flowview.java

gcc的组建

    {
      int index = -1;
      int i = 0;
      for (Iterator it = children.iterator(); it.hasNext(); i++)
        {
          View child = (View) it.next();
          if (child.getStartOffset() >= pos
              && child.getEndOffset() < pos)
            {
              index = i;
              break;
            }
        }
      return index;
    }

    /**
     * Throws an AssertionError because it must never be called. LogicalView
     * only serves as a holder for child views and has no visual
     * representation.
     */
    public float getPreferredSpan(int axis)
    {
      throw new AssertionError("This method must not be called in "
                               + "LogicalView.");
    }

    /**
     * Throws an AssertionError because it must never be called. LogicalView
     * only serves as a holder for child views and has no visual
     * representation.
     */
    public Shape modelToView(int pos, Shape a, Position.Bias b)
      throws BadLocationException
    {
      throw new AssertionError("This method must not be called in "
                               + "LogicalView.");
    }

    /**
     * Throws an AssertionError because it must never be called. LogicalView
     * only serves as a holder for child views and has no visual
     * representation.
     */
    public void paint(Graphics g, Shape s)
    {
      throw new AssertionError("This method must not be called in "
                               + "LogicalView.");
    }

    /**
     * Throws an AssertionError because it must never be called. LogicalView
     * only serves as a holder for child views and has no visual
     * representation.
     */
    public int viewToModel(float x, float y, Shape a, Position.Bias[] b)
    {
      throw new AssertionError("This method must not be called in "
                               + "LogicalView.");
    }

    /**
     * Returns the document position that is (visually) nearest to the given
     * document position <code>pos</code> in the given direction <code>d</code>.
     *
     * @param c the text component
     * @param pos the document position
     * @param b the bias for <code>pos</code>
     * @param d the direction, must be either {@link SwingConstants#NORTH},
     *        {@link SwingConstants#SOUTH}, {@link SwingConstants#WEST} or
     *        {@link SwingConstants#EAST}
     * @param biasRet an array of {@link Position.Bias} that can hold at least
     *        one element, which is filled with the bias of the return position
     *        on method exit
     *
     * @return the document position that is (visually) nearest to the given
     *         document position <code>pos</code> in the given direction
     *         <code>d</code>
     *
     * @throws BadLocationException if <code>pos</code> is not a valid offset in
     *         the document model
     */
    public int getNextVisualPositionFrom(JTextComponent c, int pos,
                                         Position.Bias b, int d,
                                         Position.Bias[] biasRet)
      throws BadLocationException
    {
      assert false : "getNextVisualPositionFrom() must not be called in "
        + "LogicalView";
      return 0;
    }
  }

  /**
   * The shared instance of FlowStrategy.
   */
  static final FlowStrategy sharedStrategy = new FlowStrategy();

  /**
   * The span of the <code>FlowView</code> that should be flowed.
   */
  protected int layoutSpan;

  /**
   * Represents the logical child elements of this view, encapsulated within
   * one parent view (an instance of a package private <code>LogicalView</code>
   * class). These will be translated to a set of real views that are then
   * displayed on screen. This translation is performed by the inner class
   * {@link FlowStrategy}.
   */
  protected View layoutPool;

  /**
   * The <code>FlowStrategy</code> to use for translating between the
   * logical and physical view.
   */
  protected FlowStrategy strategy;

  /**
   * Creates a new <code>FlowView</code> for the given
   * <code>Element</code> and <code>axis</code>.
   *
   * @param element the element that is rendered by this FlowView
   * @param axis the axis along which the view is tiled, either
   *        <code>View.X_AXIS</code> or <code>View.Y_AXIS</code>, the flow
   *        axis is orthogonal to this one
   */
  public FlowView(Element element, int axis)
  {
    super(element, axis);
    strategy = sharedStrategy;
  }

  /**
   * Returns the axis along which the view should be flowed. This is
   * orthogonal to the axis along which the boxes are tiled.
   *
   * @return the axis along which the view should be flowed
   */
  public int getFlowAxis()
  {
    int axis = getAxis();
    int flowAxis;
 
    if (axis == X_AXIS)
      flowAxis = Y_AXIS;
    else
      flowAxis = X_AXIS;

    return flowAxis;

  }

  /**
   * Returns the span of the flow for the specified child view. A flow
   * layout can be shaped by providing different span values for different
   * child indices. The default implementation returns the entire available
   * span inside the view.
   *
   * @param index the index of the child for which to return the span
   *
   * @return the span of the flow for the specified child view
   */
  public int getFlowSpan(int index)
  {
    return layoutSpan;
  }

