package org.opentrafficsim.graphs;
   
   import java.awt.event.MouseEvent;
   import java.awt.event.MouseListener;
   import java.awt.event.MouseMotionListener;
   import java.awt.geom.Point2D;
   
   import org.jfree.chart.ChartPanel;
   import org.jfree.chart.event.PlotChangeEvent;
  import org.jfree.chart.plot.PlotRenderingInfo;
  import org.jfree.chart.plot.XYPlot;
  
  /**
   * Handle mouse events for a graph.
   * <p>
   * Copyright (c) 2013-2018 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * <p>
   * $LastChangedDate: 2015-07-26 01:01:13 +0200 (Sun, 26 Jul 2015) $, @version $Revision: 1155 $, by $Author: averbraeck $,
   * initial version Aug 13, 2014 <br>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   */
  abstract class PointerHandler implements MouseListener, MouseMotionListener
  {
  
      /** {@inheritDoc} */
      @Override
      public void mouseDragged(final MouseEvent e)
      {
          // No action
      }
  
      /** {@inheritDoc} */
      @Override
      public void mouseMoved(final MouseEvent mouseEvent)
      {
          final ChartPanel cp = (ChartPanel) mouseEvent.getSource();
          final XYPlot plot = (XYPlot) cp.getChart().getPlot();
          // Show a cross hair cursor while the mouse is on the graph
          final boolean showCrossHair = cp.getScreenDataArea().contains(mouseEvent.getPoint());
          if (cp.getHorizontalAxisTrace() != showCrossHair)
          {
              cp.setHorizontalAxisTrace(showCrossHair);
              cp.setVerticalAxisTrace(showCrossHair);
              plot.notifyListeners(new PlotChangeEvent(plot));
          }
          if (showCrossHair)
          {
              Point2D p = cp.translateScreenToJava2D(mouseEvent.getPoint());
              PlotRenderingInfo pi = cp.getChartRenderingInfo().getPlotInfo();
              updateHint(plot.getDomainAxis().java2DToValue(p.getX(), pi.getDataArea(), plot.getDomainAxisEdge()),
                      plot.getRangeAxis().java2DToValue(p.getY(), pi.getDataArea(), plot.getRangeAxisEdge()));
          }
          else
          {
              updateHint(Double.NaN, Double.NaN);
          }
      }
  
      /**
       * Called when the pointer is positioned inside the data area of the graph, or when it leaves the data area. <br>
       * When the mouse is outside the data area both parameters are set to Double.NaN.
       * @param domainValue Double; the X-value (in domain units), or Double.NaN if the pointer is outside the data area
       * @param rangeValue Double; the Y-value (in domain units), or Double.NaN if the pointer is outside the data area
       */
      abstract void updateHint(double domainValue, double rangeValue);
  
      /** {@inheritDoc} */
      @Override
      public void mouseClicked(final MouseEvent e)
      {
          // No action
      }
  
      /** {@inheritDoc} */
      @Override
      public void mousePressed(final MouseEvent e)
      {
          // No action
      }
  
      /** {@inheritDoc} */
      @Override
      public void mouseReleased(final MouseEvent e)
      {
          // No action
      }
  
      /** {@inheritDoc} */
      @Override
      public void mouseEntered(final MouseEvent e)
      {
          // No action
      }
  
      /** {@inheritDoc} */
      @Override
      public void mouseExited(final MouseEvent mouseEvent)
      {
         final ChartPanel cp = (ChartPanel) mouseEvent.getSource();
         final XYPlot plot = (XYPlot) cp.getChart().getPlot();
         // Remove the cross hair cursor when the cursor moves outside the graph
         if (cp.getHorizontalAxisTrace())
         {
             cp.setHorizontalAxisTrace(false);
             cp.setVerticalAxisTrace(false);
             plot.notifyListeners(new PlotChangeEvent(plot));
         }
         updateHint(Double.NaN, Double.NaN); // Clear the hint text
     }
 }