	public:
		virtual void Init()=0;
		virtual void SwapBuffers()=0;

	};
}

 OpenGLContext.h:继承基类

#pragma once
#include"YOTO/Renderer/GraphicsContext.h"
#include"YOTO/Log.h"
struct GLFWwindow;
namespace YOTO {
	class OpenGLContext:public GraphicsContext
	{
	public:
		OpenGLContext(GLFWwindow * windowHandle);
		virtual void Init()override;
		virtual void SwapBuffers()override;
	private:
		GLFWwindow* m_WindowHandle;
	};

}

 OpenGLContext.cpp:实现Opengl的上下文：

#include "ytpch.h"
#include "OpenGLContext.h"
#include<GLFW/glfw3.h>
#include<glad/glad.h>
#include<gl/GL.h>
namespace YOTO {
	OpenGLContext::OpenGLContext(GLFWwindow* windowHandle)
		:m_WindowHandle(windowHandle)
	{
		YT_CORE_ASSERT(windowHandle, "handle为空");
	}
	void OpenGLContext::Init()
	{
		glfwMakeContextCurrent(m_WindowHandle);
		//在运行时获取OpenGL函数地址并将其保存在函数指针中供以后使用
		int status = gladLoadGLLoader((GLADloadproc)glfwGetProcAddress);
		YT_CORE_ASSERT(status, "glad初始化错误");
	}
	void OpenGLContext::SwapBuffers()
	{
		glfwSwapBuffers(m_WindowHandle);
	}
}

 测试：正常显示

 绘制三角形：

Application.h:添加缓冲区索引

#pragma once
#include"Core.h"
#include"Event/Event.h"
#include"Event/ApplicationEvent.h"
#include "YOTO/Window.h"
#include"YOTO/LayerStack.h"
#include"YOTO/ImGui/ImGuiLayer.h"
namespace YOTO {
	class YOTO_API Application
	{
	public:
		Application();
		virtual ~Application();
		void Run();
		void OnEvent(Event &e);
		void PushLayer(Layer* layer);
		void PushOverlay(Layer* layer);

		inline static Application& Get() {return * s_Instance;}
		inline Window& GetWindow() { return *m_Window; }
	private:
		bool  OnWindowClosed(WindowCloseEvent& e);
		std::unique_ptr<Window>  m_Window;
		ImGuiLayer *  m_ImGuiLayer;
		bool m_Running = true;
		LayerStack m_LayerStack;
		
		unsigned int m_VertexArray, m_VertexBuffer, m_IndexBuffer;

		static Application* s_Instance;
	};
	//在客户端定义
	Application* CreateApplication();
}

 Application.cpp:设置缓冲区然后绘制

#include"ytpch.h"
#include "Application.h"

#include"Log.h"
#include<glad/glad.h>
#include"Input.h"


namespace YOTO {
#define BIND_EVENT_FN(x) std::bind(&x, this, std::placeholders::_1)

	 Application* Application::s_Instance = nullptr;

	Application::Application() {

		YT_CORE_ASSERT(!s_Instance, "Application需要为空！")
		s_Instance = this;
		//智能指针
		m_Window = std::unique_ptr<Window>(Window::Creat());
		//设置回调函数
		m_Window->SetEventCallback(BIND_EVENT_FN(Application::OnEvent));
		//new一个Layer，放在最后层进行渲染
		m_ImGuiLayer = new ImGuiLayer();
		PushOverlay(m_ImGuiLayer);  
		//unsigned int id;
		//glGenBuffers(1, &id);


		//顶点数组：
		glGenVertexArrays(1, &m_VertexArray);
		glBindVertexArray(m_VertexArray);
		//顶点缓冲区
		glGenBuffers(1, &m_VertexBuffer);
		glBindBuffer(GL_ARRAY_BUFFER,m_VertexBuffer);

		float vertices[3 * 3] = {
			-0.5f,-0.5f,0.0f,
			0.5f,-0.5f,0.0f,
			0.0f,0.5f,0.0f,
		};
		//把数据传送给gpu，GL_STATIC_DRAW不断的用新数据刷新数组。告诉opengl这个缓冲区的数据布局
		glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
		//启用数据的索引0
		glEnableVertexAttribArray(0);
		//设置缓冲区数据格式：缓冲区序号、顶点属性的大小、什么数据类型、会不会被归一化、
		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float),nullptr);
		//创建索引缓冲区
		glGenBuffers(1, &m_IndexBuffer);
		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_IndexBuffer);
		unsigned int indices[3] = { 0,1,2 };
		//设置缓冲区格式
		glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
		//着色器
		
