8sa1-gcc/libjava/javax/swing/plaf/basic/BasicComboBoxUI.java

/* BasicComboBoxUI.java --
   Copyright (C) 2004, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02111-1307 USA.

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permission to link this library with independent modules to produce an
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package javax.swing.plaf.basic;

import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.LayoutManager;
import java.awt.Rectangle;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import javax.accessibility.Accessible;
import javax.swing.CellRendererPane;
import javax.swing.ComboBoxEditor;
import javax.swing.ComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JList;
import javax.swing.ListCellRenderer;
import javax.swing.UIDefaults;
import javax.swing.UIManager;
import javax.swing.event.ListDataEvent;
import javax.swing.event.ListDataListener;
import javax.swing.plaf.ComboBoxUI;
import javax.swing.plaf.ComponentUI;

/**
 * UI Delegate for JComboBox
 *
 * @author Olga Rodimina
 * @author Robert Schuster
 */
public class BasicComboBoxUI extends ComboBoxUI
{
  /**
   * This arrow button that is displayed in the rigth side of JComboBox. This
   * button is used to hide and show combo box's list of items
   */
  protected JButton arrowButton;

  /**
   * The combo box for which this UI delegate is for
   */
  protected JComboBox comboBox;

  /**
   * Component that is responsible for displaying/editting  selected item of
   * the combo box. By default JTextField is used as an editor for the
   * JComboBox
   */
  protected Component editor;

  /**
   * Listener listening to focus events occuring in the JComboBox
   */
  protected FocusListener focusListener;

  /**
   * tells whether JComboBox currently has focus
   */
  protected boolean hasFocus;

  /**
   * Listener listening to item events fired by the JComboBox
   */
  protected ItemListener itemListener;

  /**
   * KeyListener listening to key events that occur while JComboBox has focus
   */
  protected KeyListener keyListener;

  /**
   * MouseListener listening to mouse events occuring in the combo box
   */
  private MouseListener mouseListener;

  /**
   * List used when rendering selected item of the combo box. The selection
   * and foreground colors for combo box renderer  are configured from this
   * list
   */
  protected JList listBox;

  /**
   * ListDataListener listening to JComboBox model
   */
  protected ListDataListener listDataListener;

  /**
   * Popup list containing combo box's menu items
   */
  protected ComboPopup popup;
  protected KeyListener popupKeyListener;
  protected MouseListener popupMouseListener;
  protected MouseMotionListener popupMouseMotionListener;

  /**
   * Listener listening to changes in the bound properties of JComboBox
   */
  protected PropertyChangeListener propertyChangeListener;

  /**
   * Colors that are used to render selected item in the combo box.
   */
  private Color shadow;
  private Color darkShadow;
  private Color highlight;
  private Color lightHighlight;

  /* Size of the largest item in the comboBox */
  private Dimension largestItemSize;

  // It seems that JComboBox doesn't have a border set explicitely. So we just
  // paint the border everytime combo box is displayed. 

  /* border insets for this JComboBox*/
  private static final Insets borderInsets = new Insets(2, 2, 2, 2);

  // Width of the arrow button  
  private static int arrowButtonWidth = 15;

  // FIXME: This fields aren't used anywhere at this moment.
  protected Dimension cachedMinimumSize;
  protected CellRendererPane currentValuePane;
  protected boolean isMinimumSizeDirty;

  /**
   * Creates a new BasicComboBoxUI object.
   */
  public BasicComboBoxUI()
  {
  }

  /**
   * Factory method to create a BasicComboBoxUI for the given {@link
   * JComponent}, which should be a {@link JComboBox}.
   *
   * @param c The {@link JComponent} a UI is being created for.
   *
   * @return A BasicComboBoxUI for the {@link JComponent}.
   */
  public static ComponentUI createUI(JComponent c)
  {
    return new BasicComboBoxUI();
  }

  /**
   * This method installs the UI for the given JComponent.
   *
   * @param c The JComponent to install a UI for.
   */
  public void installUI(JComponent c)
  {
    super.installUI(c);

    if (c instanceof JComboBox)
      {
	comboBox = (JComboBox) c;
	comboBox.setOpaque(true);
	comboBox.setLayout(createLayoutManager());
	installDefaults();
	installComponents();
	installListeners();
	installKeyboardActions();
      }
  }

