/*
 * @(#)BoxView.java	1.59 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package javax.swing.text;

import java.io.PrintStream;
import java.util.Vector;
import java.awt.*;
import javax.swing.event.DocumentEvent;
import javax.swing.SizeRequirements;

/**
 * A view that arranges its children into a box shape by tiling
 * its children along an axis.  The box is somewhat like that
 * found in TeX where there is alignment of the 
 * children, flexibility of the children is considered, etc. 
 * This is a building block that might be useful to represent
 * things like a collection of lines, paragraphs, 
 * lists, columns, pages, etc.  The axis along which the children are tiled is 
 * considered the major axis.  The orthoginal axis is the minor axis.
 * <p>
 * Layout for each axis is handled separately by the methods
 * <code>layoutMajorAxis</code> and <code>layoutMinorAxis</code>.
 * Subclasses can change the layout algorithm by 
 * reimplementing these methods.    These methods will be called
 * as necessary depending upon whether or not there is cached
 * layout information and the cache is considered 
 * valid.  These methods are typically called if the given size
 * along the axis changes, or if <code>layoutChanged</code> is
 * called to force an updated layout.  The <code>layoutChanged</code>
 * method invalidates cached layout information, if there is any.
 * The requirements published to the parent view are calculated by
 * the methods <code>calculateMajorAxisRequirements</code>
 * and  <code>calculateMinorAxisRequirements</code>.
 * If the layout algorithm is changed, these methods will
 * likely need to be reimplemented.
 *
 * @author  Timothy Prinzing
 * @version 1.59 01/23/03
 */
public class BoxView extends CompositeView {

    /**
     * Constructs a <code>BoxView</code>.
     *
     * @param elem the element this view is responsible for
     * @param axis either <code>View.X_AXIS</code> or <code>View.Y_AXIS</code>
     */
    public BoxView(Element elem, int axis) {
	super(elem);
	tempRect = new Rectangle();
	this.majorAxis = axis;

	majorOffsets = new int[0];
	majorSpans = new int[0];
	majorReqValid = false;
	majorAllocValid = false;
	minorOffsets = new int[0];
	minorSpans = new int[0];
	minorReqValid = false;
	minorAllocValid = false;
    }

    /**
     * Fetches the tile axis property.  This is the axis along which
     * the child views are tiled.
     *
     * @return the major axis of the box, either 
     *  <code>View.X_AXIS</code> or <code>View.Y_AXIS</code>
     *
     * @since 1.3
     */
    public int getAxis() {
	return majorAxis;
    }

    /**
     * Sets the tile axis property.  This is the axis along which
     * the child views are tiled.
     *
     * @param axis either <code>View.X_AXIS</code> or <code>View.Y_AXIS</code>
     *
     * @since 1.3
     */
    public void setAxis(int axis) {
	boolean axisChanged = (axis != majorAxis);
	majorAxis = axis;
	if (axisChanged) {
	    preferenceChanged(null, true, true);
	}
    }

    /**
     * Invalidates the layout along an axis.  This happens
     * automatically if the preferences have changed for
     * any of the child views.  In some cases the layout
     * may need to be recalculated when the preferences
     * have not changed.  The layout can be marked as
     * invalid by calling this method.  The layout will
     * be updated the next time the <code>setSize</code> method 
     * is called on this view (typically in paint).
     *
     * @param axis either <code>View.X_AXIS</code> or <code>View.Y_AXIS</code>
     *
     * @since 1.3
     */
    public void layoutChanged(int axis) {
 	if (axis == majorAxis) {
 	    majorAllocValid = false;
 	} else {
 	    minorAllocValid = false;
 	}
    }

    /** 
     * Determines if the layout is valid along the given axis.
     *
     * @param axis either <code>View.X_AXIS</code> or <code>View.Y_AXIS</code>
     *
     * @since 1.4
     */
    protected boolean isLayoutValid(int axis) {
 	if (axis == majorAxis) {
 	    return majorAllocValid;
 	} else {
 	    return minorAllocValid;
 	}
    }

    /**
     * Paints a child.  By default
     * that is all it does, but a subclass can use this to paint 
     * things relative to the child.
     *
     * @param g the graphics context
     * @param alloc the allocated region to paint into
     * @param index the child index, >= 0 && < getViewCount()
     */
    protected void paintChild(Graphics g, Rectangle alloc, int index) {
	View child = getView(index);
	child.paint(g, alloc);
    }

