Package com.mxgraph.view

Source Code of com.mxgraph.view.mxGraph

/**
* $Id: mxGraph.java,v 1.306 2010-09-20 06:21:37 gaudenz Exp $
* Copyright (c) 2007, Gaudenz Alder
*/
package com.mxgraph.view;

import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Shape;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.w3c.dom.Element;

import com.mxgraph.canvas.mxGraphics2DCanvas;
import com.mxgraph.canvas.mxICanvas;
import com.mxgraph.canvas.mxImageCanvas;
import com.mxgraph.model.mxCell;
import com.mxgraph.model.mxGeometry;
import com.mxgraph.model.mxGraphModel;
import com.mxgraph.model.mxGraphModel.Filter;
import com.mxgraph.model.mxGraphModel.mxChildChange;
import com.mxgraph.model.mxGraphModel.mxCollapseChange;
import com.mxgraph.model.mxGraphModel.mxGeometryChange;
import com.mxgraph.model.mxGraphModel.mxRootChange;
import com.mxgraph.model.mxGraphModel.mxStyleChange;
import com.mxgraph.model.mxGraphModel.mxTerminalChange;
import com.mxgraph.model.mxGraphModel.mxValueChange;
import com.mxgraph.model.mxGraphModel.mxVisibleChange;
import com.mxgraph.model.mxICell;
import com.mxgraph.model.mxIGraphModel;
import com.mxgraph.util.mxConstants;
import com.mxgraph.util.mxEvent;
import com.mxgraph.util.mxEventObject;
import com.mxgraph.util.mxEventSource;
import com.mxgraph.util.mxPoint;
import com.mxgraph.util.mxRectangle;
import com.mxgraph.util.mxResources;
import com.mxgraph.util.mxUndoableEdit;
import com.mxgraph.util.mxUndoableEdit.mxUndoableChange;
import com.mxgraph.util.mxUtils;

/**
* Implements a graph object that allows to create diagrams from a graph model
* and stylesheet.
*
* <h3>Images</h3>
* To create an image from a graph, use the following code for a given
* XML document (doc) and File (file):
*
* <code>
* Image img = mxCellRenderer.createBufferedImage(
*     graph, null, 1, Color.WHITE, false, null);
* ImageIO.write(img, "png", file);
* </code>
*
* If the XML is given as a string rather than a document, the document can
* be obtained using mxUtils.parse.
*
* This class fires the following events:
*
* mxEvent.ROOT fires if the root in the model has changed. This event has no
* properties.
*
* mxEvent.ALIGN_CELLS fires between begin- and endUpdate in alignCells. The
* <code>cells</code> and <code>align</code> properties contain the respective
* arguments that were passed to alignCells.
*
* mxEvent.FLIP_EDGE fires between begin- and endUpdate in flipEdge. The
* <code>edge</code> property contains the edge passed to flipEdge.
*
* mxEvent.ORDER_CELLS fires between begin- and endUpdate in orderCells. The
* <code>cells</code> and <code>back</code> properties contain the respective
* arguments that were passed to orderCells.
*
* mxEvent.CELLS_ORDERED fires between begin- and endUpdate in cellsOrdered.
* The <code>cells</code> and <code>back</code> arguments contain the
* respective arguments that were passed to cellsOrdered.
*
* mxEvent.GROUP_CELLS fires between begin- and endUpdate in groupCells. The
* <code>group</code>, <code>cells</code> and <code>border</code> arguments
* contain the respective arguments that were passed to groupCells.
*
* mxEvent.UNGROUP_CELLS fires between begin- and endUpdate in ungroupCells.
* The <code>cells</code> property contains the array of cells that was passed
* to ungroupCells.
*
* mxEvent.REMOVE_CELLS_FROM_PARENT fires between begin- and endUpdate in
* removeCellsFromParent. The <code>cells</code> property contains the array of
* cells that was passed to removeCellsFromParent.
*
* mxEvent.ADD_CELLS fires between begin- and endUpdate in addCells. The
* <code>cells</code>, <code>parent</code>, <code>index</code>,
* <code>source</code> and <code>target</code> properties contain the
* respective arguments that were passed to addCells.
*
* mxEvent.CELLS_ADDED fires between begin- and endUpdate in cellsAdded. The
* <code>cells</code>, <code>parent</code>, <code>index</code>,
* <code>source</code>, <code>target</code> and <code>absolute</code>
* properties contain the respective arguments that were passed to cellsAdded.
*
* mxEvent.REMOVE_CELLS fires between begin- and endUpdate in removeCells. The
* <code>cells</code> and <code>includeEdges</code> arguments contain the
* respective arguments that were passed to removeCells.
*
* mxEvent.CELLS_REMOVED fires between begin- and endUpdate in cellsRemoved.
* The <code>cells</code> argument contains the array of cells that was
* removed.
*
* mxEvent.SPLIT_EDGE fires between begin- and endUpdate in splitEdge. The
* <code>edge</code> property contains the edge to be splitted, the
* <code>cells</code>, <code>newEdge</code>, <code>dx</code> and
* <code>dy</code> properties contain the respective arguments that were passed
* to splitEdge.
*
* mxEvent.TOGGLE_CELLS fires between begin- and endUpdate in toggleCells. The
* <code>show</code>, <code>cells</code> and <code>includeEdges</code>
* properties contain the respective arguments that were passed to toggleCells.
*
* mxEvent.FOLD_CELLS fires between begin- and endUpdate in foldCells. The
* <code>collapse</code>, <code>cells</code> and <code>recurse</code>
* properties contain the respective arguments that were passed to foldCells.
*
* mxEvent.CELLS_FOLDED fires between begin- and endUpdate in cellsFolded. The
* <code>collapse</code>, <code>cells</code> and <code>recurse</code>
* properties contain the respective arguments that were passed to cellsFolded.
*
* mxEvent.UPDATE_CELL_SIZE fires between begin- and endUpdate in
* updateCellSize. The <code>cell</code> and <code>ignoreChildren</code>
* properties contain the respective arguments that were passed to
* updateCellSize.
*
* mxEvent.RESIZE_CELLS fires between begin- and endUpdate in resizeCells. The
* <code>cells</code> and <code>bounds</code> properties contain the respective
* arguments that were passed to resizeCells.
*
* mxEvent.CELLS_RESIZED fires between begin- and endUpdate in cellsResized.
* The <code>cells</code> and <code>bounds</code> properties contain the
* respective arguments that were passed to cellsResized.
*
* mxEvent.MOVE_CELLS fires between begin- and endUpdate in moveCells. The
* <code>cells</code>, <code>dx</code>, <code>dy</code>, <code>clone</code>,
* <code>target</code> and <code>location</code> properties contain the
* respective arguments that were passed to moveCells.
*
* mxEvent.CELLS_MOVED fires between begin- and endUpdate in cellsMoved. The
* <code>cells</code>, <code>dx</code>, <code>dy</code> and
* <code>disconnect</code> properties contain the respective arguments that
* were passed to cellsMoved.
*
* mxEvent.CONNECT_CELL fires between begin- and endUpdate in connectCell. The
* <code>edge</code>, <code>terminal</code> and <code>source</code> properties
* contain the respective arguments that were passed to connectCell.
*
* mxEvent.CELL_CONNECTED fires between begin- and endUpdate in cellConnected.
* The <code>edge</code>, <code>terminal</code> and <code>source</code>
* properties contain the respective arguments that were passed to
* cellConnected.
*
* mxEvent.REPAINT fires if a repaint was requested by calling repaint. The
* <code>region</code> property contains the optional mxRectangle that was
* passed to repaint to define the dirty region.
*/
public class mxGraph extends mxEventSource
{

  /**
   * Adds required resources.
   */
  static
  {
    try
    {
      mxResources.add("com.mxgraph.resources.graph");
    }
    catch (Exception e)
    {
      // ignore
    }
  }

  /**
   * Holds the version number of this release. Current version
   * is 1.4.2.0.
   */
  public static final String VERSION = "1.4.2.0";

  /**
   *
   */
  public interface mxICellVisitor
  {

    /**
     *
     * @param vertex
     * @param edge
     */
    boolean visit(Object vertex, Object edge);

  }

  /**
   * Property change event handling.
   */
  protected PropertyChangeSupport changeSupport = new PropertyChangeSupport(
      this);

  /**
   * Holds the model that contains the cells to be displayed.
   */
  protected mxIGraphModel model;

  /**
   * Holds the view that caches the cell states.
   */
  protected mxGraphView view;

  /**
   * Holds the stylesheet that defines the appearance of the cells.
   */
  protected mxStylesheet stylesheet;

  /**
   * Holds the <mxGraphSelection> that models the current selection.
   */
  protected mxGraphSelectionModel selectionModel;

  /**
   * Specifies the grid size. Default is 10.
   */
  protected int gridSize = 10;

  /**
   * Specifies if the grid is enabled. Default is true.
   */
  protected boolean gridEnabled = true;

  /**
   * Value returned by getOverlap if isAllowOverlapParent returns
   * true for the given cell. getOverlap is used in keepInside if
   * isKeepInsideParentOnMove returns true. The value specifies the
   * portion of the child which is allowed to overlap the parent.
   */
  protected double defaultOverlap = 0.5;

  /**
   * Specifies the default parent to be used to insert new cells.
   * This is used in getDefaultParent. Default is null.
   */
  protected Object defaultParent;

  /**
   * Specifies the alternate edge style to be used if the main control point
   * on an edge is being doubleclicked. Default is null.
   */
  protected String alternateEdgeStyle;

  /**
   * Specifies the return value for isEnabled. Default is true.
   */
  protected boolean enabled = true;

  /**
   * Specifies the return value for isCell(s)Locked. Default is false.
   */
  protected boolean cellsLocked = false;

  /**
   * Specifies the return value for isCell(s)Editable. Default is true.
   */
  protected boolean cellsEditable = true;

  /**
   * Specifies the return value for isCell(s)Sizable. Default is true.
   */
  protected boolean cellsResizable = true;

  /**
   * Specifies the return value for isCell(s)Movable. Default is true.
   */
  protected boolean cellsMovable = true;

  /**
   * Specifies the return value for isCell(s)Bendable. Default is true.
   */
  protected boolean cellsBendable = true;

  /**
   * Specifies the return value for isCell(s)Selectable. Default is true.
   */
  protected boolean cellsSelectable = true;

  /**
   * Specifies the return value for isCell(s)Deletable. Default is true.
   */
  protected boolean cellsDeletable = true;

  /**
   * Specifies the return value for isCell(s)Cloneable. Default is true.
   */
  protected boolean cellsCloneable = true;

  /**
   * Specifies the return value for isCellDisconntableFromTerminal. Default
   * is true.
   */
  protected boolean cellsDisconnectable = true;

  /**
   * Specifies the return value for isLabel(s)Clipped. Default is false.
   */
  protected boolean labelsClipped = false;

  /**
   * Specifies the return value for edges in isLabelMovable. Default is true.
   */
  protected boolean edgeLabelsMovable = true;

  /**
   * Specifies the return value for vertices in isLabelMovable. Default is false.
   */
  protected boolean vertexLabelsMovable = false;

  /**
   * Specifies the return value for isDropEnabled. Default is true.
   */
  protected boolean dropEnabled = true;

  /**
   * Specifies if dropping onto edges should be enabled. Default is true.
   */
  protected boolean splitEnabled = true;

  /**
   * Specifies if the graph should automatically update the cell size
   * after an edit. This is used in isAutoSizeCell. Default is false.
   */
  protected boolean autoSizeCells = false;

  /**
   * <mxRectangle> that specifies the area in which all cells in the
   * diagram should be placed. Uses in getMaximumGraphBounds. Use a width
   * or height of 0 if you only want to give a upper, left corner.
   */
  protected mxRectangle maximumGraphBounds = null;

  /**
   * mxRectangle that specifies the minimum size of the graph canvas inside
   * the scrollpane.
   */
  protected mxRectangle minimumGraphSize = null;

  /**
   * Border to be added to the bottom and right side when the container is
   * being resized after the graph has been changed. Default is 0.
   */
  protected int border = 0;

  /**
   * Specifies if edges should appear in the foreground regardless of their
   * order in the model. This has precendence over keepEdgeInBackground
   * Default is false.
   */
  protected boolean keepEdgesInForeground = false;

  /**
   * Specifies if edges should appear in the background regardless of their
   * order in the model. Default is false.
   */
  protected boolean keepEdgesInBackground = false;

  /**
   * Specifies if the cell size should be changed to the preferred size when
   * a cell is first collapsed. Default is true.
   */
  protected boolean collapseToPreferredSize = true;

  /**
   * Specifies if negative coordinates for vertices are allowed. Default is true.
   */
  protected boolean allowNegativeCoordinates = true;

  /**
   * Specifies the return value for isConstrainChildren. Default is true.
   */
  protected boolean constrainChildren = true;

  /**
   * Specifies if a parent should contain the child bounds after a resize of
   * the child. Default is true.
   */
  protected boolean extendParents = true;

  /**
   * Specifies if parents should be extended according to the <extendParents>
   * switch if cells are added. Default is true.
   */
  protected boolean extendParentsOnAdd = true;

  /**
   * Specifies if the scale and translate should be reset if
   * the root changes in the model. Default is true.
   */
  protected boolean resetViewOnRootChange = true;

  /**
   * Specifies if loops (aka self-references) are allowed.
   * Default is false.
   */
  protected boolean resetEdgesOnResize = false;

  /**
   * Specifies if edge control points should be reset after
   * the move of a connected cell. Default is false.
   */
  protected boolean resetEdgesOnMove = false;

  /**
   * Specifies if edge control points should be reset after
   * the the edge has been reconnected. Default is true.
   */
  protected boolean resetEdgesOnConnect = true;

  /**
   * Specifies if loops (aka self-references) are allowed.
   * Default is false.
   */
  protected boolean allowLoops = false;

  /**
   * Specifies the multiplicities to be used for validation of the graph.
   */
  protected mxMultiplicity[] multiplicities;

  /**
   * Specifies the default style for loops.
   */
  protected mxEdgeStyle.mxEdgeStyleFunction defaultLoopStyle = mxEdgeStyle.Loop;

  /**
   * Specifies if multiple edges in the same direction between
   * the same pair of vertices are allowed. Default is true.
   */
  protected boolean multigraph = true;

  /**
   * Specifies if edges are connectable. Default is false.
   * This overrides the connectable field in edges.
   */
  protected boolean connectableEdges = false;

  /**
   * Specifies if edges with disconnected terminals are
   * allowed in the graph. Default is false.
   */
  protected boolean allowDanglingEdges = true;

  /**
   * Specifies if edges that are cloned should be validated and only inserted
   * if they are valid. Default is true.
   */
  protected boolean cloneInvalidEdges = false;

  /**
   * Specifies if edges should be disconnected from their terminals when they
   * are moved. Default is true.
   */
  protected boolean disconnectOnMove = true;

  /**
   * Specifies if labels should be visible. This is used in
   * getLabel. Default is true.
   */
  protected boolean labelsVisible = true;

  /**
   * Specifies the return value for isHtmlLabel. Default is false.
   */
  protected boolean htmlLabels = false;

  /**
   * Specifies if nesting of swimlanes is allowed. Default is true.
   */
  protected boolean swimlaneNesting = true;

  /**
   * Specifies the maximum number of changes that should be processed to find
   * the dirty region. If the number of changes is larger, then the complete
   * grah is repainted. A value of zero will always compute the dirty region
   * for any number of changes. Default is 1000.
   */
  protected int changesRepaintThreshold = 1000;

  /**
   * Specifies if the origin should be automatically updated.
   */
  protected boolean autoOrigin = false;

  /**
   * Holds the current automatic origin.
   */
  protected mxPoint origin = new mxPoint();

  /**
   * Fires repaint events for full repaints.
   */
  protected mxIEventListener fullRepaintHandler = new mxIEventListener()
  {
    public void invoke(Object sender, mxEventObject evt)
    {
      repaint();
    }
  };

  /**
   * Fires repaint events for model changes.
   */
  protected mxIEventListener graphModelChangeHandler = new mxIEventListener()
  {
    @SuppressWarnings("unchecked")
    public void invoke(Object sender, mxEventObject evt)
    {
      mxRectangle dirty = graphModelChanged((mxIGraphModel) sender,
          (List<mxUndoableChange>) ((mxUndoableEdit) evt
              .getProperty("edit")).getChanges());
      repaint(dirty);
    }
  };

  /**
   * Constructs a new graph with an empty
   * {@link com.mxgraph.model.mxGraphModel}.
   */
  public mxGraph()
  {
    this(null, null);
  }

  /**
   * Constructs a new graph for the specified model. If no model is
   * specified, then a new, empty {@link com.mxgraph.model.mxGraphModel} is
   * used.
   *
   * @param model Model that contains the graph data
   */
  public mxGraph(mxIGraphModel model)
  {
    this(model, null);
  }

  /**
   * Constructs a new graph for the specified model. If no model is
   * specified, then a new, empty {@link com.mxgraph.model.mxGraphModel} is
   * used.
   *
   * @param stylesheet The stylesheet to use for the graph.
   */
  public mxGraph(mxStylesheet stylesheet)
  {
    this(null, stylesheet);
  }

  /**
   * Constructs a new graph for the specified model. If no model is
   * specified, then a new, empty {@link com.mxgraph.model.mxGraphModel} is
   * used.
   *
   * @param model Model that contains the graph data
   */
  public mxGraph(mxIGraphModel model, mxStylesheet stylesheet)
  {
    selectionModel = createSelectionModel();
    setModel((model != null) ? model : new mxGraphModel());
    setStylesheet((stylesheet != null) ? stylesheet : createStylesheet());
    setView(createGraphView());
  }

  /**
   * Constructs a new selection model to be used in this graph.
   */
  protected mxGraphSelectionModel createSelectionModel()
  {
    return new mxGraphSelectionModel(this);
  }

  /**
   * Constructs a new stylesheet to be used in this graph.
   */
  protected mxStylesheet createStylesheet()
  {
    return new mxStylesheet();
  }

  /**
   * Constructs a new view to be used in this graph.
   */
  protected mxGraphView createGraphView()
  {
    return new mxGraphView(this);
  }

  /**
   * Returns the graph model that contains the graph data.
   *
   * @return Returns the model that contains the graph data
   */
  public mxIGraphModel getModel()
  {
    return model;
  }

  /**
   * Sets the graph model that contains the data, and fires an
   * mxEvent.CHANGE followed by an mxEvent.REPAINT event.
   *
   * @param value Model that contains the graph data
   */
  public void setModel(mxIGraphModel value)
  {
    if (model != null)
    {
      model.removeListener(graphModelChangeHandler);
    }

    Object oldModel = model;
    model = value;

    if (view != null)
    {
      view.revalidate();
    }

    model.addListener(mxEvent.CHANGE, graphModelChangeHandler);
    changeSupport.firePropertyChange("model", oldModel, model);
    repaint();
  }

  /**
   * Returns the view that contains the cell states.
   *
   * @return Returns the view that contains the cell states
   */
  public mxGraphView getView()
  {
    return view;
  }

  /**
   * Sets the view that contains the cell states.
   *
   * @param value View that contains the cell states
   */
  public void setView(mxGraphView value)
  {
    if (view != null)
    {
      view.removeListener(fullRepaintHandler);
    }

    Object oldView = view;
    view = value;

    if (view != null)
    {
      view.revalidate();
    }

    // Listens to changes in the view
    view.addListener(mxEvent.SCALE, fullRepaintHandler);
    view.addListener(mxEvent.TRANSLATE, fullRepaintHandler);
    view.addListener(mxEvent.SCALE_AND_TRANSLATE, fullRepaintHandler);
    view.addListener(mxEvent.UP, fullRepaintHandler);
    view.addListener(mxEvent.DOWN, fullRepaintHandler);

    changeSupport.firePropertyChange("view", oldView, view);
  }

  /**
   * Returns the stylesheet that provides the style.
   *
   * @return Returns the stylesheet that provides the style.
   */
  public mxStylesheet getStylesheet()
  {
    return stylesheet;
  }

  /**
   * Sets the stylesheet that provides the style.
   *
   * @param value Stylesheet that provides the style.
   */
  public void setStylesheet(mxStylesheet value)
  {
    mxStylesheet oldValue = stylesheet;
    stylesheet = value;

    changeSupport.firePropertyChange("stylesheet", oldValue, stylesheet);
  }

  /**
   * Returns the cells to be selected for the given list of changes.
   */
  public Object[] getSelectionCellsForChanges(List<mxUndoableChange> changes)
  {
    List<Object> cells = new ArrayList<Object>();
    Iterator<mxUndoableChange> it = changes.iterator();

    while (it.hasNext())
    {
      Object change = it.next();

      if (change instanceof mxChildChange)
      {
        cells.add(((mxChildChange) change).getChild());
      }
      else if (change instanceof mxTerminalChange)
      {
        cells.add(((mxTerminalChange) change).getCell());
      }
      else if (change instanceof mxValueChange)
      {
        cells.add(((mxValueChange) change).getCell());
      }
      else if (change instanceof mxStyleChange)
      {
        cells.add(((mxStyleChange) change).getCell());
      }
      else if (change instanceof mxGeometryChange)
      {
        cells.add(((mxGeometryChange) change).getCell());
      }
      else if (change instanceof mxCollapseChange)
      {
        cells.add(((mxCollapseChange) change).getCell());
      }
      else if (change instanceof mxVisibleChange)
      {
        mxVisibleChange vc = (mxVisibleChange) change;

        if (vc.isVisible())
        {
          cells.add(((mxVisibleChange) change).getCell());
        }
      }
    }

    return mxGraphModel.getTopmostCells(model, cells.toArray());
  }

  /**
   * Called when the graph model changes. Invokes processChange on each
   * item of the given array to update the view accordingly.
   */
  public mxRectangle graphModelChanged(mxIGraphModel sender,
      List<mxUndoableChange> changes)
  {
    int thresh = getChangesRepaintThreshold();
    boolean ignoreDirty = thresh > 0 && changes.size() > thresh;

    // Ignores dirty rectangle if there was a root change
    if (!ignoreDirty)
    {
      Iterator<mxUndoableChange> it = changes.iterator();

      while (it.hasNext())
      {
        if (it.next() instanceof mxRootChange)
        {
          ignoreDirty = true;
          break;
        }
      }
    }

    mxRectangle dirty = processChanges(changes, true, ignoreDirty);
    view.validate();

    if (isAutoOrigin())
    {
      updateOrigin();
    }

    if (!ignoreDirty)
    {
      mxRectangle tmp = processChanges(changes, false, ignoreDirty);

      if (tmp != null)
      {
        if (dirty == null)
        {
          dirty = tmp;
        }
        else
        {
          dirty.add(tmp);
        }
      }
    }

    removeSelectionCells(getRemovedCellsForChanges(changes));

    return dirty;
  }

  /**
   * Extends the canvas by doing another validation with a shifted
   * global translation if the bounds of the graph are below (0,0).
   *
   * The first validation is required to compute the bounds of the graph
   * while the second validation is required to apply the new translate.
   */
  protected void updateOrigin()
  {
    mxRectangle bounds = getGraphBounds();

    if (bounds != null)
    {
      double scale = getView().getScale();
      double x = bounds.getX() / scale - getBorder();
      double y = bounds.getY() / scale - getBorder();

      if (x < 0 || y < 0)
      {
        double x0 = Math.min(0, x);
        double y0 = Math.min(0, y);

        origin.setX(origin.getX() + x0);
        origin.setY(origin.getY() + y0);

        mxPoint t = getView().getTranslate();
        getView().setTranslate(
            new mxPoint(t.getX() - x0, t.getY() - y0));
      }
      else if ((x > 0 || y > 0)
          && (origin.getX() < 0 || origin.getY() < 0))
      {
        double dx = Math.min(-origin.getX(), x);
        double dy = Math.min(-origin.getY(), y);

        origin.setX(origin.getX() + dx);
        origin.setY(origin.getY() + dy);

        mxPoint t = getView().getTranslate();
        getView().setTranslate(
            new mxPoint(t.getX() - dx, t.getY() - dy));
      }
    }
  }