  /**
   * This method uninstalls the UI.
   *
   * @param c The JComponent that is having this UI removed.
   */
  public void uninstallUI(JComponent c)
  {
    uninstallKeyboardActions();
    uninstallListeners();
    uninstallComponents();
    uninstallDefaults();
    comboBox = null;
  }

  /**
   * This method installs the defaults that are defined in  the Basic look and
   * feel for this {@link JComboBox}.
   */
  protected void installDefaults()
  {
    UIDefaults defaults = UIManager.getLookAndFeelDefaults();

    comboBox.setBackground(defaults.getColor("ComboBox.background"));
    comboBox.setFont(defaults.getFont("ComboBox.font"));
    comboBox.setForeground(defaults.getColor("ComboBox.foreground"));

    // Set default color that should be used to to render selected item
    // of the combo box.
    shadow = defaults.getColor("Button.shadow");
    darkShadow = defaults.getColor("Button.darkShadow");
    lightHighlight = defaults.getColor("Button.light");
    highlight = defaults.getColor("Button.highlight");
  }

  /**
   * This method creates and installs the listeners for this UI.
   */
  protected void installListeners()
  {
    // install combo box's listeners
    propertyChangeListener = createPropertyChangeListener();
    comboBox.addPropertyChangeListener(propertyChangeListener);

    focusListener = createFocusListener();
    comboBox.addFocusListener(focusListener);

    itemListener = createItemListener();
    comboBox.addItemListener(itemListener);

    keyListener = createKeyListener();
    comboBox.addKeyListener(keyListener);

    mouseListener = createMouseListener();
    comboBox.addMouseListener(mouseListener);

    // install listeners that listen to combo box model
    listDataListener = createListDataListener();
    comboBox.getModel().addListDataListener(listDataListener);

    configureArrowButton();
  }

  /**
   * This method uninstalls the defaults and sets any objects created during
   * install to null
   */
  protected void uninstallDefaults()
  {
    UIDefaults defaults = UIManager.getLookAndFeelDefaults();

    comboBox.setBackground(null);
    comboBox.setFont(null);
    comboBox.setForeground(null);

    shadow = null;
    darkShadow = null;
    lightHighlight = null;
    highlight = null;
  }

  /**
   * Detaches all the listeners we attached in {@link #installListeners}.
   */
  protected void uninstallListeners()
  {
    comboBox.removePropertyChangeListener(propertyChangeListener);
    propertyChangeListener = null;

    comboBox.removeFocusListener(focusListener);
    focusListener = null;

    comboBox.removeItemListener(itemListener);
    itemListener = null;

    comboBox.removeKeyListener(keyListener);
    keyListener = null;

    comboBox.removeMouseListener(mouseListener);
    mouseListener = null;

    comboBox.getModel().removeListDataListener(listDataListener);
    listDataListener = null;

    unconfigureArrowButton();
  }

  /**
   * This method creates popup that will contain list of combo box's items
   *
   * @return popup containing list of combo box's items
   */
  protected ComboPopup createPopup()
  {
    return new BasicComboPopup(comboBox);
  }

  /**
   * Creates KeyListener to listen to key events.
   *
   * @return KeyListener that listens to key events.
   */
  protected KeyListener createKeyListener()
  {
    return new KeyHandler();
  }

  /**
   * This method create MouseListener that will listen to mouse event occuring
   * in combo box.
   *
   * @return the MouseListener
   */
  private MouseListener createMouseListener()
  {
    return new MouseHandler();
  }

  /**
   * This method create FocusListener that will listen to changes in this
   * JComboBox's focus.
   *
   * @return theFocusListener
   */
  protected FocusListener createFocusListener()
  {
    return new FocusHandler();
  }

  /**
   * This method create ListDataListener to listen to ComboBox's  data model
   *
   * @return ListDataListener
   */
  protected ListDataListener createListDataListener()
  {
    return new ListDataHandler();
  }

  /**
   * This method creates ItemListener that will listen to to the changes in
   * the JComboBox's selection.
   *
   * @return the ItemListener
   */
  protected ItemListener createItemListener()
  {
    return new ItemHandler();
  }

