flowview.java

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          View toBeBroken = row.getView(breakIndex);
          View brokenView = toBeBroken.breakView(axis,
                                                 toBeBroken.getStartOffset(),
                                                 breakX, breakSpan);
          row.replace(breakIndex, count - breakIndex,
                      new View[]{brokenView});
        }
    }
  }

  /**
   * This special subclass of <code>View</code> is used to represent
   * the logical representation of this view. It does not support any
   * visual representation, this is handled by the physical view implemented
   * in the <code>FlowView</code>.
   */
  class LogicalView extends BoxView
  {
    /**
     * Creates a new LogicalView instance.
     */
    LogicalView(Element el, int axis)
    {
      super(el, axis);
    }
  }

  /**
   * 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;

  /**
   * Indicates if the flow should be rebuild during the next layout.
   */
  private boolean layoutDirty;

  /**
   * 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;
    layoutDirty = true;
  }

  /**
   * 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(), getAxis());
        layoutPool.setParent(this);
      }
  }

  /**
   * 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)
  {
    int flowAxis = getFlowAxis();
    if (flowAxis == X_AXIS)
      {
        if (layoutSpan != width)
          {
            layoutChanged(Y_AXIS);
            layoutSpan = width;
          }
      }
    else
      {
        if (layoutSpan != height)
          {
            layoutChanged(X_AXIS);
            layoutSpan = height;
          }
      }

    if (layoutDirty)
      {
        strategy.layout(this);
        layoutDirty = false;
      }

    if (getPreferredSpan(getAxis()) != height)
      preferenceChanged(this, false, true);

    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));
    layoutDirty = true;
  }

  /**
   * 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));
    layoutDirty = true;
  }

  /**
   * 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));
    layoutDirty = true;
  }

  /**
   * 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;
  }

  /**
   * Calculates the size requirements of this <code>BoxView</code> along
   * its minor axis, that is the axis opposite to the axis specified in the
   * constructor.
   *
   * This is overridden and forwards the request to the logical view.
   *
   * @param axis the axis that is examined
   * @param r the <code>SizeRequirements</code> object to hold the result,
   *        if <code>null</code>, a new one is created
   *
   * @return the size requirements for this <code>BoxView</code> along
   *         the specified axis
   */
  protected SizeRequirements calculateMinorAxisRequirements(int axis,
                                                            SizeRequirements r)
  {
    // We need to call super here so that the alignment is properly
    // calculated.
    SizeRequirements res = super.calculateMinorAxisRequirements(axis, r);
    res.minimum = (int) layoutPool.getMinimumSpan(axis);
    res.preferred = (int) layoutPool.getPreferredSpan(axis);
    res.maximum = (int) layoutPool.getMaximumSpan(axis);
    return res;
  }
}