gcc/libjava/javax/swing/SwingUtilities.java

/* SwingUtilities.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
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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;

import java.applet.Applet;
import java.awt.Component;
import java.awt.ComponentOrientation;
import java.awt.Container;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Shape;
import java.awt.Toolkit;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.InputEvent;
import java.awt.event.KeyEvent;
import java.awt.event.MouseEvent;
import java.lang.reflect.InvocationTargetException;

import javax.swing.plaf.ActionMapUIResource;
import javax.swing.plaf.InputMapUIResource;

/**
 * This class contains a number of static utility functions which are
 * useful when drawing swing components, dispatching events, or calculating
 * regions which need painting.
 *
 * @author Graydon Hoare (graydon@redhat.com)
 */
public class SwingUtilities implements SwingConstants
{
  /** 
   * This frame should be used as parent for JWindow or JDialog 
   * that doesn't an owner
   */
  private static OwnerFrame ownerFrame;

  private SwingUtilities()
  {
    // Do nothing.
  }
  
  /**
   * Calculates the portion of the base rectangle which is inside the
   * insets.
   *
   * @param base The rectangle to apply the insets to
   * @param insets The insets to apply to the base rectangle
   * @param ret A rectangle to use for storing the return value, or
   * <code>null</code>
   *
   * @return The calculated area inside the base rectangle and its insets,
   * either stored in ret or a new Rectangle if ret is <code>null</code>
   *
   * @see #calculateInnerArea
   */
  public static Rectangle calculateInsetArea(Rectangle base, Insets insets,
                                             Rectangle ret)
  {
    if (ret == null)
      ret = new Rectangle();
    ret.setBounds(base.x + insets.left, base.y + insets.top,
                  base.width - (insets.left + insets.right),
                  base.height - (insets.top + insets.bottom));
    return ret;
  }

  /**
   * Calculates the portion of the component's bounds which is inside the
   * component's border insets. This area is usually the area a component
   * should confine its painting to. The coordinates are returned in terms
   * of the <em>component's</em> coordinate system, where (0,0) is the
   * upper left corner of the component's bounds.
   *
   * @param c The component to measure the bounds of
   * @param r A Rectangle to store the return value in, or
   * <code>null</code>
   *
   * @return The calculated area inside the component and its border
   * insets
   *
   * @see #calculateInsetArea
   */
  public static Rectangle calculateInnerArea(JComponent c, Rectangle r)
  {
    Rectangle b = getLocalBounds(c);
    return calculateInsetArea(b, c.getInsets(), r);
  }

  /**
   * Calculates the bounds of a component in the component's own coordinate
   * space. The result has the same height and width as the component's
   * bounds, but its location is set to (0,0).
   *
   * @param aComponent The component to measure
   *
   * @return The component's bounds in its local coordinate space
   */
  public static Rectangle getLocalBounds(Component aComponent)
  {
    Rectangle bounds = aComponent.getBounds();
    return new Rectangle(0, 0, bounds.width, bounds.height);
  }

  /**
   * Returns the font metrics object for a given font. The metrics can be
   * used to calculate crude bounding boxes and positioning information,
   * for laying out components with textual elements.
   *
   * @param font The font to get metrics for
   *
   * @return The font's metrics
   *
   * @see java.awt.font.GlyphMetrics
   */
  public static FontMetrics getFontMetrics(Font font)
  {
    return Toolkit.getDefaultToolkit().getFontMetrics(font);
  }

  /**
   * If <code>comp</code> is a RootPaneContainer, return its JRootPane.
   * Otherwise call <code>getAncestorOfClass(JRootPane.class, a)</code>.
   *
   * @param comp The component to get the JRootPane of
   *
   * @return a suitable JRootPane for <code>comp</code>, or <code>null</code>
   * 
   * @see javax.swing.RootPaneContainer#getRootPane
   * @see #getAncestorOfClass
   */
  public static JRootPane getRootPane(Component comp)
  {
    if (comp instanceof RootPaneContainer)
      return ((RootPaneContainer)comp).getRootPane();
    else
      return (JRootPane) getAncestorOfClass(JRootPane.class, comp);
  }

  /**
   * Returns the least ancestor of <code>comp</code> which has the
   * specified name.
   *
   * @param name The name to search for
   * @param comp The component to search the ancestors of
   *
   * @return The nearest ancestor of <code>comp</code> with the given
   * name, or <code>null</code> if no such ancestor exists
   *
   * @see java.awt.Component#getName
   * @see #getAncestorOfClass
   */
  public static Container getAncestorNamed(String name, Component comp)
  {
    while (comp != null && (comp.getName() != name))
      comp = comp.getParent();
    return (Container) comp;
  }