  /**
   * This method creates PropertyChangeListener to listen to  the changes in
   * the JComboBox's bound properties.
   *
   * @return the PropertyChangeListener
   */
  protected PropertyChangeListener createPropertyChangeListener()
  {
    return new PropertyChangeHandler();
  }

  /**
   * This method returns layout manager for the combo box.
   *
   * @return layout manager for the combo box
   */
  protected LayoutManager createLayoutManager()
  {
    return new ComboBoxLayoutManager();
  }

  /**
   * This method creates component that will be responsible for rendering the
   * selected component in the combo box.
   *
   * @return render for the combo box
   */
  protected ListCellRenderer createRenderer()
  {
    return new BasicComboBoxRenderer();
  }

  /**
   * Creates component that will be responsible for displaying/editting
   * selected item in the combo box. This editor is used only when combo box
   * is editable.
   *
   * @return component that will be responsible for  displaying/editting
   *         selected item in the combo box.
   */
  protected ComboBoxEditor createEditor()
  {
    return new BasicComboBoxEditor();
  }

  /**
   * This method installs components for this JComboBox. ArrowButton, main
   * part of combo box (upper part) and  popup list of items are created and
   * configured here.
   */
  protected void installComponents()
  {
    // create and install arrow button
    arrowButton = createArrowButton();

    comboBox.add(arrowButton);

    // Set list that will be used by BasicComboBoxRender 
    // in order to determine the right colors when rendering
    listBox = new JList();

    Color background = arrowButton.getBackground();
    listBox.setBackground(background);
    listBox.setSelectionBackground(background.darker());

    Color foreground = arrowButton.getForeground();
    listBox.setForeground(foreground);
    listBox.setSelectionForeground(foreground);

    // set editor and renderer for the combo box. Editor is used
    // only if combo box becomes editable, otherwise renderer is used
    // to paint the selected item; combobox is not editable by default. 
    comboBox.setRenderer(createRenderer());

    comboBox.setEditor(createEditor());
    editor = comboBox.getEditor().getEditorComponent();

    // create drop down list of items
    popup = createPopup();

    comboBox.revalidate();
  }

  /**
   * This method uninstalls components from this JComboBox
   */
  protected void uninstallComponents()
  {
    // uninstall arrow button
    unconfigureArrowButton();
    comboBox.remove(arrowButton);
    arrowButton = null;

    listBox = null;
    popup = null;

    comboBox.setRenderer(null);

    comboBox.setEditor(null);
    editor = null;
  }

  /**
   * This method adds editor to the combo box
   */
  public void addEditor()
  {
    comboBox.add(editor);
  }

  /**
   * This method removes editor from the combo box
   */
  public void removeEditor()
  {
    comboBox.remove(editor);
  }

  /**
   * This method configures editor for this combo box.
   */
  protected void configureEditor()
  {
    // FIXME: Need to implement. Set font and add listeners.
  }

  /**
   * This method removes all the listeners for the editor.
   */
  protected void unconfigureEditor()
  {
    // FIXME: Need to implement    
  }

  /**
   * This method adds listeners to the arrow button part of the combo box.
   */
  public void configureArrowButton()
  {
    arrowButton.addMouseListener(mouseListener);
  }

  /**
   * This method removes listeners from the arrow button part of the combo
   * box.
   */
  public void unconfigureArrowButton()
  {
    arrowButton.removeMouseListener(mouseListener);
  }

  /**
   * This method create arrow button for this JComboBox. Arrow button is
   * responsible for displaying / hiding drop down list of items  when it is
   * clicked.
   *
   * @return JButton arrow button for this JComboBox.
   */
  protected JButton createArrowButton()
  {
    return new BasicArrowButton(BasicArrowButton.SOUTH);
  }

  /**
   * This method checks if popup part of the combo box is visible on the
   * screen
   *
   * @param c The JComboBox to check
   *
   * @return true if popup part of the JComboBox is visible and false
   *         otherwise.
   */
  public boolean isPopupVisible(JComboBox c)
  {
    return popup.isVisible();
  }

  /**
   * Displays/Hides JComboBox's list of items on the screen.
   *
   * @param c The combo box, for which list of items should be
   *        displayed/hidden
   * @param v true if show popup part of the jcomboBox and false to hide.
   */
  public void setPopupVisible(JComboBox c, boolean v)
  {
    if (v)
      popup.show();
    else
      popup.hide();
  }

