这里写自定义目录标题
SDL2+Opengles2.0使用，SDL_GL_SwapWindow()立即刷新问题
初始化sdl2 + Opengles2.0
使用了glad库，库在线生成模板地址：https://glad.dav1d.de/
加入项目后sdl2初始化：
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32);
//SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 0);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
//Use OpenGL 2.1
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
//注意加入SDL_WINDOW_OPENGL参数
window = SDL_CreateWindow(NULL, G_windowRect.x, G_windowRect.y, deviceSize.w, deviceSize.h, winflag | SDL_WINDOW_OPENGL);
//创建opengl上下文
G_GLEScontext = SDL_GL_CreateContext(window);
//初始化glad，注意这个函数跟你的选择的版本有关，见glad.c文件中对应的函数
gladLoadGLES2Loader((GLADloadproc)SDL_GL_GetProcAddress);
//sdl2中设置为立即刷新模式
//问题也出在这，即使设置为立即刷新模式，SDL_GL_SwapWindow也很可能不是立即刷新的
SDL_GL_SetSwapInterval(0);
//测试下是否立即刷新
glClearColor(0.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
SDL_GL_SwapWindow(window);
//如果不是，加入这个
glFinish(); //多少能解决问题，原因不明，sdl2版本2.0.12