  /**
   * Returns the location along the flow axis where the flow span starts
   * given a child view index. The flow can be shaped by providing
   * different values here.
   *
   * @param index the index of the child for which to return the flow location
   *
   * @return the location along the flow axis where the flow span starts
   */
  public int getFlowStart(int index)
  {
    return getLeftInset(); // TODO: Is this correct?
  }

  /**
   * Creates a new view that represents a row within a flow.
   *
   * @return a view for a new row
   */
  protected abstract View createRow();

  /**
   * Loads the children of this view. The <code>FlowView</code> does not
   * directly load its children. Instead it creates a logical view
   * (@{link #layoutPool}) which is filled by the logical child views.
   * The real children are created at layout time and each represent one
   * row.
   *
   * This method is called by {@link View#setParent} in order to initialize
   * the view.
   *
   * @param vf the view factory to use for creating the child views
   */
  protected void loadChildren(ViewFactory vf)
  {
    if (layoutPool == null)
      {
        layoutPool = new LogicalView(getElement());

        Element el = getElement();
        int count = el.getElementCount();
        for (int i = 0; i < count; ++i)
          {
            Element childEl = el.getElement(i);
            View childView = vf.create(childEl);
            layoutPool.append(childView);
          }
      }
  }

  /**
   * Performs the layout of this view. If the span along the flow axis changed,
   * this first calls {@link FlowStrategy#layout} in order to rebuild the
   * rows of this view. Then the superclass's behaviour is called to arrange
   * the rows within the box.
   *
   * @param width the width of the view
   * @param height the height of the view
   */
  protected void layout(int width, int height)
  {
    boolean rebuild = false;

    int flowAxis = getFlowAxis();
    if (flowAxis == X_AXIS)
      {
        rebuild = !(width == layoutSpan);
        layoutSpan = width;
      }
    else
      {
        rebuild = !(height == layoutSpan);
        layoutSpan = height;
      }

    if (rebuild)
      strategy.layout(this);

    // TODO: If the span along the box axis has changed in the process of
    // relayouting the rows (that is, if rows have been added or removed),
    // call preferenceChanged in order to throw away cached layout information
    // of the surrounding BoxView.

    super.layout(width, height);
  }

  /**
   * Receice notification that some content has been inserted in the region
   * that this view is responsible for. This calls
   * {@link FlowStrategy#insertUpdate}.
   *
   * @param changes the document event describing the changes
   * @param a the current allocation of the view
   * @param vf the view factory that is used for creating new child views
   */
  public void insertUpdate(DocumentEvent changes, Shape a, ViewFactory vf)
  {
    // First we must send the insertUpdate to the logical view so it can
    // be updated accordingly.
    layoutPool.insertUpdate(changes, a, vf);
    strategy.insertUpdate(this, changes, getInsideAllocation(a));
  }

  /**
   * Receice notification that some content has been removed from the region
   * that this view is responsible for. This calls
   * {@link FlowStrategy#removeUpdate}.
   *
   * @param changes the document event describing the changes
   * @param a the current allocation of the view
   * @param vf the view factory that is used for creating new child views
   */
  public void removeUpdate(DocumentEvent changes, Shape a, ViewFactory vf)
  {
    strategy.removeUpdate(this, changes, getInsideAllocation(a));
  }

  /**
   * Receice notification that some attributes changed in the region
   * that this view is responsible for. This calls
   * {@link FlowStrategy#changedUpdate}.
   *
   * @param changes the document event describing the changes
   * @param a the current allocation of the view
   * @param vf the view factory that is used for creating new child views
   */
  public void changedUpdate(DocumentEvent changes, Shape a, ViewFactory vf)
  {
    strategy.changedUpdate(this, changes, getInsideAllocation(a));
  }

  /**
   * Returns the index of the child <code>View</code> for the given model
   * position.
   *
   * This is implemented to iterate over the children of this
   * view (the rows) and return the index of the first view that contains
   * the given position.
   *
   * @param pos the model position for whicht the child <code>View</code> is
   *        queried
   *
   * @return the index of the child <code>View</code> for the given model
   *         position
   */
  protected int getViewIndexAtPosition(int pos)
  {
    // First make sure we have a valid layout.
    if (!isAllocationValid())
      layout(getWidth(), getHeight());

    int count = getViewCount();
    int result = -1;

    for (int i = 0; i < count; ++i)
      {
        View child = getView(i);
        int start = child.getStartOffset();
        int end = child.getEndOffset();
        if (start <= pos && end > pos)
          {
            result = i;
            break;
          }
      }
    return result;
  }
}