  /**
   * JComboBox is focus traversable if it is editable and not otherwise.
   *
   * @param c combo box for which to check whether it is focus traversable
   *
   * @return true if focus tranversable and false otherwise
   */
  public boolean isFocusTraversable(JComboBox c)
  {
    if (comboBox.isEditable())
      return true;

    return false;
  }

  /**
   * Paints given menu item using specified graphics context
   *
   * @param g The graphics context used to paint this combo box
   * @param c comboBox which needs to be painted.
   */
  public void paint(Graphics g, JComponent c)
  {
    if (c instanceof JComboBox)
      {
	JComboBox cb = (JComboBox) c;

	paintBorder(g, comboBox.getBounds(), hasFocus);

	Rectangle rect = rectangleForCurrentValue();
	paintCurrentValueBackground(g, rect, hasFocus);
	paintCurrentValue(g, rect, hasFocus);
      }
  }

  private void paintBorder(Graphics g, Rectangle bounds, boolean hasFocus)
  {
    int x = 0;
    int y = 0;
    int width = bounds.width;
    int height = bounds.height;

    Color oldColor = g.getColor();

    if (! arrowButton.getModel().isPressed())
      BasicGraphicsUtils.drawEtchedRect(g, x, y, width, height, Color.gray,
                                        Color.white, Color.gray, Color.white);
    else
      {
	g.setColor(darkShadow);
	g.drawRect(x, y, width, height);
	g.setColor(shadow);
	g.drawRect(x + 1, y + 1, width - 3, height - 3);
      }
    g.setColor(oldColor);
  }

  /**
   * Returns preferred size for the given menu item.
   *
   * @param c comboBox for which to get preferred size
   *
   * @return $Dimension$ preferred size for the given combo box
   */
  public Dimension getPreferredSize(JComponent c)
  {
    // return null to indicate that combo box's layout will determin its
    // preferred size
    return null;
  }

  /**
   * This method returns the minimum size for this {@link JComboBox} for this
   * look and feel.
   *
   * @param c The {@link JComponent} to find the minimum size for.
   *
   * @return The dimensions of the minimum size.
   */
  public Dimension getMinimumSize(JComponent c)
  {
    return null;
  }

  /**
   * This method returns the maximum size for this {@link JComboBox} for this
   * look and feel.
   *
   * @param c The {@link JComponent} to find the maximum size for
   *
   * @return The dimensions of the minimum size.
   */
  public Dimension getMaximumSize(JComponent c)
  {
    return null;
  }

  public int getAccessibleChildrenCount(JComponent c)
  {
    // FIXME: Need to implement
    return 0;
  }

  public Accessible getAccessibleChild(JComponent c, int i)
  {
    // FIXME: Need to implement
    return null;
  }

  /**
   * Returns true if the specified key is a navigation key and false otherwise
   *
   * @param keyCode a key for which to check whether it is navigation key or
   *        not.
   *
   * @return true if the specified key is a navigation key and false otherwis
   */
  protected boolean isNavigationKey(int keyCode)
  {
    return false;
  }

  /**
   * This method selects next possible item relative to the current selection
   * to be next selected item in the combo box.
   */
  protected void selectNextPossibleValue()
  {
    int index = comboBox.getSelectedIndex();
    if (index != comboBox.getItemCount() - 1)
      comboBox.setSelectedIndex(index + 1);
  }

  /**
   * This method selects previous item relative to current selection to be
   * next selected item.
   */
  protected void selectPreviousPossibleValue()
  {
    int index = comboBox.getSelectedIndex();
    if (index != 0)
      comboBox.setSelectedIndex(index - 1);
  }

  /**
   * This method displays combo box popup if the popup is not currently shown
   * on the screen and hides it if it is  currently shown
   */
  protected void toggleOpenClose()
  {
    setPopupVisible(comboBox, ! isPopupVisible(comboBox));
  }

  /**
   * This method returns bounds in which comboBox's selected Item will be
   * displayed
   *
   * @return rectangle bounds in which comboBox's selected Item will be
   *         displayed
   */
  protected Rectangle rectangleForCurrentValue()
  {
    Rectangle cbBounds = comboBox.getBounds();

