///////////////////////////////////////////////////////////////////
//
//	graphics0.cpp
//
//	Started in Pascal by Jeff Ondich on 1/25/95
//	Last modified 5/19/98
//
//
//	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 -lg++ -lgraphics++
//
//	You will need to hit the Enter key to end the program.
//
//	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.ignore()" 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.
//		6. After the cin.ignore() at the end of the main program, add
//
//			setrgbcolor( 1, 0, 0 );
//			flood();
//			flushgraphics();
//			cin.ignore();
//
//		   What do you expect will happen?  What does happen?
//
///////////////////////////////////////////////////////////////////


#include	<iostream.h>
#include	<gpc-graphics++.h>

const int radius = 20;
const int windowWidth = 600;
const int windowHeight = 600;
const int windowBottom = 100;
const int windowLeft = 100;

void StartGraphics( void );



///////////////////////////////////////////////////////////////////
//	main program
///////////////////////////////////////////////////////////////////

int main( void )
{
	StartGraphics();

	// "RGB" stands for red-green-blue.  The parameters for
	// setrgbcolor() can range in value from 0.0 to 1.0.  All
	// zeros gives you no red, no green, and no blue.

	setrgbcolor( 1.0, 0.0, 0.0 );
	circle( windowWidth / 2, windowHeight / 2, radius );
 

	// When you're done with drawing a particular object,
	// you need to call flushgraphics(), or you won't see
	// anything.  When you get to more complicated programs,
	// you can experiment leaving the flushgraphics() calls
	// out to see what happens.

	flushgraphics();


	cin.ignore();

	return( 0 );
}


///////////////////////////////////////////////////////////////////
//	StartGraphics initializes the graphics package
//	and opens a black window for drawing.
///////////////////////////////////////////////////////////////////

void StartGraphics( void )
{
	// Call initializegraphics only once during the program,
	// before you do any other graphics
   
 	initializegraphics();


	// Open a window and flood it with a black background.

	createwindow( windowLeft, windowBottom,
					windowLeft + windowWidth, windowBottom + windowHeight );
	setrgbcolor( 0.0, 0.0, 0.0 );
	flood(); 
	flushgraphics();
}