  /**
   * Returns the least ancestor of <code>comp</code> which is an instance
   * of the specified class.
   *
   * @param c The class to search for
   * @param comp The component to search the ancestors of
   *
   * @return The nearest ancestor of <code>comp</code> which is an instance
   * of the given class, or <code>null</code> if no such ancestor exists
   *
   * @see #getAncestorOfClass
   * @see #windowForComponent
   */
  public static Container getAncestorOfClass(Class c, Component comp)
  {
    while (comp != null && (! c.isInstance(comp)))
      comp = comp.getParent();
    return (Container) comp;
  }

  /**
   * Equivalent to calling <code>getAncestorOfClass(Window, comp)</code>.
   *
   * @param comp The component to search for an ancestor window 
   *
   * @return An ancestral window, or <code>null</code> if none exists
   */
  public static Window windowForComponent(Component comp)
  {
    return (Window) getAncestorOfClass(Window.class, comp);
  }

  /**
   * Returns the "root" of the component tree containint <code>comp</code>
   * The root is defined as either the <em>least</em> ancestor of
   * <code>comp</code> which is a {@link Window}, or the <em>greatest</em>
   * ancestor of <code>comp</code> which is a {@link Applet} if no {@link
   * Window} ancestors are found.
   *
   * @param comp The component to search for a root
   *
   * @return The root of the component's tree, or <code>null</code>
   */
  public static Component getRoot(Component comp)
  {
    Applet app = null;
    Window win = null;

    while (comp != null)
      {
        if (win == null && comp instanceof Window)
          win = (Window) comp;
        else if (comp instanceof Applet)
          app = (Applet) comp;
        comp = comp.getParent();
      }

    if (win != null)
      return win;
    else
      return app;
  }

  /**
   * Return true if a descends from b, in other words if b is an
   * ancestor of a.
   *
   * @param a The child to search the ancestry of
   * @param b The potential ancestor to search for
   *
   * @return true if a is a descendent of b, false otherwise
   */
  public static boolean isDescendingFrom(Component a, Component b)
  {
    while (true)
      {
        if (a == null || b == null)
          return false;
        if (a == b)
          return true;
        a = a.getParent();
      }
  }

  /**
   * Returns the deepest descendent of parent which is both visible and
   * contains the point <code>(x,y)</code>. Returns parent when either
   * parent is not a container, or has no children which contain
   * <code>(x,y)</code>. Returns <code>null</code> when either
   * <code>(x,y)</code> is outside the bounds of parent, or parent is
   * <code>null</code>.
   * 
   * @param parent The component to search the descendents of
   * @param x Horizontal coordinate to search for
   * @param y Vertical coordinate to search for
   *
   * @return A component containing <code>(x,y)</code>, or
   * <code>null</code>
   *
   * @see java.awt.Container#findComponentAt
   */
  public static Component getDeepestComponentAt(Component parent, int x, int y)
  {
    if (parent == null || (! parent.contains(x, y)))
      return null;

    if (! (parent instanceof Container))
      return parent;

    Container c = (Container) parent;
    return c.findComponentAt(x, y);
  }

  /**
   * Converts a point from a component's local coordinate space to "screen"
   * coordinates (such as the coordinate space mouse events are delivered
   * in). This operation is equivalent to translating the point by the
   * location of the component (which is the origin of its coordinate
   * space).
   *
   * @param p The point to convert
   * @param c The component which the point is expressed in terms of
   *
   * @see convertPointFromScreen
   */
  public static void convertPointToScreen(Point p, Component c)
  {
    Point c0 = c.getLocationOnScreen();
    p.translate(c0.x, c0.y);
  }

  /**
   * Converts a point from "screen" coordinates (such as the coordinate
   * space mouse events are delivered in) to a component's local coordinate
   * space. This operation is equivalent to translating the point by the
   * negation of the component's location (which is the origin of its
   * coordinate space).
   *
   * @param p The point to convert
   * @param c The component which the point should be expressed in terms of
   */
  public static void convertPointFromScreen(Point p, Component c)
  {
    Point c0 = c.getLocationOnScreen();
    p.translate(-c0.x, -c0.y);
  }