    // Subtract width or the arrow button and border insets	    
    Rectangle rectForCurrentValue = new Rectangle(cbBounds.x
                                                  + borderInsets.left,
                                                  cbBounds.y
                                                  + borderInsets.top,
                                                  cbBounds.width
                                                  - arrowButtonWidth
                                                  - borderInsets.left
                                                  - borderInsets.right,
                                                  cbBounds.height
                                                  - borderInsets.top
                                                  - borderInsets.bottom);

    return rectForCurrentValue;
  }

  /**
   * This method returns insets of the current border.
   *
   * @return Insets representing space between combo box and its border
   */
  protected Insets getInsets()
  {
    return new Insets(0, 0, 0, 0);
  }

  /**
   * This method paints currently selected value in the main part of the combo
   * box (part without popup).
   *
   * @param g graphics context
   * @param bounds Rectangle representing the size of the area in which
   *        selected item should be drawn
   * @param hasFocus true if combo box has focus and false otherwise
   */
  public void paintCurrentValue(Graphics g, Rectangle bounds, boolean hasFocus)
  {
    if (! comboBox.isEditable())
      {
	Object currentValue = comboBox.getSelectedItem();
	boolean isPressed = arrowButton.getModel().isPressed();

	/* Gets the component to be drawn for the current value.
	 * If there is currently no selected item we will take an empty
	 * String as replacement.
	 */
	Component comp = comboBox.getRenderer()
	                             .getListCellRendererComponent(listBox,
	                                                           (currentValue != null ? currentValue : ""),
	                                                           -1,
	                                                           isPressed,
	                                                           hasFocus);
	if (! comboBox.isEnabled())
	      comp.setEnabled(false);

	g.translate(borderInsets.left, borderInsets.top);
	    comp.setBounds(0, 0, bounds.width, bounds.height);
	    comp.paint(g);
	    g.translate(-borderInsets.left, -borderInsets.top);
	    
	comboBox.revalidate();
      }
    else
      comboBox.getEditor().setItem(comboBox.getSelectedItem());
  }

  /**
   * This method paints background of part of the combo box, where currently
   * selected value is displayed. If the combo box has focus this method
   * should also paint focus rectangle around the combo box.
   *
   * @param g graphics context
   * @param bounds Rectangle representing the size of the largest item  in the
   *        comboBox
   * @param hasFocus true if combo box has fox and false otherwise
   */
  public void paintCurrentValueBackground(Graphics g, Rectangle bounds,
                                          boolean hasFocus)
  {
    // background is painted by renderer, so it seems that nothing
    // should be done here.
  }

  /**
   * Returns default size for the combo box that doesn't contain any elements
   * in it
   *
   * @return Default size of the combo box with no elements in it.
   */
  protected Dimension getDefaultSize()
  {
    return new Dimension(6, 17);
  }

  /**
   * Returns size of the largest item in the combo box. This size will be the
   * size of the combo box, not including the arrowButton.
   *
   * @return dimensions of the largest item in the combo box.
   */
  protected Dimension getLargestItemSize()
  {
    ComboBoxModel model = comboBox.getModel();
    int numItems = model.getSize();

    // if combo box doesn't have any items then simply
    // return its default size
    if (numItems == 0)
      {
	largestItemSize = getDefaultSize();
	return largestItemSize;
      }

    Dimension size = new Dimension(0, 0);

    // ComboBox's display size should be equal to the 
    // size of the largest item in the combo box. 
    ListCellRenderer renderer = comboBox.getRenderer();

    for (int i = 0; i < numItems; i++)
      {
	Object item = model.getElementAt(i);
	String s = item.toString();
	Component comp = renderer.getListCellRendererComponent(listBox, item,
	                                                       -1, false, false);

	if (comp.getPreferredSize().getWidth() > size.getWidth())
	  size = comp.getPreferredSize();
      }

    largestItemSize = size;
    return largestItemSize;
  }

  /**
   * This method installs the keyboard actions for the JComboBox as specified
   * by the look and feel.
   */
  protected void installKeyboardActions()
  {
    // FIXME: Need to implement.
  }

  /**
   * This method uninstalls the keyboard actions for the JComboBox there were
   * installed by in {@link #installListeners}.
   */
  protected void uninstallKeyboardActions()
  {
    // FIXME: Need to implement.
  }

