///////////////////////////////////////////////////////////////////
//
//	graphics3.cpp
//
//	Started in Pascal by Jeff Ondich on 1/25/95
//	Last modified 1/19/00
//
//	1. Compile it, run it, and figure out how it works.
//
//	2. Complain about the flickering.
//
//	3. To slow the motion down or speed it up,
//		change the value to which the delay
//		loop (that is, the for-loop inside the
//		while-loop) counts.
//
//	4. Try to get the ball to bounce from side to
//		side instead of up and down.
//
//	6. Can you get the colors to change gradually
//		from red to blue instead of abruptly?
//
///////////////////////////////////////////////////////////////////

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

const int windowHeight = 600;
const int windowWidth = 600;
const int circleRadius = 50;

// Prototypes

void NewCenter( int window, int& horiz, int& vert, bool& goingUp, int& ink ); 


int main()
{
	//////////////////////////////////////
	// Open the window.
	//////////////////////////////////////

	int window = g2_open_X11( windowWidth, windowHeight );
	int background_ink = g2_ink( window, 1, 1, 1 );
	g2_set_background( window, background_ink );

	cout << "Click in this window and hit Ctrl-C to stop." << endl;

	//////////////////////////////////////
	// Do the animation.
	//////////////////////////////////////

	int		x = windowWidth / 2;
	int		y = circleRadius;
	bool	goingUp = true;
	int		circle_ink = g2_ink( window, 1, 0, 0 );

	// This is an intentionally infinite loop.

	while( true )
	{
		// Draw the circle
		g2_pen( window, circle_ink );
		g2_circle( window, x, y, circleRadius );

		// Wait a while
		for( int i=0; i < 100000; i++ )
		{
		}

		// Erase the circle
		g2_pen( window, background_ink );
		g2_circle( window, x, y, circleRadius );

		// Move the circle
		NewCenter( window, x, y, goingUp, circle_ink );
	}

	return( 0 );
}


void NewCenter( int window, int& horiz, int& vert, bool& goingUp, int& ink ) 
{
	if( goingUp )
		vert = vert + 1;
	else
		vert = vert - 1;
	
	if( vert >= windowHeight - circleRadius )
	{
		goingUp = false;
		ink = g2_ink( window, 0, 0, 1 );
	}

	else if( vert <= circleRadius )
	{
		goingUp = true;
		ink = g2_ink( window, 1, 0, 0 );
	}
}