Modern OpenGL(Glad)

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引言

上一节讨论图层时制作了整个图层堆栈系统，今天我们尝试引入现代 OpenGL 为之后的实时 GUI 准备。

为项目加入图形显示和 GUI 是一件令人愉悦的事情，因为我们可以看到信息、调整数值，毕竟我们不能总是为了某些数值调整而重新编译整个项目，一个小滑块就可以解决。

我们需要一种方法来实际使用现代图形 API：OpenGL（最终这个项目会支持所有的图形 API 如 DirectX11 或 Vulkan，但 OpenGL 的跨平台性和易用性让我们考虑优先实现）。所以现在我们需要添加以 C++ 代码驱动 GPU 的现代 OpenGL 功能，因此希望能够调用存储在我们图形驱动程序中的函数（事实上之前我们已经使用了 GLFW，与之前不同，我们会使用一种叫“Glad”的东西）。

Glad 配置

GLAD是继GL3W，GLEW之后，当前最新的用来访问 OpenGL 规范接口的第三方库。好的，我们首先进入 Glad 网站：

选择 4.6 OpenGL 版本，Profile 更改为 Core：

生成一个网页包：https://glad.dav1d.de/generated/tmpj1wnkvqcglad/，点击 glad.zip 下载它：

接着我们在 /Infinite/Infinite/vendor 中新建 GLAD 文件夹，放入解压后的文件。

预生成文件

现在我们把新的 glad 引入预生成文件中：

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workspace "Infinite"
  architecture "x64"
  startproject "Sandbox"

  configurations
  {
    "Debug",
    "Release",
    "Dist"
  }

outputdir = "%{cfg.buildcfg}-%{cfg.system}-%{cfg.architecture}"

-- Include directories relative to root folder (solution directory)
IncludeDir = {}
IncludeDir["GLFW"] = "Infinite/vendor/GLFW/include"
+IncludeDir["GLAD"] = "Infinite/vendor/GLAD/include"

include "Infinite/vendor/GLFW"
+include "Infinite/vendor/GLAD"

project "Infinite"
  location "Infinite"
  kind "SharedLib"
  language "C++"

  targetdir ("bin/" .. outputdir .. "/%{prj.name}")
  objdir ("bin-int/" .. outputdir .. "/%{prj.name}")

  pchheader "ifnpch.h"
  pchsource "Infinite/src/ifnpch.cpp"

  files
  {
    "%{prj.name}/src/**.h",
    "%{prj.name}/src/**.cpp"
  }

  includedirs
  {
    "%{prj.name}/src",
    "%{prj.name}/vendor/spdlog/include",
    "%{IncludeDir.GLFW}"
+   "%{IncludeDir.GLAD}"
  }

  links
  {
    "GLFW",
+   "GLAD",
    "opengl32.lib"
  }

  filter "system:windows"
    cppdialect "C++17"
    staticruntime "On"
    systemversion "latest"

    defines
    {
      "IFN_PLATFORM_WINDOWS",
      "IFN_BUILD_DLL"
    }

    postbuildcommands
    {
      ("{COPY} %{cfg.buildtarget.relpath} ../bin/" .. outputdir .. "/Sandbox")
    }

  filter "configurations:Debug"
      defines "IFN_DEBUG"
      buildoptions "/MDd"
      symbols "On"

  filter "configurations:Release"
      defines "IFN_RELEASE"
      buildoptions "/MD"
      optimize "On"

  filter "configurations:Dist"
      defines "IFN_DIST"
      buildoptions "/MD"
      optimize "On"



project "Sandbox"
  location "Sandbox"
  kind "ConsoleApp"

  language "C++"

  targetdir ("bin/" .. outputdir .. "/%{prj.name}")
  objdir ("bin-int/" .. outputdir .. "/%{prj.name}")

  files
  {
    "%{prj.name}/src/**.h",
    "%{prj.name}/src/**.cpp"
  }

  includedirs
  {
    "Infinite/vendor/spdlog/include",
    "Infinite/src/Infinite",
    "Infinite/src/Events"
  }

  links
  {
    "Infinite"
  }

  filter "system:windows"
    cppdialect "C++17"
    staticruntime "On"
    systemversion "latest"

    defines
    {
      "IFN_PLATFORM_WINDOWS"
    }

  filter "configurations:Debug"
      defines "IFN_DEBUG"
      buildoptions "/MDd"
      symbols "On"

  filter "configurations:Release"
      defines "IFN_RELEASE"
      buildoptions "/MD"
      optimize "On"

  filter "configurations:Dist"
      defines "IFN_DIST"
      buildoptions "/MD"
      optimize "On"

复制 Infinite/vendor/GLFW 的 premake5 至 GLAD 中修改：

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project "GLAD"
	kind "StaticLib"
	language "C"

	targetdir ("bin/" .. outputdir .. "/%{prj.name}")
	objdir ("bin-int/" .. outputdir .. "/%{prj.name}")

	files
	{
		"include/glad/glad.h",
		"include/KHR/khrplatform.h",
		"src/glad.c"
	}

	includedirs
	{
		"include"
	}

	filter "system:windows"
		systemversion "latest"
		staticruntime "On"

	filter { "system.windows", "configurations:Release" }
		buildoptions "/MT"

最终我们在 VisualStudio 中成功引入了 glad：

调试

最后我们对原有的 Application.cpp 进行一些修改：

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#include "Events/ApplicationEvent.h"
#include "Log.h"

-#include <GLFW/glfw3.h>
+#include <glad/glad.h>

namespace Infinite {

	namespace Infinite {
	{
		m_Window = std::unique_ptr<Window>(Window::Create());
		m_Window->SetEventCallback(BIND_EVENT_FN(OnEvent));

+		int id;
+		glGenVertexArrays(1, &id);
	}

	Application::~Application() {}

让我们试试 gladLoadGLLoader()。int gladLoadGLLoader(GLADloadproc load)：任何的OpenGL接口调用都必须在初始化 GLAD 库后才可以正常访问。如果成功的话，该接口将返回 GL_TRUE，否则就会返回 GL_FALSE。

其中 GLADloadproc 函数声明如下：void* (*GLADloadproc)(const char* name)。

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#include "Infinite/Events/MouseEvent.h"
#include "Infinite/Events/KeyEvent.h"

#include <GLAD/glad.h>

namespace Infinite {

	static bool s_GLFWInitialized = false;
	.....

		m_Window = glfwCreateWindow((int)props.Width, (int)props.Height, m_Data.Title.c_str(), nullptr, nullptr);
		glfwMakeContextCurrent(m_Window);
+		int status = gladLoadGLLoader((GLADloadproc)glfwGetProcAddress);
+		IFN_CORE_ASSERT(status, "Failed to initialize GLAD!");
		glfwSetWindowUserPointer(m_Window, &m_Data);
		SetVSync(true);

最后成功启动项目，代表引入 GLAD 成功。