  /**
   * Converts a point <code>(x,y)</code> from the coordinate space of one
   * component to another. This is equivalent to converting the point from
   * <code>source</code> space to screen space, then back from screen space
   * to <code>destination</code> space. If exactly one of the two
   * Components is <code>null</code>, it is taken to refer to the root
   * ancestor of the other component. If both are <code>null</code>, no
   * transformation is done.
   *
   * @param source The component which the point is expressed in terms of
   * @param x Horizontal coordinate of point to transform
   * @param y Vertical coordinate of point to transform
   * @param destination The component which the return value will be
   * expressed in terms of
   *
   * @return The point <code>(x,y)</code> converted from the coordinate space of the
   * source component to the coordinate space of the destination component
   *
   * @see #convertPointToScreen
   * @see #convertPointFromScreen
   * @see #convertRectangle
   * @see #getRoot
   */
  public static Point convertPoint(Component source, int x, int y,
                                   Component destination)
  {
    Point pt = new Point(x, y);

    if (source == null && destination == null)
      return pt;

    if (source == null)
      source = getRoot(destination);

    if (destination == null)
      destination = getRoot(source);

    convertPointToScreen(pt, source);
    convertPointFromScreen(pt, destination);

    return pt;
  }
  
  public static Point convertPoint(Component source, Point aPoint, Component destination)
  {
    return convertPoint(source, aPoint.x, aPoint.y, destination);
  }

  /**
   * Converts a rectangle from the coordinate space of one component to
   * another. This is equivalent to converting the rectangle from
   * <code>source</code> space to screen space, then back from screen space
   * to <code>destination</code> space. If exactly one of the two
   * Components is <code>null</code>, it is taken to refer to the root
   * ancestor of the other component. If both are <code>null</code>, no
   * transformation is done.
   *
   * @param source The component which the rectangle is expressed in terms of
   * @param rect The rectangle to convert
   * @param destination The component which the return value will be
   * expressed in terms of
   *
   * @return A new rectangle, equal in size to the input rectangle, but
   * with its position converted from the coordinate space of the source
   * component to the coordinate space of the destination component
   *
   * @see #convertPointToScreen
   * @see #convertPointFromScreen
   * @see #convertPoint
   * @see #getRoot
   */
  public static Rectangle convertRectangle(Component source,
                                           Rectangle rect,
                                           Component destination)
  {
    Point pt = convertPoint(source, rect.x, rect.y, destination);
    return new Rectangle(pt.x, pt.y, rect.width, rect.height);
  }

  /**
   * Convert a mouse event which refrers to one component to another.  This
   * includes changing the mouse event's coordinate space, as well as the
   * source property of the event. If <code>source</code> is
   * <code>null</code>, it is taken to refer to <code>destination</code>'s
   * root component. If <code>destination</code> is <code>null</code>, the
   * new event will remain expressed in <code>source</code>'s coordinate
   * system.
   *
   * @param source The component the mouse event currently refers to
   * @param sourceEvent The mouse event to convert
   * @param destination The component the new mouse event should refer to
   *
   * @return A new mouse event expressed in terms of the destination
   * component's coordinate space, and with the destination component as
   * its source
   *
   * @see #convertPoint
   */
  public static MouseEvent convertMouseEvent(Component source,
                                             MouseEvent sourceEvent,
                                             Component destination)
  {
    Point newpt = convertPoint(source, sourceEvent.getX(), sourceEvent.getY(),
                               destination);

    return new MouseEvent(destination, sourceEvent.getID(),
                          sourceEvent.getWhen(), sourceEvent.getModifiersEx(),
                          newpt.x, newpt.y, sourceEvent.getClickCount(),
                          sourceEvent.isPopupTrigger(), sourceEvent.getButton());
  }

  /**
   * Recursively walk the component tree under <code>comp</code> calling
   * <code>updateUI</code> on each {@link JComponent} found. This causes
   * the entire tree to re-initialize its UI delegates.
   *
   * @param comp The component to walk the children of, calling <code>updateUI</code>
   */
  public static void updateComponentTreeUI(Component comp)
  {
    if (comp == null)
      return;
    
    if (comp instanceof Container)
      {
        Component[] children = ((Container)comp).getComponents();
        for (int i = 0; i < children.length; ++i)
          updateComponentTreeUI(children[i]);
      }

