component.java

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   * XXX How do we handle prior versions?
   *
   * @serial the serialization version
   */
  int componentSerializedDataVersion = 4;

  /**
   * The accessible context associated with this component. This is only set
   * by subclasses.
   *
   * @see #getAccessibleContext()
   * @serial the accessibility context
   * @since 1.2
   */
  AccessibleContext accessibleContext;


  // Guess what - listeners are special cased in serialization. See
  // readObject and writeObject.

  /** Component listener chain. */
  transient ComponentListener componentListener;

  /** Focus listener chain. */
  transient FocusListener focusListener;

  /** Key listener chain. */
  transient KeyListener keyListener;

  /** Mouse listener chain. */
  transient MouseListener mouseListener;

  /** Mouse motion listener chain. */
  transient MouseMotionListener mouseMotionListener;

  /**
   * Mouse wheel listener chain.
   *
   * @since 1.4
   */
  transient MouseWheelListener mouseWheelListener;

  /**
   * Input method listener chain.
   *
   * @since 1.2
   */
  transient InputMethodListener inputMethodListener;

  /**
   * Hierarcy listener chain.
   *
   * @since 1.3
   */
  transient HierarchyListener hierarchyListener;

  /**
   * Hierarcy bounds listener chain.
   *
   * @since 1.3
   */
  transient HierarchyBoundsListener hierarchyBoundsListener;

  // Anything else is non-serializable, and should be declared "transient".

  /** The parent. */
  transient Container parent;

  /** The associated native peer. */
  transient ComponentPeer peer;

  /** The preferred component orientation. */
  transient ComponentOrientation orientation = ComponentOrientation.UNKNOWN;

  /**
   * The associated graphics configuration.
   *
   * @since 1.4
   */
  transient GraphicsConfiguration graphicsConfig;

  /**
   * The buffer strategy for repainting.
   *
   * @since 1.4
   */
  transient BufferStrategy bufferStrategy;


  // Public and protected API.

  /**
   * Default constructor for subclasses. When Component is extended directly,
   * it forms a lightweight component that must be hosted in an opaque native
   * container higher in the tree.
   */
  protected Component()
  {
  }

  /**
   * Returns the name of this component.
   *
   * @return the name of this component
   * @see #setName(String)
   * @since 1.1
   */
  public String getName()
  {
    if (name == null && ! nameExplicitlySet)
      name = generateName();
    return name;
  }

  /**
   * Sets the name of this component to the specified name.
   *
   * @param name the new name of this component
   * @see #getName()
   * @since 1.1
   */
  public void setName(String name)
  {
    nameExplicitlySet = true;
    this.name = name;
  }

  /**
   * Returns the parent of this component.
   *
   * @return the parent of this component
   */
  public Container getParent()
  {
    return parent;
  }

  /**
   * Returns the native windowing system peer for this component. Only the
   * platform specific implementation code should call this method.
   *
   * @return the peer for this component
   * @deprecated user programs should not directly manipulate peers; use
   *             {@link #isDisplayable()} instead
   */
  // Classpath's Gtk peers rely on this.
  public ComponentPeer getPeer()
  {
    return peer;
  }

  /**
   * Set the associated drag-and-drop target, which receives events when this
   * is enabled.
   *
   * @param dt the new drop target
   * @see #isEnabled()
   */
  public void setDropTarget(DropTarget dt)
  {
    this.dropTarget = dt;
  }

  /**
   * Gets the associated drag-and-drop target, if there is one.
   *
   * @return the drop target
   */
  public DropTarget getDropTarget()
  {
    return dropTarget;
  }

  /**
   * Returns the graphics configuration of this component, if there is one.
   * If it has not been set, it is inherited from the parent.
   *
   * @return the graphics configuration, or null
   * @since 1.3
   */
  public GraphicsConfiguration getGraphicsConfiguration()
  {
    return getGraphicsConfigurationImpl();
  }

  /**
   * Returns the object used for synchronization locks on this component
   * when performing tree and layout functions.
   *
   * @return the synchronization lock for this component
   */
  public final Object getTreeLock()
  {
    return treeLock;
  }

  /**
   * Returns the toolkit in use for this component. The toolkit is associated
   * with the frame this component belongs to.
   *
   * @return the toolkit for this component
   */
  public Toolkit getToolkit()
  {
    if (peer != null)
      {
        Toolkit tk = peer.getToolkit();
        if (tk != null)
          return tk;
      }
    if (parent != null)
      return parent.getToolkit();
    return Toolkit.getDefaultToolkit();
  }

  /**
   * Tests whether or not this component is valid. A invalid component needs
   * to have its layout redone.
   *
   * @return true if this component is valid
   * @see #validate()
   * @see #invalidate()
   */
  public boolean isValid()
  {
    return valid;
  }

  /**
   * Tests if the component is displayable. It must be connected to a native
   * screen resource, and all its ancestors must be displayable. A containment
   * hierarchy is made displayable when a window is packed or made visible.
   *
   * @return true if the component is displayable
   * @see Container#add(Component)
   * @see Container#remove(Component)
   * @see Window#pack()
   * @see Window#show()
   * @see Window#dispose()
   * @since 1.2
   */
  public boolean isDisplayable()
  {
    if (parent != null)
      return parent.isDisplayable();
    return false;
  }

