/*
CHEERS:

This program draws a few lines here and there in the window

And yes.... now you can resize or move the window
*/

# include <stdlib.h>
# include <GL/glut.h>


struct Color
{
    float r, g, b;
};


struct Point
{
    float x, y;
};


void DrawLine(struct Color color, struct Point p, struct Point q)
{
    glColor3f(color.r, color.g, color.b);

    glVertex2f(p.x, p.y);
    glVertex2f(q.x, q.y);
}


void Draw(void)
{
    struct Color color;
    struct Point p, q;

    //            r    g    b    a
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glLineWidth(1.0);
    glBegin(GL_LINES);

    color.r = 0.0;
    color.g = 0.0;
    color.b = 1.0;
    p.x = 50.0;
    p.y = 125.0;
    q.x = 200.0;
    q.y = 125.0;
    DrawLine(color, p, q);

    color.r = 1.0;
    color.g = 1.0;
    color.b = 1.0;
    p.x = 50.0;
    p.y = 150.0;
    q.x = 175.0;
    q.y = 150.0;
    DrawLine(color, p, q);

    color.r = 1.0;
    color.g = 0.0;
    color.b = 1.0;
    p.x = 50.0;
    p.y = 175.0;
    q.x = 150.0;
    q.y = 175.0;
    DrawLine(color, p, q);

    glEnd();

    //You can't set the line width in between begin and end
    glLineWidth(5.0);
    glBegin(GL_LINES);

    color.r = 1.0;
    color.g = 1.0;
    color.b = 0.0;
    p.x = 50.0;
    p.y = 50.0;
    q.x = 500.0;
    q.y = 50.0;
    DrawLine(color, p, q);

    color.r = 1.0;
    color.g = 1.0;
    color.b = 0.0;
    p.x = 50.0;
    p.y = 75.0;
    q.x = 400.0;
    q.y = 75.0;
    DrawLine(color, p, q);

    color.r = 1.0;
    color.g = 0.0;
    color.b = 1.0;
    p.x = 50.0;
    p.y = 100.0;
    q.x = 300.0;
    q.y = 100.0;
    DrawLine(color, p, q);

    glEnd();

    glFlush();
}


void OnWindowResize(int width, int height)
{
    //See how the output changes if you change left and top
    int left = 0;
    int bottom = 0;

// Feel free to to change/leave this macro
# define YOU_ARE_A_LAZY_PERSON 1

    glViewport(left, bottom, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    if(YOU_ARE_A_LAZY_PERSON) gluOrtho2D(0.0, width, 0.0, height);
	else gluOrtho2D(-width/2.0, width/2.0, -height/2.0, height/2.0);
}


void OnKeyPress(unsigned char key, int x, int y)
{
# define ESC_Key 27

    switch (key)
    {
        case ESC_Key:
            exit(0);
        break;
    }

    //printf("\nThe mouse is @..(%d, %d)\n", x, y);
}


int main(int argc, char** argv)
{
    const int left = 0;
    const int top = 0;
    const int width = 512;
    const int height = 256;

    const char* windowTitle = "A few of my world-famous lines";

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(width, height); 
    glutInitWindowPosition(left, top);
    glutCreateWindow(windowTitle);
    
    glutDisplayFunc(Draw);

    //NEW FUNCTIONS in this tutorial's main function 
    glutReshapeFunc(OnWindowResize);
    glutKeyboardFunc(OnKeyPress);


    glutMainLoop();

    return 0;
}

/*
Exercise: Draw a structure like this...

                        +-------+
                        | ^  ^  |
                        | o  o  |
                        |  __   |
                        +-------+
                            |
                        ----+---
                  \    /    |   \
                   \  /     |    \
                    \/      |     \
                            |      \
                            |       \
                           / \       \
                          /   \
                         /     \
                        /       \
                       /         \
                    ---           ---


*/



//
//                  MORAL of this tutorial:
//                 ~~~~~~~~~~~~~~~~~~~~~~~~
// When life gives you lines, you make line-man from it.
//