///////////////////////////////////////////////////////////////////
//
//	graphics0.cpp
//
//	Started in Pascal by Jeff Ondich on 1/25/95
//	Last modified 1/17/00
//
//
//	This program opens a graphics window, fills it with a black
//	background, and draws a red circle in the center.
// 
//	To compile this program, use the following command:
//  	
//	g++ -o graphics0 graphics0.cpp -L/usr/X11R6/lib -lm -lX11 -lgd -lg2
//
//	Try doing these things:
//
//	0. Compile and run the program as it is.
//	1. Read the whole program to find out how it works.
//	2. What happens if you remove the "cin.get()" at the
//	   end of the main program?
//	3. Modify the code to draw a tall and skinny graphics
//	   window.  Where does the circle get drawn when you
//	   run your new version of the program?  Why?
//	4. Change the background color.  Can you make it white?
//	5. Make the circle green.
//
///////////////////////////////////////////////////////////////////

#include <iostream>
#include <g2++.h>
#include <g2_X11++.h>

const int windowHeight = 500;
const int windowWidth = 500;
const int circleRadius = 100;

int main()
{
	/////////////////////////////////////
	// I. Open a graphics window on
	// screen.  Save the return value
	// of g2_open_X11.  This return value
	// will enable you to tell the
	// drawing operations which window
	// you want to draw in.
	/////////////////////////////////////

	int window = g2_open_X11( windowWidth, windowHeight );


	/////////////////////////////////////
	// II. Define some colors.  To do
	// color graphics, you specify
	// a color through an integer
	// constructed by the g2_ink
	// function.  The parameters of
	// g2_ink include three real numbers
	// between 0.0 and 1.0, representing
	// the amount of red, green, and
	// blue in the color.  So (0,0,0)
	// means no color (black), (1,0,1)
	// means a shade of purple, and
	// (.5,0,.5) is darker purple, etc.
	/////////////////////////////////////

	int black_ink = g2_ink( window, 0, 0, 0 );
	int red_ink = g2_ink( window, 1, 0, 0 );


	/////////////////////////////////////
	// III. Clear the window, giving it
	// a background the color of your
	// choosing.
	/////////////////////////////////////

	g2_set_background( window, black_ink );


	/////////////////////////////////////
	// IV.  Draw.
	/////////////////////////////////////

	g2_pen( window, red_ink );
	g2_filled_circle( window, windowWidth / 2, windowHeight / 2, circleRadius );
 

	/////////////////////////////////////
	// V. Wait for user input before
	// closing the window and finishing
	// the program.
	/////////////////////////////////////

	cout << "Click in this terminal window and "
		<< "hit return when you're done." << endl;

	cin.get();


	/////////////////////////////////////
	// VI. Clean up after yourself by
	// closing the graphics window.
	/////////////////////////////////////

	g2_close(window);

	return( 0 );
}