  /**
   * Tests whether or not this component is visible. Except for top-level
   * frames, components are initially visible.
   *
   * @return true if the component is visible
   * @see #setVisible(boolean)
   */
  public boolean isVisible()
  {
    return visible;
  }

  /**
   * Tests whether or not this component is actually being shown on
   * the screen. This will be true if and only if it this component is
   * visible and its parent components are all visible.
   *
   * @return true if the component is showing on the screen
   * @see #setVisible(boolean)
   */
  public boolean isShowing()
  {
    if (! visible || peer == null)
      return false;

    return parent == null ? true : parent.isShowing();
  }

  /**
   * Tests whether or not this component is enabled. Components are enabled
   * by default, and must be enabled to receive user input or generate events.
   *
   * @return true if the component is enabled
   * @see #setEnabled(boolean)
   */
  public boolean isEnabled()
  {
    return enabled;
  }

  /**
   * Enables or disables this component. The component must be enabled to
   * receive events (except that lightweight components always receive mouse
   * events).
   *
   * @param enabled true to enable this component
   * @see #isEnabled()
   * @see #isLightweight()
   * @since 1.1
   */
  public void setEnabled(boolean b)
  {
    this.enabled = b;
    if (peer != null)
      peer.setEnabled(b);
  }

  /**
   * Enables this component.
   *
   * @deprecated use {@link #setEnabled(boolean)} instead
   */
  public void enable()
  {
    setEnabled(true);
  }

  /**
   * Enables or disables this component.
   *
   * @param enabled true to enable this component
   * @deprecated use {@link #setEnabled(boolean)} instead
   */
  public void enable(boolean b)
  {
    setEnabled(b);
  }

  /**
   * Disables this component.
   *
   * @deprecated use {@link #setEnabled(boolean)} instead
   */
  public void disable()
  {
    setEnabled(false);
  }

  /**
   * Checks if this image is painted to an offscreen image buffer that is
   * later copied to screen (double buffering reduces flicker). This version
   * returns false, so subclasses must override it if they provide double
   * buffering.
   *
   * @return true if this is double buffered; defaults to false
   */
  public boolean isDoubleBuffered()
  {
    return false;
  }

  /**
   * Enables or disables input method support for this component. By default,
   * components have this enabled. Input methods are given the opportunity
   * to process key events before this component and its listeners.
   *
   * @param enable true to enable input method processing
   * @see #processKeyEvent(KeyEvent)
   * @since 1.2
   */
  public void enableInputMethods(boolean enable)
  {
    // XXX Implement.
    throw new Error("not implemented");
  }

  /**
   * Makes this component visible or invisible. Note that it wtill might
   * not show the component, if a parent is invisible.
   *
   * @param visible true to make this component visible
   * @see #isVisible()
   * @since 1.1
   */
  public void setVisible(boolean b)
  {
    // Inspection by subclassing shows that Sun's implementation calls
    // show(boolean) which then calls show() or hide(). It is the show()
    // method that is overriden in subclasses like Window.
    if (peer != null)
      peer.setVisible(b);
    this.visible = b;
  }

  /**
   * Makes this component visible on the screen.
   *
   * @deprecated use {@link #setVisible(boolean)} instead
   */
  public void show()
  {
    setVisible(true);
  }

  /**
   * Makes this component visible or invisible.
   *
   * @param visible true to make this component visible
   * @deprecated use {@link #setVisible(boolean)} instead
   */
  public void show(boolean b)
  {
    setVisible(b);
  }

  /**
   * Hides this component so that it is no longer shown on the screen.
   *
   * @deprecated use {@link #setVisible(boolean)} instead
   */
  public void hide()
  {
    setVisible(false);
  }

  /**
   * Returns this component's foreground color. If not set, this is inherited
   * from the parent.
   *
   * @return this component's foreground color, or null
   * @see #setForeground(Color)
   */
  public Color getForeground()
  {
    if (foreground != null)
      return foreground;
    return parent == null ? null : parent.getForeground();
  }

  /**
   * Sets this component's foreground color to the specified color. This is a
   * bound property.
   *
   * @param c the new foreground color
   * @see #getForeground()
   */
  public void setForeground(Color c)
  {
    firePropertyChange("foreground", foreground, c);
    if (peer != null)
      peer.setForeground(c);
    foreground = c;
  }

  /**
   * Tests if the foreground was explicitly set, or just inherited from the
   * parent.
   *
   * @return true if the foreground has been set
   * @since 1.4
   */
  public boolean isForegroundSet()
  {
    return foreground != null;
  }

  /**
   * Returns this component's background color. If not set, this is inherited
   * from the parent.
   *
   * @return the background color of the component, or null
   * @see #setBackground(Color)
   */
  public Color getBackground()
  {
    if (background != null)
      return background;
    return parent == null ? null : parent.getBackground();
  }

  /**