  /**
   * This class is Layout Manager for this combo box.
   */
  public class ComboBoxLayoutManager extends Object implements LayoutManager
  {
    /**
     * Creates a new ComboBoxLayoutManager object.
     */
    public ComboBoxLayoutManager()
    {
    }

    public void addLayoutComponent(String name, Component comp)
    {
      // Do nothing
    }

    public void removeLayoutComponent(Component comp)
    {
      // Do nothing
    }

    /**
     * Returns preferred layout size of the JComboBox.
     *
     * @param parent Container for which preferred size should be calculated
     *
     * @return preferred size for the given container
     */
    public Dimension preferredLayoutSize(Container parent)
    {
      Dimension d = new Dimension(0, 0);

      if (largestItemSize == null)
	largestItemSize = getLargestItemSize();

      // add size for the area that will display selected item
      d.width += largestItemSize.getWidth();
      d.height += largestItemSize.getHeight();

      // add size of the arrow button
      d.width += arrowButtonWidth;

      // add width and height of the border
      d.width += borderInsets.left + borderInsets.right;
      d.height += borderInsets.left + borderInsets.right;

      // Add combo box's insets 	
      Insets insets = parent.getInsets();
      d.width += insets.left + insets.right;
      d.width += insets.left + insets.right;

      return d;
    }

    public Dimension minimumLayoutSize(Container parent)
    {
      return preferredLayoutSize(parent);
    }

    /**
     * This method layouts out the components in the container.  It puts arrow
     * button right end part of the comboBox. If the comboBox is editable
     * then editor is placed to the left of arrow  button, starting from the
     * beginning.
     *
     * @param parent Container that should be layed out.
     */
    public void layoutContainer(Container parent)
    {
      // Position editor component to the left of arrow button if combo box is 
      // editable
      int editorWidth = comboBox.getBounds().width - arrowButtonWidth - 2;

      if (comboBox.isEditable())
	editor.setBounds(borderInsets.left, borderInsets.top, editorWidth,
	                 comboBox.getBounds().height - borderInsets.left
	                 - borderInsets.top);

      arrowButton.setBounds(editorWidth, 2, arrowButtonWidth,
                            comboBox.getBounds().height - 4);
      comboBox.revalidate();
    }
  }

  /**
   * This class handles focus changes occuring in the combo box. This class is
   * responsible for repainting combo box whenever focus is gained or lost
   * and also for hiding popup list of items whenever combo box loses its
   * focus.
   */
  public class FocusHandler extends Object implements FocusListener
  {
    /**
     * Creates a new FocusHandler object.
     */
    public FocusHandler()
    {
    }

    /**
     * This mehtod is invoked when combo box gains focus. It repaints main
     * part of combo box  accordingally.
     *
     * @param e the FocusEvent
     */
    public void focusGained(FocusEvent e)
    {
      hasFocus = true;
      comboBox.repaint();
    }

    /**
     * This method is invoked when combo box loses focus It repaint main part
     * of combo box accordingally and  hides popup list of items.
     *
     * @param e the FocusEvent
     */
    public void focusLost(FocusEvent e)
    {
      hasFocus = false;
      comboBox.repaint();
      popup.hide();
    }
  }

  /**
   * This class handles ItemEvent fired by the JComboBox when its selected
   * item changes.
   */
  public class ItemHandler extends Object implements ItemListener
  {
    /**
     * Creates a new ItemHandler object.
     */
    public ItemHandler()
    {
    }

    /**
     * This method is invoked when selected item becomes deselected or when
     * new item becomes selected.
     *
     * @param e the ItemEvent representing item's state change.
     */
    public void itemStateChanged(ItemEvent e)
    {
      comboBox.repaint();
    }
  }

  /**
   * KeyHandler handles key events occuring while JComboBox has focus.
   */
  public class KeyHandler extends KeyAdapter
  {
    public KeyHandler()
    {
    }

    /*
     * This method is invoked whenever key is pressed while JComboBox is in
     * focus.
     */
    public void keyPressed(KeyEvent e)
    {
      // FIXME: This method calls JComboBox.selectWithKeyChar if the key that was 
      // pressed is not a navigation key. 
    }
  }

  /**
   * This class handles to the changes occuring in the JComboBox's data model
   */
  public class ListDataHandler extends Object implements ListDataListener
  {
    /**
     * Creates a new ListDataHandler object.
     */
    public ListDataHandler()
    {
    }

