/*
 *
 *  $Id$
 *
 *  This file is part of the Virtual Leaf.
 *
 *  The Virtual Leaf is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  The Virtual Leaf is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with the Virtual Leaf.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  Copyright 2010 Roeland Merks.
 *
 */


#ifndef _QCANVASARROW_H_
#define _QCANVASARROW_H_

#include <QGraphicsScene>

class QGraphicsArrowItem : public QGraphicsLineItem {

 public:
  QGraphicsArrowItem(QGraphicsItem *parent, QGraphicsScene *c) : QGraphicsLineItem(parent, c) {
  };
    
    void paint ( QPainter *p, const QStyleOptionGraphicsItem *option,
		 QWidget *widget ) {

      widget = NULL; //use assignment merely to obviate compilation warning
      option = NULL;

      // construct arrow head
      QPointF start=line().p1();
      QPointF end=line().p2();
      QPointF mid=start + (3./4.)*(end-start);
      
      double vx=end.x()-start.x();
      double vy=end.y()-start.y();

      double length = sqrt(vx*vx+vy*vy);
      if (length==0) return;
      
      // perpendicular vector
      double px=-vy/length;
      double py=vx/length;
      
      // Arrow head lines go from end point
      // to points about 3/4 of the total arrow, extending sideways about 1/4
      // of the arrow length.
      
      
      QPointF arwp1 = mid + QPointF( (int)( (length/4.)*px ),
				   (int)( (length/4.)*py ) );
      QPointF arwp2 = mid - QPointF( (int)( (length/4.)*px ),
				   (int)( (length/4.)*py ) );
      
      p->setPen(pen());
      // Draw arrow head
      p->drawLine( end, arwp1 );
      p->drawLine( end, arwp2 );
      // Draw arrow line
      p->drawLine( start, end);
    }
};

#endif