OpenGLWindow.c

#include <stdio.h>
#include <stdlib.h>
/* If using gl3.h */
/* Ensure we are using opengl's core profile only */
#define GL3_PROTOTYPES 1
#include <GL3/gl3.h>

#include <SDL.h>
#define PROGRAM_NAME "Tutorial1"

/* A simple function that prints a message, the error code returned by SDL,
* and quits the application */
void sdldie(const char *msg)
{
  printf("%s: %s\n", msg, SDL_GetError());
  SDL_Quit();
  exit(1);
}


void checkSDLError(int line = -1)
{
  #ifndef NDEBUG
  const char *error = SDL_GetError();
  if (*error != '\0')
    {
      printf("SDL Error: %s\n", error);
      if (line != -1)
        printf(" + line: %i\n", line);
        SDL_ClearError();
      }
      #endif
    }


    /* Our program's entry point */
    int main(int argc, char *argv[])
    {
      SDL_Window *mainwindow; /* Our window handle */
      SDL_GLContext maincontext; /* Our opengl context handle */

      if (SDL_Init(SDL_INIT_VIDEO) < 0) /* Initialize SDL's Video subsystem */
        sdldie("Unable to initialize SDL"); /* Or die on error */

        /* Request opengl 3.2 context.
        * SDL doesn't have the ability to choose which profile at this time of writing,
        * but it should default to the core profile */
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

        /* Turn on double buffering with a 24bit Z buffer.
        * You may need to change this to 16 or 32 for your system */
        SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
        SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

        /* Create our window centered at 512x512 resolution */
        mainwindow = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
        512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
        if (!mainwindow) /* Die if creation failed */
          sdldie("Unable to create window");

          checkSDLError(__LINE__);

          /* Create our opengl context and attach it to our window */
          maincontext = SDL_GL_CreateContext(mainwindow);
          checkSDLError(__LINE__);


          /* This makes our buffer swap syncronized with the monitor's vertical refresh */
          SDL_GL_SetSwapInterval(1);

          /* Clear our buffer with a red background */
          glClearColor ( 1.0, 0.0, 0.0, 1.0 );
          glClear ( GL_COLOR_BUFFER_BIT );
          /* Swap our back buffer to the front */
          SDL_GL_SwapWindow(mainwindow);
          /* Wait 2 seconds */
          SDL_Delay(2000);

          /* Same as above, but green */
          glClearColor ( 0.0, 1.0, 0.0, 1.0 );
          glClear ( GL_COLOR_BUFFER_BIT );
          SDL_GL_SwapWindow(mainwindow);
          SDL_Delay(2000);

          /* Same as above, but blue */
          glClearColor ( 0.0, 0.0, 1.0, 1.0 );
          glClear ( GL_COLOR_BUFFER_BIT );
          SDL_GL_SwapWindow(mainwindow);
          SDL_Delay(2000);

          /* Delete our opengl context, destroy our window, and shutdown SDL */
          SDL_GL_DeleteContext(maincontext);
          SDL_DestroyWindow(mainwindow);
          SDL_Quit();

          return 0;
        }