    // --- View methods ---------------------------------------------

    /**
     * Invalidates the layout and resizes the cache of 
     * requests/allocations.  The child allocations can still
     * be accessed for the old layout, but the new children
     * will have an offset and span of 0.
     *
     * @param index the starting index into the child views to insert
     *   the new views; this should be a value >= 0 and <= getViewCount
     * @param length the number of existing child views to remove;
     *   This should be a value >= 0 and <= (getViewCount() - offset)
     * @param elems the child views to add; this value can be 
     *   <code>null</code>to indicate no children are being added
     *   (useful to remove)
     */
    public void replace(int index, int length, View[] elems) {
	super.replace(index, length, elems);

	// invalidate cache 
	int nInserted = (elems != null) ? elems.length : 0;
	majorOffsets = updateLayoutArray(majorOffsets, index, nInserted);
	majorSpans = updateLayoutArray(majorSpans, index, nInserted);
	majorReqValid = false;
	majorAllocValid = false;
	minorOffsets = updateLayoutArray(minorOffsets, index, nInserted);
	minorSpans = updateLayoutArray(minorSpans, index, nInserted);
	minorReqValid = false;
	minorAllocValid = false;
    }

    /**
     * Resizes the given layout array to match the new number of
     * child views.  The current number of child views are used to
     * produce the new array.  The contents of the old array are
     * inserted into the new array at the appropriate places so that
     * the old layout information is transferred to the new array.
     *
     * @param oldArray the original layout array
     * @param offset location where new views will be inserted
     * @param nInserted the number of child views being inserted; 
     *		therefore the number of blank spaces to leave in the
     *		new array at location <code>offset</code>
     * @return the new layout array
     */
    int[] updateLayoutArray(int[] oldArray, int offset, int nInserted) {
	int n = getViewCount();
	int[] newArray = new int[n];

	System.arraycopy(oldArray, 0, newArray, 0, offset);
	System.arraycopy(oldArray, offset, 
			 newArray, offset + nInserted, n - nInserted - offset);
	return newArray;
    }

    /**
     * Forwards the given <code>DocumentEvent</code> to the child views
     * that need to be notified of the change to the model.
     * If a child changed its requirements and the allocation
     * was valid prior to forwarding the portion of the box
     * from the starting child to the end of the box will
     * be repainted.
     *
     * @param ec changes to the element this view is responsible
     *  for (may be <code>null</code> if there were no changes)
     * @param e the change information from the associated document
     * @param a the current allocation of the view
     * @param f the factory to use to rebuild if the view has children
     * @see #insertUpdate
     * @see #removeUpdate
     * @see #changedUpdate     
     */
    protected void forwardUpdate(DocumentEvent.ElementChange ec, 
				 DocumentEvent e, Shape a, ViewFactory f) {
	boolean wasValid = isLayoutValid(majorAxis);
	super.forwardUpdate(ec, e, a, f);

	// determine if a repaint is needed
	if (wasValid && (! isLayoutValid(majorAxis))) {
	    // Repaint is needed because one of the tiled children 
	    // have changed their span along the major axis.  If there 
	    // is a hosting component and an allocated shape we repaint.
	    Component c = getContainer();
	    if ((a != null) && (c != null)) {
		int pos = e.getOffset();
		int index = getViewIndexAtPosition(pos);
		Rectangle alloc = getInsideAllocation(a);
		if (majorAxis == X_AXIS) {
		    alloc.x += majorOffsets[index];
		    alloc.width -= majorOffsets[index];
		} else {
		    alloc.y += minorOffsets[index];
		    alloc.height -= minorOffsets[index];
		}
		c.repaint(alloc.x, alloc.y, alloc.width, alloc.height);
	    }
	}
    }

    /**
     * This is called by a child to indicate its 
     * preferred span has changed.  This is implemented to
     * throw away cached layout information so that new
     * calculations will be done the next time the children
     * need an allocation.
     *
     * @param child the child view
     * @param width true if the width preference should change
     * @param height true if the height preference should change
     */
    public void preferenceChanged(View child, boolean width, boolean height) {
	boolean majorChanged = (majorAxis == X_AXIS) ? width : height;
	boolean minorChanged = (majorAxis == X_AXIS) ? height : width;
	if (majorChanged) {
	    majorReqValid = false;
	    majorAllocValid = false;
	}
	if (minorChanged) {
	    minorReqValid = false;
	    minorAllocValid = false;
	}
	super.preferenceChanged(child, width, height);
    }

