#include "glut.h"

/* global variable declarations */

GLint window1, window2;

/* function declarations ----------------------------------*/

void myInit(){

    glClearColor(0.0, 0.0, 0.0, 1.0);
    glColor3f(1.0, 1.0, 1.0);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-1.0, 1.0, -1.0, 1.0);

} // end of myInit()

/* --------------------------------------------------------*/

void myReshape(int w, int h){

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if ( w <= h ) {  
		// redraw based on shortest side being 2 units
        gluOrtho2D(-1.0, 1.0,
			       -1.0 * (GLfloat) h / (GLfloat) w, 1.0 * (GLfloat) h / (GLfloat) w);
    } else {
        gluOrtho2D(-1.0 * (GLfloat) w / (GLfloat) h, 1.0 * (GLfloat) w / (GLfloat) h,
			       -1.0, 1.0);
	}
    glMatrixMode(GL_MODELVIEW);

	glViewport(0, 0, w, h);
} // end of myReshape()

/* --------------------------------------------------------*/

void myDisplay1()
{
    GLfloat upleftx = -1.0,
            uplefty = 1.0,
            botrightx = 1.0,
            botrighty = -1.0;

    glClear(GL_COLOR_BUFFER_BIT);

	glColor3f(1.0, 0.0, 0.0);
    glBegin(GL_LINES);
        glVertex2f(upleftx, uplefty);
        glVertex2f(botrightx, botrighty);

        glVertex2f(upleftx, botrighty);
        glVertex2f(botrightx, uplefty);
    glEnd();

    glBegin(GL_LINE_LOOP);
	    glVertex2f(upleftx, uplefty);
	    glVertex2f(upleftx, botrighty);
	    glVertex2f(botrightx, botrighty);
	    glVertex2f(botrightx, uplefty);
	glEnd();

	glFlush();
} // end of myDisplay1()

void myDisplay2()
{
    GLfloat upleftx = -1.0,
            uplefty = 1.0,
            botrightx = 1.0,
            botrighty = -1.0;

    glClear(GL_COLOR_BUFFER_BIT);

	glColor3f(0.0, 1.0, 1.0);
    glBegin(GL_LINES);
        glVertex2f(upleftx, uplefty);
        glVertex2f(botrightx, botrighty);

        glVertex2f(upleftx, botrighty);
        glVertex2f(botrightx, uplefty);
    glEnd();

    glBegin(GL_LINE_LOOP);
	    glVertex2f(upleftx, uplefty);
	    glVertex2f(upleftx, botrighty);
	    glVertex2f(botrightx, botrighty);
	    glVertex2f(botrightx, uplefty);
	glEnd();

	glFlush();
} // end of myDisplay2()

/* --------------------------------------------------------*/

int main(int argc, char **argv)
{
    glutInit(&argc, argv);

    /* set up first window */

    glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
    glutInitWindowSize(200, 200);
    glutInitWindowPosition(30, 30);
    window1 = glutCreateWindow("window # 1");

    /* register callback functions */
    glutDisplayFunc( myDisplay1 );
	glutReshapeFunc( myReshape );

    /* set up second window */

    glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
    glutInitWindowSize(200, 200);
    glutInitWindowPosition(300, 30);
    window2 = glutCreateWindow("window # 2");

    /* register callback functions */
    glutDisplayFunc( myDisplay2 );
	glutReshapeFunc( myReshape );

    /* start the event loop */
    myInit();
    glutMainLoop();

    return 0;
} // end of main