#include <iostream>
#include <winbgim.h>

// prototypes
void update_pen_color(int &c);
void draw_pixel(int c);

// constants
// (Note:  This is an alternative way of defining constants instead of
// using "const int".)
#define XDIM 500
#define YDIM 400
#define PEN_UP -1

int main()
{
    int pen_color = PEN_UP; // PEN_UP means no drawing will be performed

    initwindow(XDIM, YDIM); // open graphics window
    do 
    {
	update_pen_color(pen_color);
	draw_pixel(pen_color);
    } while (!kbhit()); // loop until user hits a key
}

// This routine sets the color to red as long as the left mouse button
// is held down, and the color to blue as long as the right mouse button
// is held down.  If both buttons are held down, the color becomes magenta
// (= red + blue).
//
// The "if" statements check to see if a mouse button press or release
// has occurred since this routine was last called.  After the color is 
// adjusted appropriately, the flag is cleared to indicate that the mouse
// button press/release has been processed.

void update_pen_color(int &c)
{
    if (ismouseclick(WM_LBUTTONDOWN))
    {
	c = (c == PEN_UP ? RED : MAGENTA);
	clearmouseclick(WM_LBUTTONDOWN);
    }
    if (ismouseclick(WM_LBUTTONUP))
    {
	c = (c == RED ? PEN_UP : BLUE);
	clearmouseclick(WM_LBUTTONUP);
    }
    if (ismouseclick(WM_RBUTTONDOWN))
    {
	c = (c == PEN_UP ? BLUE : MAGENTA);
	clearmouseclick(WM_RBUTTONDOWN);
    }
    if (ismouseclick(WM_RBUTTONUP))
    {
	c = (c == BLUE ? PEN_UP : RED);
	clearmouseclick(WM_RBUTTONUP);
    }
}

// This routine colors a pixel at the current mouse location using
// the current pen color.

void draw_pixel(int c)
{
    int mx, my;

    if (c != PEN_UP)  // don't draw if the pen is lifted up (no mouse
    {                 // buttons are pressed)

       // get mouse location
       mx = mousex();
       my = mousey();

       // color pixel at mouse location with that color
       putpixel(mx, my, c);
    }
}