    /**
     * Gets the resize weight.  A value of 0 or less is not resizable.
     *
     * @param axis may be either <code>View.X_AXIS</code> or
     *		<code>View.Y_AXIS</code>
     * @return the weight
     * @exception IllegalArgumentException for an invalid axis
     */
    public int getResizeWeight(int axis) {
	checkRequests(axis);
        if (axis == majorAxis) {
	    if ((majorRequest.preferred != majorRequest.minimum) ||
		(majorRequest.preferred != majorRequest.maximum)) {
		return 1;
	    }
	} else {
	    if ((minorRequest.preferred != minorRequest.minimum) ||
		(minorRequest.preferred != minorRequest.maximum)) {
		return 1;
	    }
	}
	return 0;
    }

    /**
     * Sets the size of the view along an axis.  This should cause 
     * layout of the view along the given axis.
     *
     * @param axis may be either <code>View.X_AXIS</code> or
     *		<code>View.Y_AXIS</code>
     * @param span the span to layout to >= 0
     */
    void setSpanOnAxis(int axis, float span) {
	if (axis == majorAxis) {
	    if (majorSpan != (int) span) {
		majorAllocValid = false;
	    }
	    if (! majorAllocValid) {
		// layout the major axis
		majorSpan = (int) span;
		checkRequests(majorAxis);
		layoutMajorAxis(majorSpan, axis, majorOffsets, majorSpans);
		majorAllocValid = true;

		// flush changes to the children
		updateChildSizes();
	    }
	} else {
	    if (((int) span) != minorSpan) { 
		minorAllocValid = false;
	    }
	    if (! minorAllocValid) {
		// layout the minor axis
		minorSpan = (int) span;
		checkRequests(axis);
		layoutMinorAxis(minorSpan, axis, minorOffsets, minorSpans);
		minorAllocValid = true;

		// flush changes to the children
		updateChildSizes();
	    }
	}
    }

    /**
     * Propagates the current allocations to the child views.
     */
    void updateChildSizes() {
	int n = getViewCount();
	if (majorAxis == X_AXIS) {
	    for (int i = 0; i < n; i++) {
		View v = getView(i);
		v.setSize((float) majorSpans[i], (float) minorSpans[i]);
	    }
	} else {
	    for (int i = 0; i < n; i++) {
		View v = getView(i);
		v.setSize((float) minorSpans[i], (float) majorSpans[i]);
	    }
	}
    }

    /**
     * Returns the size of the view along an axis.  This is implemented
     * to return zero.  
     *
     * @param axis may be either <code>View.X_AXIS</code> or
     *		<code>View.Y_AXIS</code>
     * @return the current span of the view along the given axis, >= 0
     */
    float getSpanOnAxis(int axis) {
	if (axis == majorAxis) {
	    return majorSpan;
	} else {
	    return minorSpan;
	}
    }

    /**
     * Sets the size of the view.  This should cause 
     * layout of the view if the view caches any layout
     * information.  This is implemented to call the
     * layout method with the sizes inside of the insets.
     *
     * @param width the width >= 0
     * @param height the height >= 0
     */
    public void setSize(float width, float height) {
	layout((int)(width - getLeftInset() - getRightInset()), 
	       (int)(height - getTopInset() - getBottomInset()));
    }

    /**
     * Renders the <code>BoxView</code> using the given
     * rendering surface and area 
     * on that surface.  Only the children that intersect
     * the clip bounds of the given <code>Graphics</code>
     * will be rendered.
     *
     * @param g the rendering surface to use
     * @param allocation the allocated region to render into
     * @see View#paint
     */
    public void paint(Graphics g, Shape allocation) {
	Rectangle alloc = (allocation instanceof Rectangle) ?
	                   (Rectangle)allocation : allocation.getBounds();
	int n = getViewCount();
	int x = alloc.x + getLeftInset();
	int y = alloc.y + getTopInset();
	Rectangle clip = g.getClipBounds();
	for (int i = 0; i < n; i++) {
	    tempRect.x = x + getOffset(X_AXIS, i);
	    tempRect.y = y + getOffset(Y_AXIS, i);
	    tempRect.width = getSpan(X_AXIS, i);
	    tempRect.height = getSpan(Y_AXIS, i);
	    if (tempRect.intersects(clip)) {
		paintChild(g, tempRect, i);
	    }
	}
    }