  /**
   * Returns the cells that have been removed from the model.
   */
  public Object[] getRemovedCellsForChanges(List<mxUndoableChange> changes)
  {
    List<Object> result = new ArrayList<Object>();
    Iterator<mxUndoableChange> it = changes.iterator();

    while (it.hasNext())
    {
      Object change = it.next();

      if (change instanceof mxRootChange)
      {
        break;
      }
      else if (change instanceof mxChildChange)
      {
        mxChildChange cc = (mxChildChange) change;

        if (cc.getParent() == null)
        {
          result.addAll(mxGraphModel.getDescendants(model,
              cc.getChild()));
        }
      }
      else if (change instanceof mxVisibleChange)
      {
        Object cell = ((mxVisibleChange) change).getCell();
        result.addAll(mxGraphModel.getDescendants(model, cell));
      }
    }

    return result.toArray();
  }

  /**
   * Processes the changes and returns the minimal rectangle to be
   * repainted in the buffer. A return value of null means no repaint
   * is required.
   */
  public mxRectangle processChanges(List<mxUndoableChange> changes,
      boolean invalidate, boolean ignoreDirty)
  {
    mxRectangle bounds = null;
    Iterator<mxUndoableChange> it = changes.iterator();

    while (it.hasNext())
    {
      mxRectangle rect = processChange(it.next(), invalidate, ignoreDirty);

      if (bounds == null)
      {
        bounds = rect;
      }
      else
      {
        bounds.add(rect);
      }
    }

    return bounds;
  }

  /**
   * Processes the given change and invalidates the respective cached data
   * in <view>. This fires a <root> event if the root has changed in the
   * model.
   */
  public mxRectangle processChange(mxUndoableChange change,
      boolean invalidate, boolean ignoreDirty)
  {
    mxRectangle result = null;

    if (change instanceof mxRootChange)
    {
      result = (ignoreDirty) ? null : getGraphBounds();

      if (invalidate)
      {
        clearSelection();
        removeStateForCell(((mxRootChange) change).getPrevious());

        if (isResetViewOnRootChange())
        {
          view.setEventsEnabled(false);

          try
          {
            view.scaleAndTranslate(1, 0, 0);
          }
          finally
          {
            view.setEventsEnabled(true);
          }
        }

      }

      fireEvent(new mxEventObject(mxEvent.ROOT));
    }
    else if (change instanceof mxChildChange)
    {
      mxChildChange cc = (mxChildChange) change;

      // Repaints the parent area if it is a rendered cell (vertex or
      // edge) otherwise only the child area is repainted, same holds
      // if the parent and previous are the same object, in which case
      // only the child area needs to be repainted (change of order)
      if (!ignoreDirty)
      {
        if (cc.getParent() != cc.getPrevious())
        {
          if (model.isVertex(cc.getParent())
              || model.isEdge(cc.getParent()))
          {
            result = getBoundingBox(cc.getParent(), true, true);
          }

          if (model.isVertex(cc.getPrevious())
              || model.isEdge(cc.getPrevious()))
          {
            if (result != null)
            {
              result.add(getBoundingBox(cc.getPrevious(), true,
                  true));
            }
            else
            {
              result = getBoundingBox(cc.getPrevious(), true,
                  true);
            }
          }
        }

        if (result == null)
        {
          result = getBoundingBox(cc.getChild(), true, true);
        }
      }

      if (invalidate)
      {
        if (cc.getParent() != null)
        {
          view.clear(cc.getChild(), false, true);
        }
        else
        {
          removeStateForCell(cc.getChild());
        }
      }
    }
    else if (change instanceof mxTerminalChange)
    {
      Object cell = ((mxTerminalChange) change).getCell();

      if (!ignoreDirty)
      {
        result = getBoundingBox(cell, true);
      }

      if (invalidate)
      {
        view.invalidate(cell);
      }
    }
    else if (change instanceof mxValueChange)
    {
      Object cell = ((mxValueChange) change).getCell();

      if (!ignoreDirty)
      {
        result = getBoundingBox(cell);
      }

      if (invalidate)
      {
        view.clear(cell, false, false);
      }
    }
    else if (change instanceof mxStyleChange)
    {
      Object cell = ((mxStyleChange) change).getCell();

      if (!ignoreDirty)
      {
        result = getBoundingBox(cell, true);
      }

      if (invalidate)
      {
        // TODO: Add includeEdges argument to clear method for
        // not having to call invalidate in this case (where it
        // is possible that the perimeter has changed, which
        // means the connected edges need to be invalidated)
        view.clear(cell, false, false);
        view.invalidate(cell);
      }
    }
    else if (change instanceof mxGeometryChange)
    {
      Object cell = ((mxGeometryChange) change).getCell();

      if (!ignoreDirty)
      {
        result = getBoundingBox(cell, true, true);
      }

      if (invalidate)
      {
        view.invalidate(cell);
      }
    }
    else if (change instanceof mxCollapseChange)
    {
      Object cell = ((mxCollapseChange) change).getCell();

      if (!ignoreDirty)
      {
        result = getBoundingBox(((mxCollapseChange) change).getCell(),
            true, true);
      }

      if (invalidate)
      {
        removeStateForCell(cell);
      }
    }
    else if (change instanceof mxVisibleChange)
    {
      Object cell = ((mxVisibleChange) change).getCell();

      if (!ignoreDirty)
      {
        result = getBoundingBox(((mxVisibleChange) change).getCell(),
            true, true);
      }

      if (invalidate)
      {
        removeStateForCell(cell);
      }
    }

    return result;
  }

  /**
   * Removes all cached information for the given cell and its descendants.
   * This is called when a cell was removed from the model.
   *
   * @param cell Cell that was removed from the model.
   */
  protected void removeStateForCell(Object cell)
  {
    int childCount = model.getChildCount(cell);

    for (int i = 0; i < childCount; i++)
    {
      removeStateForCell(model.getChildAt(cell, i));
    }

    view.removeState(cell);
  }

  //
  // Cell styles
  //

  /**
   * Returns an array of key, value pairs representing the cell style for the
   * given cell. If no string is defined in the model that specifies the
   * style, then the default style for the cell is returned or <EMPTY_ARRAY>,
   * if not style can be found.
   *
   * @param cell Cell whose style should be returned.
   * @return Returns the style of the cell.
   */
  public Map<String, Object> getCellStyle(Object cell)
  {
    Map<String, Object> style = (model.isEdge(cell)) ? stylesheet
        .getDefaultEdgeStyle() : stylesheet.getDefaultVertexStyle();

    String name = model.getStyle(cell);

    if (name != null)
    {
      style = stylesheet.getCellStyle(name, style);
    }

    if (style == null)
    {
      style = mxStylesheet.EMPTY_STYLE;
    }

    return style;
  }

  /**
   * Sets the style of the selection cells to the given value.
   *
   * @param style String representing the new style of the cells.
   */
  public Object[] setCellStyle(String style)
  {
    return setCellStyle(style, null);
  }

  /**
   * Sets the style of the specified cells. If no cells are given, then the
   * selection cells are changed.
   *
   * @param style String representing the new style of the cells.
   * @param cells Optional array of <mxCells> to set the style for. Default is the
   * selection cells.
   */
  public Object[] setCellStyle(String style, Object[] cells)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    if (cells != null)
    {
      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          model.setStyle(cells[i], style);
        }
      }
      finally
      {
        model.endUpdate();
      }
    }

    return cells;
  }

  /**
   * Toggles the boolean value for the given key in the style of the
   * given cell. If no cell is specified then the selection cell is
   * used.
   *
   * @param key Key for the boolean value to be toggled.
   * @param defaultValue Default boolean value if no value is defined.
   * @param cell Cell whose style should be modified.
   */
  public Object toggleCellStyle(String key, boolean defaultValue, Object cell)
  {
    return toggleCellStyles(key, defaultValue, new Object[] { cell })[0];
  }

  /**
   * Toggles the boolean value for the given key in the style of the
   * selection cells.
   *
   * @param key Key for the boolean value to be toggled.
   * @param defaultValue Default boolean value if no value is defined.
   */
  public Object[] toggleCellStyles(String key, boolean defaultValue)
  {
    return toggleCellStyles(key, defaultValue, null);
  }

  /**
   * Toggles the boolean value for the given key in the style of the given
   * cells. If no cells are specified, then the selection cells are used. For
   * example, this can be used to toggle mxConstants.STYLE_ROUNDED or any
   * other style with a boolean value.
   *
   * @param key String representing the key of the boolean style to be toggled.
   * @param defaultValue Default boolean value if no value is defined.
   * @param cells Cells whose styles should be modified.
   */
  public Object[] toggleCellStyles(String key, boolean defaultValue,
      Object[] cells)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    if (cells != null && cells.length > 0)
    {
      mxCellState state = view.getState(cells[0]);
      Map<String, Object> style = (state != null) ? state.getStyle()
          : getCellStyle(cells[0]);

      if (style != null)
      {
        String value = (mxUtils.isTrue(style, key, defaultValue)) ? "0"
            : "1";
        setCellStyles(key, value, cells);
      }
    }

    return cells;
  }

  /**
   * Sets the key to value in the styles of the selection cells.
   *
   * @param key String representing the key to be assigned.
   * @param value String representing the new value for the key.
   */
  public Object[] setCellStyles(String key, String value)
  {
    return setCellStyles(key, value, null);
  }

  /**
   * Sets the key to value in the styles of the given cells. This will modify
   * the existing cell styles in-place and override any existing assignment
   * for the given key. If no cells are specified, then the selection cells
   * are changed. If no value is specified, then the respective key is
   * removed from the styles.
   *
   * @param key String representing the key to be assigned.
   * @param value String representing the new value for the key.
   * @param cells Array of cells to change the style for.
   */
  public Object[] setCellStyles(String key, String value, Object[] cells)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    mxUtils.setCellStyles(model, cells, key, value);

    return cells;
  }

  /**
   * Toggles the given bit for the given key in the styles of the selection
   * cells.
   *
   * @param key String representing the key to toggle the flag in.
   * @param flag Integer that represents the bit to be toggled.
   */
  public Object[] toggleCellStyleFlags(String key, int flag)
  {
    return toggleCellStyleFlags(key, flag, null);
  }

  /**
   * Toggles the given bit for the given key in the styles of the specified
   * cells.
   *
   * @param key String representing the key to toggle the flag in.
   * @param flag Integer that represents the bit to be toggled.
   * @param cells Optional array of <mxCells> to change the style for. Default is
   * the selection cells.
   */
  public Object[] toggleCellStyleFlags(String key, int flag, Object[] cells)
  {
    return setCellStyleFlags(key, flag, null, cells);
  }

  /**
   * Sets or toggles the given bit for the given key in the styles of the
   * selection cells.
   *
   * @param key String representing the key to toggle the flag in.
   * @param flag Integer that represents the bit to be toggled.
   * @param value Boolean value to be used or null if the value should be
   * toggled.
   */
  public Object[] setCellStyleFlags(String key, int flag, boolean value)
  {
    return setCellStyleFlags(key, flag, value, null);
  }

  /**
   * Sets or toggles the given bit for the given key in the styles of the
   * specified cells.
   *
   * @param key String representing the key to toggle the flag in.
   * @param flag Integer that represents the bit to be toggled.
   * @param value Boolean value to be used or null if the value should be
   * toggled.
   * @param cells Optional array of cells to change the style for. If no
   * cells are specified then the selection cells are used.
   */
  public Object[] setCellStyleFlags(String key, int flag, Boolean value,
      Object[] cells)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    if (cells != null && cells.length > 0)
    {
      if (value == null)
      {
        mxCellState state = view.getState(cells[0]);
        Map<String, Object> style = (state != null) ? state.getStyle()
            : getCellStyle(cells[0]);

        if (style != null)
        {
          int current = mxUtils.getInt(style, key);
          value = !((current & flag) == flag);
        }
      }

      mxUtils.setCellStyleFlags(model, cells, key, flag, value);
    }

    return cells;
  }

  //
  // Cell alignment and orientation
  //

  /**
   * Aligns the selection cells vertically or horizontally according to the
   * given alignment.
   *
   * @param align Specifies the alignment. Possible values are all constants
   * in mxConstants with an ALIGN prefix.
   */
  public Object[] alignCells(String align)
  {
    return alignCells(align, null);
  }

  /**
   * Aligns the given cells vertically or horizontally according to the given
   * alignment.
   *
   * @param align Specifies the alignment. Possible values are all constants
   * in mxConstants with an ALIGN prefix.
   * @param cells Array of cells to be aligned.
   */
  public Object[] alignCells(String align, Object[] cells)
  {
    return alignCells(align, cells, null);
  }

  /**
   * Aligns the given cells vertically or horizontally according to the given
   * alignment using the optional parameter as the coordinate.
   *
   * @param align Specifies the alignment. Possible values are all constants
   * in mxConstants with an ALIGN prefix.
   * @param cells Array of cells to be aligned.
   * @param param Optional coordinate for the alignment.
   */
  public Object[] alignCells(String align, Object[] cells, Object param)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    if (cells != null && cells.length > 1)
    {
      // Finds the required coordinate for the alignment
      if (param == null)
      {
        for (int i = 0; i < cells.length; i++)
        {
          mxGeometry geo = getCellGeometry(cells[i]);

          if (geo != null && !model.isEdge(cells[i]))
          {
            if (param == null)
            {
              if (align == null
                  || align.equals(mxConstants.ALIGN_LEFT))
              {
                param = geo.getX();
              }
              else if (align.equals(mxConstants.ALIGN_CENTER))
              {
                param = geo.getX() + geo.getWidth() / 2;
                break;
              }
              else if (align.equals(mxConstants.ALIGN_RIGHT))
              {
                param = geo.getX() + geo.getWidth();
              }
              else if (align.equals(mxConstants.ALIGN_TOP))
              {
                param = geo.getY();
              }
              else if (align.equals(mxConstants.ALIGN_MIDDLE))
              {
                param = geo.getY() + geo.getHeight() / 2;
                break;
              }
              else if (align.equals(mxConstants.ALIGN_BOTTOM))
              {
                param = geo.getY() + geo.getHeight();
              }
            }
            else
            {
              double tmp = Double.parseDouble(String
                  .valueOf(param));

              if (align == null
                  || align.equals(mxConstants.ALIGN_LEFT))
              {
                param = Math.min(tmp, geo.getX());
              }
              else if (align.equals(mxConstants.ALIGN_RIGHT))
              {
                param = Math.max(tmp,
                    geo.getX() + geo.getWidth());
              }
              else if (align.equals(mxConstants.ALIGN_TOP))
              {
                param = Math.min(tmp, geo.getY());
              }
              else if (align.equals(mxConstants.ALIGN_BOTTOM))
              {
                param = Math.max(tmp,
                    geo.getY() + geo.getHeight());
              }
            }
          }
        }
      }

      // Aligns the cells to the coordinate
      model.beginUpdate();
      try
      {
        double tmp = Double.parseDouble(String.valueOf(param));

        for (int i = 0; i < cells.length; i++)
        {
          mxGeometry geo = getCellGeometry(cells[i]);

          if (geo != null && !model.isEdge(cells[i]))
          {
            geo = (mxGeometry) geo.clone();

            if (align == null
                || align.equals(mxConstants.ALIGN_LEFT))
            {
              geo.setX(tmp);
            }
            else if (align.equals(mxConstants.ALIGN_CENTER))
            {
              geo.setX(tmp - geo.getWidth() / 2);
            }
            else if (align.equals(mxConstants.ALIGN_RIGHT))
            {
              geo.setX(tmp - geo.getWidth());
            }
            else if (align.equals(mxConstants.ALIGN_TOP))
            {
              geo.setY(tmp);
            }
            else if (align.equals(mxConstants.ALIGN_MIDDLE))
            {
              geo.setY(tmp - geo.getHeight() / 2);
            }
            else if (align.equals(mxConstants.ALIGN_BOTTOM))
            {
              geo.setY(tmp - geo.getHeight());
            }

            model.setGeometry(cells[i], geo);

            if (isResetEdgesOnMove())
            {
              resetEdges(new Object[] { cells[i] });
            }
          }
        }

        fireEvent(new mxEventObject(mxEvent.ALIGN_CELLS, "cells",
            cells, "align", align));
      }
      finally
      {
        model.endUpdate();
      }
    }

    return cells;
  }

  /**
   * Called when the main control point of the edge is double-clicked. This
   * implementation switches between null (default) and alternateEdgeStyle
   * and resets the edges control points. Finally, a flip event is fired
   * before endUpdate is called on the model.
   *
   * @param edge Cell that represents the edge to be flipped.
   * @return Returns the edge that has been flipped.
   */
  public Object flipEdge(Object edge)
  {
    if (edge != null && alternateEdgeStyle != null)
    {
      model.beginUpdate();
      try
      {
        String style = model.getStyle(edge);

        if (style == null || style.length() == 0)
        {
          model.setStyle(edge, alternateEdgeStyle);
        }
        else
        {
          model.setStyle(edge, null);
        }

        // Removes all existing control points
        resetEdge(edge);
        fireEvent(new mxEventObject(mxEvent.FLIP_EDGE, "edge", edge));
      }
      finally
      {
        model.endUpdate();
      }
    }

    return edge;
  }

  //
  // Order
  //

  /**
   * Moves the selection cells to the front or back. This is a shortcut method.
   *
   * @param back Specifies if the cells should be moved to back.
   */
  public Object[] orderCells(boolean back)
  {
    return orderCells(back, null);
  }

  /**
   * Moves the given cells to the front or back. The change is carried out
   * using cellsOrdered. This method fires mxEvent.ORDER_CELLS while the
   * transaction is in progress.
   *
   * @param back Specifies if the cells should be moved to back.
   * @param cells Array of cells whose order should be changed. If null is
   * specified then the selection cells are used.
   */
  public Object[] orderCells(boolean back, Object[] cells)
  {
    if (cells == null)
    {
      cells = mxUtils.sortCells(getSelectionCells(), true);
    }

    model.beginUpdate();
    try
    {
      cellsOrdered(cells, back);
      fireEvent(new mxEventObject(mxEvent.ORDER_CELLS, "cells", cells,
          "back", back));
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  /**
   * Moves the given cells to the front or back. This method fires
   * mxEvent.CELLS_ORDERED while the transaction is in progress.
   *
   * @param cells Array of cells whose order should be changed.
   * @param back Specifies if the cells should be moved to back.
   */
  public void cellsOrdered(Object[] cells, boolean back)
  {
    if (cells != null)
    {
      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          Object parent = model.getParent(cells[i]);

          if (back)
          {
            model.add(parent, cells[i], i);
          }
          else
          {
            model.add(parent, cells[i],
                model.getChildCount(parent) - 1);
          }
        }

        fireEvent(new mxEventObject(mxEvent.CELLS_ORDERED, "cells",
            cells, "back", back));
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  //
  // Grouping
  //

  /**
   * Groups the selection cells. This is a shortcut method.
   *
   * @return Returns the new group.
   */
  public Object groupCells()
  {
    return groupCells(null);
  }

  /**
   * Groups the selection cells and adds them to the given group. This is a
   * shortcut method.
   *
   * @return Returns the new group.
   */
  public Object groupCells(Object group)
  {
    return groupCells(group, 0);
  }

  /**
   * Groups the selection cells and adds them to the given group. This is a
   * shortcut method.
   *
   * @return Returns the new group.
   */
  public Object groupCells(Object group, double border)
  {
    return groupCells(group, border, null);
  }

  /**
   * Adds the cells into the given group. The change is carried out using
   * cellsAdded, cellsMoved and cellsResized. This method fires
   * mxEvent.GROUP_CELLS while the transaction is in progress. Returns the
   * new group. A group is only created if there is at least one entry in the
   * given array of cells.
   *
   * @param group Cell that represents the target group. If null is specified
   * then a new group is created using createGroupCell.
   * @param border Integer that specifies the border between the child area
   * and the group bounds.
   * @param cells Optional array of cells to be grouped. If null is specified
   * then the selection cells are used.
   */
  public Object groupCells(Object group, double border, Object[] cells)
  {
    if (cells == null)
    {
      cells = mxUtils.sortCells(getSelectionCells(), true);
    }

    cells = getCellsForGroup(cells);

    if (group == null)
    {
      group = createGroupCell(cells);
    }

    mxRectangle bounds = getBoundsForGroup(group, cells, border);

    if (cells.length > 0 && bounds != null)
    {
      Object parent = model.getParent(cells[0]);

      model.beginUpdate();
      try
      {
        // Checks if the group has a geometry and
        // creates one if one does not exist
        if (getCellGeometry(group) == null)
        {
          model.setGeometry(group, new mxGeometry());
        }

        // Adds the children into the group and moves
        int index = model.getChildCount(group);
        cellsAdded(cells, group, index, null, null, false);
        cellsMoved(cells, -bounds.getX(), -bounds.getY(), false, true);

        // Adds the group into the parent and resizes
        index = model.getChildCount(parent);
        cellsAdded(new Object[] { group }, parent, index, null, null,
            false);
        cellsResized(new Object[] { group },
            new mxRectangle[] { bounds });

        fireEvent(new mxEventObject(mxEvent.GROUP_CELLS, "group",
            group, "cells", cells, "border", border));
      }
      finally
      {
        model.endUpdate();
      }
    }

    return group;
  }

  /**
   * Returns the cells with the same parent as the first cell
   * in the given array.
   */
  public Object[] getCellsForGroup(Object[] cells)
  {
    List<Object> result = new ArrayList<Object>(cells.length);

    if (cells != null && cells.length > 0)
    {
      Object parent = model.getParent(cells[0]);
      result.add(cells[0]);

      // Filters selection cells with the same parent
      for (int i = 1; i < cells.length; i++)
      {
        if (model.getParent(cells[i]) == parent)
        {
          result.add(cells[i]);
        }
      }
    }

    return result.toArray();
  }

  /**
   * Returns the bounds to be used for the given group and children. This
   * implementation computes the bounding box of the geometries of all
   * vertices in the given children array. Edges are ignored. If the group
   * cell is a swimlane the title region is added to the bounds.
   */
  public mxRectangle getBoundsForGroup(Object group, Object[] children,
      double border)
  {
    mxRectangle result = getBoundingBoxFromGeometry(children);

    if (result != null)
    {
      if (isSwimlane(group))
      {
        mxRectangle size = getStartSize(group);

        result.setX(result.getX() - size.getWidth());
        result.setY(result.getY() - size.getHeight());
        result.setWidth(result.getWidth() + size.getWidth());
        result.setHeight(result.getHeight() + size.getHeight());
      }

      // Adds the border
      result.setX(result.getX() - border);
      result.setY(result.getY() - border);
      result.setWidth(result.getWidth() + 2 * border);
      result.setHeight(result.getHeight() + 2 * border);
    }

    return result;
  }

  /**
   * Hook for creating the group cell to hold the given array of <mxCells> if
   * no group cell was given to the <group> function. The children are just
   * for informational purpose, they will be added to the returned group
   * later. Note that the returned group should have a geometry. The
   * coordinates of which are later overridden.
   *
   * @param cells
   * @return Returns a new group cell.
   */
  public Object createGroupCell(Object[] cells)
  {
    mxCell group = new mxCell("", new mxGeometry(), null);
    group.setVertex(true);
    group.setConnectable(false);

    return group;
  }

  /**
   * Ungroups the selection cells. This is a shortcut method.
   */
  public Object[] ungroupCells()
  {
    return ungroupCells(null);
  }

