/* -*-ePiX-*- */
#include "epix.h"
using namespace ePiX;

void Arrow(const P& tail, const P& head, double t = 0.5)
{
  P tmp(tail + t*(head - tail));
  line(tmp, head);
  arrow(tail, tmp);
}

void Arrow(const P& tail, const P& head, double t,
	   const P& offset, const std::string& msg, epix_label_posn al)
{
  P tmp(tail + t*(head - tail));
  line(tmp, head);
  arrow(tail, tmp);

  label(tmp, offset, msg, al);
}

int main()
{
  picture(P(-2, -2), P(4, 2), "4.5 x 3in");

  begin();
  arrow_width(6);
  arrow_ratio(2);
  arrow_inset(0.75);

  P O(0, 0), pP(1.25, 0.5), pQ(0.75, 1.5), pR(pP + pQ), pS(pR.x1(), pP.x2());

  bold();

  line(P(xmin(), 0), P(xmax(), 0));
  line(P(0, ymin()), P(0, ymax()));

  line(pP, pP & E_1);
  line(pQ, pQ & E_1);
  line(pR, pR & E_1);
  line(pP, pS);

  Arrow(O, pP, 0.8);
  Arrow(O, pQ, 0.8);

  label(P(xmin(), 0), P(0, -4), "$X'$", b);
  label(P(xmax(), 0), P(0, -4), "$X$", b);

  label(P(0, ymin(), 0), P(-2, 0), "$Y'$", l);
  label(P(0, ymax(), 0), P(-2, 0), "$Y$", l);

  label(O, P(-2, -4), "$O$", bl);

  label(pP & E_1, P(0, -4), "$M$", b);
  label(pQ & E_1, P(0, -4), "$M_{1}$", b);
  label(pR & E_1, P(0, -4), "$M'$", b);

  label(pP, P(-2, 2), "$P$", tl);
  label(pQ, P(-2, 2), "$Q$", tl);
  label(pR, P(2, 2), "$R$", tr);
  label(pS, P(2, 0), "$S$", r);

  dashed();
  dash_size(2);
  line(pP, pR);
  line(pQ, pR);

  Arrow(O, pR, 0.8);

  tikz_format();
  end();
}