    /**
     * Fetches the allocation for the given child view. 
     * This enables finding out where various views
     * are located.  This is implemented to return
     * <code>null</code> if the layout is invalid,
     * otherwise the superclass behavior is executed.
     *
     * @param index the index of the child, >= 0 && < getViewCount()
     * @param a  the allocation to this view
     * @return the allocation to the child; or <code>null</code>
     *		if <code>a</code> is <code>null</code>
     *		or <code>null</code> if the layout is invalid
     */
    public Shape getChildAllocation(int index, Shape a) {
	if (a != null) {
	    Shape ca = super.getChildAllocation(index, a);
	    if ((ca != null) && (! isAllocationValid())) {
		// The child allocation may not have been set yet.
		Rectangle r = (ca instanceof Rectangle) ? 
		    (Rectangle) ca : ca.getBounds();
		if ((r.width == 0) && (r.height == 0)) {
		    return null;
		}
	    }
	    return ca;
	}
	return null;
    }

    /**
     * Provides a mapping from the document model coordinate space
     * to the coordinate space of the view mapped to it.  This makes
     * sure the allocation is valid before calling the superclass.
     *
     * @param pos the position to convert >= 0
     * @param a the allocated region to render into
     * @return the bounding box of the given position
     * @exception BadLocationException  if the given position does
     *  not represent a valid location in the associated document
     * @see View#modelToView
     */
    public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException {
	if (! isAllocationValid()) {
	    Rectangle alloc = a.getBounds();
	    setSize(alloc.width, alloc.height);
	}
	return super.modelToView(pos, a, b);
    }

    /**
     * Provides a mapping from the view coordinate space to the logical
     * coordinate space of the model.
     *
     * @param x   x coordinate of the view location to convert >= 0
     * @param y   y coordinate of the view location to convert >= 0
     * @param a the allocated region to render into
     * @return the location within the model that best represents the
     *  given point in the view >= 0
     * @see View#viewToModel
     */
    public int viewToModel(float x, float y, Shape a, Position.Bias[] bias) {
	if (! isAllocationValid()) {
	    Rectangle alloc = a.getBounds();
	    setSize(alloc.width, alloc.height);
	}
	return super.viewToModel(x, y, a, bias);
    }

    /**
     * Determines the desired alignment for this view along an
     * axis.  This is implemented to give the total alignment
     * needed to position the children with the alignment points
     * lined up along the axis orthoginal to the axis that is
     * being tiled.  The axis being tiled will request to be
     * centered (i.e. 0.5f).
     *
     * @param axis may be either <code>View.X_AXIS</code>
     *   or <code>View.Y_AXIS</code>
     * @return the desired alignment >= 0.0f && <= 1.0f; this should
     *   be a value between 0.0 and 1.0 where 0 indicates alignment at the
     *   origin and 1.0 indicates alignment to the full span
     *   away from the origin; an alignment of 0.5 would be the
     *   center of the view
     * @exception IllegalArgumentException for an invalid axis
     */
    public float getAlignment(int axis) {
	checkRequests(axis);
	if (axis == majorAxis) {
	    return majorRequest.alignment;
	} else {
	    return minorRequest.alignment;
	}
    }

    /**
     * Determines the preferred span for this view along an
     * axis.
     *
     * @param axis may be either <code>View.X_AXIS</code>
     *		 or <code>View.Y_AXIS</code>
     * @return   the span the view would like to be rendered into >= 0;
     *           typically the view is told to render into the span
     *           that is returned, although there is no guarantee; 
     *           the parent may choose to resize or break the view
     * @exception IllegalArgumentException for an invalid axis type
     */
    public float getPreferredSpan(int axis) {
	checkRequests(axis);
	float marginSpan = (axis == X_AXIS) ? getLeftInset() + getRightInset() :
	    getTopInset() + getBottomInset();
	if (axis == majorAxis) {
	    return ((float)majorRequest.preferred) + marginSpan;
	} else {
	    return ((float)minorRequest.preferred) + marginSpan;
	}
    }

    /**
     * Determines the minimum span for this view along an
     * axis.
     *
     * @param axis may be either <code>View.X_AXIS</code>
     *		 or <code>View.Y_AXIS</code>
     * @return  the span the view would like to be rendered into >= 0;
     *           typically the view is told to render into the span
     *           that is returned, although there is no guarantee;  
     *           the parent may choose to resize or break the view
     * @exception IllegalArgumentException for an invalid axis type
     */
    public float getMinimumSpan(int axis) {
	checkRequests(axis);
	float marginSpan = (axis == X_AXIS) ? getLeftInset() + getRightInset() :
	    getTopInset() + getBottomInset();
	if (axis == majorAxis) {
	    return ((float)majorRequest.minimum) + marginSpan;
	} else {
	    return ((float)minorRequest.minimum) + marginSpan;
	}
    }