  /**
   * Ungroups the given cells by moving the children the children to their
   * parents parent and removing the empty groups.
   *
   * @param cells Array of cells to be ungrouped. If null is specified then
   * the selection cells are used.
   * @return Returns the children that have been removed from the groups.
   */
  public Object[] ungroupCells(Object[] cells)
  {
    List<Object> result = new ArrayList<Object>();

    if (cells == null)
    {
      cells = getSelectionCells();

      // Finds the cells with children
      List<Object> tmp = new ArrayList<Object>(cells.length);

      for (int i = 0; i < cells.length; i++)
      {
        if (model.getChildCount(cells[i]) > 0)
        {
          tmp.add(cells[i]);
        }
      }

      cells = tmp.toArray();
    }

    if (cells != null && cells.length > 0)
    {
      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          Object[] children = mxGraphModel.getChildren(model,
              cells[i]);

          if (children != null && children.length > 0)
          {
            Object parent = model.getParent(cells[i]);
            int index = model.getChildCount(parent);

            cellsAdded(children, parent, index, null, null, true);
            result.addAll(Arrays.asList(children));
          }
        }

        cellsRemoved(addAllEdges(cells));
        fireEvent(new mxEventObject(mxEvent.UNGROUP_CELLS, "cells",
            cells));
      }
      finally
      {
        model.endUpdate();
      }
    }

    return result.toArray();
  }

  /**
   * Removes the selection cells from their parents and adds them to the
   * default parent returned by getDefaultParent.
   */
  public Object[] removeCellsFromParent()
  {
    return removeCellsFromParent(null);
  }

  /**
   * Removes the specified cells from their parents and adds them to the
   * default parent.
   *
   * @param cells Array of cells to be removed from their parents.
   * @return Returns the cells that were removed from their parents.
   */
  public Object[] removeCellsFromParent(Object[] cells)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    model.beginUpdate();
    try
    {
      Object parent = getDefaultParent();
      int index = model.getChildCount(parent);

      cellsAdded(cells, parent, index, null, null, true);
      fireEvent(new mxEventObject(mxEvent.REMOVE_CELLS_FROM_PARENT,
          "cells", cells));
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  /**
   * Updates the bounds of the given array of groups so that it includes
   * all child vertices.
   */
  public Object[] updateGroupBounds()
  {
    return updateGroupBounds(null);
  }

  /**
   * Updates the bounds of the given array of groups so that it includes
   * all child vertices.
   *
   * @param cells The groups whose bounds should be updated.
   */
  public Object[] updateGroupBounds(Object[] cells)
  {
    return updateGroupBounds(cells, 0);
  }

  /**
   * Updates the bounds of the given array of groups so that it includes
   * all child vertices.
   *
   * @param cells The groups whose bounds should be updated.
   * @param border The border to be added in the group.
   */
  public Object[] updateGroupBounds(Object[] cells, int border)
  {
    return updateGroupBounds(cells, border, false);
  }

  /**
   * Updates the bounds of the given array of groups so that it includes
   * all child vertices.
   *
   * @param cells The groups whose bounds should be updated.
   * @param border The border to be added in the group.
   * @param moveParent Specifies if the group should be moved.
   */
  public Object[] updateGroupBounds(Object[] cells, int border,
      boolean moveParent)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    model.beginUpdate();
    try
    {
      for (int i = 0; i < cells.length; i++)
      {
        mxGeometry geo = getCellGeometry(cells[i]);

        if (geo != null)
        {
          Object[] children = getChildCells(cells[i]);

          if (children != null && children.length > 0)
          {
            mxRectangle childBounds = getBoundingBoxFromGeometry(children);

            if (childBounds.getWidth() > 0
                && childBounds.getHeight() > 0)
            {
              mxRectangle size = (isSwimlane(cells[i])) ? getStartSize(cells[i])
                  : new mxRectangle();

              geo = (mxGeometry) geo.clone();

              if (moveParent)
              {
                geo.setX(geo.getX() + childBounds.getX()
                    - size.getWidth() - border);
                geo.setY(geo.getY() + childBounds.getY()
                    - size.getHeight() - border);
              }

              geo.setWidth(childBounds.getWidth()
                  + size.getWidth() + 2 * border);
              geo.setHeight(childBounds.getHeight()
                  + size.getHeight() + 2 * border);

              model.setGeometry(cells[i], geo);
              moveCells(children,
                  -childBounds.getX() + size.getWidth()
                      + border, -childBounds.getY()
                      + size.getHeight() + border);
            }
          }
        }
      }
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  //
  // Cell cloning, insertion and removal
  //

  /**
   * Clones all cells in the given array. To clone all children in a cell and
   * add them to another graph:
   *
   * <code>
   * graph2.addCells(graph.cloneCells(new Object[] { parent }));
   * </code>
   */
  public Object[] cloneCells(Object[] cells)
  {
    return cloneCells(cells, true);
  }

  /**
   * Returns the clones for the given cells. If the terminal of an edge is
   * not in the given array, then the respective end is assigned a terminal
   * point and the terminal is removed. If a cloned edge is invalid and
   * allowInvalidEdges is false, then a null pointer will be at this position
   * in the returned array. Use getCloneableCells on the input array to only
   * clone the cells where isCellCloneable returns true.
   *
   * @param cells Array of mxCells to be cloned.
   * @return Returns the clones of the given cells.
   */
  public Object[] cloneCells(Object[] cells, boolean allowInvalidEdges)
  {
    Object[] clones = null;

    if (cells != null)
    {
      Collection<Object> tmp = new LinkedHashSet<Object>(cells.length);
      tmp.addAll(Arrays.asList(cells));

      if (!tmp.isEmpty())
      {
        double scale = view.getScale();
        mxPoint trans = view.getTranslate();
        clones = model.cloneCells(cells, true);

        for (int i = 0; i < cells.length; i++)
        {
          if (!allowInvalidEdges
              && model.isEdge(clones[i])
              && getEdgeValidationError(clones[i],
                  model.getTerminal(clones[i], true),
                  model.getTerminal(clones[i], false)) != null)
          {
            clones[i] = null;
          }
          else
          {
            mxGeometry g = model.getGeometry(clones[i]);

            if (g != null)
            {
              mxCellState state = view.getState(cells[i]);
              mxCellState pstate = view.getState(model
                  .getParent(cells[i]));

              if (state != null && pstate != null)
              {
                double dx = pstate.getOrigin().getX();
                double dy = pstate.getOrigin().getY();

                if (model.isEdge(clones[i]))
                {
                  // Checks if the source is cloned or sets the terminal point
                  Object src = model.getTerminal(cells[i],
                      true);

                  while (src != null && !tmp.contains(src))
                  {
                    src = model.getParent(src);
                  }

                  if (src == null)
                  {
                    mxPoint pt = state.getAbsolutePoint(0);
                    g.setTerminalPoint(
                        new mxPoint(pt.getX() / scale
                            - trans.getX(), pt
                            .getY()
                            / scale
                            - trans.getY()), true);
                  }

                  // Checks if the target is cloned or sets the terminal point
                  Object trg = model.getTerminal(cells[i],
                      false);

                  while (trg != null && !tmp.contains(trg))
                  {
                    trg = model.getParent(trg);
                  }

                  if (trg == null)
                  {
                    mxPoint pt = state
                        .getAbsolutePoint(state
                            .getAbsolutePointCount() - 1);
                    g.setTerminalPoint(
                        new mxPoint(pt.getX() / scale
                            - trans.getX(), pt
                            .getY()
                            / scale
                            - trans.getY()), false);
                  }

                  // Translates the control points
                  List<mxPoint> points = g.getPoints();

                  if (points != null)
                  {
                    Iterator<mxPoint> it = points
                        .iterator();

                    while (it.hasNext())
                    {
                      mxPoint pt = it.next();
                      pt.setX(pt.getX() + dx);
                      pt.setY(pt.getY() + dy);
                    }
                  }
                }
                else
                {
                  g.setX(g.getX() + dx);
                  g.setY(g.getY() + dy);
                }
              }
            }
          }
        }
      }
      else
      {
        clones = new Object[] {};
      }
    }

    return clones;
  }

  /**
   * Creates and adds a new vertex with an empty style.
   */
  public Object insertVertex(Object parent, String id, Object value,
      double x, double y, double width, double height)
  {
    return insertVertex(parent, id, value, x, y, width, height, null);
  }

  /**
   * Adds a new vertex into the given parent using value as the user object
   * and the given coordinates as the geometry of the new vertex. The id and
   * style are used for the respective properties of the new cell, which is
   * returned.
   *
   * @param parent Cell that specifies the parent of the new vertex.
   * @param id Optional string that defines the Id of the new vertex.
   * @param value Object to be used as the user object.
   * @param x Integer that defines the x coordinate of the vertex.
   * @param y Integer that defines the y coordinate of the vertex.
   * @param width Integer that defines the width of the vertex.
   * @param height Integer that defines the height of the vertex.
   * @param style Optional string that defines the cell style.
   * @return Returns the new vertex that has been inserted.
   */
  public Object insertVertex(Object parent, String id, Object value,
      double x, double y, double width, double height, String style)
  {
    Object vertex = createVertex(parent, id, value, x, y, width, height,
        style);

    return addCell(vertex, parent);
  }

  /**
   * Hook method that creates the new vertex for insertVertex.
   *
   * @param parent Cell that specifies the parent of the new vertex.
   * @param id Optional string that defines the Id of the new vertex.
   * @param value Object to be used as the user object.
   * @param x Integer that defines the x coordinate of the vertex.
   * @param y Integer that defines the y coordinate of the vertex.
   * @param width Integer that defines the width of the vertex.
   * @param height Integer that defines the height of the vertex.
   * @param style Optional string that defines the cell style.
   * @return Returns the new vertex to be inserted.
   */
  public Object createVertex(Object parent, String id, Object value,
      double x, double y, double width, double height, String style)
  {
    mxGeometry geometry = new mxGeometry(x, y, width, height);
    mxCell vertex = new mxCell(value, geometry, style);

    vertex.setId(id);
    vertex.setVertex(true);
    vertex.setConnectable(true);

    return vertex;
  }

  /**
   * Creates and adds a new edge with an empty style.
   */
  public Object insertEdge(Object parent, String id, Object value,
      Object source, Object target)
  {
    return insertEdge(parent, id, value, source, target, null);
  }

  /**
   * Adds a new edge into the given parent using value as the user object and
   * the given source and target as the terminals of the new edge. The Id and
   * style are used for the respective properties of the new cell, which is
   * returned.
   *
   * @param parent Cell that specifies the parent of the new edge.
   * @param id Optional string that defines the Id of the new edge.
   * @param value Object to be used as the user object.
   * @param source Cell that defines the source of the edge.
   * @param target Cell that defines the target of the edge.
   * @param style Optional string that defines the cell style.
   * @return Returns the new edge that has been inserted.
   */
  public Object insertEdge(Object parent, String id, Object value,
      Object source, Object target, String style)
  {
    Object edge = createEdge(parent, id, value, source, target, style);

    return addEdge(edge, parent, source, target, null);
  }

  /**
   * Hook method that creates the new edge for insertEdge. This
   * implementation does not set the source and target of the edge, these
   * are set when the edge is added to the model.
   *
   * @param parent Cell that specifies the parent of the new edge.
   * @param id Optional string that defines the Id of the new edge.
   * @param value Object to be used as the user object.
   * @param source Cell that defines the source of the edge.
   * @param target Cell that defines the target of the edge.
   * @param style Optional string that defines the cell style.
   * @return Returns the new edge to be inserted.
   */
  public Object createEdge(Object parent, String id, Object value,
      Object source, Object target, String style)
  {
    mxCell edge = new mxCell(value, new mxGeometry(), style);

    edge.setId(id);
    edge.setEdge(true);
    edge.getGeometry().setRelative(true);

    return edge;
  }

  /**
   * Adds the edge to the parent and connects it to the given source and
   * target terminals. This is a shortcut method.
   *
   * @param edge Edge to be inserted into the given parent.
   * @param parent Object that represents the new parent. If no parent is
   * given then the default parent is used.
   * @param source Optional cell that represents the source terminal.
   * @param target Optional cell that represents the target terminal.
   * @param index Optional index to insert the cells at. Default is to append.
   * @return Returns the edge that was added.
   */
  public Object addEdge(Object edge, Object parent, Object source,
      Object target, Integer index)
  {
    return addCell(edge, parent, index, source, target);
  }

  /**
   * Adds the cell to the default parent. This is a shortcut method.
   *
   * @param cell Cell to be inserted.
   * @return Returns the cell that was added.
   */
  public Object addCell(Object cell)
  {
    return addCell(cell, null);
  }

  /**
   * Adds the cell to the parent. This is a shortcut method.
   *
   * @param cell Cell tobe inserted.
   * @param parent Object that represents the new parent. If no parent is
   * given then the default parent is used.
   * @return Returns the cell that was added.
   */
  public Object addCell(Object cell, Object parent)
  {
    return addCell(cell, parent, null, null, null);
  }

  /**
   * Adds the cell to the parent and connects it to the given source and
   * target terminals. This is a shortcut method.
   *
   * @param cell Cell to be inserted into the given parent.
   * @param parent Object that represents the new parent. If no parent is
   * given then the default parent is used.
   * @param index Optional index to insert the cells at. Default is to append.
   * @param source Optional cell that represents the source terminal.
   * @param target Optional cell that represents the target terminal.
   * @return Returns the cell that was added.
   */
  public Object addCell(Object cell, Object parent, Integer index,
      Object source, Object target)
  {
    return addCells(new Object[] { cell }, parent, index, source, target)[0];
  }

  /**
   * Adds the cells to the default parent. This is a shortcut method.
   *
   * @param cells Array of cells to be inserted.
   * @return Returns the cells that were added.
   */
  public Object[] addCells(Object[] cells)
  {
    return addCells(cells, null);
  }

  /**
   * Adds the cells to the parent. This is a shortcut method.
   *
   * @param cells Array of cells to be inserted.
   * @param parent Optional cell that represents the new parent. If no parent
   * is specified then the default parent is used.
   * @return Returns the cells that were added.
   */
  public Object[] addCells(Object[] cells, Object parent)
  {
    return addCells(cells, parent, null);
  }

  /**
   * Adds the cells to the parent at the given index. This is a shortcut method.
   *
   * @param cells Array of cells to be inserted.
   * @param parent Optional cell that represents the new parent. If no parent
   * is specified then the default parent is used.
   * @param index Optional index to insert the cells at. Default is to append.
   * @return Returns the cells that were added.
   */
  public Object[] addCells(Object[] cells, Object parent, Integer index)
  {
    return addCells(cells, parent, index, null, null);
  }

  /**
   * Adds the cells to the parent at the given index, connecting each cell to
   * the optional source and target terminal. The change is carried out using
   * cellsAdded. This method fires mxEvent.ADD_CELLS while the transaction
   * is in progress.
   *
   * @param cells Array of cells to be added.
   * @param parent Optional cell that represents the new parent. If no parent
   * is specified then the default parent is used.
   * @param index Optional index to insert the cells at. Default is to append.
   * @param source Optional source terminal for all inserted cells.
   * @param target Optional target terminal for all inserted cells.
   * @return Returns the cells that were added.
   */
  public Object[] addCells(Object[] cells, Object parent, Integer index,
      Object source, Object target)
  {
    if (parent == null)
    {
      parent = getDefaultParent();
    }

    if (index == null)
    {
      index = model.getChildCount(parent);
    }

    model.beginUpdate();
    try
    {
      cellsAdded(cells, parent, index, source, target, false);
      fireEvent(new mxEventObject(mxEvent.ADD_CELLS, "cells", cells,
          "parent", parent, "index", index, "source", source,
          "target", target));
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  /**
   * Adds the specified cells to the given parent. This method fires
   * mxEvent.CELLS_ADDED while the transaction is in progress.
   */
  public void cellsAdded(Object[] cells, Object parent, Integer index,
      Object source, Object target, boolean absolute)
  {
    if (cells != null && parent != null && index != null)
    {
      model.beginUpdate();
      try
      {
        mxCellState parentState = (absolute) ? view.getState(parent)
            : null;
        mxPoint o1 = (parentState != null) ? parentState.getOrigin()
            : null;
        mxPoint zero = new mxPoint(0, 0);

        for (int i = 0; i < cells.length; i++)
        {
          Object previous = model.getParent(cells[i]);

          // Keeps the cell at its absolute location
          if (o1 != null && cells[i] != parent && parent != previous)
          {
            mxCellState oldState = view.getState(previous);
            mxPoint o2 = (oldState != null) ? oldState.getOrigin()
                : zero;
            mxGeometry geo = model.getGeometry(cells[i]);

            if (geo != null)
            {
              double dx = o2.getX() - o1.getX();
              double dy = o2.getY() - o1.getY();

              geo = (mxGeometry) geo.clone();
              geo.translate(dx, dy);

              if (!geo.isRelative() && model.isVertex(cells[i])
                  && !isAllowNegativeCoordinates())
              {
                geo.setX(Math.max(0, geo.getX()));
                geo.setY(Math.max(0, geo.getY()));
              }

              model.setGeometry(cells[i], geo);
            }
          }

          // Decrements all following indices
          // if cell is already in parent
          if (parent == previous)
          {
            index--;
          }

          model.add(parent, cells[i], index + i);

          // Extends the parent
          if (isExtendParentsOnAdd() && isExtendParent(cells[i]))
          {
            extendParent(cells[i]);
          }

          // Constrains the child
          constrainChild(cells[i]);

          // Sets the source terminal
          if (source != null)
          {
            cellConnected(cells[i], source, true, null);
          }

          // Sets the target terminal
          if (target != null)
          {
            cellConnected(cells[i], target, false, null);
          }
        }

        fireEvent(new mxEventObject(mxEvent.CELLS_ADDED, "cells",
            cells, "parent", parent, "index", index, "source",
            source, "target", target, "absolute", absolute));

      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Removes the selection cells from the graph.
   *
   * @return Returns the cells that have been removed.
   */
  public Object[] removeCells()
  {
    return removeCells(null);
  }

  /**
   * Removes the given cells from the graph.
   *
   * @param cells Array of cells to remove.
   * @return Returns the cells that have been removed.
   */
  public Object[] removeCells(Object[] cells)
  {
    return removeCells(cells, true);
  }

  /**
   * Removes the given cells from the graph including all connected edges if
   * includeEdges is true. The change is carried out using cellsRemoved. This
   * method fires mxEvent.REMOVE_CELLS while the transaction is in progress.
   *
   * @param cells Array of cells to remove. If null is specified then the
   * selection cells which are deletable are used.
   * @param includeEdges Specifies if all connected edges should be removed as
   * well.
   */
  public Object[] removeCells(Object[] cells, boolean includeEdges)
  {
    if (cells == null)
    {
      cells = getDeletableCells(getSelectionCells());
    }

    // Adds all edges to the cells
    if (includeEdges)
    {
      cells = getDeletableCells(addAllEdges(cells));
    }

    model.beginUpdate();
    try
    {
      cellsRemoved(cells);
      fireEvent(new mxEventObject(mxEvent.REMOVE_CELLS, "cells", cells,
          "includeEdges", includeEdges));
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  /**
   * Removes the given cells from the model. This method fires
   * mxEvent.CELLS_REMOVED while the transaction is in progress.
   *
   * @param cells Array of cells to remove.
   */
  public void cellsRemoved(Object[] cells)
  {
    if (cells != null && cells.length > 0)
    {
      double scale = view.getScale();
      mxPoint tr = view.getTranslate();

      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          // Disconnects edges which are not in cells
          Collection<Object> cellSet = new HashSet<Object>();
          cellSet.addAll(Arrays.asList(cells));
          Object[] edges = getConnections(cells[i]);

          for (int j = 0; j < edges.length; j++)
          {
            if (!cellSet.contains(edges[j]))
            {
              mxGeometry geo = model.getGeometry(edges[j]);

              if (geo != null)
              {
                mxCellState state = view.getState(edges[j]);

                if (state != null)
                {
                  geo = (mxGeometry) geo.clone();
                  boolean source = view.getVisibleTerminal(
                      edges[j], true) == cells[i];
                  int n = (source) ? 0 : state
                      .getAbsolutePointCount() - 1;
                  mxPoint pt = state.getAbsolutePoint(n);

                  geo.setTerminalPoint(new mxPoint(pt.getX()
                      / scale - tr.getX(), pt.getY()
                      / scale - tr.getY()), source);
                  model.setTerminal(edges[j], null, source);
                  model.setGeometry(edges[j], geo);
                }
              }
            }
          }

          model.remove(cells[i]);
        }

        fireEvent(new mxEventObject(mxEvent.CELLS_REMOVED, "cells",
            cells));
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   *
   */
  public Object splitEdge(Object edge, Object[] cells)
  {
    return splitEdge(edge, cells, null, 0, 0);
  }

  /**
   *
   */
  public Object splitEdge(Object edge, Object[] cells, double dx, double dy)
  {
    return splitEdge(edge, cells, null, dx, dy);
  }

  /**
   * Splits the given edge by adding a newEdge between the previous source
   * and the given cell and reconnecting the source of the given edge to the
   * given cell. Fires mxEvent.SPLIT_EDGE while the transaction is in
   * progress.
   *
   * @param edge Object that represents the edge to be splitted.
   * @param cells Array that contains the cells to insert into the edge.
   * @param newEdge Object that represents the edge to be inserted.
   * @return Returns the new edge that has been inserted.
   */
  public Object splitEdge(Object edge, Object[] cells, Object newEdge,
      double dx, double dy)
  {
    if (newEdge == null)
    {
      newEdge = cloneCells(new Object[] { edge })[0];
    }

    Object parent = model.getParent(edge);
    Object source = model.getTerminal(edge, true);

    model.beginUpdate();
    try
    {
      cellsMoved(cells, dx, dy, false, false);
      cellsAdded(cells, parent, model.getChildCount(parent), null, null,
          true);
      cellsAdded(new Object[] { newEdge }, parent,
          model.getChildCount(parent), source, cells[0], false);
      cellConnected(edge, cells[0], true, null);
      fireEvent(new mxEventObject(mxEvent.SPLIT_EDGE, "edge", edge,
          "cells", cells, "newEdge", newEdge, "dx", dx, "dy", dy));
    }
    finally
    {
      model.endUpdate();
    }

    return newEdge;
  }

  //
  // Cell visibility
  //

  /**
   * Sets the visible state of the selection cells. This is a shortcut
   * method.
   *
   * @param show Boolean that specifies the visible state to be assigned.
   * @return Returns the cells whose visible state was changed.
   */
  public Object[] toggleCells(boolean show)
  {
    return toggleCells(show, null);
  }

  /**
   * Sets the visible state of the specified cells. This is a shortcut
   * method.
   *
   * @param show Boolean that specifies the visible state to be assigned.
   * @param cells Array of cells whose visible state should be changed.
   * @return Returns the cells whose visible state was changed.
   */
  public Object[] toggleCells(boolean show, Object[] cells)
  {
    return toggleCells(show, cells, true);
  }

  /**
   * Sets the visible state of the specified cells and all connected edges
   * if includeEdges is true. The change is carried out using cellsToggled.
   * This method fires mxEvent.TOGGLE_CELLS while the transaction is in
   * progress.
   *
   * @param show Boolean that specifies the visible state to be assigned.
   * @param cells Array of cells whose visible state should be changed. If
   * null is specified then the selection cells are used.
   * @return Returns the cells whose visible state was changed.
   */
  public Object[] toggleCells(boolean show, Object[] cells,
      boolean includeEdges)
  {
    if (cells == null)
    {
      cells = getSelectionCells();
    }