    if (comp instanceof JComponent)
      ((JComponent)comp).updateUI();
  }


  /**
   * <p>Layout a "compound label" consisting of a text string and an icon
   * which is to be placed near the rendered text. Once the text and icon
   * are laid out, the text rectangle and icon rectangle parameters are
   * altered to store the calculated positions.</p>
   *
   * <p>The size of the text is calculated from the provided font metrics
   * object.  This object should be the metrics of the font you intend to
   * paint the label with.</p>
   *
   * <p>The position values control where the text is placed relative to
   * the icon. The horizontal position value should be one of the constants
   * <code>LEADING</code>, <code>TRAILING</code>, <code>LEFT</code>,
   * <code>RIGHT</code> or <code>CENTER</code>. The vertical position value
   * should be one fo the constants <code>TOP</code>, <code>BOTTOM</code>
   * or <code>CENTER</code>.</p>
   *
   * <p>The text-icon gap value controls the number of pixels between the
   * icon and the text.</p>
   *
   * <p>The alignment values control where the text and icon are placed, as
   * a combined unit, within the view rectangle. The horizontal alignment
   * value should be one of the constants <code>LEADING</code>,
   * <code>TRAILING</code>, <code>LEFT</code>, <code>RIGHT</code> or
   * <code>CENTER</code>. The vertical alignment valus should be one of the
   * constants <code>TOP</code>, <code>BOTTOM</code> or
   * <code>CENTER</code>.</p>
   *
   * <p>If the <code>LEADING</code> or <code>TRAILING</code> constants are
   * given for horizontal alignment or horizontal text position, they are
   * interpreted relative to the provided component's orientation property,
   * a constant in the {@link java.awt.ComponentOrientation} class. For
   * example, if the component's orientation is <code>LEFT_TO_RIGHT</code>,
   * then the <code>LEADING</code> value is a synonym for <code>LEFT</code>
   * and the <code>TRAILING</code> value is a synonym for
   * <code>RIGHT</code></p>
   *
   * <p>If the text and icon are equal to or larger than the view
   * rectangle, the horizontal and vertical alignment values have no
   * affect.</p>
   *
   * @param c A component used for its orientation value
   * @param fm The font metrics used to measure the text
   * @param text The text to place in the compound label
   * @param icon The icon to place next to the text
   * @param verticalAlignment The vertical alignment of the label relative
   * to its component
   * @param horizontalAlignment The horizontal alignment of the label
   * relative to its component
   * @param verticalTextPosition The vertical position of the label's text
   * relative to its icon
   * @param horizontalTextPosition The horizontal position of the label's
   * text relative to its icon
   * @param viewR The view rectangle, specifying the area which layout is
   * constrained to
   * @param iconR A rectangle which is modified to hold the laid-out
   * position of the icon
   * @param textR A rectangle which is modified to hold the laid-out
   * position of the text
   * @param textIconGap The distance between text and icon
   *
   * @return The string of characters, possibly truncated with an elipsis,
   * which is laid out in this label
   */

  public static String layoutCompoundLabel(JComponent c, 
                                           FontMetrics fm,
                                           String text, 
                                           Icon icon, 
                                           int verticalAlignment,
                                           int horizontalAlignment, 
                                           int verticalTextPosition,
                                           int horizontalTextPosition, 
                                           Rectangle viewR,
                                           Rectangle iconR, 
                                           Rectangle textR, 
                                           int textIconGap)
  {

    // Fix up the orientation-based horizontal positions.

    if (horizontalTextPosition == LEADING)
      {
        if (c.getComponentOrientation() == ComponentOrientation.RIGHT_TO_LEFT)
          horizontalTextPosition = RIGHT;
        else
          horizontalTextPosition = LEFT;
      }
    else if (horizontalTextPosition == TRAILING)
      {
        if (c.getComponentOrientation() == ComponentOrientation.RIGHT_TO_LEFT)
          horizontalTextPosition = LEFT;
        else
          horizontalTextPosition = RIGHT;
      }

    // Fix up the orientation-based alignments.

    if (horizontalAlignment == LEADING)
      {
        if (c.getComponentOrientation() == ComponentOrientation.RIGHT_TO_LEFT)
          horizontalAlignment = RIGHT;
        else
          horizontalAlignment = LEFT;
      }
    else if (horizontalAlignment == TRAILING)
      {
        if (c.getComponentOrientation() == ComponentOrientation.RIGHT_TO_LEFT)
          horizontalAlignment = LEFT;
        else
          horizontalAlignment = RIGHT;
      }
    
    return layoutCompoundLabel(fm, text, icon,
                               verticalAlignment,
                               horizontalAlignment,
                               verticalTextPosition,
                               horizontalTextPosition,
                               viewR, iconR, textR, textIconGap);
  }

