jlayeredpane.java

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   * from the "front" (position 0) to the "back" (position N-1), and drawn from 
   * the back towards the front.
   *
   * @param c the component to change the position of
   * @param position the position to assign the component to
   *
   * @see #getPosition
   */
  public void setPosition(Component c, int position)
  {
    int layer = getLayer(c);
    int index = insertIndexForLayer(layer, position);
    setComponentZOrder(c, index);
  }
    
  /**
   * Return an array of all components within a layer of this
   * container. Components are ordered front-to-back, with the "front"
   * element (which draws last) at position 0 of the returned array.
   *
   * @param layer the layer to return components from
   *
   * @return the components in the layer
   */
  public Component[] getComponentsInLayer(int layer)
  {
    Component[] inLayer = new Component[getComponentCountInLayer(layer)];
    Component[] components = getComponents();
    int j = 0;
    for (int i = 0; i < components.length; ++i)
      {
        if (layer == getLayer(components[i]))
          {
            inLayer[j] = components[i];
            j++;
          }
      }
    return inLayer;
  }

  /**
   * Return the number of components within a layer of this
   * container.
   *
   * @param layer the layer count components in
   *
   * @return the number of components in the layer
   */
  public int getComponentCountInLayer(int layer)
  {
    Component[] components = getComponents();
    int count = 0;
    for (int i = components.length - 1; i >= 0; --i)
      {
        if (getLayer(components[i]) == layer)
          count++;
      }
    return count;
  }

  /**
   * Return a hashtable mapping child components of this container to
   * Integer objects representing the component's layer assignments.
   */
  protected Hashtable getComponentToLayer()
  {
    return componentToLayer;
  }

  /**
   * Return the index of a component within the underlying (contiguous)
   * array of children. This is a "raw" number which does not represent the
   * child's position in a layer, but rather its position in the logical
   * drawing order of all children of the container.
   *
   * @param c the component to look up.
   *
   * @return the external index of the component or <code>-1</code> if
   *         <code>c</code> is not a child of this layered pane 
   */
  public int getIndexOf(Component c) 
  {
    return getComponentZOrder(c);
  }

  /**
   * Return an Integer object which holds the same int value as the
   * parameter. This is strictly an optimization to minimize the number of
   * identical Integer objects which we allocate.
   *
   * @param layer the layer number as an int.
   *
   * @return the layer number as an Integer, possibly shared.
   */
  protected Integer getObjectForLayer(int layer)
  {
    switch (layer)
	    {
	    case -30000:
        return FRAME_CONTENT_LAYER;

	    case 0:
        return DEFAULT_LAYER;

	    case 100:
        return PALETTE_LAYER;

	    case 200:
        return MODAL_LAYER;

	    case 300:
        return POPUP_LAYER;

	    case 400:
        return DRAG_LAYER;

	    default:
        break;
	    }

    return new Integer(layer);
  }

  /**
   * Computes an index at which to request the superclass {@link
   * java.awt.Container} inserts a component, given an abstract layer and
   * position number.
   *
   * @param layer the layer in which to insert a component.
   * @param position the position in the layer at which to insert a component.
   *
   * @return the index at which to insert the component.
   */
  protected int insertIndexForLayer(int layer, int position)
  {
    // position < 0 means insert at greatest position within layer.
    if (position < 0)
      position = Integer.MAX_VALUE;

    Component[] components = getComponents();
    int index = 0;

    // Try to find the start index of the specified layer.
    int p = -1;
    for (int i = 0; i < components.length; i++)
      {
        int l = getLayer(components[i]);
        if (l > layer)
          index++;
        // If we are in the layer we look for, try to find the position.
        else if (l == layer)
          {
            p++;
            if (p < position)
              index++;
            else
              break;
          }
        // No need to look further if the layer at i is smaller than layer.
        else
          break;
      }
    return index;
  }

  /**
   * Removes a child from this container. The child is specified by
   * index. After removal, the child no longer occupies a layer.
   *
   * @param index the index of the child component to remove.
   */
  public void remove(int index)
  {
    Component c = getComponent(index);
    if (! (c instanceof JComponent))
      componentToLayer.remove(c);
    super.remove(index);
  }

  /**
   * Removes all components from this container.
   *
   * @since 1.5
   */
  public void removeAll()
  {
	componentToLayer.clear();
	super.removeAll();
  }

