OpenGL - Not getting background color - c++

Question

I am trying to build a simple OpenGL application in C++. I am using FLTK to build a Window, and within that I am drawing using OpenGL. The following is my code:
// Make the GUI here
#define WIN32
#include <GL/glew.h>
#include <GL/glut.h>
#include <FL/gl.h>
#include <FL/Fl.H>
#include <FL/Fl_Double_Window.H>
#include <FL/Fl_Color_Chooser.H>
#include <FL/Fl_Gl_Window.H>
#include <FL/Fl_Menu_Bar.H>
#include <FL/fl_draw.H>
#include <FL/Fl_Button.H>
class Block
{
public:
Block(int x, int y, int z)
{
xyz[0] = x;
xyz[1] = y;
xyz[2] = z;
}
int getX(){ return xyz[0];}
int getY(){ return xyz[1];}
int getZ(){ return xyz[2];}
void setX(int x){ xyz[0]=x;}
void setY(int y){ xyz[1]=y;}
void setZ(int z){ xyz[2]=z;}
private:
int xyz[3];
};
// Snake is an array blocks.
Block* snake;
// Mouse is a single block
Block* mouse;
void renderEverything();
class GlWindow : public Fl_Gl_Window
{
public:
// Call back for draw
void draw()
{
glTranslatef(0.0f,0.0f, -10.0f);
// Get the current state of the universe and draw it
glClearColor(1.0f, 0.0f, 0.0f, 1.0f); // Clear the background of our window to red
glClear(GL_COLOR_BUFFER_BIT); //Clear the colour buffer (more buffers later on)
glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations
// Render everything
renderEverything();
//glutSolidCube(5);
glFlush(); // Flush the OpenGL buffers to the window
}
// To handle key-events
void handle()
{
}
// Constructor
GlWindow(int X, int Y, int W, int H, const char* L=0): Fl_Gl_Window(X,Y,W,H,L)
{
}
};
void renderEverything()
{
glBegin(GL_QUADS);
glVertex3f(-1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();
}
void buildGUI(int argc, char** argv)
{
// Main Window
Fl_Double_Window *window = new Fl_Double_Window(800,500);
window->label("Snake3D");
window->color(FL_LIGHT3);
window->begin();
// Menu Bar
Fl_Menu_Bar* menubar = new Fl_Menu_Bar(0,0,800,30);
menubar->color(FL_LIGHT3);
menubar->down_color(fl_rgb_color(0,145,255));
menubar->box(FL_THIN_UP_BOX);
menubar->add("File/Exit");
menubar->add("Help/About");
// OpenGL Window
GlWindow* gameWindow = new GlWindow(200,30,600,470);
// Start Button
Fl_Button* startButton = new Fl_Button(50,200,100,30,"Start");
Fl_Button* pauseButton = new Fl_Button(50,300,100,30,"Pause");
window->show();
window->end();
Fl::run();
}
int main(int argc, char ** argv)
{
// Build GUI
buildGUI(argc,argv);
}
According to the tutorial I am following, I should get a red background. But only half of my screen is colored
What might be going wrong?