  /**
   * <p>Layout a "compound label" consisting of a text string and an icon
   * which is to be placed near the rendered text. Once the text and icon
   * are laid out, the text rectangle and icon rectangle parameters are
   * altered to store the calculated positions.</p>
   *
   * <p>The size of the text is calculated from the provided font metrics
   * object.  This object should be the metrics of the font you intend to
   * paint the label with.</p>
   *
   * <p>The position values control where the text is placed relative to
   * the icon. The horizontal position value should be one of the constants
   * <code>LEFT</code>, <code>RIGHT</code> or <code>CENTER</code>. The
   * vertical position value should be one fo the constants
   * <code>TOP</code>, <code>BOTTOM</code> or <code>CENTER</code>.</p>
   *
   * <p>The text-icon gap value controls the number of pixels between the
   * icon and the text.</p>
   *
   * <p>The alignment values control where the text and icon are placed, as
   * a combined unit, within the view rectangle. The horizontal alignment
   * value should be one of the constants <code>LEFT</code>, <code>RIGHT</code> or
   * <code>CENTER</code>. The vertical alignment valus should be one of the
   * constants <code>TOP</code>, <code>BOTTOM</code> or
   * <code>CENTER</code>.</p>
   *
   * <p>If the text and icon are equal to or larger than the view
   * rectangle, the horizontal and vertical alignment values have no
   * affect.</p>
   *
   * <p>Note that this method does <em>not</em> know how to deal with
   * horizontal alignments or positions given as <code>LEADING</code> or
   * <code>TRAILING</code> values. Use the other overloaded variant of this
   * method if you wish to use such values.
   *
   * @param fm The font metrics used to measure the text
   * @param text The text to place in the compound label
   * @param icon The icon to place next to the text
   * @param verticalAlignment The vertical alignment of the label relative
   * to its component
   * @param horizontalAlignment The horizontal alignment of the label
   * relative to its component
   * @param verticalTextPosition The vertical position of the label's text
   * relative to its icon
   * @param horizontalTextPosition The horizontal position of the label's
   * text relative to its icon
   * @param viewR The view rectangle, specifying the area which layout is
   * constrained to
   * @param iconR A rectangle which is modified to hold the laid-out
   * position of the icon
   * @param textR A rectangle which is modified to hold the laid-out
   * position of the text
   * @param textIconGap The distance between text and icon
   *
   * @return The string of characters, possibly truncated with an elipsis,
   * which is laid out in this label
   */

  public static String layoutCompoundLabel(FontMetrics fm,
                                           String text,
                                           Icon icon,
                                           int verticalAlignment,
                                           int horizontalAlignment,
                                           int verticalTextPosition,
                                           int horizontalTextPosition,
                                           Rectangle viewR,
                                           Rectangle iconR,
                                           Rectangle textR,
                                           int textIconGap)
  {

    // Work out basic height and width.

    if (icon == null)
      {
        textIconGap = 0;
        iconR.width = 0;
        iconR.height = 0;
      }
    else
      {
        iconR.width = icon.getIconWidth();
        iconR.height = icon.getIconHeight();
      }
    if (text == null)
      {
        textIconGap = 0;
	textR.width = 0;
	textR.height = 0;
      }
    else
      {
        textR.width = fm.stringWidth(text);
        textR.height = fm.getHeight(); 
      }

    // Work out the position of text and icon, assuming the top-left coord
    // starts at (0,0). We will fix that up momentarily, after these
    // "position" decisions are made and we look at alignment.

    switch (horizontalTextPosition)
      {
      case LEFT:
        textR.x = 0;
        iconR.x = textR.width + textIconGap;
        break;
      case RIGHT:
        iconR.x = 0;
        textR.x = iconR.width + textIconGap;
        break;
      case CENTER:
        int centerLine = Math.max(textR.width, iconR.width) / 2;
        textR.x = centerLine - textR.width/2;
        iconR.x = centerLine - iconR.width/2;
        break;
      }

    switch (verticalTextPosition)
      {
      case TOP:
        textR.y = 0;
        iconR.y = (horizontalTextPosition == CENTER 
                   ? textR.height + textIconGap : 0);
        break;
      case BOTTOM:
        iconR.y = 0;
        textR.y = (horizontalTextPosition == CENTER
                   ? iconR.height + textIconGap 
                   : iconR.height - textR.height);
        break;
      case CENTER:
        int centerLine = Math.max(textR.height, iconR.height) / 2;
        textR.y = centerLine - textR.height/2;
        iconR.y = centerLine - iconR.height/2;
        break;
      }
    // The two rectangles are laid out correctly now, but only assuming
    // that their upper left corner is at (0,0). If we have any alignment other
    // than TOP and LEFT, we need to adjust them.

