// OPEN_GL_test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

// Initial square position and size

GLfloat x1 = 0.0f;
GLfloat y1 = 0.0f;
GLfloat rsize = 25;

// Step size in x and y directions
// (number of pixels to move each time)
GLfloat xstep = 1.0f;
GLfloat ystep = 1.0f;

// Keep track of windows changing width and height
GLfloat windowWidth;
GLfloat windowHeight;

///////////////////////////////////////////////////////////

// Called to draw scene

void RenderScene(void)
    {
    // Clear the window with current clearing color
    glClear(GL_COLOR_BUFFER_BIT);
       // Set current drawing color to red
    //           R     G       B
    glColor3f(1.0f, 0.0f, 0.0f);

    // Draw a filled rectangle with current color
    glRectf(x1, y1, x1 + rsize, y1 - rsize);

	// Flush drawing commands and swap
    glutSwapBuffers();
    }
///////////////////////////////////////////////////////////

// Called by GLUT library when idle (window not being
// resized or moved)

void TimerFunction(int value)
    {    // Reverse direction when you reach left or right edge
    if(x1 > windowWidth-rsize || x1 < -windowWidth)
        xstep = -xstep;

	// Reverse direction when you reach top or bottom edge
    if(y1 > windowHeight || y1 < -windowHeight + rsize)
									        ystep = -ystep;
    // Actually move the square
    x1 += xstep;
    y1 += ystep;

    // Check bounds. This is in case the window is made
    // smaller while the rectangle is bouncing and the
    // rectangle suddenly finds itself outside the new
    // clipping volume
    if(x1 > (windowWidth-rsize + xstep))
				        x1 = windowWidth-rsize-1;
    else if(x1 < -(windowWidth + xstep))
					    x1 = - windowWidth -1;
    if(y1 > (windowHeight + ystep))
				        y1 = windowHeight-1;
    else if(y1 < -windowHeight + rsize - ystep)
						y1 = -windowHeight + rsize -1;

     // Redraw the scene with new coordinates
    glutPostRedisplay();
    glutTimerFunc(33,TimerFunction, 1);
    }

///////////////////////////////////////////////////////////
// Setup the rendering state

void SetupRC(void)
    {    // Set clear color to blue
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
    }
///////////////////////////////////////////////////////////
// Called by GLUT library when the window has changed size

void ChangeSize(GLsizei w, GLsizei h)
    {
    GLfloat aspectRatio;
    // Prevent a divide by zero
    if(h == 0)
	        h = 1;
    // Set Viewport to window dimensions
    glViewport(0, 0, w, h);

	// Reset coordinate system
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    // Establish clipping volume (left, right, bottom, top, near, far)
    aspectRatio = (GLfloat)w / (GLfloat)h;
    if (w <= h)
        {      windowWidth = 100;
		        windowHeight = 100 / aspectRatio;
	        glOrtho (-100.0, 100.0, -windowHeight, windowHeight, 1.0, -1.0);
        }
    else
        {       windowWidth = 100 * aspectRatio;
	        windowHeight = 100;
        glOrtho (-windowWidth, windowWidth, -100.0, 100.0, 1.0, -1.0);
        }

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();
    }

///////////////////////////////////////////////////////////

int _tmain(int argc, _TCHAR* argv[])
{
glutInit(&argc, (char **)argv);
 glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
 glutCreateWindow ((char *)argv[0]);
    //glutCreateWindow("Bounce");
    glutDisplayFunc(RenderScene);
    glutReshapeFunc(ChangeSize);
    glutTimerFunc(33, TimerFunction, 1);
    SetupRC();
    glutMainLoop();
return 0;
}