Very basic SDL2 OpenGL application

sdl2_opengl.cpp

#include <iostream>

#define _USE_MATH_DEFINES
#include <cmath>

#include <SDL2/SDL.h>
#include <SDL2/SDL_opengl.h>

const int SCREEN_WIDTH = 800;
const int SCREEN_HEIGHT = 600;

const int OPENGL_MAJOR_VERSION = 2;
const int OPENGL_MINOR_VERSION = 1;

const SDL_GLprofile OPENGL_PROFILE = SDL_GLprofile::SDL_GL_CONTEXT_PROFILE_CORE;

void perspectiveGL(GLdouble fovY, GLdouble aspect, GLdouble zNear, GLdouble zFar) {
	GLdouble fW, fH;
	fH = tan(fovY / 360 * M_PI) * zNear;
	fW = fH * aspect;
	glFrustum(-fW, fW, -fH, fH, zNear, zFar);
}

void Display_InitGL() {
	glShadeModel( GL_SMOOTH);
	glClearColor(0.2f, 0.2f, 0.2f, 0.2f);
	glEnable( GL_DEPTH_TEST);
}

int Display_SetViewport(int width, int height) {
	if (height == 0) {
		height = 1;
	}

	GLfloat ratio = (GLfloat) width / (GLfloat) height;

	glViewport(0, 0, (GLsizei) width, (GLsizei) height);
	glMatrixMode( GL_PROJECTION );
	glLoadIdentity();
	perspectiveGL(45.0f, ratio, 0.1f, 100.0f);
    glMatrixMode( GL_MODELVIEW );
	glLoadIdentity();

	return 1;
}

void Display_Render(SDL_Window* displayWindow) {
	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

	glLoadIdentity();
	glTranslatef(-1.5f, 0.0f, -6.0f);

	glBegin( GL_TRIANGLES );
	glColor4f(0, 1, 0, 1);
	glVertex3f(0.0f, 1.0f, 0.0f); /* Top */
    glColor4f(0, 0, 1, 1);
	glVertex3f(-1.0f, -1.0f, 0.0f); /* Bottom Left */
    glColor4f(1, 0, 0, 1);
	glVertex3f(1.0f, -1.0f, 0.0f); /* Bottom Right */
	glEnd();

	glTranslatef(3.0f, 0.0f, 0.0f);

	glBegin( GL_QUADS );
	glColor4f(0, 1, 0, 1);
	glVertex3f(-1.0f, 1.0f, 0.0f); /* Top Left */
	glColor4f(1, 1, 1, 1);
	glVertex3f(1.0f, 1.0f, 0.0f); /* Top Right */
	glColor4f(1, 0, 0, 1);
	glVertex3f(1.0f, -1.0f, 0.0f); /* Bottom Right */
	glColor4f(0, 0, 0, 1);
	glVertex3f(-1.0f, -1.0f, 0.0f); /* Bottom Left */
	glEnd();

	SDL_GL_SwapWindow(displayWindow);
}

int main(int argc, char *argv[]) {

	if (SDL_Init( SDL_INIT_VIDEO) < 0) {
		std::cerr << "There was an error initing SDL2: " << SDL_GetError() << std::endl;
		return 1;
	}

	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, OPENGL_PROFILE);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, OPENGL_MAJOR_VERSION);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, OPENGL_MINOR_VERSION);

	SDL_Window* displayWindow = SDL_CreateWindow("SDL2 OpenGL test", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, SCREEN_WIDTH,
			SCREEN_HEIGHT, SDL_WINDOW_OPENGL);

	if (displayWindow == NULL) {
		std::cerr << "There was an error creating the window: " << SDL_GetError() << std::endl;
		return 1;
	}

	SDL_GLContext context = SDL_GL_CreateContext(displayWindow);

	if (context == NULL) {
		std::cerr << "There was an error creating OpenGL context: " << SDL_GetError() << std::endl;
		return 1;
	}

	const unsigned char *version = glGetString(GL_VERSION);
	if (version == NULL) {
		std::cerr << "There was an error with OpenGL configuration:" << std::endl;
		return 1;
	}

	SDL_GL_MakeCurrent(displayWindow, context);

	Display_InitGL();
	Display_SetViewport(SCREEN_WIDTH, SCREEN_HEIGHT);
	Display_Render(displayWindow);

    SDL_Event event;

    while( true ) {
        while( SDL_PollEvent(&event) ) {
            if ( event.type == SDL_QUIT ) {
                SDL_GL_DeleteContext(context);
	            SDL_Quit();
                return 0;
            }
        }
        SDL_Delay(10);
	    Display_Render(displayWindow);
    }
}