    Rectangle u = textR.union(iconR);
    int horizontalAdjustment = viewR.x;
    int verticalAdjustment = viewR.y;
    switch (verticalAlignment)
      {
      case TOP:
        break;
      case BOTTOM:
        verticalAdjustment += (viewR.height - u.height);
        break;
      case CENTER:
        verticalAdjustment += ((viewR.height/2) - (u.height/2));
        break;
      }
    switch (horizontalAlignment)
      {
      case LEFT:
        break;
      case RIGHT:
        horizontalAdjustment += (viewR.width - u.width);
        break;
      case CENTER:
        horizontalAdjustment += ((viewR.width/2) - (u.width/2));
        break;
      }

    iconR.x += horizontalAdjustment;
    iconR.y += verticalAdjustment;

    textR.x += horizontalAdjustment;
    textR.y += verticalAdjustment;

    return text;
  }

  /** 
   * Calls {@link java.awt.EventQueue.invokeLater} with the
   * specified {@link Runnable}. 
   */
  public static void invokeLater(Runnable doRun)
  {
    java.awt.EventQueue.invokeLater(doRun);
  }

  /** 
   * Calls {@link java.awt.EventQueue.invokeAndWait} with the
   * specified {@link Runnable}. 
   */
  public static void invokeAndWait(Runnable doRun)
    throws InterruptedException,
    InvocationTargetException
  {
    java.awt.EventQueue.invokeAndWait(doRun);
  }

  /** 
   * Calls {@link java.awt.EventQueue.isEventDispatchThread}.
   */
  public static boolean isEventDispatchThread()
  {
    return java.awt.EventQueue.isDispatchThread();
  }
  
  /**
   * This method paints the given component at the given position and size.
   * The component will be reparented to the container given.
   * 
   * @param g The Graphics object to draw with.
   * @param c The Component to draw
   * @param p The Container to reparent to.
   * @param x The x coordinate to draw at.
   * @param y The y coordinate to draw at.
   * @param w The width of the drawing area.
   * @param h The height of the drawing area.
   */
  public static void paintComponent(Graphics g, Component c, Container p, 
                                    int x, int y, int w, int h)
  {       
    Container parent = c.getParent();
    if (parent != null)
      parent.remove(c);
    if (p != null)
      p.add(c);
    
    Shape savedClip = g.getClip();
    
    g.setClip(x, y, w, h);
    g.translate(x, y);

    c.paint(g);
    
    g.translate(-x, -y);
    g.setClip(savedClip);
  }

  /**
   * This method paints the given component in the given rectangle.
   * The component will be reparented to the container given.
   * 
   * @param g The Graphics object to draw with.
   * @param c The Component to draw
   * @param p The Container to reparent to.
   * @param r The rectangle that describes the drawing area.
   */  
  public static void paintComponent(Graphics g, Component c, 
                                    Container p, Rectangle r)
  {
    paintComponent(g, c, p, r.x, r.y, r.width, r.height);
  }
  
  /**
   * This method returns the common Frame owner used in JDialogs or
   * JWindow when no owner is provided.
   *
   * @return The common Frame 
   */
  static Frame getOwnerFrame()
  {
    if (ownerFrame == null)
      ownerFrame = new OwnerFrame();
    return ownerFrame;
  }

  /**
   * Checks if left mouse button was clicked.
   *
   * @param event the event to check
   *
   * @return true if left mouse was clicked, false otherwise.
   */
  public static boolean isLeftMouseButton(MouseEvent event)
  {
    return ((event.getModifiersEx() & InputEvent.BUTTON1_DOWN_MASK)
	     == InputEvent.BUTTON1_DOWN_MASK);
  }

  /**
   * Checks if middle mouse button was clicked.
   *
   * @param event the event to check
   *
   * @return true if middle mouse was clicked, false otherwise.
   */
  public static boolean isMiddleMouseButton(MouseEvent event)
  {
    return ((event.getModifiersEx() & InputEvent.BUTTON2_DOWN_MASK)
	     == InputEvent.BUTTON2_DOWN_MASK);
  }

  /**
   * Checks if right mouse button was clicked.
   *
   * @param event the event to check
   *
   * @return true if right mouse was clicked, false otherwise.
   */
  public static boolean isRightMouseButton(MouseEvent event)
  {
    return ((event.getModifiersEx() & InputEvent.BUTTON3_DOWN_MASK)
	     == InputEvent.BUTTON3_DOWN_MASK);
  }
  
  /**
   * This frame should be used when constructing a Window/JDialog without
   * a parent. In this case, we are forced to use this frame as a window's
   * parent, because we simply cannot pass null instead of parent to Window
   * constructor, since doing it will result in NullPointerException.
   */
  private static class OwnerFrame extends Frame
  {
    public void setVisible(boolean b)
    {
      // Do nothing here. 
    }
    
    public boolean isShowing()
    {
      return true;
    }
  }

  public static boolean notifyAction(Action action,
                                     KeyStroke ks,
                                     KeyEvent event,
                                     Object sender,
                                     int modifiers)
  {
    if (action != null && action.isEnabled())
      {
        String name = (String) action.getValue(Action.ACTION_COMMAND_KEY);
        if (name == null
            && event.getKeyChar() != KeyEvent.CHAR_UNDEFINED)
          name = new String(new char[] {event.getKeyChar()});
        action.actionPerformed(new ActionEvent(sender,
                                               ActionEvent.ACTION_PERFORMED,
                                               name, modifiers));
        return true;
      }
    return false;
  }