    // Adds all connected edges recursively
    if (includeEdges)
    {
      cells = addAllEdges(cells);
    }

    model.beginUpdate();
    try
    {
      cellsToggled(cells, show);
      fireEvent(new mxEventObject(mxEvent.TOGGLE_CELLS, "show", show,
          "cells", cells, "includeEdges", includeEdges));
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  /**
   * Sets the visible state of the specified cells.
   *
   * @param cells Array of cells whose visible state should be changed.
   * @param show Boolean that specifies the visible state to be assigned.
   */
  public void cellsToggled(Object[] cells, boolean show)
  {
    if (cells != null && cells.length > 0)
    {
      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          model.setVisible(cells[i], show);
        }
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  //
  // Folding
  //

  /**
   * Sets the collapsed state of the selection cells without recursion.
   * This is a shortcut method.
   *
   * @param collapse Boolean that specifies the collapsed state to be
   * assigned.
   * @return Returns the cells whose collapsed state was changed.
   */
  public Object[] foldCells(boolean collapse)
  {
    return foldCells(collapse, false);
  }

  /**
   * Sets the collapsed state of the selection cells. This is a shortcut
   * method.
   *
   * @param collapse Boolean that specifies the collapsed state to be
   * assigned.
   * @param recurse Boolean that specifies if the collapsed state should
   * be assigned to all descendants.
   * @return Returns the cells whose collapsed state was changed.
   */
  public Object[] foldCells(boolean collapse, boolean recurse)
  {
    return foldCells(collapse, recurse, null);
  }

  /**
   * Sets the collapsed state of the specified cells and all descendants
   * if recurse is true. The change is carried out using cellsFolded.
   * This method fires mxEvent.FOLD_CELLS while the transaction is in
   * progress. Returns the cells whose collapsed state was changed.
   *
   * @param collapse Boolean indicating the collapsed state to be assigned.
   * @param recurse Boolean indicating if the collapsed state of all
   * descendants should be set.
   * @param cells Array of cells whose collapsed state should be set. If
   * null is specified then the foldable selection cells are used.
   */
  public Object[] foldCells(boolean collapse, boolean recurse, Object[] cells)
  {
    if (cells == null)
    {
      cells = getFoldableCells(getSelectionCells(), collapse);
    }

    model.beginUpdate();
    try
    {
      cellsFolded(cells, collapse, recurse);
      fireEvent(new mxEventObject(mxEvent.FOLD_CELLS, "cells", cells,
          "collapse", collapse, "recurse", recurse));
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  /**
   * Sets the collapsed state of the specified cells. This method fires
   * mxEvent.CELLS_FOLDED while the transaction is in progress. Returns the
   * cells whose collapsed state was changed.
   *
   * @param cells Array of cells whose collapsed state should be set.
   * @param collapse Boolean indicating the collapsed state to be assigned.
   * @param recurse Boolean indicating if the collapsed state of all
   * descendants should be set.
   */
  public void cellsFolded(Object[] cells, boolean collapse, boolean recurse)
  {
    if (cells != null && cells.length > 0)
    {
      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          if (collapse != isCellCollapsed(cells[i]))
          {
            model.setCollapsed(cells[i], collapse);
            swapBounds(cells[i], collapse);

            if (isExtendParent(cells[i]))
            {
              extendParent(cells[i]);
            }

            if (recurse)
            {
              Object[] children = mxGraphModel.getChildren(model,
                  cells[i]);
              cellsFolded(children, collapse, recurse);
            }
          }
        }

        fireEvent(new mxEventObject(mxEvent.CELLS_FOLDED, "cells",
            cells, "collapse", collapse, "recurse", recurse));
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Swaps the alternate and the actual bounds in the geometry of the given
   * cell invoking updateAlternateBounds before carrying out the swap.
   *
   * @param cell Cell for which the bounds should be swapped.
   * @param willCollapse Boolean indicating if the cell is going to be collapsed.
   */
  public void swapBounds(Object cell, boolean willCollapse)
  {
    if (cell != null)
    {
      mxGeometry geo = model.getGeometry(cell);

      if (geo != null)
      {
        geo = (mxGeometry) geo.clone();

        updateAlternateBounds(cell, geo, willCollapse);
        geo.swap();

        model.setGeometry(cell, geo);
      }
    }
  }

  /**
   * Updates or sets the alternate bounds in the given geometry for the given
   * cell depending on whether the cell is going to be collapsed. If no
   * alternate bounds are defined in the geometry and
   * collapseToPreferredSize is true, then the preferred size is used for
   * the alternate bounds. The top, left corner is always kept at the same
   * location.
   *
   * @param cell Cell for which the geometry is being udpated.
   * @param geo Geometry for which the alternate bounds should be updated.
   * @param willCollapse Boolean indicating if the cell is going to be collapsed.
   */
  public void updateAlternateBounds(Object cell, mxGeometry geo,
      boolean willCollapse)
  {
    if (cell != null && geo != null)
    {
      if (geo.getAlternateBounds() == null)
      {
        mxRectangle bounds = null;

        if (isCollapseToPreferredSize())
        {
          bounds = getPreferredSizeForCell(cell);

          if (isSwimlane(cell))
          {
            mxRectangle size = getStartSize(cell);

            bounds.setHeight(Math.max(bounds.getHeight(),
                size.getHeight()));
            bounds.setWidth(Math.max(bounds.getWidth(),
                size.getWidth()));
          }
        }

        if (bounds == null)
        {
          bounds = geo;
        }

        geo.setAlternateBounds(new mxRectangle(geo.getX(), geo.getY(),
            bounds.getWidth(), bounds.getHeight()));
      }
      else
      {
        geo.getAlternateBounds().setX(geo.getX());
        geo.getAlternateBounds().setY(geo.getY());
      }
    }
  }

  /**
   * Returns an array with the given cells and all edges that are connected
   * to a cell or one of its descendants.
   */
  public Object[] addAllEdges(Object[] cells)
  {
    List<Object> allCells = new ArrayList<Object>(cells.length);
    allCells.addAll(Arrays.asList(cells));
    allCells.addAll(Arrays.asList(getAllEdges(cells)));

    return allCells.toArray();
  }

  /**
   * Returns all edges connected to the given cells or their descendants.
   */
  public Object[] getAllEdges(Object[] cells)
  {
    List<Object> edges = new ArrayList<Object>();

    if (cells != null)
    {
      for (int i = 0; i < cells.length; i++)
      {
        int edgeCount = model.getEdgeCount(cells[i]);

        for (int j = 0; j < edgeCount; j++)
        {
          edges.add(model.getEdgeAt(cells[i], j));
        }

        // Recurses
        Object[] children = mxGraphModel.getChildren(model, cells[i]);
        edges.addAll(Arrays.asList(getAllEdges(children)));
      }
    }

    return edges.toArray();
  }

  //
  // Cell sizing
  //

  /**
   * Updates the size of the given cell in the model using
   * getPreferredSizeForCell to get the new size. This function
   * fires beforeUpdateSize and afterUpdateSize events.
   *
   * @param cell <mxCell> for which the size should be changed.
   */
  public Object updateCellSize(Object cell)
  {
    return updateCellSize(cell, false);
  }

  /**
   * Updates the size of the given cell in the model using
   * getPreferredSizeForCell to get the new size. This function
   * fires mxEvent.UPDATE_CELL_SIZE.
   *
   * @param cell Cell for which the size should be changed.
   */
  public Object updateCellSize(Object cell, boolean ignoreChildren)
  {
    model.beginUpdate();
    try
    {
      cellSizeUpdated(cell, ignoreChildren);
      fireEvent(new mxEventObject(mxEvent.UPDATE_CELL_SIZE, "cell", cell,
          "ignoreChildren", ignoreChildren));
    }
    finally
    {
      model.endUpdate();
    }

    return cell;
  }

  /**
   * Updates the size of the given cell in the model using
   * getPreferredSizeForCell to get the new size.
   *
   * @param cell Cell for which the size should be changed.
   */
  public void cellSizeUpdated(Object cell, boolean ignoreChildren)
  {
    if (cell != null)
    {
      model.beginUpdate();
      try
      {
        mxRectangle size = getPreferredSizeForCell(cell);
        mxGeometry geo = model.getGeometry(cell);

        if (size != null && geo != null)
        {
          boolean collapsed = isCellCollapsed(cell);
          geo = (mxGeometry) geo.clone();

          if (isSwimlane(cell))
          {
            mxCellState state = view.getState(cell);
            Map<String, Object> style = (state != null) ? state
                .getStyle() : getCellStyle(cell);
            String cellStyle = model.getStyle(cell);

            if (cellStyle == null)
            {
              cellStyle = "";
            }

            if (mxUtils.isTrue(style, mxConstants.STYLE_HORIZONTAL,
                true))
            {
              cellStyle = mxUtils.setStyle(cellStyle,
                  mxConstants.STYLE_STARTSIZE,
                  String.valueOf(size.getHeight() + 8));

              if (collapsed)
              {
                geo.setHeight(size.getHeight() + 8);
              }

              geo.setWidth(size.getWidth());
            }
            else
            {
              cellStyle = mxUtils.setStyle(cellStyle,
                  mxConstants.STYLE_STARTSIZE,
                  String.valueOf(size.getWidth() + 8));

              if (collapsed)
              {
                geo.setWidth(size.getWidth() + 8);
              }

              geo.setHeight(size.getHeight());
            }

            model.setStyle(cell, cellStyle);
          }
          else
          {
            geo.setWidth(size.getWidth());
            geo.setHeight(size.getHeight());
          }

          if (!ignoreChildren && !collapsed)
          {
            mxRectangle bounds = view.getBounds(mxGraphModel
                .getChildren(model, cell));

            if (bounds != null)
            {
              mxPoint tr = view.getTranslate();
              double scale = view.getScale();

              double width = (bounds.getX() + bounds.getWidth())
                  / scale - geo.getX() - tr.getX();
              double height = (bounds.getY() + bounds.getHeight())
                  / scale - geo.getY() - tr.getY();

              geo.setWidth(Math.max(geo.getWidth(), width));
              geo.setHeight(Math.max(geo.getHeight(), height));
            }
          }

          cellsResized(new Object[] { cell },
              new mxRectangle[] { geo });
        }
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Returns the preferred width and height of the given <mxCell> as an
   * <mxRectangle>.
   *
   * @param cell <mxCell> for which the preferred size should be returned.
   */
  public mxRectangle getPreferredSizeForCell(Object cell)
  {
    mxRectangle result = null;

    if (cell != null)
    {
      mxCellState state = view.getState(cell);
      Map<String, Object> style = (state != null) ? state.style
          : getCellStyle(cell);

      if (style != null && !model.isEdge(cell))
      {
        double dx = 0;
        double dy = 0;

        // Adds dimension of image if shape is a label
        if (getImage(state) != null
            || mxUtils.getString(style, mxConstants.STYLE_IMAGE) != null)
        {
          if (mxUtils.getString(style, mxConstants.STYLE_SHAPE, "")
              .equals(mxConstants.SHAPE_LABEL))
          {
            if (mxUtils.getString(style,
                mxConstants.STYLE_VERTICAL_ALIGN, "").equals(
                mxConstants.ALIGN_MIDDLE))
            {
              dx += mxUtils.getDouble(style,
                  mxConstants.STYLE_IMAGE_WIDTH,
                  mxConstants.DEFAULT_IMAGESIZE);
            }

            if (mxUtils.getString(style, mxConstants.STYLE_ALIGN,
                "").equals(mxConstants.ALIGN_CENTER))
            {
              dy += mxUtils.getDouble(style,
                  mxConstants.STYLE_IMAGE_HEIGHT,
                  mxConstants.DEFAULT_IMAGESIZE);
            }
          }
        }

        // Adds spacings
        double spacing = mxUtils.getDouble(style,
            mxConstants.STYLE_SPACING);
        dx += 2 * spacing;
        dx += mxUtils.getDouble(style, mxConstants.STYLE_SPACING_LEFT);
        dx += mxUtils.getDouble(style, mxConstants.STYLE_SPACING_RIGHT);

        dy += 2 * spacing;
        dy += mxUtils.getDouble(style, mxConstants.STYLE_SPACING_TOP);
        dy += mxUtils
            .getDouble(style, mxConstants.STYLE_SPACING_BOTTOM);

        // LATER: Add space for collapse/expand icon if applicable

        // Adds space for label
        String value = getLabel(cell);

        if (value != null && value.length() > 0)
        {
          // FIXME: Check word-wrap style and balance width/height
          mxRectangle size = mxUtils.getLabelSize(value, style,
              isHtmlLabel(cell), 0);
          double width = size.getWidth() + dx;
          double height = size.getHeight() + dy;

          if (!mxUtils.isTrue(style, mxConstants.STYLE_HORIZONTAL,
              true))
          {
            double tmp = height;

            height = width;
            width = tmp;
          }

          if (gridEnabled)
          {
            width = snap(width + gridSize / 2);
            height = snap(height + gridSize / 2);
          }

          result = new mxRectangle(0, 0, width, height);
        }
        else
        {
          double gs2 = 4 * gridSize;
          result = new mxRectangle(0, 0, gs2, gs2);
        }
      }
    }

    return result;
  }

  /**
   * Sets the bounds of the given cell using resizeCells. Returns the
   * cell which was passed to the function.
   *
   * @param cell <mxCell> whose bounds should be changed.
   * @param bounds <mxRectangle> that represents the new bounds.
   */
  public Object resizeCell(Object cell, mxRectangle bounds)
  {
    return resizeCells(new Object[] { cell }, new mxRectangle[] { bounds })[0];
  }

  /**
   * Sets the bounds of the given cells and fires a mxEvent.RESIZE_CELLS
   * event. while the transaction is in progress. Returns the cells which
   * have been passed to the function.
   *
   * @param cells Array of cells whose bounds should be changed.
   * @param bounds Array of rectangles that represents the new bounds.
   */
  public Object[] resizeCells(Object[] cells, mxRectangle[] bounds)
  {
    model.beginUpdate();
    try
    {
      cellsResized(cells, bounds);
      fireEvent(new mxEventObject(mxEvent.RESIZE_CELLS, "cells", cells,
          "bounds", bounds));
    }
    finally
    {
      model.endUpdate();
    }

    return cells;
  }

  /**
   * Sets the bounds of the given cells and fires a <mxEvent.CELLS_RESIZED>
   * event. If extendParents is true, then the parent is extended if a child
   * size is changed so that it overlaps with the parent.
   *
   * @param cells Array of <mxCells> whose bounds should be changed.
   * @param bounds Array of <mxRectangles> that represents the new bounds.
   */
  public void cellsResized(Object[] cells, mxRectangle[] bounds)
  {
    if (cells != null && bounds != null && cells.length == bounds.length)
    {
      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          mxRectangle tmp = bounds[i];
          mxGeometry geo = model.getGeometry(cells[i]);

          if (geo != null
              && (geo.getX() != tmp.getX()
                  || geo.getY() != tmp.getY()
                  || geo.getWidth() != tmp.getWidth() || geo
                  .getHeight() != tmp.getHeight()))
          {
            geo = (mxGeometry) geo.clone();

            if (geo.isRelative())
            {
              mxPoint offset = geo.getOffset();

              if (offset != null)
              {
                offset.setX(offset.getX() + tmp.getX()
                    - geo.getX());
                offset.setY(offset.getY() + tmp.getY()
                    - geo.getY());
              }
            }
            else
            {
              geo.setX(tmp.getX());
              geo.setY(tmp.getY());
            }

            geo.setWidth(tmp.getWidth());
            geo.setHeight(tmp.getHeight());

            if (!geo.isRelative() && model.isVertex(cells[i])
                && !isAllowNegativeCoordinates())
            {
              geo.setX(Math.max(0, geo.getX()));
              geo.setY(Math.max(0, geo.getY()));
            }

            model.setGeometry(cells[i], geo);

            if (isExtendParent(cells[i]))
            {
              extendParent(cells[i]);
            }
          }
        }

        if (isResetEdgesOnResize())
        {
          resetEdges(cells);
        }

        // RENAME BOUNDSARRAY TO BOUNDS
        fireEvent(new mxEventObject(mxEvent.CELLS_RESIZED, "cells",
            cells, "bounds", bounds));
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Resizes the parents recursively so that they contain the complete area
   * of the resized child cell.
   *
   * @param cell <mxCell> that has been resized.
   */
  public void extendParent(Object cell)
  {
    if (cell != null)
    {
      Object parent = model.getParent(cell);
      mxGeometry p = model.getGeometry(parent);

      if (parent != null && p != null && !isCellCollapsed(parent))
      {
        mxGeometry geo = model.getGeometry(cell);

        if (geo != null
            && (p.getWidth() < geo.getX() + geo.getWidth() || p
                .getHeight() < geo.getY() + geo.getHeight()))
        {
          p = (mxGeometry) p.clone();

          p.setWidth(Math.max(p.getWidth(),
              geo.getX() + geo.getWidth()));
          p.setHeight(Math.max(p.getHeight(),
              geo.getY() + geo.getHeight()));

          cellsResized(new Object[] { parent },
              new mxRectangle[] { p });
        }
      }
    }
  }

  //
  // Cell moving
  //

  /**
   * Moves the cells by the given amount. This is a shortcut method.
   */
  public Object[] moveCells(Object[] cells, double dx, double dy)
  {
    return moveCells(cells, dx, dy, false);
  }

  /**
   * Moves or clones the cells and moves the cells or clones by the given
   * amount. This is a shortcut method.
   */
  public Object[] moveCells(Object[] cells, double dx, double dy,
      boolean clone)
  {
    return moveCells(cells, dx, dy, clone, null, null);
  }

  /**
   * Moves or clones the specified cells and moves the cells or clones by the
   * given amount, adding them to the optional target cell. The location is
   * the position of the mouse pointer as the mouse was released. The change
   * is carried out using cellsMoved. This method fires mxEvent.MOVE_CELLS
   * while the transaction is in progress.
   *
   * @param cells Array of cells to be moved, cloned or added to the target.
   * @param dx Integer that specifies the x-coordinate of the vector.
   * @param dy Integer that specifies the y-coordinate of the vector.
   * @param clone Boolean indicating if the cells should be cloned.
   * @param target Cell that represents the new parent of the cells.
   * @param location Location where the mouse was released.
   * @return Returns the cells that were moved.
   */
  public Object[] moveCells(Object[] cells, double dx, double dy,
      boolean clone, Object target, Point location)
  {
    if (cells != null && (dx != 0 || dy != 0 || clone || target != null))
    {
      model.beginUpdate();
      try
      {
        if (clone)
        {
          cells = cloneCells(cells, isCloneInvalidEdges());

          if (target == null)
          {
            target = getDefaultParent();
          }
        }

        cellsMoved(cells, dx, dy, !clone && isDisconnectOnMove()
            && isAllowDanglingEdges(), target == null);

        if (target != null)
        {
          Integer index = model.getChildCount(target);
          cellsAdded(cells, target, index, null, null, true);
        }

        fireEvent(new mxEventObject(mxEvent.MOVE_CELLS, "cells", cells,
            "dx", dx, "dy", dy, "clone", clone, "target", target,
            "location", location));
      }
      finally
      {
        model.endUpdate();
      }
    }

    return cells;
  }

  /**
   * Moves the specified cells by the given vector, disconnecting the cells
   * using disconnectGraph if disconnect is true. This method fires
   * mxEvent.CELLS_MOVED while the transaction is in progress.
   */
  public void cellsMoved(Object[] cells, double dx, double dy,
      boolean disconnect, boolean constrain)
  {
    if (cells != null && (dx != 0 || dy != 0))
    {
      model.beginUpdate();
      try
      {
        if (disconnect)
        {
          disconnectGraph(cells);
        }

        for (int i = 0; i < cells.length; i++)
        {
          translateCell(cells[i], dx, dy);

          if (constrain)
          {
            constrainChild(cells[i]);
          }
        }

        if (isResetEdgesOnMove())
        {
          resetEdges(cells);
        }

        fireEvent(new mxEventObject(mxEvent.CELLS_MOVED, "cells",
            cells, "dx", dx, "dy", dy, "disconnect", disconnect));
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Translates the geometry of the given cell and stores the new,
   * translated geometry in the model as an atomic change.
   */
  public void translateCell(Object cell, double dx, double dy)
  {
    mxGeometry geo = model.getGeometry(cell);

    if (geo != null)
    {
      geo = (mxGeometry) geo.clone();
      geo.translate(dx, dy);

      if (!geo.isRelative() && model.isVertex(cell)
          && !isAllowNegativeCoordinates())
      {
        geo.setX(Math.max(0, geo.getX()));
        geo.setY(Math.max(0, geo.getY()));
      }

      if (geo.isRelative() && !model.isEdge(cell))
      {
        if (geo.getOffset() == null)
        {
          geo.setOffset(new mxPoint(dx, dy));
        }
        else
        {
          mxPoint offset = geo.getOffset();

          offset.setX(offset.getX() + dx);
          offset.setY(offset.getY() + dy);
        }
      }

      model.setGeometry(cell, geo);
    }
  }

  /**
   * Returns the mxRectangle inside which a cell is to be kept.
   */
  public mxRectangle getCellContainmentArea(Object cell)
  {
    if (cell != null && !model.isEdge(cell))
    {
      Object parent = model.getParent(cell);

      if (parent == getDefaultParent() || parent == getCurrentRoot())
      {
        return getMaximumGraphBounds();
      }
      else if (parent != null && parent != getDefaultParent())
      {
        mxGeometry g = model.getGeometry(parent);

        if (g != null)
        {
          double x = 0;
          double y = 0;
          double w = g.getWidth();
          double h = g.getHeight();

          if (isSwimlane(parent))
          {
            mxRectangle size = getStartSize(parent);

            x = size.getWidth();
            w -= size.getWidth();
            y = size.getHeight();
            h -= size.getHeight();
          }

          return new mxRectangle(x, y, w, h);
        }
      }
    }

    return null;
  }

  /**
   * @return the maximumGraphBounds
   */
  public mxRectangle getMaximumGraphBounds()
  {
    return maximumGraphBounds;
  }

  /**
   * @param value the maximumGraphBounds to set
   */
  public void setMaximumGraphBounds(mxRectangle value)
  {
    mxRectangle oldValue = maximumGraphBounds;
    maximumGraphBounds = value;

    changeSupport.firePropertyChange("maximumGraphBounds", oldValue,
        maximumGraphBounds);
  }

  /**
   * Keeps the given cell inside the bounds returned by
   * getCellContainmentArea for its parent, according to the rules defined by
   * getOverlap and isConstrainChild. This modifies the cell's geometry
   * in-place and does not clone it.
   *
   * @param cell Cell which should be constrained.
   */
  public void constrainChild(Object cell)
  {
    if (cell != null)
    {
      mxGeometry geo = model.getGeometry(cell);
      mxRectangle area = (isConstrainChild(cell)) ? getCellContainmentArea(cell)
          : getMaximumGraphBounds();

      if (geo != null && area != null)
      {
        // Keeps child within the content area of the parent
        if (!geo.isRelative()
            && (geo.getX() < area.getX()
                || geo.getY() < area.getY()
                || area.getWidth() < geo.getX()
                    + geo.getWidth() || area.getHeight() < geo
                .getY() + geo.getHeight()))
        {
          double overlap = getOverlap(cell);

          if (area.getWidth() > 0)
          {
            geo.setX(Math.min(geo.getX(),
                area.getX() + area.getWidth() - (1 - overlap)
                    * geo.getWidth()));
          }

          if (area.getHeight() > 0)
          {
            geo.setY(Math.min(geo.getY(),
                area.getY() + area.getHeight() - (1 - overlap)
                    * geo.getHeight()));
          }

          geo.setX(Math.max(geo.getX(), area.getX() - geo.getWidth()
              * overlap));
          geo.setY(Math.max(geo.getY(), area.getY() - geo.getHeight()
              * overlap));
        }
      }
    }
  }