    /**
     * Determines the maximum span for this view along an
     * axis.
     *
     * @param axis may be either <code>View.X_AXIS</code>
     *		 or <code>View.Y_AXIS</code>
     * @return   the span the view would like to be rendered into >= 0;
     *           typically the view is told to render into the span
     *           that is returned, although there is no guarantee;  
     *           the parent may choose to resize or break the view
     * @exception IllegalArgumentException for an invalid axis type
     */
    public float getMaximumSpan(int axis) {
	checkRequests(axis);
	float marginSpan = (axis == X_AXIS) ? getLeftInset() + getRightInset() :
	    getTopInset() + getBottomInset();
	if (axis == majorAxis) {
	    return ((float)majorRequest.maximum) + marginSpan;
	} else {
	    return ((float)minorRequest.maximum) + marginSpan;
	}
    }

    // --- local methods ----------------------------------------------------

    /**
     * Are the allocations for the children still
     * valid?
     *
     * @return true if allocations still valid
     */
    protected boolean isAllocationValid() {
	return (majorAllocValid && minorAllocValid);
    }
   
    /**
     * Determines if a point falls before an allocated region.
     *
     * @param x the X coordinate >= 0
     * @param y the Y coordinate >= 0
     * @param innerAlloc the allocated region; this is the area
     *   inside of the insets
     * @return true if the point lies before the region else false
     */
    protected boolean isBefore(int x, int y, Rectangle innerAlloc) {
	if (majorAxis == View.X_AXIS) {
	    return (x < innerAlloc.x);
	} else {
	    return (y < innerAlloc.y);
	}
    }

    /**
     * Determines if a point falls after an allocated region.
     *
     * @param x the X coordinate >= 0
     * @param y the Y coordinate >= 0
     * @param innerAlloc the allocated region; this is the area
     *   inside of the insets
     * @return true if the point lies after the region else false
     */
    protected boolean isAfter(int x, int y, Rectangle innerAlloc) {
	if (majorAxis == View.X_AXIS) {
	    return (x > (innerAlloc.width + innerAlloc.x));
	} else {
	    return (y > (innerAlloc.height + innerAlloc.y));
	}
    }

    /**
     * Fetches the child view at the given coordinates.
     *
     * @param x the X coordinate >= 0
     * @param y the Y coordinate >= 0
     * @param alloc the parents inner allocation on entry, which should
     *   be changed to the childs allocation on exit
     * @return the view
     */
    protected View getViewAtPoint(int x, int y, Rectangle alloc) {
	int n = getViewCount();
	if (majorAxis == View.X_AXIS) {
	    if (x < (alloc.x + majorOffsets[0])) {
		childAllocation(0, alloc);
		return getView(0);
	    }
	    for (int i = 0; i < n; i++) {
		if (x < (alloc.x + majorOffsets[i])) {
		    childAllocation(i - 1, alloc);
		    return getView(i - 1);
		}
	    }
	    childAllocation(n - 1, alloc);
	    return getView(n - 1);
	} else {
	    if (y < (alloc.y + majorOffsets[0])) {
		childAllocation(0, alloc);
		return getView(0);
	    }
	    for (int i = 0; i < n; i++) {
		if (y < (alloc.y + majorOffsets[i])) {
		    childAllocation(i - 1, alloc);
		    return getView(i - 1);
		}
	    }
	    childAllocation(n - 1, alloc);
	    return getView(n - 1);
	}
    }

    /**
     * Allocates a region for a child view.  
     *
     * @param index the index of the child view to
     *   allocate, >= 0 && < getViewCount()
     * @param alloc the allocated region
     */
    protected void childAllocation(int index, Rectangle alloc) {
	alloc.x += getOffset(X_AXIS, index);
	alloc.y += getOffset(Y_AXIS, index);
	alloc.width = getSpan(X_AXIS, index);
	alloc.height = getSpan(Y_AXIS, index);
    }

    /**
     * Perform layout on the box
     *
     * @param width the width (inside of the insets) >= 0
     * @param height the height (inside of the insets) >= 0
     */
    protected void layout(int width, int height) {
	setSpanOnAxis(X_AXIS, width);
	setSpanOnAxis(Y_AXIS, height);
    }

    /**
     * Returns the current width of the box.  This is the width that
     * it was last allocated.
     * @return the current width of the box
     */
    public int getWidth() {
	int span;
	if (majorAxis == X_AXIS) {
	    span = majorSpan;
	} else {
	    span = minorSpan;
	}
	span += getLeftInset() - getRightInset();
	return span;
    }

    /**
     * Returns the current height of the box.  This is the height that
     * it was last allocated.
     * @return the current height of the box
     */
    public int getHeight() {
	int span;
	if (majorAxis == Y_AXIS) {
	    span = majorSpan;
	} else {
	    span = minorSpan;
	}
	span += getTopInset() - getBottomInset();
	return span;
    }

