// GLRect.c
// Just draw a single rectangle in the middle of the screen
// OpenGL SuperBible, 3rd Edition
// Richard S. Wright Jr.
// rwright@starstonesoftware.com

#include "../common/openglsb.h"

///////////////////////////////////////////////////////////
// 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(-25.0f, 25.0f, 25.0f, -25.0f);

	// Flush drawing commands
    glFlush();
	}


///////////////////////////////////////////////////////////
// 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 chanaged size
void ChangeSize(int w, int 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) 
		glOrtho (-100.0, 100.0, -100 / aspectRatio, 100.0 / aspectRatio, 1.0, -1.0);
    else 
		glOrtho (-100.0 * aspectRatio, 100.0 * aspectRatio, -100.0, 100.0, 1.0, -1.0);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	}

///////////////////////////////////////////////////////////
// Main program entry point
int main(int argc, char* argv[])
    {
        glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
        glutInitWindowSize(800, 600);
	glutCreateWindow("GLRect");
	glutDisplayFunc(RenderScene);
        glutReshapeFunc(ChangeSize);
	SetupRC();
	glutMainLoop();
        
        return 0;
    }