Setting up OpenGL with GLFW, GLEW

CMakeLists.txt

cmake_minimum_required (VERSION 2.8)
project (glfw_test)

find_package( glfw3 REQUIRED )
find_package( GLEW REQUIRED )
find_package( OpenGL REQUIRED )


set(CMAKE_CXX_FLAGS "-std=c++11")
add_executable( glDemo gl_test.cpp )

target_link_libraries( helloDemo glfw GLEW GL )

gl_test.cpp

#include <iostream>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <ctime>
#include <sys/time.h>

// Refer : http://www.learnopengl.com/
using namespace std;

void key_callback( GLFWwindow* window, int key, int scancode, int action, int mode )
{
    if( action == GLFW_PRESS )
        cout << "you pressed something..\n";

    if( action == GLFW_RELEASE )
        cout << "you released the key\n";

    if( key == GLFW_KEY_ESCAPE && action == GLFW_PRESS )
        glfwSetWindowShouldClose(window, GL_TRUE);
}

long get_time_micro()
{
    timeval curTime;
    gettimeofday(&curTime, NULL);
    long micro = curTime.tv_usec;
    return micro;
}

void flicker( bool& flag )
{
    if( flag )
    {
        glClearColor( 0.9f, 0.2f, 0.4f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        flag = false;
    }
    else
    {
        glClearColor( 0.2f, 0.9f, 0.4f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        flag = true;
    }
}

int main( int argc, char ** argv )
{
    // glfw-init
    glfwInit();
    glfwWindowHint( GLFW_CONTEXT_VERSION_MAJOR, 3 );
    glfwWindowHint( GLFW_CONTEXT_VERSION_MINOR, 3 );
    glfwWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
    glfwWindowHint( GLFW_RESIZABLE, GL_FALSE );

    // glfw-window make
    GLFWwindow * window = glfwCreateWindow(800,600, "LearnOpenGL", nullptr, nullptr);
    if( window == nullptr )
    {
        cout << "Failed to create glfw window\n";
        return 1;
    }
    glfwMakeContextCurrent(window);

    // glew-init
    glewExperimental = GL_TRUE;
    if( glewInit() != GLEW_OK )
    {
        cout << "Failed to init GLEW\n";
        return 1;
    }

    // set view-port
    int width, height;
    glfwGetFramebufferSize( window, &width, &height );
    glViewport(0,0, width, height );

    // setup call backs
    glfwSetKeyCallback( window, key_callback );


    // game-loop
    long prev = get_time_micro();
    bool flag = true;
    while( !glfwWindowShouldClose(window))
    {
        long curr = get_time_micro();
        printf( "%-2ld msec\n", (curr - prev)/1000 );
        prev = curr;

        // pool-events
        glfwPollEvents();

        long renderStart = get_time_micro();
        // render
        flicker( flag );

        // end rendering
        printf( "%-2ld micro-sec (render)\n", (get_time_micro() - renderStart) );

        // swap-buffers
        glfwSwapBuffers(window);
    }
    glfwTerminate();
    


    return 0;
}