    /**
     * Performs layout for the major axis of the box (i.e. the
     * axis that it represents).  The results of the layout should
     * be placed in the given arrays which represent the allocations
     * to the children along the major axis.
     *
     * @param targetSpan the total span given to the view, which
     *  would be used to layout the children
     * @param axis the axis being layed out
     * @param offsets the offsets from the origin of the view for
     *  each of the child views; this is a return value and is
     *  filled in by the implementation of this method
     * @param spans the span of each child view; this is a return
     *  value and is filled in by the implementation of this method
     * @return the offset and span for each child view in the
     *  offsets and spans parameters
     */
    protected void layoutMajorAxis(int targetSpan, int axis, int[] offsets, int[] spans) {
	/*
	 * first pass, calculate the preferred sizes
	 * and the flexibility to adjust the sizes.
	 */
	long minimum = 0;
	long maximum = 0;
	long preferred = 0;
	int n = getViewCount();
	for (int i = 0; i < n; i++) {
	    View v = getView(i);
	    spans[i] = (int) v.getPreferredSpan(axis);
	    preferred += spans[i];
	    minimum += v.getMinimumSpan(axis);
	    maximum += v.getMaximumSpan(axis);
	}

	/*
	 * Second pass, expand or contract by as much as possible to reach
	 * the target span.  
	 */

	// determine the adjustment to be made
	long desiredAdjustment = targetSpan - preferred;
	float adjustmentFactor = 0.0f;
	if (desiredAdjustment != 0) {
	    float maximumAdjustment = (desiredAdjustment > 0) ? 
		maximum - preferred : preferred - minimum;
            if (maximumAdjustment == 0.0f) {
                adjustmentFactor = 0.0f;
            }
            else {
                adjustmentFactor = desiredAdjustment / maximumAdjustment;
                adjustmentFactor = Math.min(adjustmentFactor, 1.0f);
                adjustmentFactor = Math.max(adjustmentFactor, -1.0f);
            }
	}

	// make the adjustments
	int totalOffset = 0;
	for (int i = 0; i < n; i++) {
	    View v = getView(i);
	    offsets[i] = totalOffset;
	    int availableSpan = (adjustmentFactor > 0.0f) ? 
		(int) v.getMaximumSpan(axis) - spans[i] : 
		spans[i] - (int) v.getMinimumSpan(axis);
            float adjF = adjustmentFactor * availableSpan;
            if (adjF < 0) {
                adjF -= .5f;
            }
            else {
                adjF += .5f;
            }
	    int adj = (int)adjF;
	    spans[i] += adj;
	    totalOffset = (int) Math.min((long) totalOffset + (long) spans[i], Integer.MAX_VALUE);
	}
    }

    /**
     * Performs layout for the minor axis of the box (i.e. the
     * axis orthoginal to the axis that it represents).  The results 
     * of the layout should be placed in the given arrays which represent 
     * the allocations to the children along the minor axis.
     *
     * @param targetSpan the total span given to the view, which
     *  would be used to layout the children
     * @param axis the axis being layed out
     * @param offsets the offsets from the origin of the view for
     *  each of the child views; this is a return value and is
     *  filled in by the implementation of this method
     * @param spans the span of each child view; this is a return
     *  value and is filled in by the implementation of this method
     * @return the offset and span for each child view in the
     *  offsets and spans parameters
     */
    protected void layoutMinorAxis(int targetSpan, int axis, int[] offsets, int[] spans) {
	int n = getViewCount();
	for (int i = 0; i < n; i++) {
	    View v = getView(i);
	    int min = (int) v.getMinimumSpan(axis);
	    int max = (int) v.getMaximumSpan(axis);
	    if (max < targetSpan) {
		// can't make the child this wide, align it
		float align = v.getAlignment(axis);
		offsets[i] = (int) ((targetSpan - max) * align);
		spans[i] = max;
	    } else {
		// make it the target width, or as small as it can get.
		offsets[i] = 0;
		spans[i] = Math.max(min, targetSpan);
	    }
	}
    }

