JMenuBar.java

/* JMenuBar.java --
   Copyright (C) 2002, 2004, 2005, 2006  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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General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package javax.swing;

import java.awt.Component;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.event.KeyEvent;
import java.awt.event.MouseEvent;

import javax.accessibility.Accessible;
import javax.accessibility.AccessibleContext;
import javax.accessibility.AccessibleRole;
import javax.accessibility.AccessibleSelection;
import javax.accessibility.AccessibleStateSet;
import javax.swing.plaf.MenuBarUI;

import javax.swing.border.Border;

/**
 * JMenuBar is a container for menu's. For a menu bar to be seen on the
 * screen, at least one menu should be added to it. Just like adding
 * components to container, one can use add() to add menu's to the menu bar.
 * Menu's will be displayed in the menu  bar in the order they were added.
 * The JMenuBar uses selectionModel to keep track of selected menu index.
 * JMenuBar's selectionModel will fire ChangeEvents to its registered 
 * listeners when the selected index changes.
 */
public class JMenuBar extends JComponent implements Accessible, MenuElement
{
  /**
   * Provides accessibility support for <code>JMenuBar</code>.
   * 
   * @author Roman Kennke (kennke@aicas.com)
   */
  protected class AccessibleJMenuBar extends AccessibleJComponent
    implements AccessibleSelection
  {

    /**
     * Returns the number of selected items in the menu bar. Possible values
     * are <code>0</code> if nothing is selected, or <code>1</code> if one
     * item is selected.
     *
     * @return the number of selected items in the menu bar
     */
    public int getAccessibleSelectionCount()
    {
      int count = 0;
      if (getSelectionModel().getSelectedIndex() != -1)
        count = 1;
      return count;
    }

    /**
     * Returns the selected with index <code>i</code> menu, or
     * <code>null</code> if the specified menu is not selected.
     *
     * @param i the index of the menu to return
     *
     * @return the selected with index <code>i</code> menu, or
     *         <code>null</code> if the specified menu is not selected
     */
    public Accessible getAccessibleSelection(int i)
    {
      if (getSelectionModel().getSelectedIndex() != i)
        return null;
      return getMenu(i);
    }

    /**
     * Returns <code>true</code> if the specified menu is selected,
     * <code>false</code> otherwise.
     *
     * @param i the index of the menu to check
     *
     *@return <code>true</code> if the specified menu is selected,
     *        <code>false</code> otherwise
     */
    public boolean isAccessibleChildSelected(int i)
    {
      return getSelectionModel().getSelectedIndex() == i;
    }

    /**
     * Selects the menu with index <code>i</code>. If another menu is already
     * selected, this will be deselected.
     *
     * @param i the menu to be selected
     */
    public void addAccessibleSelection(int i)
    {
      getSelectionModel().setSelectedIndex(i);
    }

    /**
     * Deselects the menu with index <code>i</code>.
     *
     * @param i the menu index to be deselected
     */
    public void removeAccessibleSelection(int i)
    {
      if (getSelectionModel().getSelectedIndex() == i)
        getSelectionModel().clearSelection();
    }

    /**
     * Deselects all possibly selected menus.
     */
    public void clearAccessibleSelection()
    {
      getSelectionModel().clearSelection();
    }

    /**
     * In menu bars it is not possible to select all items, so this method
     * does nothing.
     */
    public void selectAllAccessibleSelection()
    {
      // In menu bars it is not possible to select all items, so this method
      // does nothing.
    }

    /**
     * Returns the accessible role of <code>JMenuBar</code>, which is
     * {@link AccessibleRole#MENU_BAR}.
     *
     * @return the accessible role of <code>JMenuBar</code>, which is
     *         {@link AccessibleRole#MENU_BAR}
     */
    public AccessibleRole getAccessibleRole()
    {
      return AccessibleRole.MENU_BAR;
    }

    /**
     * Returns the <code>AccessibleSelection</code> for this object. This
     * method returns <code>this</code>, since the
     * <code>AccessibleJMenuBar</code> manages its selection itself.
     *
     * @return the <code>AccessibleSelection</code> for this object
     */
    public AccessibleSelection getAccessibleSelection()
    {
      return this;
    }