  /**
   * <p>Change the shared, UI-managed {@link ActionMap} for a given
   * component. ActionMaps are arranged in a hierarchy, in order to
   * encourage sharing of common actions between components. The hierarchy
   * unfortunately places UI-managed ActionMaps at the <em>end</em> of the
   * parent-pointer chain, as illustrated:</p>
   *
   * <pre>
   *  [{@link javax.swing.JComponent#getActionMap()}] 
   *          --&gt; [{@link javax.swing.ActionMap}] 
   *     parent --&gt; [{@link javax.swing.text.KeymapActionMap}] 
   *       parent --&gt; [{@link javax.swing.plaf.ActionMapUIResource}]
   * </pre>
   *
   * <p>Our goal with this method is to replace the first ActionMap along
   * this chain which is an instance of {@link ActionMapUIResource}, since
   * these are the ActionMaps which are supposed to be shared between
   * components.</p>
   *
   * <p>If the provided ActionMap is <code>null</code>, we interpret the
   * call as a request to remove the UI-managed ActionMap from the
   * component's ActionMap parent chain.</p>
   */
  public static void replaceUIActionMap(JComponent component, 
                                        ActionMap uiActionMap)
  {
    ActionMap child = component.getActionMap();
    if (child == null)
      component.setActionMap(uiActionMap);
    else
      {
        while(child.getParent() != null
              && !(child.getParent() instanceof ActionMapUIResource))
          child = child.getParent();
        if (child != null)
          child.setParent(uiActionMap);
      }
  }

  /**
   * <p>Change the shared, UI-managed {@link InputMap} for a given
   * component. InputMaps are arranged in a hierarchy, in order to
   * encourage sharing of common input mappings between components. The
   * hierarchy unfortunately places UI-managed InputMaps at the
   * <em>end</em> of the parent-pointer chain, as illustrated:</p>
   *
   * <pre>
   *  [{@link javax.swing.JComponent#getInputMap()}] 
   *          --&gt; [{@link javax.swing.InputMap}] 
   *     parent --&gt; [{@link javax.swing.text.KeymapWrapper}] 
   *       parent --&gt; [{@link javax.swing.plaf.InputMapUIResource}]
   * </pre>
   *
   * <p>Our goal with this method is to replace the first InputMap along
   * this chain which is an instance of {@link InputMapUIResource}, since
   * these are the InputMaps which are supposed to be shared between
   * components.</p>
   *
   * <p>If the provided InputMap is <code>null</code>, we interpret the
   * call as a request to remove the UI-managed InputMap from the
   * component's InputMap parent chain.</p>
   */
  public static void replaceUIInputMap(JComponent component, 
                                       int condition, 
                                       InputMap uiInputMap)
  {
    InputMap child = component.getInputMap(condition);
    if (child == null)
      component.setInputMap(condition, uiInputMap);
    else
      {
        while(child.getParent() != null
              && !(child.getParent() instanceof InputMapUIResource))
          child = child.getParent();
        if (child != null)
          child.setParent(uiInputMap);
      }
  }

  /**
   * Subtracts a rectangle from another and return the area as an array
   * of rectangles.
   * Returns the areas of rectA which are not covered by rectB.
   * If the rectangles do not overlap, or if either parameter is
   * <code>null</code>, a zero-size array is returned.
   * @param rectA The first rectangle
   * @param rectB The rectangle to subtract from the first
   * @return An array of rectangles representing the area in rectA
   * not overlapped by rectB
   */
  public static Rectangle[] computeDifference(Rectangle rectA, Rectangle rectB)
  {
    if (rectA == null || rectB == null)
      return new Rectangle[0];

    Rectangle[] r = new Rectangle[4];
    int x1 = rectA.x;
    int y1 = rectA.y;
    int w1 = rectA.width;
    int h1 = rectA.height;
    int x2 = rectB.x;
    int y2 = rectB.y;
    int w2 = rectB.width;
    int h2 = rectB.height;