  /**
   * Resets the control points of the edges that are connected to the given
   * cells if not both ends of the edge are in the given cells array.
   *
   * @param cells Array of mxCells for which the connected edges should be
   * reset.
   */
  public void resetEdges(Object[] cells)
  {
    if (cells != null)
    {
      // Prepares a hashtable for faster cell lookups
      HashSet<Object> set = new HashSet<Object>(Arrays.asList(cells));

      model.beginUpdate();
      try
      {
        for (int i = 0; i < cells.length; i++)
        {
          Object[] edges = mxGraphModel.getEdges(model, cells[i]);

          if (edges != null)
          {
            for (int j = 0; j < edges.length; j++)
            {
              Object source = view.getVisibleTerminal(edges[j],
                  true);
              Object target = view.getVisibleTerminal(edges[j],
                  false);

              // Checks if one of the terminals is not in the given array
              if (!set.contains(source) || !set.contains(target))
              {
                resetEdge(edges[j]);
              }
            }
          }

          resetEdges(mxGraphModel.getChildren(model, cells[i]));
        }
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Resets the control points of the given edge.
   */
  public Object resetEdge(Object edge)
  {
    mxGeometry geo = model.getGeometry(edge);

    if (geo != null)
    {
      // Resets the control points
      List<mxPoint> points = geo.getPoints();

      if (points != null && !points.isEmpty())
      {
        geo = (mxGeometry) geo.clone();
        geo.setPoints(null);
        model.setGeometry(edge, geo);
      }
    }

    return edge;
  }

  //
  // Cell connecting and connection constraints
  //

  /**
   * Returns an array of all constraints for the given terminal.
   *
   * @param terminal Cell state that represents the terminal.
   * @param source Specifies if the terminal is the source or target.
   */
  public mxConnectionConstraint[] getAllConnectionConstraints(
      mxCellState terminal, boolean source)
  {
    return null;
  }

  /**
   * Returns an connection constraint that describes the given connection
   * point. This result can then be passed to getConnectionPoint.
   *
   * @param edge Cell state that represents the edge.
   * @param terminal Cell state that represents the terminal.
   * @param source Boolean indicating if the terminal is the source or target.
   */
  public mxConnectionConstraint getConnectionConstraint(mxCellState edge,
      mxCellState terminal, boolean source)
  {
    mxPoint point = null;
    Object x = edge.getStyle()
        .get((source) ? mxConstants.STYLE_EXIT_X
            : mxConstants.STYLE_ENTRY_X);

    if (x != null)
    {
      Object y = edge.getStyle().get(
          (source) ? mxConstants.STYLE_EXIT_Y
              : mxConstants.STYLE_ENTRY_Y);

      if (y != null)
      {
        point = new mxPoint(Double.parseDouble(x.toString()),
            Double.parseDouble(y.toString()));
      }
    }

    boolean perimeter = false;

    if (point != null)
    {
      perimeter = mxUtils.isTrue(edge.style,
          (source) ? mxConstants.STYLE_EXIT_PERIMETER
              : mxConstants.STYLE_ENTRY_PERIMETER, true);
    }

    return new mxConnectionConstraint(point, perimeter);
  }

  /**
   * Sets the connection constraint that describes the given connection point.
   * If no constraint is given then nothing is changed. To remove an existing
   * constraint from the given edge, use an empty constraint instead.
   *
   * @param edge Cell that represents the edge.
   * @param terminal Cell that represents the terminal.
   * @param source Boolean indicating if the terminal is the source or target.
   * @param constraint Optional connection constraint to be used for this connection.
   */
  public void setConnectionConstraint(Object edge, Object terminal,
      boolean source, mxConnectionConstraint constraint)
  {
    if (constraint != null)
    {
      model.beginUpdate();
      try
      {
        Object[] cells = new Object[] { edge };

        // FIXME, constraint can't be null, we've checked that above
        if (constraint == null || constraint.point == null)
        {
          setCellStyles((source) ? mxConstants.STYLE_EXIT_X
              : mxConstants.STYLE_ENTRY_X, null, cells);
          setCellStyles((source) ? mxConstants.STYLE_EXIT_Y
              : mxConstants.STYLE_ENTRY_Y, null, cells);
          setCellStyles((source) ? mxConstants.STYLE_EXIT_PERIMETER
              : mxConstants.STYLE_ENTRY_PERIMETER, null, cells);
        }
        else if (constraint.point != null)
        {
          setCellStyles((source) ? mxConstants.STYLE_EXIT_X
              : mxConstants.STYLE_ENTRY_X,
              String.valueOf(constraint.point.getX()), cells);
          setCellStyles((source) ? mxConstants.STYLE_EXIT_Y
              : mxConstants.STYLE_ENTRY_Y,
              String.valueOf(constraint.point.getY()), cells);

          // Only writes 0 since 1 is default
          if (!constraint.perimeter)
          {
            setCellStyles(
                (source) ? mxConstants.STYLE_EXIT_PERIMETER
                    : mxConstants.STYLE_ENTRY_PERIMETER,
                "0", cells);
          }
          else
          {
            setCellStyles(
                (source) ? mxConstants.STYLE_EXIT_PERIMETER
                    : mxConstants.STYLE_ENTRY_PERIMETER,
                null, cells);
          }
        }
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Sets the connection constraint that describes the given connection point.
   * If no constraint is given then nothing is changed. To remove an existing
   * constraint from the given edge, use an empty constraint instead.
   *
   * @param vertex Cell state that represents the vertex.
   * @param constraint Connection constraint that represents the connection point
   * constraint as returned by getConnectionConstraint.
   */
  public mxPoint getConnectionPoint(mxCellState vertex,
      mxConnectionConstraint constraint)
  {
    mxPoint point = null;

    if (vertex != null && constraint.point != null)
    {
      point = new mxPoint(vertex.getX() + constraint.getPoint().getX()
          * vertex.getWidth(), vertex.getY()
          + constraint.getPoint().getY() * vertex.getHeight());
    }

    if (point != null && constraint.perimeter)
    {
      point = view.getPerimeterPoint(vertex, point, false);
    }

    return point;
  }

  /**
   * Connects the specified end of the given edge to the given terminal
   * using cellConnected and fires mxEvent.CONNECT_CELL while the transaction
   * is in progress.
   */
  public Object connectCell(Object edge, Object terminal, boolean source)
  {
    return connectCell(edge, terminal, source, null);
  }

  /**
   * Connects the specified end of the given edge to the given terminal
   * using cellConnected and fires mxEvent.CONNECT_CELL while the transaction
   * is in progress.
   *
   * @param edge Edge whose terminal should be updated.
   * @param terminal New terminal to be used.
   * @param source Specifies if the new terminal is the source or target.
   * @param constraint Optional constraint to be used for this connection.
   * @return Returns the update edge.
   */
  public Object connectCell(Object edge, Object terminal, boolean source,
      mxConnectionConstraint constraint)
  {
    model.beginUpdate();
    try
    {
      Object previous = model.getTerminal(edge, source);
      cellConnected(edge, terminal, source, constraint);
      fireEvent(new mxEventObject(mxEvent.CONNECT_CELL, "edge", edge,
          "terminal", terminal, "source", source, "previous",
          previous));
    }
    finally
    {
      model.endUpdate();
    }

    return edge;
  }

  /**
   * Sets the new terminal for the given edge and resets the edge points if
   * isResetEdgesOnConnect returns true. This method fires
   * <mxEvent.CELL_CONNECTED> while the transaction is in progress.
   *
   * @param edge Edge whose terminal should be updated.
   * @param terminal New terminal to be used.
   * @param source Specifies if the new terminal is the source or target.
   * @param constraint Constraint to be used for this connection.
   */
  public void cellConnected(Object edge, Object terminal, boolean source,
      mxConnectionConstraint constraint)
  {
    if (edge != null)
    {
      model.beginUpdate();
      try
      {
        Object previous = model.getTerminal(edge, source);

        // Updates the constraint
        setConnectionConstraint(edge, terminal, source, constraint);

        // Checks if the new terminal is a port
        String id = null;

        if (isPort(terminal) && terminal instanceof mxICell)
        {
          id = ((mxICell) terminal).getId();
          terminal = getTerminalForPort(terminal, source);
        }

        // Sets or resets all previous information for connecting to a child port
        String key = (source) ? mxConstants.STYLE_SOURCE_PORT
            : mxConstants.STYLE_TARGET_PORT;
        setCellStyles(key, id, new Object[] { edge });
        model.setTerminal(edge, terminal, source);

        if (isResetEdgesOnConnect())
        {
          resetEdge(edge);
        }

        fireEvent(new mxEventObject(mxEvent.CELL_CONNECTED, "edge",
            edge, "terminal", terminal, "source", source,
            "previous", previous));
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  /**
   * Disconnects the given edges from the terminals which are not in the
   * given array.
   *
   * @param cells Array of <mxCells> to be disconnected.
   */
  public void disconnectGraph(Object[] cells)
  {
    if (cells != null)
    {
      model.beginUpdate();
      try
      {
        double scale = view.getScale();
        mxPoint tr = view.getTranslate();

        // Prepares a hashtable for faster cell lookups
        Set<Object> hash = new HashSet<Object>();

        for (int i = 0; i < cells.length; i++)
        {
          hash.add(cells[i]);
        }

        for (int i = 0; i < cells.length; i++)
        {
          if (model.isEdge(cells[i]))
          {
            mxGeometry geo = model.getGeometry(cells[i]);

            if (geo != null)
            {
              mxCellState state = view.getState(cells[i]);
              mxCellState pstate = view.getState(model
                  .getParent(cells[i]));

              if (state != null && pstate != null)
              {
                geo = (mxGeometry) geo.clone();

                double dx = -pstate.getOrigin().getX();
                double dy = -pstate.getOrigin().getY();

                Object src = model.getTerminal(cells[i], true);

                if (src != null
                    && isCellDisconnectable(cells[i], src,
                        true))
                {
                  while (src != null && !hash.contains(src))
                  {
                    src = model.getParent(src);
                  }

                  if (src == null)
                  {
                    mxPoint pt = state.getAbsolutePoint(0);
                    geo.setTerminalPoint(
                        new mxPoint(pt.getX() / scale
                            - tr.getX() + dx, pt
                            .getY()
                            / scale
                            - tr.getY() + dy), true);
                    model.setTerminal(cells[i], null, true);
                  }
                }

                Object trg = model.getTerminal(cells[i], false);

                if (trg != null
                    && isCellDisconnectable(cells[i], trg,
                        false))
                {
                  while (trg != null && !hash.contains(trg))
                  {
                    trg = model.getParent(trg);
                  }

                  if (trg == null)
                  {
                    int n = state.getAbsolutePointCount() - 1;
                    mxPoint pt = state.getAbsolutePoint(n);
                    geo.setTerminalPoint(
                        new mxPoint(pt.getX() / scale
                            - tr.getX() + dx, pt
                            .getY()
                            / scale
                            - tr.getY() + dy),
                        false);
                    model.setTerminal(cells[i], null, false);
                  }
                }
              }

              model.setGeometry(cells[i], geo);
            }
          }
        }
      }
      finally
      {
        model.endUpdate();
      }
    }
  }

  //
  // Drilldown
  //

  /**
   * Returns the current root of the displayed cell hierarchy. This is a
   * shortcut to <mxGraphView.currentRoot> in <view>.
   *
   * @return Returns the current root in the view.
   */
  public Object getCurrentRoot()
  {
    return view.getCurrentRoot();
  }

  /**
   * Returns the translation to be used if the given cell is the root cell as
   * an <mxPoint>. This implementation returns null.
   *
   * @param cell Cell that represents the root of the view.
   * @return Returns the translation of the graph for the given root cell.
   */
  public mxPoint getTranslateForRoot(Object cell)
  {
    return null;
  }

  /**
   * Returns true if the given cell is a "port", that is, when connecting to
   * it, the cell returned by getTerminalForPort should be used as the
   * terminal and the port should be referenced by the ID in either the
   * mxConstants.STYLE_SOURCE_PORT or the or the
   * mxConstants.STYLE_TARGET_PORT. Note that a port should not be movable.
   * This implementation always returns false.
   *
   * A typical implementation of this method looks as follows:
   *
   * <code>
   * public boolean isPort(Object cell)
   * {
   *   mxGeometry geo = getCellGeometry(cell);
   *  
   *   return (geo != null) ? geo.isRelative() : false;
   * }
   * </code>
   *
   * @param cell Cell that represents the port.
   * @return Returns true if the cell is a port.
   */
  public boolean isPort(Object cell)
  {
    return false;
  }

  /**
   * Returns the terminal to be used for a given port. This implementation
   * always returns the parent cell.
   *
   * @param cell Cell that represents the port.
   * @param source If the cell is the source or target port.
   * @return Returns the terminal to be used for the given port.
   */
  public Object getTerminalForPort(Object cell, boolean source)
  {
    return getModel().getParent(cell);
  }

  /**
   * Returns the offset to be used for the cells inside the given cell. The
   * root and layer cells may be identified using mxGraphModel.isRoot and
   * mxGraphModel.isLayer. This implementation returns null.
   *
   * @param cell Cell whose offset should be returned.
   * @return Returns the child offset for the given cell.
   */
  public mxPoint getChildOffsetForCell(Object cell)
  {
    return null;
  }

  /**
   *
   */
  public void enterGroup()
  {
    enterGroup(null);
  }

  /**
   * Uses the given cell as the root of the displayed cell hierarchy. If no
   * cell is specified then the selection cell is used. The cell is only used
   * if <isValidRoot> returns true.
   *
   * @param cell
   */
  public void enterGroup(Object cell)
  {
    if (cell == null)
    {
      cell = getSelectionCell();
    }

    if (cell != null && isValidRoot(cell))
    {
      view.setCurrentRoot(cell);
      clearSelection();
    }
  }

  /**
   * Changes the current root to the next valid root in the displayed cell
   * hierarchy.
   */
  public void exitGroup()
  {
    Object root = model.getRoot();
    Object current = getCurrentRoot();

    if (current != null)
    {
      Object next = model.getParent(current);

      // Finds the next valid root in the hierarchy
      while (next != root && !isValidRoot(next)
          && model.getParent(next) != root)
      {
        next = model.getParent(next);
      }

      // Clears the current root if the new root is
      // the model's root or one of the layers.
      if (next == root || model.getParent(next) == root)
      {
        view.setCurrentRoot(null);
      }
      else
      {
        view.setCurrentRoot(next);
      }

      mxCellState state = view.getState(current);

      // Selects the previous root in the graph
      if (state != null)
      {
        setSelectionCell(current);
      }
    }
  }

  /**
   * Uses the root of the model as the root of the displayed cell hierarchy
   * and selects the previous root.
   */
  public void home()
  {
    Object current = getCurrentRoot();

    if (current != null)
    {
      view.setCurrentRoot(null);
      mxCellState state = view.getState(current);

      if (state != null)
      {
        setSelectionCell(current);
      }
    }
  }

  /**
   * Returns true if the given cell is a valid root for the cell display
   * hierarchy. This implementation returns true for all non-null values.
   *
   * @param cell <mxCell> which should be checked as a possible root.
   * @return Returns true if the given cell is a valid root.
   */
  public boolean isValidRoot(Object cell)
  {
    return (cell != null);
  }

  //
  // Graph display
  //

  /**
   * Returns the bounds of the visible graph.
   */
  public mxRectangle getGraphBounds()
  {
    return view.getGraphBounds();
  }

  /**
   * Returns the bounds of the given cell.
   */
  public mxRectangle getCellBounds(Object cell)
  {
    return getCellBounds(cell, false);
  }

  /**
   * Returns the bounds of the given cell including all connected edges
   * if includeEdge is true.
   */
  public mxRectangle getCellBounds(Object cell, boolean includeEdges)
  {
    return getCellBounds(cell, includeEdges, false);
  }

  /**
   * Returns the bounds of the given cell including all connected edges
   * if includeEdge is true.
   */
  public mxRectangle getCellBounds(Object cell, boolean includeEdges,
      boolean includeDescendants)
  {
    return getCellBounds(cell, includeEdges, includeDescendants, false);
  }

  /**
   * Returns the bounding box for the geometries of the vertices in the
   * given array of cells.
   */
  public mxRectangle getBoundingBoxFromGeometry(Object[] cells)
  {
    mxRectangle result = null;

    if (cells != null)
    {
      for (int i = 0; i < cells.length; i++)
      {
        if (getModel().isVertex(cells[i]))
        {
          mxGeometry geo = getCellGeometry(cells[i]);

          if (result == null)
          {
            result = new mxRectangle(geo);
          }
          else
          {
            result.add(geo);
          }
        }
      }
    }

    return result;
  }

  /**
   * Returns the bounds of the given cell.
   */
  public mxRectangle getBoundingBox(Object cell)
  {
    return getBoundingBox(cell, false);
  }

  /**
   * Returns the bounding box of the given cell including all connected edges
   * if includeEdge is true.
   */
  public mxRectangle getBoundingBox(Object cell, boolean includeEdges)
  {
    return getBoundingBox(cell, includeEdges, false);
  }

  /**
   * Returns the bounding box of the given cell including all connected edges
   * if includeEdge is true.
   */
  public mxRectangle getBoundingBox(Object cell, boolean includeEdges,
      boolean includeDescendants)
  {
    return getCellBounds(cell, includeEdges, includeDescendants, true);
  }

  /**
   * Returns the bounding box of the given cells and their descendants.
   */
  public mxRectangle getPaintBounds(Object[] cells)
  {
    return getBoundsForCells(cells, false, true, true);
  }

  /**
   * Returns the bounds for the given cells.
   */
  public mxRectangle getBoundsForCells(Object[] cells, boolean includeEdges,
      boolean includeDescendants, boolean boundingBox)
  {
    mxRectangle result = null;

    if (cells != null && cells.length > 0)
    {
      for (int i = 0; i < cells.length; i++)
      {
        mxRectangle tmp = getCellBounds(cells[i], includeEdges,
            includeDescendants, boundingBox);

        if (tmp != null)
        {
          if (result == null)
          {
            result = new mxRectangle(tmp);
          }
          else
          {
            result.add(tmp);
          }
        }
      }
    }

    return result;
  }

  /**
   * Returns the bounds of the given cell including all connected edges
   * if includeEdge is true.
   */
  public mxRectangle getCellBounds(Object cell, boolean includeEdges,
      boolean includeDescendants, boolean boundingBox)
  {
    mxRectangle result = null;
    Object[] cells;

    // Recursively includes connected edges
    if (includeEdges)
    {
      Set<Object> allCells = new HashSet<Object>();
      allCells.add(cell);

      Set<Object> edges = new HashSet<Object>(
          Arrays.asList(getEdges(cell)));

      while (!edges.isEmpty() && !allCells.containsAll(edges))
      {
        allCells.addAll(edges);

        Set<Object> tmp = new HashSet<Object>();
        Iterator<Object> it = edges.iterator();

        while (it.hasNext())
        {
          Object edge = it.next();
          tmp.addAll(Arrays.asList(getEdges(edge)));
        }

        edges = tmp;
      }

      cells = allCells.toArray();
    }
    else
    {
      cells = new Object[] { cell };
    }

    if (boundingBox)
    {
      result = view.getBoundingBox(cells);
    }
    else
    {
      result = view.getBounds(cells);
    }

    // Recursively includes the bounds of the children
    if (includeDescendants)
    {
      int childCount = model.getChildCount(cell);

      for (int i = 0; i < childCount; i++)
      {
        mxRectangle tmp = getCellBounds(model.getChildAt(cell, i),
            includeEdges, true, boundingBox);

        if (result != null)
        {
          result.add(tmp);
        }
        else
        {
          result = tmp;
        }
      }
    }

    return result;
  }

  /**
   * Clears all cell states or the states for the hierarchy starting at the
   * given cell and validates the graph.
   */
  public void refresh()
  {
    view.reload();
    repaint();
  }

  /**
   * Fires a repaint event.
   */
  public void repaint()
  {
    repaint(null);
  }

  /**
   * Fires a repaint event. The optional region is the rectangle that needs
   * to be repainted.
   */
  public void repaint(mxRectangle region)
  {
    fireEvent(new mxEventObject(mxEvent.REPAINT, "region", region));
  }

  /**
   * Snaps the given numeric value to the grid if <gridEnabled> is true.
   *
   * @param value Numeric value to be snapped to the grid.
   * @return Returns the value aligned to the grid.
   */
  public double snap(double value)
  {
    if (gridEnabled)
    {
      value = Math.round(value / gridSize) * gridSize;
    }

    return value;
  }

  /**
   * Returns the geometry for the given cell.
   *
   * @param cell Cell whose geometry should be returned.
   * @return Returns the geometry of the cell.
   */
  public mxGeometry getCellGeometry(Object cell)
  {
    return model.getGeometry(cell);
  }

  /**
   * Returns true if the given cell is visible in this graph. This
   * implementation uses <mxGraphModel.isVisible>. Subclassers can override
   * this to implement specific visibility for cells in only one graph, that
   * is, without affecting the visible state of the cell.
   *
   * When using dynamic filter expressions for cell visibility, then the
   * graph should be revalidated after the filter expression has changed.
   *
   * @param cell Cell whose visible state should be returned.
   * @return Returns the visible state of the cell.
   */
  public boolean isCellVisible(Object cell)
  {
    return model.isVisible(cell);
  }

  /**
   * Returns true if the given cell is collapsed in this graph. This
   * implementation uses <mxGraphModel.isCollapsed>. Subclassers can override
   * this to implement specific collapsed states for cells in only one graph,
   * that is, without affecting the collapsed state of the cell.
   *
   * When using dynamic filter expressions for the collapsed state, then the
   * graph should be revalidated after the filter expression has changed.
   *
   * @param cell Cell whose collapsed state should be returned.
   * @return Returns the collapsed state of the cell.
   */
  public boolean isCellCollapsed(Object cell)
  {
    return model.isCollapsed(cell);
  }

  /**
   * Returns true if the given cell is connectable in this graph. This
   * implementation uses <mxGraphModel.isConnectable>. Subclassers can override
   * this to implement specific connectable states for cells in only one graph,
   * that is, without affecting the connectable state of the cell in the model.
   *
   * @param cell Cell whose connectable state should be returned.
   * @return Returns the connectable state of the cell.
   */
  public boolean isCellConnectable(Object cell)
  {
    return model.isConnectable(cell);
  }

  /**
   * Returns true if perimeter points should be computed such that the
   * resulting edge has only horizontal or vertical segments.
   *
   * @param edge Cell state that represents the edge.
   */
  public boolean isOrthogonal(mxCellState edge)
  {
    if (edge.getStyle().containsKey(mxConstants.STYLE_ORTHOGONAL))
    {
      return mxUtils
          .isTrue(edge.getStyle(), mxConstants.STYLE_ORTHOGONAL);
    }

    mxEdgeStyle.mxEdgeStyleFunction tmp = view.getEdgeStyle(edge, null,
        null, null);

    return tmp == mxEdgeStyle.ElbowConnector
        || tmp == mxEdgeStyle.SideToSide
        || tmp == mxEdgeStyle.TopToBottom
        || tmp == mxEdgeStyle.EntityRelation;
  }