    /**
     * Returns the state of this <code>AccessibleJMenuBar</code>.
     *
     * @return the state of this <code>AccessibleJMenuBar</code>.
     */
    public AccessibleStateSet getAccessibleStateSet()
    {
      AccessibleStateSet stateSet = super.getAccessibleStateSet();
      // TODO: Figure out what state must be added to the super state set.
      return stateSet;
    }
  }

  private static final long serialVersionUID = -8191026883931977036L;

  /** JMenuBar's model. It keeps track of selected menu's index */
  private transient SingleSelectionModel selectionModel;

  /* borderPainted property indicating if the menuBar's border will be painted*/
  private boolean borderPainted;

  /* margin between menu bar's border and its menues*/
  private Insets margin;

  /**
   * Creates a new JMenuBar object.
   */
  public JMenuBar()
  {
    selectionModel = new DefaultSingleSelectionModel();
    borderPainted = true;
    updateUI();
  }

  /**
   * Adds menu to the menu bar
   *
   * @param c menu to add
   *
   * @return reference to the added menu
   */
  public JMenu add(JMenu c)
  {
    c.setAlignmentX(Component.LEFT_ALIGNMENT);
    super.add(c);
    return c;
  }

  /**
   * This method overrides addNotify() in the Container to register
   * this menu bar with the current keyboard manager.
   */
  public void addNotify()
  {
    super.addNotify();
    KeyboardManager.getManager().registerJMenuBar(this);
  }

  public AccessibleContext getAccessibleContext()
  {
    if (accessibleContext == null)
      accessibleContext = new AccessibleJMenuBar();
    return accessibleContext;
  }

  /**
   * Returns reference to this menu bar
   *
   * @return reference to this menu bar
   */
  public Component getComponent()
  {
    return this;
  }

  /**
   * Returns component at the specified index.
   *
   * @param i index of the component to get
   *
   * @return component at the specified index. Null is returned if
   * component at the specified index doesn't exist.
   * @deprecated Replaced by getComponent(int)
   */
  public Component getComponentAtIndex(int i)
  {
    return getComponent(i);
  }

  /**
   * Returns index of the specified component
   *
   * @param c Component to search for
   *
   * @return index of the specified component. -1 is returned if
   * specified component doesnt' exist in the menu bar.
   */
  public int getComponentIndex(Component c)
  {
    Component[] comps = getComponents();

    int index = -1;

    for (int i = 0; i < comps.length; i++)
      {
	if (comps[i].equals(c))
	  {
	    index = i;
	    break;
	  }
      }

    return index;
  }

  /**
   * DOCUMENT ME!
   *
   * @return DOCUMENT ME!
   */
  public JMenu getHelpMenu()
  {
    return null;
  }

  /**
   * Returns margin betweeen menu bar's border and its menues
   *
   * @return margin between menu bar's border and its menues
   */
  public Insets getMargin()
  {
    if (margin == null)
      return new Insets(0, 0, 0, 0);
    else
      return margin;
  }

  /**
   * Return menu at the specified index. If component at the
   * specified index is not a menu, then null is returned.
   *
   * @param index index to look for the menu
   *
   * @return menu at specified index, or null if menu doesn't exist
   * at the specified index.
   */
  public JMenu getMenu(int index)
  {
    if (getComponentAtIndex(index) instanceof JMenu)
      return (JMenu) getComponentAtIndex(index);
    else
      return null;
  }

  /**
   * Returns number of menu's in this menu bar
   *
   * @return number of menu's in this menu bar
   */
  public int getMenuCount()
  {
    return getComponentCount();
  }

  /**
   * Returns selection model for this menu bar. SelectionModel
   * keeps track of the selected menu in the menu bar. Whenever
   * selected property of selectionModel changes, the ChangeEvent
   * will be fired its ChangeListeners.
   *
   * @return selection model for this menu bar.
   */
  public SingleSelectionModel getSelectionModel()
  {
    return selectionModel;
  }

