基于opengl编写一个简易的2d渲染框架02——搭建opengl环境

// 定义函数原型
typedef void (*GL_GENBUFFERS) (GLsizei, GLuint*);
// 找到正确的函数并赋值给函数指针
GL_GENBUFFERS glGenBuffers  = (GL_GENBUFFERS)wglGetProcAddress("glGenBuffers");
// 现在函数可以被正常调用了
GLuint buffer;
glGenBuffers(1, &buffer);

#define GLEW_STATIC
#include <GL/glew.h>

#pragma once
#define GLEW_STATIC

#include "Common.h"
#include <Windows.h>
#include "GLEW\glew.h"

namespace Simple2D
{
    class RenderWindow;

    class DLL_export GraphicsContext
    {
    public:
        GraphicsContext(RenderWindow* renderWindow);
        ~GraphicsContext();

        void createOpenGLContext();
        void flip();

    private:
        RenderWindow* pRenderWindow;

        HGLRC openglContext;
        HDC deviceContext;
    };
}

#include "GraphicsContext.h"
#include "RenderWindow.h"

namespace Simple2D
{
    GraphicsContext::GraphicsContext(RenderWindow* renderWindow)
        : pRenderWindow(renderWindow)
        , openglRenderContext(0)
        , deviceContext(0)
    {
        this->createOpenGLContext();
    }

    GraphicsContext::~GraphicsContext()
    {
        wglDeleteContext(openglRenderContext);
        ReleaseDC(pRenderWindow->getHwnd(), deviceContext);
    }

    void GraphicsContext::createOpenGLContext()
    {
        if ( openglRenderContext == 0 ) {
            deviceContext = GetDC(pRenderWindow->getHwnd());

            PIXELFORMATDESCRIPTOR pfd = { 0 };
            int color_deep = GetDeviceCaps(deviceContext, BITSPIXEL);

            pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
            pfd.nVersion = 1;
            pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
            pfd.iPixelType = PFD_TYPE_RGBA;
            pfd.cColorBits = color_deep;
            pfd.cDepthBits = 0;
            pfd.cStencilBits = 0;
            pfd.iLayerType = PFD_MAIN_PLANE;

            int pixle_format = ChoosePixelFormat(deviceContext, &pfd);
            SetPixelFormat(deviceContext, pixle_format, &pfd);

            /* 创建 OpenGL 渲染上下文 */
            openglRenderContext = wglCreateContext(deviceContext);
            if ( openglRenderContext == 0 ) exit(0);

            /* 选择 openglRenderContext 作为当前线程的 openglRenderContext */
            if ( wglMakeCurrent(deviceContext, openglRenderContext) == 0 ) exit(1);

            /* GLEW 是用来管理 OpenGL 的函数指针的，所以在调用任何 OpenGL 的函数之前我们需要初始化GLEW */
            if ( glewInit() != GLEW_OK ) exit(1);

            /* 设置视口，大小为客户区大小 */
            SIZE size = pRenderWindow->getClientSize();
            glViewport(0, 0, size.cx, size.cy);
        }
    }

    void GraphicsContext::flip()
    {
        /* 使用一个自定义的颜色清空屏幕，这里使用红色 */
        glClearColor(1.0f, 0, 0, 1.0f);

        /* 调用glClear函数来清空屏幕的颜色缓冲 */
        glClear(GL_COLOR_BUFFER_BIT);

        // 交换当前缓冲区和后台缓冲区
        SwapBuffers(deviceContext);
    }
}

#pragma once

#include <Windows.h>
#include "RenderWindow.h"
#include "GraphicsContext.h"

using namespace Simple2D;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    RenderWindow window(DEFAULT_WIN_W, DEFAULT_WIN_H);
    GraphicsContext graphicsContext(&window);

    MSG msg = { 0 };
    while ( msg.message != WM_QUIT ) {
        if ( PeekMessage(&msg, 0, 0, 0, PM_REMOVE) ) {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        else {
            graphicsContext.flip();
        }
    }

    return 0;
}