		
		//shader
	}
	Application::~Application() {

	}
	/// <summary>
	/// 所有的Window事件都会在这触发，作为参数e
	/// </summary>
	/// <param name="e"></param>
	void Application::OnEvent(Event& e) {
		//根据事件类型绑定对应事件
		EventDispatcher dispatcher(e);
		dispatcher.Dispatch<WindowCloseEvent>(BIND_EVENT_FN(Application::OnWindowClosed));
		//输出事件信息
		YT_CORE_INFO("Application：{0}",e);
		for (auto it = m_LayerStack.end(); it != m_LayerStack.begin();) {
			(*--it)->OnEvent(e);
			if (e.m_Handled)
				break;
		}
	}

	bool Application::OnWindowClosed(WindowCloseEvent& e) {
		m_Running = false;
		return true;
	}
	void Application::Run() {
		WindowResizeEvent e(1280, 720);
		if (e.IsInCategory(EventCategoryApplication)) {
			YT_CORE_TRACE(e);
		}
		if (e.IsInCategory(EventCategoryInput)) {
			YT_CORE_ERROR(e);
		}

		while (m_Running)
		{
			glClearColor(0.2f, 0.2f, 0.2f,1);
			glClear(GL_COLOR_BUFFER_BIT);

			glBindVertexArray(m_VertexArray);
			glDrawElements(GL_TRIANGLES,3,GL_UNSIGNED_INT,nullptr); 
			for (Layer* layer : m_LayerStack) {
				layer->OnUpdate();
			}
			//将ImGui的刷新放到APP中，与Update分开
			m_ImGuiLayer->Begin();
			
			for (Layer* layer : m_LayerStack) {
				layer->OnImGuiRender();
			}
			m_ImGuiLayer->End();
			m_Window->OnUpdate();
		}
	}
	void Application::PushLayer(Layer* layer) {
		m_LayerStack.PushLayer(layer);
		layer->OnAttach();
	}
	void Application::PushOverlay(Layer* layer) {
		m_LayerStack.PushOverlay(layer);
		layer->OnAttach();
	}
}

 OpenGLContext.cpp:显示显卡的基本信息：

#include "ytpch.h"
#include "OpenGLContext.h"
#include<GLFW/glfw3.h>
#include<glad/glad.h>
#include<gl/GL.h>
namespace YOTO {
	OpenGLContext::OpenGLContext(GLFWwindow* windowHandle)
		:m_WindowHandle(windowHandle)
	{
		YT_CORE_ASSERT(windowHandle, "handle为空");
	}
	void OpenGLContext::Init()
	{
		glfwMakeContextCurrent(m_WindowHandle);
		//在运行时获取OpenGL函数地址并将其保存在函数指针中供以后使用
		int status = gladLoadGLLoader((GLADloadproc)glfwGetProcAddress);
		YT_CORE_ASSERT(status, "glad初始化错误");
		// 将我们窗口的上下文设置为当前线程的主上下文
		glfwMakeContextCurrent(m_WindowHandle);
		// 获取显卡OpenGL函数定义的地址
		int statu = gladLoadGLLoader((GLADloadproc)glfwGetProcAddress);
		YT_CORE_ASSERT(status, "Failed to initialize Glad!");

		YT_CORE_INFO("OpenGL 信息:");
		YT_CORE_INFO("	Vendor：{0}", (const char*)glGetString(GL_VENDOR));
		YT_CORE_INFO("	显卡名：{0}", (const char*)glGetString(GL_RENDERER));
		YT_CORE_INFO("	版本：{0}", (const char*)glGetString(GL_VERSION));

	}
	void OpenGLContext::SwapBuffers()
	{
		glfwSwapBuffers(m_WindowHandle);
	}
}

 测试：

cool ！

原文地址:https://blog.csdn.net/weixin_61943345/article/details/135885214

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