    // (outer box = rectA)
    // ------------- 
    // |_____0_____|
    // |  |rectB|  |
    // |_1|_____|_2|
    // |     3     |
    // -------------
    int H0 = (y2 > y1) ? y2 - y1 : 0; // height of box 0
    int H3 = (y2 + h2 < y1 + h1) ? y1 + h1 - y2 - h2 : 0; // height box 3
    int W1 = (x2 > x1) ? x2 - x1 : 0; // width box 1
    int W2 = (x1 + w1 > x2 + w2) ? x1 + w1 - x2 - w2 : 0; // w. box 2
    int H12 = (H0 + H3 < h1) ? h1 - H0 - H3 : 0; // height box 1 & 2

    if (H0 > 0)
      r[0] = new Rectangle(x1, y1, w1, H0);
    else
      r[0] = null;

    if (W1 > 0 && H12 > 0)
      r[1] = new Rectangle(x1, y1 + H0, W1, H12);
    else
      r[1] = null;

    if (W2 > 0 && H12 > 0)
      r[2] = new Rectangle(x2 + w2, y1 + H0, W2, H12);
    else
      r[2] = null;

    if (H3 > 0)
      r[3] = new Rectangle(x1, y1 + H0 + H12, w1, H3);
    else
      r[3] = null;

    // sort out null objects
    int n = 0;
    for (int i = 0; i < 4; i++)
      if (r[i] != null)
	n++;
    Rectangle[] out = new Rectangle[n];
    for (int i = 3; i >= 0; i--)
      if (r[i] != null)
	out[--n] = r[i];

    return out;
  }

  /**
   * Calculates the intersection of two rectangles.
   *
   * @param x upper-left x coodinate of first rectangle
   * @param x upper-left y coodinate of first rectangle
   * @param w width of first rectangle
   * @param h height of first rectangle
   * @param rect a Rectangle object of the second rectangle
   * @throws a NullPointerException if rect is null.
   *
   * @return a rectangle corresponding to the intersection of the
   * two rectangles. A zero rectangle is returned if the rectangles
   * do not overlap.
   */
  public static Rectangle computeIntersection(int x, int y, int w, int h,
                                              Rectangle rect)
  {
    int x2 = (int) rect.getX();
    int y2 = (int) rect.getY();
    int w2 = (int) rect.getWidth();
    int h2 = (int) rect.getHeight();

    int dx = (x > x2) ? x : x2;
    int dy = (y > y2) ? y : y2;
    int dw = (x + w < x2 + w2) ? (x + w - dx) : (x2 + w2 - dx);
    int dh = (y + h < y2 + h2) ? (y + h - dy) : (y2 + h2 - dy);

    if (dw >= 0 && dh >= 0)
      return new Rectangle(dx, dy, dw, dh);

    return new Rectangle(0, 0, 0, 0);
  }
  
  /**
   * Calculates the width of a given string.
   *
   * @param fm the <code>FontMetrics</code> object to use
   * @param str the string
   * 
   * @return the width of the the string.
   */
  public static int computeStringWidth(FontMetrics fm, String str)
  {
    return fm.stringWidth(str);
  }

  /**
   * Calculates the union of two rectangles.
   *
   * @param x upper-left x coodinate of first rectangle
   * @param x upper-left y coodinate of first rectangle
   * @param w width of first rectangle
   * @param h height of first rectangle
   * @param rect a Rectangle object of the second rectangle
   * @throws a NullPointerException if rect is null.
   *
   * @return a rectangle corresponding to the union of the
   * two rectangles. A rectangle encompassing both is returned if the
   * rectangles do not overlap.
   */
  public static Rectangle computeUnion(int x, int y, int w, int h,
                                       Rectangle rect)
  {
    int x2 = (int) rect.getX();
    int y2 = (int) rect.getY();
    int w2 = (int) rect.getWidth();
    int h2 = (int) rect.getHeight();

    int dx = (x < x2) ? x : x2;
    int dy = (y < y2) ? y : y2;
    int dw = (x + w > x2 + w2) ? (x + w - dx) : (x2 + w2 - dx);
    int dh = (y + h > y2 + h2) ? (y + h - dy) : (y2 + h2 - dy);

    if (dw >= 0 && dh >= 0)
      return new Rectangle(dx, dy, dw, dh);

    return new Rectangle(0, 0, 0, 0);
  }

  /**
   * Tests if a rectangle contains another.
   * @param a first rectangle
   * @param b second rectangle
   * @return true if a contains b, false otherwise
   * @throws NullPointerException
   */
  public static boolean isRectangleContainingRectangle(Rectangle a, Rectangle b)
  {
    // Note: zero-size rects inclusive, differs from Rectangle.contains()
    return b.width >= 0 && b.height >= 0 && b.width >= 0 && b.height >= 0
           && b.x >= a.x && b.x + b.width <= a.x + a.width && b.y >= a.y
           && b.y + b.height <= a.y + a.height;
  }
}