  /**
   * <p>Set the layer property for a component, within this container. The
   * component will be implicitly mapped to the bottom-most position in the
   * layer, but only if added <em>after</em> calling this method.</p>
   *
   * <p>Read that carefully: this method should be called <em>before</em> the
   * component is added to the container.</p>
   *
   * @param c the component to set the layer property for.
   * @param layer the layer number to assign to the component.
   */
  public void setLayer(Component c, int layer)
  {
    setLayer(c, layer, -1);
  }

  /**
   * Set the layer and position of a component, within this container.
   *
   * @param c the child component to set the layer property for.
   * @param layer the layer number to assign to the component.
   * @param position the position number to assign to the component.
   */
  public void setLayer(Component c, int layer, int position)
  {
    Integer layerObj = getObjectForLayer(layer);
    if (c instanceof JComponent)
      {
        JComponent jc = (JComponent) c;
        jc.putClientProperty(LAYER_PROPERTY, layerObj);
      }
    else
      componentToLayer.put (c, layerObj);

    // Set position only of component is already added to this layered pane.
    if (getIndexOf(c) != -1)
      setPosition(c, position);
  }

  /**
   * Overrides the default implementation from {@link java.awt.Container}
   * such that <code>layerConstraint</code> is interpreted as an {@link
   * Integer}, specifying the layer to which the component will be added
   * (at the bottom position).
   *
   * The argument <code>index</code> specifies the position within the layer
   * at which the component should be added, where <code>0</code> is the top
   * position greater values specify positions below that and <code>-1</code>
   * specifies the bottom position.
   *
   * @param comp the component to add
   * @param layerConstraint an integer specifying the layer to add the
   *        component to
   * @param index the position within the layer
   */
  protected void addImpl(Component comp, Object layerConstraint, int index) 
  {
    int layer;
    if (layerConstraint != null && layerConstraint instanceof Integer)
      layer = ((Integer) layerConstraint).intValue();
    else
	  layer = getLayer(comp);

    int newIdx = insertIndexForLayer(layer, index);
    setLayer(comp, layer);
    super.addImpl(comp, layerConstraint, newIdx);
  }

  /**
   * Sets the layer property for a JComponent.
   *
   * @param component the component for which to set the layer
   * @param layer the layer property to set
   */
  public static void putLayer(JComponent component, int layer)
  {
    component.putClientProperty(LAYER_PROPERTY, new Integer(layer));
  }

  /**
   * Returns the accessible context for this <code>JLayeredPane</code>.
   *
   * @return the accessible context for this <code>JLayeredPane</code>
   */
  public AccessibleContext getAccessibleContext()
  {
    if (accessibleContext == null)
      accessibleContext = new AccessibleJLayeredPane();
    return accessibleContext;
  }

  /**
   * This method is overridden order to provide a reasonable painting
   * mechanism for <code>JLayeredPane</code>. This is necessary since
   * <code>JLayeredPane</code>'s do not have an own UI delegate.
   *
   * Basically this method clears the background for the
   * <code>JLayeredPane</code> and then calls <code>super.paint(g)</code>.
   *
   * @param g the graphics context to use
   */
  public void paint(Graphics g)
  {
    if (isOpaque())
      {
        Color oldColor = g.getColor();
        Rectangle clip = g.getClipBounds();
        g.setColor(getBackground());
        g.fillRect(clip.x, clip.y, clip.width, clip.height);
        g.setColor(oldColor);
      }
    super.paint(g);
  }

  /**
   * Returns <code>false</code> if components in this layered pane can overlap,
   * otherwise <code>true</code>.
   *
   * @return <code>false</code> if components in this layered pane can overlap,
   *         otherwise <code>true</code>
   */
  public boolean isOptimizedDrawingEnabled()
  {
    int numChildren = getComponentCount();
    boolean result = true;
    for (int i = 0; i < numChildren; ++i)
      {
    	Component c1 = getComponent(i);
    	if (! c1.isVisible())
          continue;
    	Rectangle r1 = c1.getBounds();
    	if (r1.isEmpty())
          continue;

    	for (int j = i + 1; j < numChildren; ++j)
          {
            Component c2 = getComponent(j);
            if (! c2.isVisible())
              continue;
            Rectangle r2 = c2.getBounds();
            if (r2.isEmpty())
              continue;
            if (r1.intersects(r2))
              {
                result = false;
                break;
              }
            if (result == false)
              break;
          }
      }
    return result;
  }
}