SDL2 使用高版本opengl

Posted 2022-09-16 qianbo_insist

sdl2

sdl本身是一个非常好的画图工具，无论二维和三维他都给我们创立了一个良好的基础，本身是可以使用directx和opengl来绘制的，如果要保证跨平台，暂时是可以使用opengl来做。
下面是class Window的示例代码，创建窗口时我们可以使用OPENGL标识

uint32_t flags = SDL_WINDOW_OPENGL;
m_window = SDL_CreateWindow("Engine!", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, mode.w, mode.h, flags);

剩下一定要使用SDL_GL_CONTEXT_PROFILE_MASK, 这样才能设置版本

  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);

然后就可以在sdl opengl里面设置版本了

  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);

还有就是我们事先使用了glew，这样可以使用更多的opengl函数，也可以使用glad，这两者一致，选一个就可以，在运行过程中创建窗口和context完毕以后，就可以使用opengl函数glGetString 来打印使用opengl的函数

log_info("the opengl version get:%s",glGetString(GL_VERSION));

ke
可以看到我们使用了opengl version 4.5.0, NVIDIA 516.94 是所用驱动版本，下面是较为完整的代码演示：

Window::Window(void)

  m_quit = false;

  if (SDL_Init(SDL_INIT_EVERYTHING & ~(SDL_INIT_TIMER | SDL_INIT_HAPTIC)) != 0)
  
    log_err("SDL_Init error: %s", SDL_GetError());
  

  SDL_DisplayMode mode;
  SDL_GetCurrentDisplayMode(0, &mode);

  SDL_GL_SetAttribute(SDL_GL_RED_SIZE, BITS_PER_CHANNEL);
  SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, BITS_PER_CHANNEL);
  SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, BITS_PER_CHANNEL);
  SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, BITS_PER_CHANNEL);
  SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, BITS_PER_CHANNEL * 4);
  SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, BITS_PER_CHANNEL * 2);
  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

#if defined(GLES3)
  log_info("Using GLES 3");
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#elif defined(GLES2)
  log_info("Using GLES 2");
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#elif defined(EMSCRIPTEN)
  log_info("Using GLES 2");
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#else
  log_info("Using GL 4");
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
#endif

  m_fullscreen = false;

  uint32_t flags = SDL_WINDOW_OPENGL;

  if (m_fullscreen) 
    flags |= SDL_WINDOW_FULLSCREEN;
  

  m_window = SDL_CreateWindow("Engine!", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, mode.w, mode.h, flags);
  if (m_window == nullptr)
  
    log_err("SDL_CreateWindow error: %s", SDL_GetError());
  

  m_glContext = SDL_GL_CreateContext(m_window);
  if (m_glContext == nullptr)
  
    log_err("SDL_GL_CreateContext error: %s", SDL_GetError());
  
  log_info("the opengl version get:%s",glGetString(GL_VERSION));
  SDL_GL_SetSwapInterval(0);

  int display_w, display_h;
  SDL_GL_GetDrawableSize(m_window, &display_w, &display_h);
  this->m_width = display_w;
  this->m_height = display_h;

  log_info("Window init to: %i x %i", this->m_width, this->m_height);