// File: spinmen.cxx
// Written by Michael Main (main@colorado.edu)
// This program opens a large, square graphics window and
// draws five tilted snowmen of various sizes and locations.
// The program then does an animation (with double buffering),
// so that the snowmen's heads spin around their bodies.

// Directives:
#include <cmath>
#include <cstdlib>
#include <iostream>
#include <graphics.h>
using namespace std;

// Named constants:
const int S = 500; // Width and height of the graphics window.
const int X3 = int(0.93*S);

// Prototypes:
// This function draws a snowman with the center of the body
// at (x,y), the radius of the body given by the 3rd
// paramter. The head is at an angle of theta radians from the
// center of the body (with 0 radians being to the right),
// and the head has a radius that is half that of the body.
void draw_snowman(int x, int y, int radius, float theta);

// Function definitions:
//----------------------------------------------------------
int main( )
{
    double delta = 0.0; // How far have the head's spun so far?
    
    // 1. Initialize the graphics window w/double buffering:
    initwindow(S, S, "At the north pole!", 0, 0, true);

    while (true)
    {
	// 2-1. Draw five tilted snowmen:
	clearviewport( );
	draw_snowman(S/5, S/3, S/17, M_PI/2 + delta);
	draw_snowman(S/5, 2*S/3, S/50, M_PI/4 + delta);
	draw_snowman(X3, int(0.64*S), S/6, -M_PI/2 + delta); 
	draw_snowman(int(0.88*S), int(0.12*S), S/73, 3.14159 + delta);
	draw_snowman(int(0.66*S), int(0.1*S), S/39, 0 + delta);

	// 2-2. Swap and delay:
	swapbuffers( );
	delay(1000/30); // One 30th of a second

	// 2-3. Computations for next frame:
	delta -= 0.1;
    }

    // 3. Finish:
    return EXIT_SUCCESS;
}
//----------------------------------------------------------

//----------------------------------------------------------
void draw_snowman(int x, int y, int radius, float theta)
{
    int hradius = radius/2;
    int d = radius + hradius;
    int hx = int(x + d*cos(theta));
    int hy = int(y - d*sin(theta));

    circle(x, y, radius);    // This draws the body
    circle(hx, hy, hradius); // This draws the head
}
//----------------------------------------------------------