    /**
     * This method is invoked content's of JComboBox's data model  are changed
     *
     * @param e ListDataEvent describing the change.
     */
    public void contentsChanged(ListDataEvent e)
    {
      // if the item is selected or deselected
    }

    /**
     * This method is invoked when items were added to the JComboBox's data
     * model.
     *
     * @param e ListDataEvent describing the change.
     */
    public void intervalAdded(ListDataEvent e)
    {
      // must determine if the size of the combo box should change
      int start = e.getIndex0();
      int end = e.getIndex1();

      ComboBoxModel model = comboBox.getModel();
      ListCellRenderer renderer = comboBox.getRenderer();

      if (largestItemSize == null)
	largestItemSize = new Dimension(0, 0);

      for (int i = start - 1; i < end; i++)
        {
	  Object item = model.getElementAt(i);
	  Component comp = renderer.getListCellRendererComponent(new JList(),
	                                                         item, -1,
	                                                         false, false);
	  if (comp.getPreferredSize().getWidth() > largestItemSize.getWidth())
	    largestItemSize = comp.getPreferredSize();
        }
    }

    /**
     * This method is invoked when items were removed from the JComboBox's
     * data model.
     *
     * @param e ListDataEvent describing the change.
     */
    public void intervalRemoved(ListDataEvent e)
    {
      // recalculate display size of the JComboBox.
      largestItemSize = getLargestItemSize();
      comboBox.repaint();
    }
  }

  /**
   * This class handles PropertyChangeEvents fired by JComboBox.
   */
  public class PropertyChangeHandler extends Object
    implements PropertyChangeListener
  {
    public PropertyChangeHandler()
    {
    }

    /**
     * This method is invoked whenever bound property of JComboBox changes.
     */
    public void propertyChange(PropertyChangeEvent e)
    {
      if (e.getPropertyName().equals("enabled"))
        {
	  arrowButton.setEnabled(comboBox.isEnabled());

	  if (comboBox.isEditable())
	    comboBox.getEditor().getEditorComponent().setEnabled(comboBox
	                                                         .isEnabled());
        }
      else if (e.getPropertyName().equals("editable"))
        {
	  if (comboBox.isEditable())
	    {
	      configureEditor();
	      addEditor();
	    }
	  else
	    {
	      unconfigureEditor();
	      removeEditor();
	    }

	  comboBox.revalidate();
	  comboBox.repaint();
        }
      else if (e.getPropertyName().equals("dataModel"))
        {
	  // remove ListDataListener from old model and add it to new model
	  ComboBoxModel oldModel = (ComboBoxModel) e.getOldValue();
	  if (oldModel != null)
	    oldModel.removeListDataListener(listDataListener);

	  if ((ComboBoxModel) e.getNewValue() != null)
	    comboBox.getModel().addListDataListener(listDataListener);
        }

      // FIXME: Need to handle changes in other bound properties.	
    }
  }

  /**
   * MouseHandler listens to mouse events occuring in the combo box. This
   * class is responsible for repainting this JComboBox whenever the mouse is
   * being pressed or released over it.
   */
  private class MouseHandler extends MouseAdapter
  {
    /**
     * This method is invoked when mouse is pressed over the combo box. It
     * repaints the combo box accordinglly
     *
     * @param e the MouseEvent
     */
    public void mousePressed(MouseEvent e)
    {
      if (comboBox.isEnabled())
        {
	  if (e.getSource() instanceof JComboBox)
	    {
	      arrowButton.getModel().setPressed(true);
	      arrowButton.getModel().setArmed(true);
	    }

	  comboBox.repaint();

	  if (e.getSource() instanceof BasicArrowButton)
	    toggleOpenClose();
        }
    }

    /**
     * This method is invoked when mouse is released over the combo box. It
     * repaints the combo box accordinglly
     *
     * @param e the MouseEvent
     */
    public void mouseReleased(MouseEvent e)
    {
      if (comboBox.isEnabled())
        {
	  if (e.getSource() instanceof JComboBox)
	    {
	      arrowButton.getModel().setPressed(false);
	      arrowButton.getModel().setArmed(false);
	    }

	  comboBox.repaint();
        }
    }
  }
}