gcc/libjava/classpath/javax/swing/MenuSelectionManager.java

/* MenuSelectionManager.java --
   Copyright (C) 2002, 2004 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
the Free Software Foundation; either version 2, or (at your option)
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GNU Classpath is distributed in the hope that it will be useful, but
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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.

Linking this library statically or dynamically with other modules is
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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.Dimension;
import java.awt.Point;
import java.awt.event.KeyEvent;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.Vector;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;

/**
 * This class manages current menu selectection. It provides
 * methods to clear and set current selected menu path.
 * It also fires StateChange event to its registered
 * listeners whenever selected path of the current menu hierarchy
 * changes.
 *
 */
public class MenuSelectionManager
{
  /** ChangeEvent fired when selected path changes*/
  protected ChangeEvent changeEvent = new ChangeEvent(this);

  /** List of listeners for this MenuSelectionManager */
  protected EventListenerList listenerList = new EventListenerList();

  /** Default manager for the current menu hierarchy*/
  private static final MenuSelectionManager manager = new MenuSelectionManager();

  /** Path to the currently selected menu */
  private Vector selectedPath = new Vector();

  /**
   * Fires StateChange event to registered listeners
   */
  protected void fireStateChanged()
  {
    ChangeListener[] listeners = getChangeListeners();

    for (int i = 0; i < listeners.length; i++)
      listeners[i].stateChanged(changeEvent);
  }

  /**
   * Adds ChangeListener to this MenuSelectionManager
   *
   * @param listener ChangeListener to add
   */
  public void addChangeListener(ChangeListener listener)
  {
    listenerList.add(ChangeListener.class, listener);
  }

  /**
   * Removes ChangeListener from the list of registered listeners
   * for this MenuSelectionManager.
   *
   * @param listener ChangeListner to remove
   */
  public void removeChangeListener(ChangeListener listener)
  {
    listenerList.remove(ChangeListener.class, listener);
  }

  /**
   * Returns list of registered listeners with MenuSelectionManager
   *
   * @since 1.4
   */
  public ChangeListener[] getChangeListeners()
  {
    return (ChangeListener[]) listenerList.getListeners(ChangeListener.class);
  }

  /**
   * Unselects all the menu elements on the selection path
   */
  public void clearSelectedPath()
  {
    // Send events from the bottom most item in the menu - hierarchy to the
    // top most
    for (int i = selectedPath.size() - 1; i >= 0; i--)
      ((MenuElement) selectedPath.get(i)).menuSelectionChanged(false);

    // clear selected path
    selectedPath.clear();

    // notify all listeners that the selected path was changed    
    fireStateChanged();
  }

  /**
   * This method returns menu element on the selected path that contains
   * given source point. If no menu element on the selected path contains this
   * point, then null is returned.
   *
   * @param source Component relative to which sourcePoint is given
   * @param sourcePoint point for which we want to find menu element that contains it
   *
   * @return Returns menu element that contains given source point and belongs
   * to the currently selected path. Null is return if no such menu element found.
   */
  public Component componentForPoint(Component source, Point sourcePoint)
  {
    // Convert sourcePoint to screen coordinates.
    Point sourcePointOnScreen = sourcePoint;
    
    if (source.isShowing())
      SwingUtilities.convertPointToScreen(sourcePointOnScreen, source);

    Point compPointOnScreen;
    Component resultComp = null;

    // For each menu element on the selected path, express its location 
    // in terms of screen coordinates and check if there is any 
    // menu element on the selected path that contains given source point.
    for (int i = 0; i < selectedPath.size(); i++)
      {
	Component comp = ((Component) selectedPath.get(i));
	Dimension size = comp.getSize();

	// convert location of this menu item to screen coordinates
	compPointOnScreen = comp.getLocationOnScreen();

	if (compPointOnScreen.x <= sourcePointOnScreen.x
	    && sourcePointOnScreen.x < compPointOnScreen.x + size.width
	    && compPointOnScreen.y <= sourcePointOnScreen.y
	    && sourcePointOnScreen.y < compPointOnScreen.y + size.height)
	  {
	    Point p = sourcePointOnScreen;
        
        if (comp.isShowing())
          SwingUtilities.convertPointFromScreen(p, comp);
        
	    resultComp = SwingUtilities.getDeepestComponentAt(comp, p.x, p.y);
	    break;
	  }
      }
    return resultComp;
  }

  /**
   * Returns shared instance of MenuSelection Manager
   *
   * @return default Manager
   */
  public static MenuSelectionManager defaultManager()
  {
    return manager;
  }

  /**
   * Returns path representing current menu selection
   *
   * @return Current selection path
   */
  public MenuElement[] getSelectedPath()
  {
    MenuElement[] path = new MenuElement[selectedPath.size()];

    for (int i = 0; i < path.length; i++)
      path[i] = (MenuElement) selectedPath.get(i);

    return path;
  }

  /**
   * Returns true if specified component is part of current menu
   * heirarchy and false otherwise
   *
   * @param c Component for which to check
   * @return True if specified component is part of current menu
   */
  public boolean isComponentPartOfCurrentMenu(Component c)
  {
    MenuElement[] subElements;
    boolean ret = false;
    for (int i = 0; i < selectedPath.size(); i++)
      {
        // Check first element.
        MenuElement first = (MenuElement) selectedPath.get(i);
        if (SwingUtilities.isDescendingFrom(c, first.getComponent()))
          {
            ret = true;
            break;
          }
        else
          {
            // Check sub elements.
            subElements = first.getSubElements();
            for (int j = 0; j < subElements.length; j++)
              {
                MenuElement me = subElements[j]; 
                if (me != null
                    && (SwingUtilities.isDescendingFrom(c, me.getComponent())))
                  {
                    ret = true;
                    break;
                  }
              }
          }
      }

      return ret;
  }

  /**
   * Processes key events on behalf of the MenuElements. MenuElement
   * instances should always forward their key events to this method and
   * get their {@link MenuElement#processKeyEvent(KeyEvent, MenuElement[],
   * MenuSelectionManager)} eventually called back.
   *
   * @param e the key event
   */
  public void processKeyEvent(KeyEvent e)
  {
    MenuElement[] selection = (MenuElement[])
                    selectedPath.toArray(new MenuElement[selectedPath.size()]);
    if (selection.length == 0)
      return;

