SDL2 + OpenGL2.1 Template

sdl-gl-main-template.cpp

///
///  main.cpp
///  SDL 2 + OpenGL 2.1 
///  Template
///
///  Created by Michael Wildman on 16/08/14.
///  Copyright (c) 2014 Michael Wildman. All rights reserved.
///

#include <iostream>
#include <SDL2/sdl.h>
#include <SDL2/SDL_opengl.h>
#include <OpenGl/glu.h>


// Function stubs
bool init();
bool initGL();
void handleKeys(unsigned char key, GLint x, GLint y);
void update();
void render();
void close();

// Global variables
const GLint WINDOW_WIDTH = 800;
const GLint WINDOW_HEIGHT = 600;

SDL_Window* sdlWindow = NULL;
SDL_GLContext sdlGlContext;

///
/// Main program entry point
///
int main(int argc, char* argv[])
{
    if (!init())
    {
        std::cout << "Failed to initialize!" << std::endl;
    }
    else
    {
        bool quit = false;  // Main loop flag
        SDL_Event e;        // Event handler
        
        SDL_StartTextInput();
        
        // Main loop
        while (!quit)
        {
            while (SDL_PollEvent(&e) != 0)
            {
                // User requests quit
                if (e.type == SDL_QUIT)
                {
                    quit = true;
                }
                // Handle keypress with mouse position
                else if (e.type == SDL_TEXTINPUT)
                {
                    GLint x = 0, y = 0;
                    SDL_GetMouseState(&x, &y);
                    
                    handleKeys(e.text.text[0], x, y);
                }
            }
            
            // OpenGL render
            render();
            
            // Update the screen
            SDL_GL_SwapWindow(sdlWindow);
        }
        
        SDL_StopTextInput();
    }
    
    close();
    
    return 0;
}



///
/// Handle keypress with mouse position
///
void handleKeys(unsigned char key, GLint x, GLint y)
{
     // Keypress handling here!
}

///
/// Per frame game state update
///
void update()
{
    // update state here!

}

///
/// OpenGL rendering
///
void render()
{
    
    glClear(GL_COLOR_BUFFER_BIT);
    glPointSize(5);
    
    glColor3f(0.0, 0.0, 0.0);
    
    glBegin(GL_POINTS);
    
    glVertex2f(0.0, 0.0);
    
    glVertex2f(10.0, 0);
    
    glEnd();
    
}

// Initialize everything
bool init()
{
    bool success = true;
    
    if (SDL_Init(SDL_INIT_VIDEO) < 0)
    {
        std::cout << "SDL could not initialize! SDL Error: " << SDL_GetError() << std::endl;
        success = false;
    }
    else
    {
        // Use OpenGL2.1
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
        
        if ((sdlWindow = SDL_CreateWindow("SDL Window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL)) == NULL)
        {
            std::cout << "Window could not be created! SDL Error: " << SDL_GetError() << std::endl;
            success = false;
        }
        else
        {
            if ((sdlGlContext = SDL_GL_CreateContext(sdlWindow)) == NULL)
            {
                std::cout << "OpenGL context could not be created! SDL Error: " << SDL_GetError() << std::endl;
                success = false;
            }
            else
            {
                // Use Vsync (allowed to fail)
                if (SDL_GL_SetSwapInterval(1) < 0)
                {
                    std::cout << "Warning: Unable to set VSync! SDL Error: " << SDL_GetError() << std::endl;
                }
                
                if (!initGL())
                {
                    std::cout << "Unable to initialize OpenGL! SDL Error: " << SDL_GetError() << std::endl;
                    success = false;
                }
            }
        }
    }
    
    return success;
}

// Initialize OpenGL (Projection, ModelView, ClearColor)
bool initGL()
{
    bool success = true;
    GLenum error = GL_NO_ERROR;
    
    // Initialize gl projection matrix
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    
    if ((error = glGetError()) != GL_NO_ERROR)
    {
        std::cout << "Error initializing OpenGL! " << std::endl << gluErrorString(error) << std::endl;
        success = false;
    }
    
    // Initialize Modelview matrix
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    if ((error = glGetError()) != GL_NO_ERROR)
    {
        std::cout << "Error initializing OpenGL! " << std::endl << gluErrorString(error) << std::endl;
        success = false;
    }
    
    // Set clear color
    glClearColor(1.f, 1.f, 1.f, 0.f);
    
    if ((error = glGetError()) != GL_NO_ERROR)
    {
        std::cout << "Error initializing OpenGL! " << std::endl << gluErrorString(error) << std::endl;
        success = false;
    }
    
    return success;
}

// Shutdown SDL
void close()
{
    SDL_DestroyWindow(sdlWindow);
    sdlWindow = NULL;
    
    SDL_Quit();
}