  /**
   * Returns true if the given cell state is a loop.
   *
   * @param state <mxCellState> that represents a potential loop.
   * @return Returns true if the given cell is a loop.
   */
  public boolean isLoop(mxCellState state)
  {
    Object src = view.getVisibleTerminal(state.getCell(), true);
    Object trg = view.getVisibleTerminal(state.getCell(), false);

    return (src != null && src == trg);
  }

  //
  // Cell validation
  //

  /**
   *
   */
  public void setMultiplicities(mxMultiplicity[] value)
  {
    mxMultiplicity[] oldValue = multiplicities;
    multiplicities = value;

    changeSupport.firePropertyChange("multiplicities", oldValue,
        multiplicities);
  }

  /**
   *
   */
  public mxMultiplicity[] getMultiplicities()
  {
    return multiplicities;
  }

  /**
   * Checks if the return value of getEdgeValidationError for the given
   * arguments is null.
   *
   * @param edge Cell that represents the edge to validate.
   * @param source Cell that represents the source terminal.
   * @param target Cell that represents the target terminal.
   */
  public boolean isEdgeValid(Object edge, Object source, Object target)
  {
    return getEdgeValidationError(edge, source, target) == null;
  }

  /**
   * Returns the validation error message to be displayed when inserting or
   * changing an edges' connectivity. A return value of null means the edge
   * is valid, a return value of '' means it's not valid, but do not display
   * an error message. Any other (non-empty) string returned from this method
   * is displayed as an error message when trying to connect an edge to a
   * source and target. This implementation uses the multiplicities, as
   * well as multigraph and allowDanglingEdges to generate validation
   * errors.
   *
   * @param edge Cell that represents the edge to validate.
   * @param source Cell that represents the source terminal.
   * @param target Cell that represents the target terminal.
   */
  public String getEdgeValidationError(Object edge, Object source,
      Object target)
  {
    if (edge != null && model.getTerminal(edge, true) == null
        && model.getTerminal(edge, false) == null)
    {
      return null;
    }

    // Checks if we're dealing with a loop
    if (!isAllowLoops() && source == target && source != null)
    {
      return "";
    }

    // Checks if the connection is generally allowed
    if (!isValidConnection(source, target))
    {
      return "";
    }

    if (source != null && target != null)
    {
      StringBuffer error = new StringBuffer();

      // Checks if the cells are already connected
      // and adds an error message if required     
      if (!multigraph)
      {
        Object[] tmp = mxGraphModel.getEdgesBetween(model, source,
            target, true);

        // Checks if the source and target are not connected by another edge
        if (tmp.length > 1 || (tmp.length == 1 && tmp[0] != edge))
        {
          error.append(mxResources.get("alreadyConnected",
              "Already Connected") + "\n");
        }
      }

      // Gets the number of outgoing edges from the source
      // and the number of incoming edges from the target
      // without counting the edge being currently changed.
      int sourceOut = mxGraphModel.getDirectedEdgeCount(model, source,
          true, edge);
      int targetIn = mxGraphModel.getDirectedEdgeCount(model, target,
          false, edge);

      // Checks the change against each multiplicity rule
      if (multiplicities != null)
      {
        for (int i = 0; i < multiplicities.length; i++)
        {
          String err = multiplicities[i].check(this, edge, source,
              target, sourceOut, targetIn);

          if (err != null)
          {
            error.append(err);
          }
        }
      }

      // Validates the source and target terminals independently
      String err = validateEdge(edge, source, target);

      if (err != null)
      {
        error.append(err);
      }

      return (error.length() > 0) ? error.toString() : null;
    }

    return (allowDanglingEdges) ? null : "";
  }

  /**
   * Hook method for subclassers to return an error message for the given
   * edge and terminals. This implementation returns null.
   *
   * @param edge Cell that represents the edge to validate.
   * @param source Cell that represents the source terminal.
   * @param target Cell that represents the target terminal.
   */
  public String validateEdge(Object edge, Object source, Object target)
  {
    return null;
  }

  /**
   * Checks all multiplicities that cannot be enforced while the graph is
   * being modified, namely, all multiplicities that require a minimum of
   * 1 edge.
   *
   * @param cell Cell for which the multiplicities should be checked.
   */
  public String getCellValidationError(Object cell)
  {
    int outCount = mxGraphModel.getDirectedEdgeCount(model, cell, true);
    int inCount = mxGraphModel.getDirectedEdgeCount(model, cell, false);
    StringBuffer error = new StringBuffer();
    Object value = model.getValue(cell);

    for (int i = 0; i < multiplicities.length; i++)
    {
      mxMultiplicity rule = multiplicities[i];
      int max = rule.getMaxValue();

      if (rule.source
          && mxUtils.isNode(value, rule.type, rule.attr, rule.value)
          && ((max == 0 && outCount > 0)
              || (rule.min == 1 && outCount == 0) || (max == 1 && outCount > 1)))
      {
        error.append(rule.countError + '\n');
      }
      else if (!rule.source
          && mxUtils.isNode(value, rule.type, rule.attr, rule.value)
          && ((max == 0 && inCount > 0)
              || (rule.min == 1 && inCount == 0) || (max == 1 && inCount > 1)))
      {
        error.append(rule.countError + '\n');
      }
    }

    return (error.length() > 0) ? error.toString() : null;
  }

  /**
   * Hook method for subclassers to return an error message for the given
   * cell and validation context. This implementation returns null.
   *
   * @param cell Cell that represents the cell to validate.
   * @param context Hashtable that represents the global validation state.
   */
  public String validateCell(Object cell, Hashtable<Object, Object> context)
  {
    return null;
  }

  //
  // Graph appearance
  //

  /**
   * @return the labelsVisible
   */
  public boolean isLabelsVisible()
  {
    return labelsVisible;
  }

  /**
   * @param value the labelsVisible to set
   */
  public void setLabelsVisible(boolean value)
  {
    boolean oldValue = labelsVisible;
    labelsVisible = value;

    changeSupport.firePropertyChange("labelsVisible", oldValue,
        labelsVisible);
  }

  /**
   * @param value the htmlLabels to set
   */
  public void setHtmlLabels(boolean value)
  {
    boolean oldValue = htmlLabels;
    htmlLabels = value;

    changeSupport.firePropertyChange("htmlLabels", oldValue, htmlLabels);
  }

  /**
   *
   */
  public boolean isHtmlLabels()
  {
    return htmlLabels;
  }

  /**
   * Returns the textual representation for the given cell.
   *
   * @param cell Cell to be converted to a string.
   * @return Returns the textual representation of the cell.
   */
  public String convertValueToString(Object cell)
  {
    Object result = model.getValue(cell);

    return (result != null) ? result.toString() : "";
  }

  /**
   * Returns a string or DOM node that represents the label for the given
   * cell. This implementation uses <convertValueToString> if <labelsVisible>
   * is true. Otherwise it returns an empty string.
   *
   * @param cell <mxCell> whose label should be returned.
   * @return Returns the label for the given cell.
   */
  public String getLabel(Object cell)
  {
    String result = "";

    if (cell != null)
    {
      mxCellState state = view.getState(cell);
      Map<String, Object> style = (state != null) ? state.getStyle()
          : getCellStyle(cell);

      if (labelsVisible
          && !mxUtils.isTrue(style, mxConstants.STYLE_NOLABEL, false))
      {
        result = convertValueToString(cell);
      }
    }

    return result;
  }

  /**
   * Sets the new label for a cell. If autoSize is true then
   * <cellSizeUpdated> will be called.
   *
   * @param cell Cell whose label should be changed.
   * @param value New label to be assigned.
   * @param autoSize Specifies if cellSizeUpdated should be called.
   */
  public void cellLabelChanged(Object cell, Object value, boolean autoSize)
  {
    model.beginUpdate();
    try
    {
      getModel().setValue(cell, value);

      if (autoSize)
      {
        cellSizeUpdated(cell, false);
      }
    }
    finally
    {
      model.endUpdate();
    }
  }

  /**
   * Returns true if the label must be rendered as HTML markup. The default
   * implementation returns <htmlLabels>.
   *
   * @param cell <mxCell> whose label should be displayed as HTML markup.
   * @return Returns true if the given cell label is HTML markup.
   */
  public boolean isHtmlLabel(Object cell)
  {
    return isHtmlLabels();
  }

  /**
   * Returns the tooltip to be used for the given cell.
   */
  public String getToolTipForCell(Object cell)
  {
    return convertValueToString(cell);
  }

  /**
   * Returns the start size of the given swimlane, that is, the width or
   * height of the part that contains the title, depending on the
   * horizontal style. The return value is an <mxRectangle> with either
   * width or height set as appropriate.
   *
   * @param swimlane <mxCell> whose start size should be returned.
   * @return Returns the startsize for the given swimlane.
   */
  public mxRectangle getStartSize(Object swimlane)
  {
    mxRectangle result = new mxRectangle();
    mxCellState state = view.getState(swimlane);
    Map<String, Object> style = (state != null) ? state.getStyle()
        : getCellStyle(swimlane);

    if (style != null)
    {
      double size = mxUtils.getDouble(style, mxConstants.STYLE_STARTSIZE,
          mxConstants.DEFAULT_STARTSIZE);

      if (mxUtils.isTrue(style, mxConstants.STYLE_HORIZONTAL, true))
      {
        result.setHeight(size);
      }
      else
      {
        result.setWidth(size);
      }
    }

    return result;
  }

  /**
   * Returns the image URL for the given cell state. This implementation
   * returns the value stored under <mxConstants.STYLE_IMAGE> in the cell
   * style.
   *
   * @param state
   * @return Returns the image associated with the given cell state.
   */
  public String getImage(mxCellState state)
  {
    return (state != null && state.getStyle() != null) ? mxUtils.getString(
        state.getStyle(), mxConstants.STYLE_IMAGE) : null;
  }

  /**
   * Returns the value of <border>.
   *
   * @return Returns the border.
   */
  public int getBorder()
  {
    return border;
  }

  /**
   * Sets the value of <border>.
   *
   * @param value Positive integer that represents the border to be used.
   */
  public void setBorder(int value)
  {
    border = value;
  }

  /**
   * Returns the default edge style used for loops.
   *
   * @return Returns the default loop style.
   */
  public mxEdgeStyle.mxEdgeStyleFunction getDefaultLoopStyle()
  {
    return defaultLoopStyle;
  }

  /**
   * Sets the default style used for loops.
   *
   * @param value Default style to be used for loops.
   */
  public void setDefaultLoopStyle(mxEdgeStyle.mxEdgeStyleFunction value)
  {
    mxEdgeStyle.mxEdgeStyleFunction oldValue = defaultLoopStyle;
    defaultLoopStyle = value;

    changeSupport.firePropertyChange("defaultLoopStyle", oldValue,
        defaultLoopStyle);
  }

  /**
   * Returns true if the given cell is a swimlane. This implementation always
   * returns false.
   *
   * @param cell Cell that should be checked.
   * @return Returns true if the cell is a swimlane.
   */
  public boolean isSwimlane(Object cell)
  {
    if (cell != null)
    {
      if (model.getParent(cell) != model.getRoot())
      {
        mxCellState state = view.getState(cell);
        Map<String, Object> style = (state != null) ? state.getStyle()
            : getCellStyle(cell);

        if (style != null && !model.isEdge(cell))
        {
          return mxUtils
              .getString(style, mxConstants.STYLE_SHAPE, "")
              .equals(mxConstants.SHAPE_SWIMLANE);
        }
      }
    }

    return false;
  }

  //
  // Cells and labels control options
  //

  /**
   * Returns true if the given cell may not be moved, sized, bended,
   * disconnected, edited or selected. This implementation returns true for
   * all vertices with a relative geometry if cellsLocked is false.
   *
   * @param cell Cell whose locked state should be returned.
   * @return Returns true if the given cell is locked.
   */
  public boolean isCellLocked(Object cell)
  {
    mxGeometry geometry = model.getGeometry(cell);

    return isCellsLocked()
        || (geometry != null && model.isVertex(cell) && geometry
            .isRelative());
  }

  /**
   * Returns cellsLocked, the default return value for isCellLocked.
   */
  public boolean isCellsLocked()
  {
    return cellsLocked;
  }

  /**
   * Sets cellsLocked, the default return value for isCellLocked and fires a
   * property change event for cellsLocked.
   */
  public void setCellsLocked(boolean value)
  {
    boolean oldValue = cellsLocked;
    cellsLocked = value;

    changeSupport.firePropertyChange("cellsLocked", oldValue, cellsLocked);
  }

  /**
   * Returns true if the given cell is movable. This implementation returns editable.
   *
   * @param cell Cell whose editable state should be returned.
   * @return Returns true if the cell is editable.
   */
  public boolean isCellEditable(Object cell)
  {
    return isCellsEditable() && !isCellLocked(cell);
  }

  /**
   * Returns true if editing is allowed in this graph.
   *
   * @return Returns true if the graph is editable.
   */
  public boolean isCellsEditable()
  {
    return cellsEditable;
  }

  /**
   * Sets if the graph is editable.
   */
  public void setCellsEditable(boolean value)
  {
    boolean oldValue = cellsEditable;
    cellsEditable = value;

    changeSupport.firePropertyChange("cellsEditable", oldValue,
        cellsEditable);
  }

  /**
   * Returns true if the given cell is resizable. This implementation returns
   * cellsSizable for all cells.
   *
   * @param cell Cell whose resizable state should be returned.
   * @return Returns true if the cell is sizable.
   */
  public boolean isCellResizable(Object cell)
  {
    return isCellsResizable() && !isCellLocked(cell);
  }

  /**
   * Returns true if the given cell is resizable. This implementation return sizable.
   */
  public boolean isCellsResizable()
  {
    return cellsResizable;
  }

  /**
   * Sets if the graph is resizable.
   */
  public void setCellsResizable(boolean value)
  {
    boolean oldValue = cellsResizable;
    cellsResizable = value;

    changeSupport.firePropertyChange("cellsResizable", oldValue,
        cellsResizable);
  }

  /**
   * Returns the cells which are movable in the given array of cells.
   */
  public Object[] getMovableCells(Object[] cells)
  {
    return mxGraphModel.filterCells(cells, new Filter()
    {
      public boolean filter(Object cell)
      {
        return isCellMovable(cell);
      }
    });
  }

  /**
   * Returns true if the given cell is movable. This implementation
   * returns movable.
   *
   * @param cell Cell whose movable state should be returned.
   * @return Returns true if the cell is movable.
   */
  public boolean isCellMovable(Object cell)
  {
    return isCellsMovable() && !isCellLocked(cell);
  }

  /**
   * Returns cellsMovable.
   */
  public boolean isCellsMovable()
  {
    return cellsMovable;
  }

  /**
   * Sets cellsMovable.
   */
  public void setCellsMovable(boolean value)
  {
    boolean oldValue = cellsMovable;
    cellsMovable = value;

    changeSupport
        .firePropertyChange("cellsMovable", oldValue, cellsMovable);
  }

  /**
   * Returns true if the given cell is bendable. This implementation returns
   * bendable. This is used in mxElbowEdgeHandler to determine if the middle
   * handle should be shown.
   *
   * @param cell Cell whose bendable state should be returned.
   * @return Returns true if the cell is bendable.
   */
  public boolean isCellBendable(Object cell)
  {
    return isCellsBendable() && !isCellLocked(cell);
  }

  /**
   * Returns cellsBendable.
   */
  public boolean isCellsBendable()
  {
    return cellsBendable;
  }

  /**
   * Sets cellsBendable.
   */
  public void setCellsBendable(boolean value)
  {
    boolean oldValue = cellsBendable;
    cellsBendable = value;

    changeSupport.firePropertyChange("cellsBendable", oldValue,
        cellsBendable);
  }

  /**
   * Returns true if the given cell is selectable. This implementation returns
   * <selectable>.
   *
   * @param cell <mxCell> whose selectable state should be returned.
   * @return Returns true if the given cell is selectable.
   */
  public boolean isCellSelectable(Object cell)
  {
    return isCellsSelectable();
  }

  /**
   * Returns cellsSelectable.
   */
  public boolean isCellsSelectable()
  {
    return cellsSelectable;
  }

  /**
   * Sets cellsSelectable.
   */
  public void setCellsSelectable(boolean value)
  {
    boolean oldValue = cellsSelectable;
    cellsSelectable = value;

    changeSupport.firePropertyChange("cellsSelectable", oldValue,
        cellsSelectable);
  }

  /**
   * Returns the cells which are movable in the given array of cells.
   */
  public Object[] getDeletableCells(Object[] cells)
  {
    return mxGraphModel.filterCells(cells, new Filter()
    {
      public boolean filter(Object cell)
      {
        return isCellDeletable(cell);
      }
    });
  }

  /**
   * Returns true if the given cell is movable. This implementation always
   * returns true.
   *
   * @param cell Cell whose movable state should be returned.
   * @return Returns true if the cell is movable.
   */
  public boolean isCellDeletable(Object cell)
  {
    return isCellsDeletable();
  }

  /**
   * Returns cellsDeletable.
   */
  public boolean isCellsDeletable()
  {
    return cellsDeletable;
  }

  /**
   * Sets cellsDeletable.
   */
  public void setCellsDeletable(boolean value)
  {
    boolean oldValue = cellsDeletable;
    cellsDeletable = value;

    changeSupport.firePropertyChange("cellsDeletable", oldValue,
        cellsDeletable);
  }

  /**
   * Returns the cells which are movable in the given array of cells.
   */
  public Object[] getCloneableCells(Object[] cells)
  {
    return mxGraphModel.filterCells(cells, new Filter()
    {
      public boolean filter(Object cell)
      {
        return isCellCloneable(cell);
      }
    });
  }

  /**
   * Returns the constant true. This does not use the cloneable field to
   * return a value for a given cell, it is simply a hook for subclassers
   * to disallow cloning of individual cells.
   */
  public boolean isCellCloneable(Object cell)
  {
    return isCellsCloneable();
  }

  /**
   * Returns cellsCloneable.
   */
  public boolean isCellsCloneable()
  {
    return cellsCloneable;
  }

  /**
   * Specifies if the graph should allow cloning of cells by holding down the
   * control key while cells are being moved. This implementation updates
   * cellsCloneable.
   *
   * @param value Boolean indicating if the graph should be cloneable.
   */
  public void setCellsCloneable(boolean value)
  {
    boolean oldValue = cellsCloneable;
    cellsCloneable = value;

    changeSupport.firePropertyChange("cellsCloneable", oldValue,
        cellsCloneable);
  }

  /**
   * Returns true if the given cell is disconnectable from the source or
   * target terminal. This returns <disconnectable> for all given cells if
   * <isLocked> does not return true for the given cell.
   *
   * @param cell <mxCell> whose disconnectable state should be returned.
   * @param terminal <mxCell> that represents the source or target terminal.
   * @param source Boolean indicating if the source or target terminal is to be
   * disconnected.
   * @return Returns true if the given edge can be disconnected from the given
   * terminal.
   */
  public boolean isCellDisconnectable(Object cell, Object terminal,
      boolean source)
  {
    return isCellsDisconnectable() && !isCellLocked(cell);
  }

  /**
   * Returns cellsDisconnectable.
   */
  public boolean isCellsDisconnectable()
  {
    return cellsDisconnectable;
  }

  /**
   * Sets cellsDisconnectable.
   *
   * @param value Boolean indicating if the graph should allow disconnecting of
   * edges.
   */
  public void setCellsDisconnectable(boolean value)
  {
    boolean oldValue = cellsDisconnectable;
    cellsDisconnectable = value;

    changeSupport.firePropertyChange("cellsDisconnectable", oldValue,
        cellsDisconnectable);
  }

  /**
   * Returns true if the overflow portion of labels should be hidden. If this
   * returns true then vertex labels will be clipped to the size of the vertices.
   * This implementation returns true if <mxConstants.STYLE_OVERFLOW> in the
   * style of the given cell is "hidden".
   *
   * @param cell Cell whose label should be clipped.
   * @return Returns true if the cell label should be clipped.
   */
  public boolean isLabelClipped(Object cell)
  {
    if (!isLabelsClipped())
    {
      mxCellState state = view.getState(cell);
      Map<String, Object> style = (state != null) ? state.getStyle()
          : getCellStyle(cell);

      return (style != null) ? mxUtils.getString(style,
          mxConstants.STYLE_OVERFLOW, "").equals("hidden") : false;
    }

    return isLabelsClipped();
  }

  /**
   * Returns labelsClipped.
   */
  public boolean isLabelsClipped()
  {
    return labelsClipped;
  }

  /**
   * Sets labelsClipped.
   */
  public void setLabelsClipped(boolean value)
  {
    boolean oldValue = labelsClipped;
    labelsClipped = value;

    changeSupport.firePropertyChange("labelsClipped", oldValue,
        labelsClipped);
  }

  /**
   * Returns true if the given edges's label is moveable. This returns
   * <movable> for all given cells if <isLocked> does not return true
   * for the given cell.
   *
   * @param cell <mxCell> whose label should be moved.
   * @return Returns true if the label of the given cell is movable.
   */
  public boolean isLabelMovable(Object cell)
  {
    return !isCellLocked(cell)
        && ((model.isEdge(cell) && isEdgeLabelsMovable()) || (model
            .isVertex(cell) && isVertexLabelsMovable()));
  }

  /**
   * Returns vertexLabelsMovable.
   */
  public boolean isVertexLabelsMovable()
  {
    return vertexLabelsMovable;
  }

  /**
   * Sets vertexLabelsMovable.
   */
  public void setVertexLabelsMovable(boolean value)
  {
    boolean oldValue = vertexLabelsMovable;
    vertexLabelsMovable = value;

    changeSupport.firePropertyChange("vertexLabelsMovable", oldValue,
        vertexLabelsMovable);
  }

  /**
   * Returns edgeLabelsMovable.
   */
  public boolean isEdgeLabelsMovable()
  {
    return edgeLabelsMovable;
  }

  /**
   * Returns edgeLabelsMovable.
   */
  public void setEdgeLabelsMovable(boolean value)
  {
    boolean oldValue = edgeLabelsMovable;
    edgeLabelsMovable = value;

    changeSupport.firePropertyChange("edgeLabelsMovable", oldValue,
        edgeLabelsMovable);
  }

  //
  // Graph control options
  //

  /**
   * Returns true if the graph is <enabled>.
   *
   * @return Returns true if the graph is enabled.
   */
  public boolean isEnabled()
  {
    return enabled;
  }

  /**
   * Specifies if the graph should allow any interactions. This
   * implementation updates <enabled>.
   *
   * @param value Boolean indicating if the graph should be enabled.
   */
  public void setEnabled(boolean value)
  {
    boolean oldValue = enabled;
    enabled = value;

    changeSupport.firePropertyChange("enabled", oldValue, enabled);
  }

  /**
   * Returns true if the graph allows drop into other cells.
   */
  public boolean isDropEnabled()
  {
    return dropEnabled;
  }

  /**
   * Sets dropEnabled.
   */
  public void setDropEnabled(boolean value)
  {
    boolean oldValue = dropEnabled;
    dropEnabled = value;

    changeSupport.firePropertyChange("dropEnabled", oldValue, dropEnabled);
  }

  /**
   * Affects the return values of isValidDropTarget to allow for edges as
   * drop targets. The splitEdge method is called in mxGraphHandler if
   * mxGraphComponent.isSplitEvent returns true for a given configuration.
   */
  public boolean isSplitEnabled()
  {
    return splitEnabled;
  }

  /**
   * Sets splitEnabled.
   */
  public void setSplitEnabled(boolean value)
  {
    splitEnabled = value;
  }

  /**
   * Returns multigraph.
   */
  public boolean isMultigraph()
  {
    return multigraph;
  }

