Using glfw and glew - c++

Question

I have problem understanding some opengl stuff using GLFW and GLEW.
i have 3 files shown below:
main.cpp:
#include "gamewindow.h"
int main() {
GameWindow *gameWindow = new GameWindow(1024, 768, "FirstOpenGLGame");
/* Loop until the user closes the window */
while (gameWindow->getRunning()) {
/* Render here */
gameWindow->render();
gameWindow->update();
gameWindow->setRunning();
}
delete gameWindow;
glfwTerminate();
return 0;
}
This is where the problem is, gamewindow.cpp:
#include "gamewindow.h"
GameWindow::GameWindow(int width, int height, const char* title) : _running(true), _height(1024), _width(1024 * (16/9))
{
/* Initialize the library */
/* Create a windowed mode window and its OpenGL context */
window = glfwCreateWindow(width, height, title, NULL, NULL);
if(!window) {
glfwTerminate();
exit(0);
}
/* Make the window's context current */
glfwMakeContextCurrent(window);
if(!glewInit()){ // <-- problem is this
glfwTerminate();
exit(EXIT_FAILURE);
}
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
coordSettings();
}
void GameWindow::setRunning() {
_running = !glfwWindowShouldClose(window);
}
bool GameWindow::getRunning() {
return _running;
}
void GameWindow::render() {
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0f, 0.0f, 0.0f);
glBegin(GL_QUADS);
glVertex2d(0.0f, 0.0f);
glVertex2d(100.0f, 0.0f);
glVertex2d(100.0f, 800.0f);
glVertex2d(0.0f, 800.0f);
glEnd();
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
void GameWindow::update() {
}
void GameWindow::coordSettings() {
glViewport( 0, 0, _width, _height );
glMatrixMode(GL_PROJECTION);
glOrtho(0.0, _width, 0.0, _height, 0.0, -1.0);
glMatrixMode(GL_MODELVIEW);
}
and last the header file gamewindow.h:
#ifndef GAMEWINDOW_H
#define GAMEWINDOW_H
#include <iostream>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
class GameWindow
{
private:
GLFWwindow* window;
bool _running;
GLfloat _width;
GLfloat _height;
void coordSettings();
public:
GameWindow(int width, int height, const char* title);
void setRunning();
bool getRunning();
void render();
void update();
};
#endif // GAMEWINDOW_H
everything works fine, but then i try to call glewInit() (without really understanding is i need to, or when i need to) but then nothing works. the program starts, but there is no window with a quad in it, like before. why is this? how is GLEW even used, and do i need it?