    /**
     * Calculates the size requirements for the major axis
     * </code>axis</code>.
     *
     * @param axis the axis being studied
     * @param r the <code>SizeRequirements</code> object;
     *		if <code>null</code> one will be created
     * @return the newly initialized <code>SizeRequirements</code> object
     * @see javax.swing.SizeRequirements
     */
    protected SizeRequirements calculateMajorAxisRequirements(int axis, SizeRequirements r) {
	// calculate tiled request
	float min = 0;
	float pref = 0;
	float max = 0;

	int n = getViewCount();
	for (int i = 0; i < n; i++) {
	    View v = getView(i);
	    min += v.getMinimumSpan(axis);
	    pref += v.getPreferredSpan(axis);
	    max += v.getMaximumSpan(axis);
	}

	if (r == null) {
	    r = new SizeRequirements();
	}
	r.alignment = 0.5f;
	r.minimum = (int) min;
	r.preferred = (int) pref;
	r.maximum = (int) max;
	return r;
    }

    /**
     * Calculates the size requirements for the minor axis
     * <code>axis</code>.
     *
     * @param axis the axis being studied
     * @param r the <code>SizeRequirements</code> object;
     *		if <code>null</code> one will be created
     * @return the newly initialized <code>SizeRequirements</code> object
     * @see javax.swing.SizeRequirements
     */
    protected SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r) {
	int min = 0;
	long pref = 0;
	int max = Integer.MAX_VALUE;
	int n = getViewCount();
	for (int i = 0; i < n; i++) {
	    View v = getView(i);
	    min = Math.max((int) v.getMinimumSpan(axis), min);
	    pref = Math.max((int) v.getPreferredSpan(axis), pref);
	    max = Math.max((int) v.getMaximumSpan(axis), max);
	}

	if (r == null) {
	    r = new SizeRequirements();
	    r.alignment = 0.5f;
	}
	r.preferred = (int) pref;
	r.minimum = min;
	r.maximum = max;
	return r;
    }

    /**
     * Checks the request cache and update if needed.
     * @param axis the axis being studied
     * @exception IllegalArgumentException if <code>axis</code> is
     *	neither <code>View.X_AXIS</code> nor </code>View.Y_AXIS</code>
     */
    void checkRequests(int axis) {
	if ((axis != X_AXIS) && (axis != Y_AXIS)) {
	    throw new IllegalArgumentException("Invalid axis: " + axis);
	}
	if (axis == majorAxis) {
            if (!majorReqValid) {
                majorRequest = calculateMajorAxisRequirements(axis,
                                                              majorRequest);
                majorReqValid = true;
            }
	} else if (! minorReqValid) {
	    minorRequest = calculateMinorAxisRequirements(axis, minorRequest);
	    minorReqValid = true;
	}
    }

    /**
     * Computes the location and extent of each child view
     * in this <code>BoxView</code> given the <code>targetSpan</code>,
     * which is the width (or height) of the region we have to
     * work with.
     *
     * @param targetSpan the total span given to the view, which
     *  would be used to layout the children
     * @param axis the axis being studied, either
     *		<code>View.X_AXIS</code> or <code>View.Y_AXIS</code>
     * @param offsets an empty array filled by this method with 
     *		values specifying the location	of each child view 
     * @param spans  an empty array filled by this method with
     *		values specifying the extent of each child view
     */
    protected void baselineLayout(int targetSpan, int axis, int[] offsets, int[] spans) {
        int totalAscent = (int)(targetSpan * getAlignment(axis));
        int totalDescent = targetSpan - totalAscent;

        int n = getViewCount();

        for (int i = 0; i < n; i++) {
            View v = getView(i);
            float align = v.getAlignment(axis);
            int viewSpan;

            if (v.getResizeWeight(axis) > 0) {
                // if resizable then resize to the best fit

                // the smallest span possible
                int minSpan = (int)v.getMinimumSpan(axis);
                // the largest span possible
                int maxSpan = (int)v.getMaximumSpan(axis);

                if (align == 0.0f) {
                    // if the alignment is 0 then we need to fit into the descent
                    viewSpan = Math.max(Math.min(maxSpan, totalDescent), minSpan);
                } else if (align == 1.0f) {
                    // if the alignment is 1 then we need to fit into the ascent
                    viewSpan = Math.max(Math.min(maxSpan, totalAscent), minSpan);
                } else {
                    // figure out the span that we must fit into
                    int fitSpan = (int)Math.min(totalAscent / align,
                                                totalDescent / (1.0f - align));
                    // fit into the calculated span
                    viewSpan = Math.max(Math.min(maxSpan, fitSpan), minSpan);
                }
            } else {
                // otherwise use the preferred spans
                viewSpan = (int)v.getPreferredSpan(axis);
            }

            offsets[i] = totalAscent - (int)(viewSpan * align);
            spans[i] = viewSpan;
        }     
    }