  /**
   * Sets multigraph.
   */
  public void setMultigraph(boolean value)
  {
    boolean oldValue = multigraph;
    multigraph = value;

    changeSupport.firePropertyChange("multigraph", oldValue, multigraph);
  }

  /**
   * Returns swimlaneNesting.
   */
  public boolean isSwimlaneNesting()
  {
    return swimlaneNesting;
  }

  /**
   * Sets swimlaneNesting.
   */
  public void setSwimlaneNesting(boolean value)
  {
    boolean oldValue = swimlaneNesting;
    swimlaneNesting = value;

    changeSupport.firePropertyChange("swimlaneNesting", oldValue,
        swimlaneNesting);
  }

  /**
   * Returns allowDanglingEdges
   */
  public boolean isAllowDanglingEdges()
  {
    return allowDanglingEdges;
  }

  /**
   * Sets allowDanglingEdges.
   */
  public void setAllowDanglingEdges(boolean value)
  {
    boolean oldValue = allowDanglingEdges;
    allowDanglingEdges = value;

    changeSupport.firePropertyChange("allowDanglingEdges", oldValue,
        allowDanglingEdges);
  }

  /**
   * Returns cloneInvalidEdges.
   */
  public boolean isCloneInvalidEdges()
  {
    return cloneInvalidEdges;
  }

  /**
   * Sets cloneInvalidEdge.
   */
  public void setCloneInvalidEdges(boolean value)
  {
    boolean oldValue = cloneInvalidEdges;
    cloneInvalidEdges = value;

    changeSupport.firePropertyChange("cloneInvalidEdges", oldValue,
        cloneInvalidEdges);
  }

  /**
   * Returns disconnectOnMove
   */
  public boolean isDisconnectOnMove()
  {
    return disconnectOnMove;
  }

  /**
   * Sets disconnectOnMove.
   */
  public void setDisconnectOnMove(boolean value)
  {
    boolean oldValue = disconnectOnMove;
    disconnectOnMove = value;

    changeSupport.firePropertyChange("disconnectOnMove", oldValue,
        disconnectOnMove);

  }

  /**
   * Returns allowLoops.
   */
  public boolean isAllowLoops()
  {
    return allowLoops;
  }

  /**
   * Sets allowLoops.
   */
  public void setAllowLoops(boolean value)
  {
    boolean oldValue = allowLoops;
    allowLoops = value;

    changeSupport.firePropertyChange("allowLoops", oldValue, allowLoops);
  }

  /**
   * Returns connectableEdges.
   */
  public boolean isConnectableEdges()
  {
    return connectableEdges;
  }

  /**
   * Sets connetableEdges.
   */
  public void setConnectableEdges(boolean value)
  {
    boolean oldValue = connectableEdges;
    connectableEdges = value;

    changeSupport.firePropertyChange("connectableEdges", oldValue,
        connectableEdges);

  }

  /**
   * Returns resetEdgesOnMove.
   */
  public boolean isResetEdgesOnMove()
  {
    return resetEdgesOnMove;
  }

  /**
   * Sets resetEdgesOnMove.
   */
  public void setResetEdgesOnMove(boolean value)
  {
    boolean oldValue = resetEdgesOnMove;
    resetEdgesOnMove = value;

    changeSupport.firePropertyChange("resetEdgesOnMove", oldValue,
        resetEdgesOnMove);
  }

  /**
   * Returns resetViewOnRootChange.
   */
  public boolean isResetViewOnRootChange()
  {
    return resetViewOnRootChange;
  }

  /**
   * Sets resetEdgesOnResize.
   */
  public void setResetViewOnRootChange(boolean value)
  {
    boolean oldValue = resetViewOnRootChange;
    resetViewOnRootChange = value;

    changeSupport.firePropertyChange("resetViewOnRootChange", oldValue,
        resetViewOnRootChange);
  }

  /**
   * Returns resetEdgesOnResize.
   */
  public boolean isResetEdgesOnResize()
  {
    return resetEdgesOnResize;
  }

  /**
   * Sets resetEdgesOnResize.
   */
  public void setResetEdgesOnResize(boolean value)
  {
    boolean oldValue = resetEdgesOnResize;
    resetEdgesOnResize = value;

    changeSupport.firePropertyChange("resetEdgesOnResize", oldValue,
        resetEdgesOnResize);
  }

  /**
   * Returns resetEdgesOnConnect.
   */
  public boolean isResetEdgesOnConnect()
  {
    return resetEdgesOnConnect;
  }

  /**
   * Sets resetEdgesOnConnect.
   */
  public void setResetEdgesOnConnect(boolean value)
  {
    boolean oldValue = resetEdgesOnConnect;
    resetEdgesOnConnect = value;

    changeSupport.firePropertyChange("resetEdgesOnConnect", oldValue,
        resetEdgesOnResize);
  }

  /**
   * Returns true if the size of the given cell should automatically be
   * updated after a change of the label. This implementation returns
   * autoSize for all given cells.
   *
   * @param cell Cell that should be resized.
   * @return Returns true if the size of the given cell should be updated.
   */
  public boolean isAutoSizeCell(Object cell)
  {
    return isAutoSizeCells();
  }

  /**
   * Returns true if the size of the given cell should automatically be
   * updated after a change of the label. This implementation returns
   * autoSize for all given cells.
   */
  public boolean isAutoSizeCells()
  {
    return autoSizeCells;
  }

  /**
   * Specifies if cell sizes should be automatically updated after a label
   * change. This implementation sets autoSize to the given parameter.
   *
   * @param value Boolean indicating if cells should be resized
   * automatically.
   */
  public void setAutoSizeCells(boolean value)
  {
    boolean oldValue = autoSizeCells;
    autoSizeCells = value;

    changeSupport.firePropertyChange("autoSizeCells", oldValue,
        autoSizeCells);
  }

  /**
   * Returns true if the parent of the given cell should be extended if the
   * child has been resized so that it overlaps the parent. This
     * implementation returns ExtendParents if cell is not an edge.
   *
   * @param cell Cell that has been resized.
   */
  public boolean isExtendParent(Object cell)
  {
    return !getModel().isEdge(cell) && isExtendParents();
  }

  /**
   * Returns extendParents.
   */
  public boolean isExtendParents()
  {
    return extendParents;
  }

  /**
   * Sets extendParents.
   */
  public void setExtendParents(boolean value)
  {
    boolean oldValue = extendParents;
    extendParents = value;

    changeSupport.firePropertyChange("extendParents", oldValue,
        extendParents);
  }

  /**
   * Returns extendParentsOnAdd.
   */
  public boolean isExtendParentsOnAdd()
  {
    return extendParentsOnAdd;
  }

  /**
   * Sets extendParentsOnAdd.
   */
  public void setExtendParentsOnAdd(boolean value)
  {
    boolean oldValue = extendParentsOnAdd;
    extendParentsOnAdd = value;

    changeSupport.firePropertyChange("extendParentsOnAdd", oldValue,
        extendParentsOnAdd);
  }

  /**
   * Returns true if the given cell should be kept inside the bounds of its
   * parent according to the rules defined by getOverlap and
   * isAllowOverlapParent. This implementation returns
   * isConstrainChildren() for all given cells.
   */
  public boolean isConstrainChild(Object cell)
  {
    return isConstrainChildren();
  }

  /**
   * Returns constrainChildren.
   *
   * @return the keepInsideParentOnMove
   */
  public boolean isConstrainChildren()
  {
    return constrainChildren;
  }

  /**
   * @param value the constrainChildren to set
   */
  public void setConstrainChildren(boolean value)
  {
    boolean oldValue = constrainChildren;
    constrainChildren = value;

    changeSupport.firePropertyChange("constrainChildren", oldValue,
        constrainChildren);
  }

  /**
   * Returns autoOrigin.
   */
  public boolean isAutoOrigin()
  {
    return autoOrigin;
  }

  /**
   * @param value the autoOrigin to set
   */
  public void setAutoOrigin(boolean value)
  {
    boolean oldValue = autoOrigin;
    autoOrigin = value;

    changeSupport.firePropertyChange("autoOrigin", oldValue, autoOrigin);
  }

  /**
   * Returns origin.
   */
  public mxPoint getOrigin()
  {
    return origin;
  }

  /**
   * @param value the origin to set
   */
  public void setOrigin(mxPoint value)
  {
    mxPoint oldValue = origin;
    origin = value;

    changeSupport.firePropertyChange("origin", oldValue, origin);
  }

  /**
   * @return Returns changesRepaintThreshold.
   */
  public int getChangesRepaintThreshold()
  {
    return changesRepaintThreshold;
  }

  /**
   * @param value the changesRepaintThreshold to set
   */
  public void setChangesRepaintThreshold(int value)
  {
    int oldValue = changesRepaintThreshold;
    changesRepaintThreshold = value;

    changeSupport.firePropertyChange("changesRepaintThreshold", oldValue,
        changesRepaintThreshold);
  }

  /**
   * Returns isAllowNegativeCoordinates.
   *
   * @return the allowNegativeCoordinates
   */
  public boolean isAllowNegativeCoordinates()
  {
    return allowNegativeCoordinates;
  }

  /**
   * @param value the allowNegativeCoordinates to set
   */
  public void setAllowNegativeCoordinates(boolean value)
  {
    boolean oldValue = allowNegativeCoordinates;
    allowNegativeCoordinates = value;

    changeSupport.firePropertyChange("allowNegativeCoordinates", oldValue,
        allowNegativeCoordinates);
  }

  /**
   * Returns collapseToPreferredSize.
   *
   * @return the collapseToPreferredSize
   */
  public boolean isCollapseToPreferredSize()
  {
    return collapseToPreferredSize;
  }

  /**
   * @param value the collapseToPreferredSize to set
   */
  public void setCollapseToPreferredSize(boolean value)
  {
    boolean oldValue = collapseToPreferredSize;
    collapseToPreferredSize = value;

    changeSupport.firePropertyChange("collapseToPreferredSize", oldValue,
        collapseToPreferredSize);
  }

  /**
   * @return Returns true if edges are rendered in the foreground.
   */
  public boolean isKeepEdgesInForeground()
  {
    return keepEdgesInForeground;
  }

  /**
   * @param value the keepEdgesInForeground to set
   */
  public void setKeepEdgesInForeground(boolean value)
  {
    boolean oldValue = keepEdgesInForeground;
    keepEdgesInForeground = value;

    changeSupport.firePropertyChange("keepEdgesInForeground", oldValue,
        keepEdgesInForeground);
  }

  /**
   * @return Returns true if edges are rendered in the background.
   */
  public boolean isKeepEdgesInBackground()
  {
    return keepEdgesInBackground;
  }

  /**
   * @param value the keepEdgesInBackground to set
   */
  public void setKeepEdgesInBackground(boolean value)
  {
    boolean oldValue = keepEdgesInBackground;
    keepEdgesInBackground = value;

    changeSupport.firePropertyChange("keepEdgesInBackground", oldValue,
        keepEdgesInBackground);
  }

  /**
   * Returns true if the given cell is a valid source for new connections.
   * This implementation returns true for all non-null values and is
   * called by is called by <isValidConnection>.
   *
   * @param cell Object that represents a possible source or null.
   * @return Returns true if the given cell is a valid source terminal.
   */
  public boolean isValidSource(Object cell)
  {
    return (cell == null && allowDanglingEdges)
        || (cell != null
            && (!model.isEdge(cell) || isConnectableEdges()) && isCellConnectable(cell));
  }

  /**
   * Returns isValidSource for the given cell. This is called by
   * isValidConnection.
   *
   * @param cell Object that represents a possible target or null.
   * @return Returns true if the given cell is a valid target.
   */
  public boolean isValidTarget(Object cell)
  {
    return isValidSource(cell);
  }

  /**
   * Returns true if the given target cell is a valid target for source.
   * This is a boolean implementation for not allowing connections between
   * certain pairs of vertices and is called by <getEdgeValidationError>.
   * This implementation returns true if <isValidSource> returns true for
   * the source and <isValidTarget> returns true for the target.
   *
   * @param source Object that represents the source cell.
   * @param target Object that represents the target cell.
   * @return Returns true if the the connection between the given terminals
   * is valid.
   */
  public boolean isValidConnection(Object source, Object target)
  {
    return isValidSource(source) && isValidTarget(target)
        && (isAllowLoops() || source != target);
  }

  /**
   * Returns the minimum size of the diagram.
   *
   * @return Returns the minimum container size.
   */
  public mxRectangle getMinimumGraphSize()
  {
    return minimumGraphSize;
  }

  /**
   * @param value the minimumGraphSize to set
   */
  public void setMinimumGraphSize(mxRectangle value)
  {
    mxRectangle oldValue = minimumGraphSize;
    minimumGraphSize = value;

    changeSupport.firePropertyChange("minimumGraphSize", oldValue, value);
  }

  /**
   * Returns a decimal number representing the amount of the width and height
   * of the given cell that is allowed to overlap its parent. A value of 0
   * means all children must stay inside the parent, 1 means the child is
   * allowed to be placed outside of the parent such that it touches one of
   * the parents sides. If <isAllowOverlapParent> returns false for the given
   * cell, then this method returns 0.
   *
   * @param cell
   * @return Returns the overlapping value for the given cell inside its
   * parent.
   */
  public double getOverlap(Object cell)
  {
    return (isAllowOverlapParent(cell)) ? getDefaultOverlap() : 0;
  }

  /**
   * Gets defaultOverlap.
   */
  public double getDefaultOverlap()
  {
    return defaultOverlap;
  }

  /**
   * Sets defaultOverlap.
   */
  public void setDefaultOverlap(double value)
  {
    double oldValue = defaultOverlap;
    defaultOverlap = value;

    changeSupport.firePropertyChange("defaultOverlap", oldValue, value);
  }

  /**
   * Returns true if the given cell is allowed to be placed outside of the
   * parents area.
   *
   * @param cell
   * @return Returns true if the given cell may overlap its parent.
   */
  public boolean isAllowOverlapParent(Object cell)
  {
    return false;
  }

  /**
   * Returns the cells which are movable in the given array of cells.
   */
  public Object[] getFoldableCells(Object[] cells, final boolean collapse)
  {
    return mxGraphModel.filterCells(cells, new Filter()
    {
      public boolean filter(Object cell)
      {
        return isCellFoldable(cell, collapse);
      }
    });
  }

  /**
   * Returns true if the given cell is expandable. This implementation
   * returns true if the cell has at least one child.
   *
   * @param cell <mxCell> whose expandable state should be returned.
   * @return Returns true if the given cell is expandable.
   */
  public boolean isCellFoldable(Object cell, boolean collapse)
  {
    return model.getChildCount(cell) > 0;
  }

  /**
   * Returns true if the grid is enabled.
   *
   * @return Returns the enabled state of the grid.
   */
  public boolean isGridEnabled()
  {
    return gridEnabled;
  }

  /**
   * Sets if the grid is enabled.
   *
   * @param value Specifies if the grid should be enabled.
   */
  public void setGridEnabled(boolean value)
  {
    boolean oldValue = gridEnabled;
    gridEnabled = value;

    changeSupport.firePropertyChange("gridEnabled", oldValue, gridSize);
  }

  /**
   * Returns the grid size.
   *
   * @return Returns the grid size
   */
  public int getGridSize()
  {
    return gridSize;
  }

  /**
   * Sets the grid size and fires a property change event for gridSize.
   *
   * @param value New grid size to be used.
   */
  public void setGridSize(int value)
  {
    int oldValue = gridSize;
    gridSize = value;

    changeSupport.firePropertyChange("gridSize", oldValue, gridSize);
  }

  /**
   * Returns alternateEdgeStyle.
   */
  public String getAlternateEdgeStyle()
  {
    return alternateEdgeStyle;
  }

  /**
   * Sets alternateEdgeStyle.
   */
  public void setAlternateEdgeStyle(String value)
  {
    String oldValue = alternateEdgeStyle;
    alternateEdgeStyle = value;

    changeSupport.firePropertyChange("alternateEdgeStyle", oldValue,
        alternateEdgeStyle);
  }

  /**
   * Returns true if the given cell is a valid drop target for the specified
   * cells. This returns true if the cell is a swimlane, has children and is
   * not collapsed, or if splitEnabled is true and isSplitTarget returns
   * true for the given arguments
   *
   * @param cell Object that represents the possible drop target.
   * @param cells Objects that are going to be dropped.
   * @return Returns true if the cell is a valid drop target for the given
   * cells.
   */
  public boolean isValidDropTarget(Object cell, Object[] cells)
  {
    return cell != null
        && ((isSplitEnabled() && isSplitTarget(cell, cells)) || (!model
            .isEdge(cell) && (isSwimlane(cell) || (model
            .getChildCount(cell) > 0 && !isCellCollapsed(cell)))));
  }

  /**
   * Returns true if split is enabled and the given edge may be splitted into
   * two edges with the given cell as a new terminal between the two.
   *
   * @param target Object that represents the edge to be splitted.
   * @param cells Array of cells to add into the given edge.
   * @return Returns true if the given edge may be splitted by the given
   * cell.
   */
  public boolean isSplitTarget(Object target, Object[] cells)
  {
    if (target != null && cells != null && cells.length == 1)
    {
      Object src = model.getTerminal(target, true);
      Object trg = model.getTerminal(target, false);

      return (model.isEdge(target)
          && isCellConnectable(cells[0])
          && getEdgeValidationError(target,
              model.getTerminal(target, true), cells[0]) == null
          && !model.isAncestor(cells[0], src) && !model.isAncestor(
          cells[0], trg));
    }

    return false;
  }

  /**
   * Returns the given cell if it is a drop target for the given cells or the
   * nearest ancestor that may be used as a drop target for the given cells.
   * If the given array contains a swimlane and swimlaneNesting is false
   * then this always returns null. If no cell is given, then the bottommost
   * swimlane at the location of the given event is returned.
   *
   * This function should only be used if isDropEnabled returns true.
   */
  public Object getDropTarget(Object[] cells, Point pt, Object cell)
  {
    if (!isSwimlaneNesting())
    {
      for (int i = 0; i < cells.length; i++)
      {
        if (isSwimlane(cells[i]))
        {
          return null;
        }
      }
    }

    // FIXME the else below does nothing if swimlane is null
    Object swimlane = null; //getSwimlaneAt(pt.x, pt.y);

    if (cell == null)
    {
      cell = swimlane;
    }
    else if (swimlane != null)
    {
      // Checks if the cell is an ancestor of the swimlane
      // under the mouse and uses the swimlane in that case
      Object tmp = model.getParent(swimlane);

      while (tmp != null && isSwimlane(tmp) && tmp != cell)
      {
        tmp = model.getParent(tmp);
      }

      if (tmp == cell)
      {
        cell = swimlane;
      }
    }

    while (cell != null && !isValidDropTarget(cell, cells)
        && model.getParent(cell) != model.getRoot())
    {
      cell = model.getParent(cell);
    }

    return (model.getParent(cell) != model.getRoot() && !mxUtils.contains(
        cells, cell)) ? cell : null;
  };

  //
  // Cell retrieval
  //

  /**
   * Returns the first child of the root in the model, that is, the first or
   * default layer of the diagram.
   *
   * @return Returns the default parent for new cells.
   */
  public Object getDefaultParent()
  {
    Object parent = defaultParent;

    if (parent == null)
    {
      parent = view.getCurrentRoot();

      if (parent == null)
      {
        Object root = model.getRoot();
        parent = model.getChildAt(root, 0);
      }
    }

    return parent;
  }

  /**
   * Sets the default parent to be returned by getDefaultParent.
   * Set this to null to return the first child of the root in
   * getDefaultParent.
   */
  public void setDefaultParent(Object value)
  {
    defaultParent = value;
  }

  /**
   * Returns the visible child vertices of the given parent.
   *
   * @param parent Cell whose children should be returned.
   */
  public Object[] getChildVertices(Object parent)
  {
    return getChildCells(parent, true, false);
  }

  /**
   * Returns the visible child edges of the given parent.
   *
   * @param parent Cell whose children should be returned.
   */
  public Object[] getChildEdges(Object parent)
  {
    return getChildCells(parent, false, true);
  }

  /**
   * Returns the visible children of the given parent.
   *
   * @param parent Cell whose children should be returned.
   */
  public Object[] getChildCells(Object parent)
  {
    return getChildCells(parent, false, false);
  }

  /**
   * Returns the visible child vertices or edges in the given parent. If
   * vertices and edges is false, then all children are returned.
   *
   * @param parent Cell whose children should be returned.
   * @param vertices Specifies if child vertices should be returned.
   * @param edges Specifies if child edges should be returned.
   * @return Returns the child vertices and edges.
   */
  public Object[] getChildCells(Object parent, boolean vertices, boolean edges)
  {
    Object[] cells = mxGraphModel.getChildCells(model, parent, vertices,
        edges);
    List<Object> result = new ArrayList<Object>(cells.length);

    // Filters out the non-visible child cells
    for (int i = 0; i < cells.length; i++)
    {
      if (isCellVisible(cells[i]))
      {
        result.add(cells[i]);
      }
    }

    return result.toArray();
  }

  /**
   * Returns all visible edges connected to the given cell without loops.
   *
   * @param cell Cell whose connections should be returned.
   * @return Returns the connected edges for the given cell.
   */
  public Object[] getConnections(Object cell)
  {
    return getConnections(cell, null);
  }

  /**
   * Returns all visible edges connected to the given cell without loops.
   * If the optional parent argument is specified, then only child
   * edges of the given parent are returned.
   *
   * @param cell Cell whose connections should be returned.
   * @param parent Optional parent of the opposite end for a connection
   * to be returned.
   * @return Returns the connected edges for the given cell.
   */
  public Object[] getConnections(Object cell, Object parent)
  {
    return getEdges(cell, parent, true, true, false);
  }

  /**
   * Returns all incoming visible edges connected to the given cell without
   * loops.
   *
   * @param cell Cell whose incoming edges should be returned.
   * @return Returns the incoming edges of the given cell.
   */
  public Object[] getIncomingEdges(Object cell)
  {
    return getIncomingEdges(cell, null);
  }

  /**
   * Returns the visible incoming edges for the given cell. If the optional
   * parent argument is specified, then only child edges of the given parent
   * are returned.
   *
   * @param cell Cell whose incoming edges should be returned.
   * @param parent Optional parent of the opposite end for an edge
   * to be returned.
   * @return Returns the incoming edges of the given cell.
   */
  public Object[] getIncomingEdges(Object cell, Object parent)
  {
    return getEdges(cell, parent, true, false, false);
  }

  /**
   * Returns all outgoing visible edges connected to the given cell without
   * loops.
   *
   * @param cell Cell whose outgoing edges should be returned.
   * @return Returns the outgoing edges of the given cell.
   */
  public Object[] getOutgoingEdges(Object cell)
  {
    return getOutgoingEdges(cell, null);
  }

  /**
   * Returns the visible outgoing edges for the given cell. If the optional
   * parent argument is specified, then only child edges of the given parent
   * are returned.
   *
   * @param cell Cell whose outgoing edges should be returned.
   * @param parent Optional parent of the opposite end for an edge
   * to be returned.
   * @return Returns the outgoing edges of the given cell.
   */
  public Object[] getOutgoingEdges(Object cell, Object parent)
  {
    return getEdges(cell, parent, false, true, false);
  }

  /**
   * Returns all visible edges connected to the given cell including loops.
   *
   * @param cell Cell whose edges should be returned.
   * @return Returns the edges of the given cell.
   */
  public Object[] getEdges(Object cell)
  {
    return getEdges(cell, null);
  }