    MenuElement[] path;
    for (int index = selection.length - 1; index >= 0; index--)
      {
        MenuElement el = selection[index];
        // This method's main purpose is to forward key events to the
        // relevant menu items, so that they can act in response to their
        // mnemonics beeing typed. So we also need to forward the key event
        // to all the subelements of the currently selected menu elements
        // in the path.
        MenuElement[] subEls = el.getSubElements();
        path = null;
        for (int subIndex = 0; subIndex < subEls.length; subIndex++)
          {
            MenuElement sub = subEls[subIndex];
            // Skip elements that are not showing or not enabled.
            if (sub == null || ! sub.getComponent().isShowing()
                || ! sub.getComponent().isEnabled())
              {
                continue;
              }

            if (path == null)
              {
                path = new MenuElement[index + 2];
                System.arraycopy(selection, 0, path, 0, index + 1);
              }
            path[index + 1] = sub;
            sub.processKeyEvent(e, path, this);
            if (e.isConsumed())
              break;
          }
        if (e.isConsumed())
          break;
      }

    // Dispatch to first element in selection if it hasn't been consumed.
    if (! e.isConsumed())
      {
        path = new MenuElement[1];
        path[0] = selection[0];
        path[0].processKeyEvent(e, path, this);
      }
  }

  /**
   * Forwards given mouse event to all of the source subcomponents.
   *
   * @param event Mouse event
   */
  public void processMouseEvent(MouseEvent event)
  {
    Component source = ((Component) event.getSource());

    // In the case of drag event, event.getSource() returns component
    // where drag event originated. However menu element processing this 
    // event should be the one over which mouse is currently located, 
    // which is not necessary the source of the drag event.     
    Component mouseOverMenuComp;

    // find over which menu element the mouse is currently located
    if (event.getID() == MouseEvent.MOUSE_DRAGGED
        || event.getID() == MouseEvent.MOUSE_RELEASED)
      mouseOverMenuComp = componentForPoint(source, event.getPoint());
    else
      mouseOverMenuComp = source;

    // Process this event only if mouse is located over some menu element
    if (mouseOverMenuComp != null && (mouseOverMenuComp instanceof MenuElement))
      {
	MenuElement[] path = getPath(mouseOverMenuComp);
	((MenuElement) mouseOverMenuComp).processMouseEvent(event, path,
	                                                    manager);

	// FIXME: Java specification says that mouse events should be
	// forwarded to subcomponents. The code below does it, but
	// menu's work fine without it. This code is commented for now.	  

	/*
	MenuElement[] subComponents = ((MenuElement) mouseOverMenuComp)
	                              .getSubElements();

	for (int i = 0; i < subComponents.length; i++)
	 {
	      subComponents[i].processMouseEvent(event, path, manager);
	 }
	*/
      }
    else
      {
	if (event.getID() == MouseEvent.MOUSE_RELEASED)
	  clearSelectedPath();
      }
  }

  /**
   * Sets menu selection to the specified path
   *
   * @param path new selection path
   */
  public void setSelectedPath(MenuElement[] path)
  {
    if (path == null)
      {
	clearSelectedPath();
	return;
      }

    int minSize = path.length; // size of the smaller path.
    int currentSize = selectedPath.size();
    int firstDiff = 0;

    // Search first item that is different in the current and new path.
    for (int i = 0; i < minSize; i++)
      {
        if (i < currentSize && (MenuElement) selectedPath.get(i) == path[i])
          firstDiff++;
        else
          break;
      }

    // Remove items from selection and send notification.
    for (int i = currentSize - 1; i >= firstDiff; i--)
      {
        MenuElement el = (MenuElement) selectedPath.get(i);
        selectedPath.remove(i);
        el.menuSelectionChanged(false);
      }

    // Add new items to selection and send notification.
    for (int i = firstDiff; i < minSize; i++)
      {
        if (path[i] != null)
          {
            selectedPath.add(path[i]);
            path[i].menuSelectionChanged(true);
          }
      }

    fireStateChanged();
  }

  /**
   * Returns path to the specified component
   *
   * @param c component for which to find path for
   *
   * @return path to the specified component
   */
  private MenuElement[] getPath(Component c)
  {
    // FIXME: There is the same method in BasicMenuItemUI. However I
    // cannot use it here instead of this method, since I cannot assume that 
    // all the menu elements on the selected path are JMenuItem or JMenu.
    // For now I've just duplicated it here. Please 
    // fix me or delete me if another better approach will be found, and 
    // this method will not be necessary.
    ArrayList path = new ArrayList();

    // if given component is JMenu, we also need to include 
    // it's popup menu in the path 
    if (c instanceof JMenu)
      path.add(((JMenu) c).getPopupMenu());
    while (c instanceof MenuElement)
      {
	path.add(0, (MenuElement) c);

	if (c instanceof JPopupMenu)
	  c = ((JPopupMenu) c).getInvoker();
	else
	  c = c.getParent();
      }

    MenuElement[] pathArray = new MenuElement[path.size()];
    path.toArray(pathArray);
    return pathArray;
  }
}