  /**
   * Method of MenuElement interface. It returns subcomponents
   * of the menu bar, which are all the menues that it contains.
   *
   * @return MenuElement[] array containing menues in this menu bar
   */
  public MenuElement[] getSubElements()
  {
    MenuElement[] subElements = new MenuElement[getComponentCount()];

    int j = 0;
    boolean doResize = false;
    MenuElement menu;
    for (int i = 0; i < getComponentCount(); i++)
      {
        menu = getMenu(i);
        if (menu != null)
          {
            subElements[j++] = (MenuElement) menu;
          }
        else
          doResize = true;
      }

    if (! doResize)
      return subElements;
    else
      {
        MenuElement[] subElements2 = new MenuElement[j];
        for (int i = 0; i < j; i++)
          subElements2[i] = subElements[i];

        return subElements2;
      }
  }

  /**
    * Set the "UI" property of the menu bar, which is a look and feel class
    * responsible for handling the menuBar's input events and painting it.
    *
    * @return The current "UI" property
    */
  public MenuBarUI getUI()
  {
    return (MenuBarUI) ui;
  }

  /**
   * This method returns a name to identify which look and feel class will be
   * the UI delegate for the menu bar.
   *
   * @return The Look and Feel classID. "MenuBarUI"
   */
  public String getUIClassID()
  {
    return "MenuBarUI";
  }

  /**
   * Returns true if menu bar paints its border and false otherwise
   *
   * @return true if menu bar paints its border and false otherwise
   */
  public boolean isBorderPainted()
  {
    return borderPainted;
  }

  /**
   * Returns true if some menu in menu bar is selected.
   *
   * @return true if some menu in menu bar is selected and false otherwise
   */
  public boolean isSelected()
  {
    return selectionModel.isSelected();
  }

  /**
   * This method does nothing by default. This method is need for the
   * MenuElement interface to be implemented.
   *
   * @param isIncluded true if menuBar is included in the selection
   * and false otherwise
   */
  public void menuSelectionChanged(boolean isIncluded)
  {
    // Do nothing - needed for implementation of MenuElement interface
  }

  /**
   * Paints border of the menu bar, if its borderPainted property is set to
   * true.
   *
   * @param g The graphics context with which to paint the border
   */
  protected void paintBorder(Graphics g)
  {
    if (borderPainted)
      {
        Border border = getBorder();
        if (border != null)
          getBorder().paintBorder(this, g, 0, 0, getSize(null).width,
                                  getSize(null).height);
      }
  }

  /**
   * A string that describes this JMenuBar. Normally only used
   * for debugging.
   *
   * @return A string describing this JMenuBar
   */
  protected String paramString()
  {
    StringBuffer sb = new StringBuffer();
    sb.append(super.paramString());
    sb.append(",margin=");
    if (getMargin() != null)
      sb.append(getMargin());
    sb.append(",paintBorder=").append(isBorderPainted());
    return sb.toString();
  }

  /**
   * Process key events forwarded from MenuSelectionManager. This method
   * doesn't do anything. It is here to conform to the MenuElement interface.
   *
   * @param e event forwarded from MenuSelectionManager
   * @param path path to the menu element from which event was generated
   * @param manager MenuSelectionManager for the current menu hierarchy
   *
   */
  public void processKeyEvent(KeyEvent e, MenuElement[] path,
                              MenuSelectionManager manager)
  {
    // Do nothing - needed for implementation of MenuElement interface
  }

  /**
   * This method overrides JComponent.processKeyBinding to allow the 
   * JMenuBar to check all the child components (recursiveley) to see 
   * if they'll consume the event.
   * 
   * @param ks the KeyStroke for the event
   * @param e the KeyEvent for the event
   * @param condition the focus condition for the binding
   * @param pressed true if the key is pressed 
   */
  protected boolean processKeyBinding(KeyStroke ks, KeyEvent e, int condition,
                                      boolean pressed)
  {
    // See if the regular JComponent behavior consumes the event
    if (super.processKeyBinding(ks, e, condition, pressed))
      return true;
    
    // If not, have to recursively check all the child menu elements to see 
    // if they want it    
    MenuElement[] children = getSubElements();
    for (int i = 0; i < children.length; i++)
      if (processKeyBindingHelper(children[i], ks, e, condition, pressed))
        return true;
    return false;
  }
  