  /**
   * Returns all visible edges connected to the given cell including loops.
   *
   * @param cell Cell whose edges should be returned.
   * @param parent Optional parent of the opposite end for an edge
   * to be returned.
   * @return Returns the edges of the given cell.
   */
  public Object[] getEdges(Object cell, Object parent)
  {
    return getEdges(cell, parent, true, true, true);
  }

  /**
   * Returns the incoming and/or outgoing edges for the given cell.
   * If the optional parent argument is specified, then only edges are returned
   * where the opposite is in the given parent cell.
   *
   * @param cell Cell whose edges should be returned.
   * @param parent Optional parent of the opposite end for an edge to be
   * returned.
   * @param incoming Specifies if incoming edges should be included in the
   * result.
   * @param outgoing Specifies if outgoing edges should be included in the
   * result.
   * @param includeLoops Specifies if loops should be included in the result.
   * @return Returns the edges connected to the given cell.
   */
  public Object[] getEdges(Object cell, Object parent, boolean incoming,
      boolean outgoing, boolean includeLoops)
  {
    boolean isCollapsed = isCellCollapsed(cell);
    List<Object> edges = new ArrayList<Object>();
    int childCount = model.getChildCount(cell);

    for (int i = 0; i < childCount; i++)
    {
      Object child = model.getChildAt(cell, i);

      if (isCollapsed || !isCellVisible(child))
      {
        edges.addAll(Arrays.asList(mxGraphModel.getEdges(model, child,
            incoming, outgoing, includeLoops)));
      }
    }

    edges.addAll(Arrays.asList(mxGraphModel.getEdges(model, cell, incoming,
        outgoing, includeLoops)));
    List<Object> result = new ArrayList<Object>(edges.size());
    Iterator<Object> it = edges.iterator();

    while (it.hasNext())
    {
      Object edge = it.next();
      Object source = view.getVisibleTerminal(edge, true);
      Object target = view.getVisibleTerminal(edge, false);

      if (includeLoops
          || ((source != target) && ((incoming && target == cell && (parent == null || model
              .getParent(source) == parent)) || (outgoing
              && source == cell && (parent == null || model
              .getParent(target) == parent)))))
      {
        result.add(edge);
      }
    }

    return result.toArray();
  }

  /**
   * Returns all distinct visible opposite cells of the terminal on the given
   * edges.
   *
   * @param edges
   * @param terminal
   * @return Returns the terminals at the opposite ends of the given edges.
   */
  public Object[] getOpposites(Object[] edges, Object terminal)
  {
    return getOpposites(edges, terminal, true, true);
  }

  /**
   * Returns all distincts visible opposite cells for the specified terminal
   * on the given edges.
   *
   * @param edges Edges whose opposite terminals should be returned.
   * @param terminal Terminal that specifies the end whose opposite should be
   * returned.
   * @param sources Specifies if source terminals should be included in the
   * result.
   * @param targets Specifies if targer terminals should be included in the
   * result.
   * @return Returns the cells at the oppsite ends of the given edges.
   */
  public Object[] getOpposites(Object[] edges, Object terminal,
      boolean sources, boolean targets)
  {
    Collection<Object> terminals = new LinkedHashSet<Object>();

    if (edges != null)
    {
      for (int i = 0; i < edges.length; i++)
      {
        Object source = view.getVisibleTerminal(edges[i], true);
        Object target = view.getVisibleTerminal(edges[i], false);

        // Checks if the terminal is the source of
        // the edge and if the target should be
        // stored in the result
        if (targets && source == terminal && target != null
            && target != terminal)
        {
          terminals.add(target);
        }

        // Checks if the terminal is the taget of
        // the edge and if the source should be
        // stored in the result
        else if (sources && target == terminal && source != null
            && source != terminal)
        {
          terminals.add(source);
        }
      }
    }

    return terminals.toArray();
  }

  /**
   * Returns the edges between the given source and target. This takes into
   * account collapsed and invisible cells and returns the connected edges
   * as displayed on the screen.
   *
   * @param source
   * @param target
   * @return Returns all edges between the given terminals.
   */
  public Object[] getEdgesBetween(Object source, Object target)
  {
    return getEdgesBetween(source, target, false);
  }

  /**
   * Returns the edges between the given source and target. This takes into
   * account collapsed and invisible cells and returns the connected edges
   * as displayed on the screen.
   *
   * @param source
   * @param target
   * @param directed
   * @return Returns all edges between the given terminals.
   */
  public Object[] getEdgesBetween(Object source, Object target,
      boolean directed)
  {
    Object[] edges = getEdges(source);
    List<Object> result = new ArrayList<Object>(edges.length);

    // Checks if the edge is connected to the correct
    // cell and adds any match to the result
    for (int i = 0; i < edges.length; i++)
    {
      Object src = view.getVisibleTerminal(edges[i], true);
      Object trg = view.getVisibleTerminal(edges[i], false);

      if ((src == source && trg == target)
          || (!directed && src == target && trg == source))
      {
        result.add(edges[i]);
      }
    }

    return result.toArray();
  }

  /**
   * Returns the children of the given parent that are contained in the
   * halfpane from the given point (x0, y0) rightwards and downwards
   * depending on rightHalfpane and bottomHalfpane.
   *
   * @param x0 X-coordinate of the origin.
   * @param y0 Y-coordinate of the origin.
   * @param parent <mxCell> whose children should be checked.
   * @param rightHalfpane Boolean indicating if the cells in the right halfpane
   * from the origin should be returned.
   * @param bottomHalfpane Boolean indicating if the cells in the bottom halfpane
   * from the origin should be returned.
   * @return Returns the cells beyond the given halfpane.
   */
  public Object[] getCellsBeyond(double x0, double y0, Object parent,
      boolean rightHalfpane, boolean bottomHalfpane)
  {
    if (parent == null)
    {
      parent = getDefaultParent();
    }

    int childCount = model.getChildCount(parent);
    List<Object> result = new ArrayList<Object>(childCount);

    if (rightHalfpane || bottomHalfpane)
    {

      if (parent != null)
      {
        for (int i = 0; i < childCount; i++)
        {
          Object child = model.getChildAt(parent, i);
          mxCellState state = view.getState(child);

          if (isCellVisible(child) && state != null)
          {
            if ((!rightHalfpane || state.getX() >= x0)
                && (!bottomHalfpane || state.getY() >= y0))
            {
              result.add(child);
            }
          }
        }
      }
    }

    return result.toArray();
  }

  /**
   * Returns all visible children in the given parent which do not have
   * incoming edges. If the result is empty then the with the greatest
   * difference between incoming and outgoing edges is returned. This
   * takes into account edges that are being promoted to the given
   * root due to invisible children or collapsed cells.
   *
   * @param parent Cell whose children should be checked.
   * @return Array of tree roots in parent.
   */
  public Object[] findTreeRoots(Object parent)
  {
    return findTreeRoots(parent, false);
  }

  /**
   * Returns all visible children in the given parent which do not have
   * incoming edges. If the result is empty then the children with the
   * maximum difference between incoming and outgoing edges are returned.
   * This takes into account edges that are being promoted to the given
   * root due to invisible children or collapsed cells.
   *
   * @param parent Cell whose children should be checked.
   * @param isolate Specifies if edges should be ignored if the opposite
   * end is not a child of the given parent cell.
   * @return Array of tree roots in parent.
   */
  public Object[] findTreeRoots(Object parent, boolean isolate)
  {
    return findTreeRoots(parent, isolate, false);
  }

  /**
   * Returns all visible children in the given parent which do not have
   * incoming edges. If the result is empty then the children with the
   * maximum difference between incoming and outgoing edges are returned.
   * This takes into account edges that are being promoted to the given
   * root due to invisible children or collapsed cells.
   *
   * @param parent Cell whose children should be checked.
   * @param isolate Specifies if edges should be ignored if the opposite
   * end is not a child of the given parent cell.
   * @param invert Specifies if outgoing or incoming edges should be counted
   * for a tree root. If false then outgoing edges will be counted.
   * @return Array of tree roots in parent.
   */
  public Object[] findTreeRoots(Object parent, boolean isolate, boolean invert)
  {
    List<Object> roots = new ArrayList<Object>();

    if (parent != null)
    {
      int childCount = model.getChildCount(parent);
      Object best = null;
      int maxDiff = 0;

      for (int i = 0; i < childCount; i++)
      {
        Object cell = model.getChildAt(parent, i);

        if (model.isVertex(cell) && isCellVisible(cell))
        {
          Object[] conns = getConnections(cell, (isolate) ? parent
              : null);
          int fanOut = 0;
          int fanIn = 0;

          for (int j = 0; j < conns.length; j++)
          {
            Object src = view.getVisibleTerminal(conns[j], true);

            if (src == cell)
            {
              fanOut++;
            }
            else
            {
              fanIn++;
            }
          }

          if ((invert && fanOut == 0 && fanIn >= 0)
              || (!invert && fanIn == 0 && fanOut >= 0))
          {
            roots.add(cell);
          }

          int diff = (invert) ? fanIn - fanOut : fanOut - fanIn;

          if (diff >= maxDiff)
          {
            maxDiff = diff;
            best = cell;
            if (!roots.contains(cell))
              roots.add(cell);
          }
        }
      }

    }

    return roots.toArray();
  }

  /**
   * Traverses the tree starting at the given vertex. Here is how to use this
   * method for a given vertex (root) which is typically the root of a tree:
   * <code>
   * graph.traverse(root, true, new mxICellVisitor()
   * {
   *   public boolean visit(Object vertex, Object edge)
   *   {
   *     System.out.println("edge="+graph.convertValueToString(edge)+
   *       " vertex="+graph.convertValueToString(vertex));
   *    
   *     return true;
   *   }
   * });
   * </code>
   *
   * @param vertex
   * @param directed
   * @param visitor
   */
  public void traverse(Object vertex, boolean directed, mxICellVisitor visitor)
  {
    traverse(vertex, directed, visitor, null, null);
  }

  /**
   * Traverses the (directed) graph invoking the given function for each
   * visited vertex and edge. The function is invoked with the current vertex
   * and the incoming edge as a parameter. This implementation makes sure
   * each vertex is only visited once. The function may return false if the
   * traversal should stop at the given vertex.
   *
   * @param vertex <mxCell> that represents the vertex where the traversal starts.
   * @param directed Optional boolean indicating if edges should only be traversed
   * from source to target. Default is true.
   * @param visitor Visitor that takes the current vertex and the incoming edge.
   * The traversal stops if the function returns false.
   * @param edge Optional <mxCell> that represents the incoming edge. This is
   * null for the first step of the traversal.
   * @param visited Optional array of cell paths for the visited cells.
   */
  public void traverse(Object vertex, boolean directed,
      mxICellVisitor visitor, Object edge, Set<Object> visited)
  {
    if (vertex != null && visitor != null)
    {
      if (visited == null)
      {
        visited = new HashSet<Object>();
      }

      if (!visited.contains(vertex))
      {
        visited.add(vertex);

        if (visitor.visit(vertex, edge))
        {
          int edgeCount = model.getEdgeCount(vertex);

          if (edgeCount > 0)
          {
            for (int i = 0; i < edgeCount; i++)
            {
              Object e = model.getEdgeAt(vertex, i);
              boolean isSource = model.getTerminal(e, true) == vertex;

              if (!directed || isSource)
              {
                Object next = model.getTerminal(e, !isSource);
                traverse(next, directed, visitor, e, visited);
              }
            }
          }
        }
      }
    }
  }

  //
  // Selection
  //

  /**
   *
   */
  public mxGraphSelectionModel getSelectionModel()
  {
    return selectionModel;
  }

  /**
   *
   */
  public int getSelectionCount()
  {
    return selectionModel.size();
  }

  /**
   *
   * @param cell
   * @return Returns true if the given cell is selected.
   */
  public boolean isCellSelected(Object cell)
  {
    return selectionModel.isSelected(cell);
  }

  /**
   *
   * @return Returns true if the selection is empty.
   */
  public boolean isSelectionEmpty()
  {
    return selectionModel.isEmpty();
  }

  /**
   *
   */
  public void clearSelection()
  {
    selectionModel.clear();
  }

  /**
   *
   * @return Returns the selection cell.
   */
  public Object getSelectionCell()
  {
    return selectionModel.getCell();
  }

  /**
   *
   * @param cell
   */
  public void setSelectionCell(Object cell)
  {
    selectionModel.setCell(cell);
  }

  /**
   *
   * @return Returns the selection cells.
   */
  public Object[] getSelectionCells()
  {
    return selectionModel.getCells();
  }

  /**
   *
   */
  public void setSelectionCells(Object[] cells)
  {
    selectionModel.setCells(cells);
  }

  /**
   *
   * @param cells
   */
  public void setSelectionCells(Collection<Object> cells)
  {
    if (cells != null)
    {
      setSelectionCells(cells.toArray());
    }
  }

  /**
   *
   */
  public void addSelectionCell(Object cell)
  {
    selectionModel.addCell(cell);
  }

  /**
   *
   */
  public void addSelectionCells(Object[] cells)
  {
    selectionModel.addCells(cells);
  }

  /**
   *
   */
  public void removeSelectionCell(Object cell)
  {
    selectionModel.removeCell(cell);
  }

  /**
   *
   */
  public void removeSelectionCells(Object[] cells)
  {
    selectionModel.removeCells(cells);
  }

  /**
   * Selects the next cell.
   */
  public void selectNextCell()
  {
    selectCell(true, false, false);
  }

  /**
   * Selects the previous cell.
   */
  public void selectPreviousCell()
  {
    selectCell(false, false, false);
  }

  /**
   * Selects the parent cell.
   */
  public void selectParentCell()
  {
    selectCell(false, true, false);
  }

  /**
   * Selects the first child cell.
   */
  public void selectChildCell()
  {
    selectCell(false, false, true);
  }

  /**
   * Selects the next, parent, first child or previous cell, if all arguments
   * are false.
   *
   * @param isNext
   * @param isParent
   * @param isChild
   */
  public void selectCell(boolean isNext, boolean isParent, boolean isChild)
  {
    Object cell = getSelectionCell();

    if (getSelectionCount() > 1)
    {
      clearSelection();
    }

    Object parent = (cell != null) ? model.getParent(cell)
        : getDefaultParent();
    int childCount = model.getChildCount(parent);

    if (cell == null && childCount > 0)
    {
      Object child = model.getChildAt(parent, 0);
      setSelectionCell(child);
    }
    else if ((cell == null || isParent) && view.getState(parent) != null
        && model.getGeometry(parent) != null)
    {
      if (getCurrentRoot() != parent)
      {
        setSelectionCell(parent);
      }
    }
    else if (cell != null && isChild)
    {
      int tmp = model.getChildCount(cell);

      if (tmp > 0)
      {
        Object child = model.getChildAt(cell, 0);
        setSelectionCell(child);
      }
    }
    else if (childCount > 0)
    {
      int i = ((mxICell) parent).getIndex((mxICell) cell);

      if (isNext)
      {
        i++;
        setSelectionCell(model.getChildAt(parent, i % childCount));
      }
      else
      {
        i--;
        int index = (i < 0) ? childCount - 1 : i;
        setSelectionCell(model.getChildAt(parent, index));
      }
    }
  }

  /**
   * Selects all vertices inside the default parent.
   */
  public void selectVertices()
  {
    selectVertices(null);
  }

  /**
   * Selects all vertices inside the given parent or the default parent
   * if no parent is given.
   */
  public void selectVertices(Object parent)
  {
    selectCells(true, false, parent);
  }

  /**
   * Selects all vertices inside the default parent.
   */
  public void selectEdges()
  {
    selectEdges(null);
  }

  /**
   * Selects all vertices inside the given parent or the default parent
   * if no parent is given.
   */
  public void selectEdges(Object parent)
  {
    selectCells(false, true, parent);
  }

  /**
   * Selects all vertices and/or edges depending on the given boolean
   * arguments recursively, starting at the default parent. Use
   * <code>selectAll</code> to select all cells.
   * 
   * @param vertices Boolean indicating if vertices should be selected.
   * @param edges Boolean indicating if edges should be selected.
   */
  public void selectCells(boolean vertices, boolean edges)
  {
    selectCells(vertices, edges, null);
  }

  /**
   * Selects all vertices and/or edges depending on the given boolean
   * arguments recursively, starting at the given parent or the default
   * parent if no parent is specified. Use <code>selectAll</code> to select
   * all cells.
   *
   * @param vertices Boolean indicating if vertices should be selected.
   * @param edges Boolean indicating if edges should be selected.
   * @param parent Optional cell that acts as the root of the recursion.
   * Default is <code>defaultParent</code>.
   */
  public void selectCells(final boolean vertices, final boolean edges,
      Object parent)
  {
    if (parent == null)
    {
      parent = getDefaultParent();
    }

    Collection<Object> cells = mxGraphModel.filterDescendants(getModel(),
        new mxGraphModel.Filter()
        {

          /**
           *
           */
          public boolean filter(Object cell)
          {
            return view.getState(cell) != null
                && model.getChildCount(cell) == 0
                && ((model.isVertex(cell) && vertices) || (model
                    .isEdge(cell) && edges));
          }

        });
    setSelectionCells(cells);
  }

  /**
   *
   */
  public void selectAll()
  {
    selectAll(null);
  }

  /**
   * Selects all children of the given parent cell or the children of the
   * default parent if no parent is specified. To select leaf vertices and/or
   * edges use <selectCells>.
   *
   * @param parent  Optional <mxCell> whose children should be selected.
   * Default is <defaultParent>.
   */
  public void selectAll(Object parent)
  {
    if (parent == null)
    {
      parent = getDefaultParent();
    }

    Object[] children = mxGraphModel.getChildren(model, parent);

    if (children != null)
    {
      setSelectionCells(children);
    }
  }

  //
  // Images and drawing
  //

  /**
   * Draws the graph onto the given canvas.
   *
   * @param canvas Canvas onto which the graph should be drawn.
   */
  public void drawGraph(mxICanvas canvas)
  {
    drawCell(canvas, getModel().getRoot());
  }

  /**
   * Draws the given cell and its descendants onto the specified canvas.
   *
   * @param canvas Canvas onto which the cell should be drawn.
   * @param cell Cell that should be drawn onto the canvas.
   */
  public void drawCell(mxICanvas canvas, Object cell)
  {
    drawState(canvas, getView().getState(cell), getLabel(cell));

    // Draws the children on top of their parent
    int childCount = model.getChildCount(cell);

    for (int i = 0; i < childCount; i++)
    {
      Object child = model.getChildAt(cell, i);
      drawCell(canvas, child);
    }
  }

  /**
   * Draws the cell state with the given label onto the canvas. No
   * children or descendants are painted here. This method invokes
   * cellDrawn after the cell, but not its descendants have been
   * painted.
   *
   * @param canvas Canvas onto which the cell should be drawn.
   * @param state State of the cell to be drawn.
   * @param label Label of the cell to be dranw.
   */
  public void drawState(mxICanvas canvas, mxCellState state, String label)
  {
    Object cell = (state != null) ? state.getCell() : null;

    if (cell != null && cell != view.getCurrentRoot()
        && cell != model.getRoot()
        && (model.isVertex(cell) || model.isEdge(cell)))
    {
      Object obj = canvas.drawCell(state);
      Object lab = null;

      // Holds the current clipping region in case the label will
      // be clipped
      Shape clip = null;
      Rectangle newClip = state.getRectangle();

      // Indirection for image canvas that contains a graphics canvas
      mxICanvas clippedCanvas = (isLabelClipped(state.getCell())) ? canvas
          : null;

      if (clippedCanvas instanceof mxImageCanvas)
      {
        clippedCanvas = ((mxImageCanvas) clippedCanvas)
            .getGraphicsCanvas();
        // TODO: Shift newClip to match the image offset
        //Point pt = ((mxImageCanvas) canvas).getTranslate();
        //newClip.translate(-pt.x, -pt.y);
      }

      if (clippedCanvas instanceof mxGraphics2DCanvas)
      {
        Graphics g = ((mxGraphics2DCanvas) clippedCanvas).getGraphics();
        clip = g.getClip();
        g.setClip(newClip);
      }

      if (label != null && state.getLabelBounds() != null)
      {
        lab = canvas.drawLabel(label, state, isHtmlLabel(cell));
      }

      // Restores the previous clipping region
      if (clippedCanvas instanceof mxGraphics2DCanvas)
      {
        ((mxGraphics2DCanvas) clippedCanvas).getGraphics()
            .setClip(clip);
      }

      // Invokes the cellDrawn callback with the object which was created
      // by the canvas to represent the cell graphically
      if (obj != null)
      {
        cellDrawn(canvas, state, obj, lab);
      }
    }
  }

  /**
   * Called when a cell has been painted as the specified object, typically a
   * DOM node that represents the given cell graphically in a document.
   */
  protected void cellDrawn(mxICanvas canvas, mxCellState state,
      Object element, Object labelElement)
  {
    if (element instanceof Element)
    {
      String link = getLinkForCell(state.getCell());

      if (link != null)
      {
        String title = getToolTipForCell(state.getCell());
        Element elem = (Element) element;

        if (elem.getNodeName().startsWith("v:"))
        {
          elem.setAttribute("href", link.toString());

          if (title != null)
          {
            elem.setAttribute("title", title);
          }
        }
        else if (elem.getOwnerDocument().getElementsByTagName("svg")
            .getLength() > 0)
        {
          Element xlink = elem.getOwnerDocument().createElement("a");
          xlink.setAttribute("xlink:href", link.toString());

          elem.getParentNode().replaceChild(xlink, elem);
          xlink.appendChild(elem);

          if (title != null)
          {
            xlink.setAttribute("xlink:title", title);
          }

          elem = xlink;
        }
        else
        {
          Element a = elem.getOwnerDocument().createElement("a");
          a.setAttribute("href", link.toString());
          a.setAttribute("style", "text-decoration:none;");

          elem.getParentNode().replaceChild(a, elem);
          a.appendChild(elem);

          if (title != null)
          {
            a.setAttribute("title", title);
          }

          elem = a;
        }

        String target = getTargetForCell(state.getCell());

        if (target != null)
        {
          elem.setAttribute("target", target);
        }
      }
    }
  }

  /**
   * Returns the hyperlink to be used for the given cell.
   */
  protected String getLinkForCell(Object cell)
  {
    return null;
  }

  /**
   * Returns the hyperlink to be used for the given cell.
   */
  protected String getTargetForCell(Object cell)
  {
    return null;
  }

  //
  // Redirected to change support
  //

  /**
   * @param listener
   * @see java.beans.PropertyChangeSupport#addPropertyChangeListener(java.beans.PropertyChangeListener)
   */
  public void addPropertyChangeListener(PropertyChangeListener listener)
  {
    changeSupport.addPropertyChangeListener(listener);
  }

  /**
   * @param propertyName
   * @param listener
   * @see java.beans.PropertyChangeSupport#addPropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)
   */
  public void addPropertyChangeListener(String propertyName,
      PropertyChangeListener listener)
  {
    changeSupport.addPropertyChangeListener(propertyName, listener);
  }

  /**
   * @param listener
   * @see java.beans.PropertyChangeSupport#removePropertyChangeListener(java.beans.PropertyChangeListener)
   */
  public void removePropertyChangeListener(PropertyChangeListener listener)
  {
    changeSupport.removePropertyChangeListener(listener);
  }

  /**
   * @param propertyName
   * @param listener
   * @see java.beans.PropertyChangeSupport#removePropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)
   */
  public void removePropertyChangeListener(String propertyName,
      PropertyChangeListener listener)
  {
    changeSupport.removePropertyChangeListener(propertyName, listener);
  }

  /**
   * Prints the version number on the console.
   */
  public static void main(String[] args)
  {
    System.out.println("mxGraph version \"" + VERSION + "\"");
  }

}
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