  /**
   * This is a helper method to recursively check the children of this
   * JMenuBar to see if they will consume a key event via key bindings.  
   * This is used for menu accelerators.
   * @param menuElement the menuElement to check (and check all its children)
   * @param ks the KeyStroke for the event
   * @param e the KeyEvent that may be consumed
   * @param condition the focus condition for the binding
   * @param pressed true if the key was pressed
   * @return true <code>menuElement</code> or one of its children consume
   * the event (processKeyBinding returns true for menuElement or one of
   * its children).
   */
  static boolean processKeyBindingHelper(MenuElement menuElement, KeyStroke ks,
                                         KeyEvent e, int condition,
                                         boolean pressed)
  {
    if (menuElement == null)
      return false;

    // First check the menuElement itself, if it's a JComponent
    if (menuElement instanceof JComponent
        && ((JComponent) menuElement).processKeyBinding(ks, e, condition,
                                                        pressed))
      return true;
    
    // If that didn't consume it, check all the children recursively
    MenuElement[] children = menuElement.getSubElements();
    for (int i = 0; i < children.length; i++)
      if (processKeyBindingHelper(children[i], ks, e, condition, pressed))
        return true;
    return false;
  }
  
  /**
   * Process mouse events forwarded from MenuSelectionManager. This method
   * doesn't do anything. It is here to conform to the MenuElement interface.
   *
   * @param event event forwarded from MenuSelectionManager
   * @param path path to the menu element from which event was generated
   * @param manager MenuSelectionManager for the current menu hierarchy
   *
   */
  public void processMouseEvent(MouseEvent event, MenuElement[] path,
                                MenuSelectionManager manager)
  {
    // Do nothing - needed for implementation of MenuElement interface
  }

  /**
   * This method overrides removeNotify() in the Container to
   * unregister this menu bar from the current keyboard manager.
   */
  public void removeNotify()
  {
    KeyboardManager.getManager().unregisterJMenuBar(this);
    super.removeNotify();
  }

  /**
   * Sets painting status of the border. If 'b' is true then menu bar's
   * border will be painted, and it will not be painted otherwise.
   *
   * @param b indicates if menu bar's border should be painted.
   */
  public void setBorderPainted(boolean b)
  {
    if (b != borderPainted)
      {
	boolean old = borderPainted;
	borderPainted = b;
	firePropertyChange("borderPainted", old, b);
	revalidate();
	repaint();
      }
  }

  /**
   * Sets help menu for this menu bar
   *
   * @param menu help menu
   *
   * @specnote The specification states that this method is not yet implemented
   *           and should throw an exception.
   */
  public void setHelpMenu(JMenu menu)
  {
    // We throw an Error here, just as Sun's JDK does.
    throw new Error("setHelpMenu() not yet implemented.");
  }

  /**
   * Sets the menu bar's "margin" bound property,  which represents
   * distance between the menubar's border and its menus.
   * icon. When marging property is modified, PropertyChangeEvent will
   * be fired to menuBar's PropertyChangeListener's.
   *
   * @param m distance between the menubar's border and its menus.
   *
   */
  public void setMargin(Insets m)
  {
    if (m != margin)
      {
	Insets oldMargin = margin;
	margin = m;
	firePropertyChange("margin", oldMargin, margin);
      }
  }

  /**
   * Changes menu bar's selection to the specified menu.
   * This method updates selected index of menu bar's selection model,
   * which results in a model firing change event.
   *
   * @param sel menu to select
   */
  public void setSelected(Component sel)
  {
    int index = getComponentIndex(sel);
    selectionModel.setSelectedIndex(index);
  }

  /**
   * Sets menuBar's selection model to the one specified
   *
   * @param model SingleSelectionModel that needs to be set for this menu bar
   */
  public void setSelectionModel(SingleSelectionModel model)
  {
    if (selectionModel != model)
      {
	SingleSelectionModel oldModel = selectionModel;
	selectionModel = model;
	firePropertyChange("model", oldModel, selectionModel);
      }
  }

  /**
   * Set the "UI" property of the menu bar, which is a look and feel class
   * responsible for handling menuBar's input events and painting it.
   *
   * @param ui The new "UI" property
   */
  public void setUI(MenuBarUI ui)
  {
    super.setUI(ui);
  }

  /**
   * Set the "UI" property to a class constructed, via the {@link
   * UIManager}, from the current look and feel.
   */
  public void updateUI()
  {
    setUI((MenuBarUI) UIManager.getUI(this));
  }
}