    /**
     * Calculates the size requirements for this <code>BoxView</code>
     * by examining the size of each child view.
     *
     * @param axis the axis being studied
     * @param r the <code>SizeRequirements</code> object;
     *		if <code>null</code> one will be created
     * @return the newly initialized <code>SizeRequirements</code> object
     */
    protected SizeRequirements baselineRequirements(int axis, SizeRequirements r) {
        SizeRequirements totalAscent = new SizeRequirements();
        SizeRequirements totalDescent = new SizeRequirements();
        
        if (r == null) {
            r = new SizeRequirements();
        }
        
        r.alignment = 0.5f;

        int n = getViewCount();

        // loop through all children calculating the max of all their ascents and
        // descents at minimum, preferred, and maximum sizes
        for (int i = 0; i < n; i++) {
            View v = getView(i);
            float align = v.getAlignment(axis);
            int span;
            int ascent;
            int descent;

            // find the maximum of the preferred ascents and descents
            span = (int)v.getPreferredSpan(axis);
            ascent = (int)(align * span);
            descent = span - ascent;
            totalAscent.preferred = Math.max(ascent, totalAscent.preferred);
            totalDescent.preferred = Math.max(descent, totalDescent.preferred);
            
            if (v.getResizeWeight(axis) > 0) {
                // if the view is resizable then do the same for the minimum and
                // maximum ascents and descents
                span = (int)v.getMinimumSpan(axis);
                ascent = (int)(align * span);
                descent = span - ascent;
                totalAscent.minimum = Math.max(ascent, totalAscent.minimum);
                totalDescent.minimum = Math.max(descent, totalDescent.minimum);

                span = (int)v.getMaximumSpan(axis);
                ascent = (int)(align * span);
                descent = span - ascent;
                totalAscent.maximum = Math.max(ascent, totalAscent.maximum);
                totalDescent.maximum = Math.max(descent, totalDescent.maximum);
            } else {
                // otherwise use the preferred
                totalAscent.minimum = Math.max(ascent, totalAscent.minimum);
                totalDescent.minimum = Math.max(descent, totalDescent.minimum);
                totalAscent.maximum = Math.max(ascent, totalAscent.maximum);
                totalDescent.maximum = Math.max(descent, totalDescent.maximum);
            }
        }
        
        // we now have an overall preferred, minimum, and maximum ascent and descent

        // calculate the preferred span as the sum of the preferred ascent and preferred descent
        r.preferred = (int)Math.min((long)totalAscent.preferred + (long)totalDescent.preferred,
                                    Integer.MAX_VALUE);

        // calculate the preferred alignment as the preferred ascent divided by the preferred span
        if (r.preferred > 0) {
            r.alignment = (float)totalAscent.preferred / r.preferred;
        }
        

        if (r.alignment == 0.0f) {
            // if the preferred alignment is 0 then the minimum and maximum spans are simply
            // the minimum and maximum descents since there's nothing above the baseline
            r.minimum = totalDescent.minimum;
            r.maximum = totalDescent.maximum;
        } else if (r.alignment == 1.0f) {
            // if the preferred alignment is 1 then the minimum and maximum spans are simply
            // the minimum and maximum ascents since there's nothing below the baseline
            r.minimum = totalAscent.minimum;
            r.maximum = totalAscent.maximum;
        } else {
            // we want to honor the preferred alignment so we calculate two possible minimum
            // span values using 1) the minimum ascent and the alignment, and 2) the minimum
            // descent and the alignment. We'll choose the larger of these two numbers.
            r.minimum = Math.max((int)(totalAscent.minimum / r.alignment),
                                 (int)(totalDescent.minimum / (1.0f - r.alignment)));
            // a similar calculation is made for the maximum but we choose the smaller number.
            r.maximum = Math.min((int)(totalAscent.maximum / r.alignment),
                                 (int)(totalDescent.maximum / (1.0f - r.alignment)));
        }

        return r;
    }

    /**
     * Fetches the offset of a particular child's current layout.
     * @param axis the axis being studied
     * @param childIndex the index of the requested child
     * @return the offset (location) for the specified child
     */
    protected int getOffset(int axis, int childIndex) {
	int[] offsets = (axis == majorAxis) ? majorOffsets : minorOffsets;
	return offsets[childIndex];
    }

    /**
     * Fetches the span of a particular childs current layout.
     * @param axis the axis being studied
     * @param childIndex the index of the requested child
     * @return the span (width or height) of the specified child
     */
    protected int getSpan(int axis, int childIndex) {
	int[] spans = (axis == majorAxis) ? majorSpans : minorSpans;
	return spans[childIndex];
    }

    /**
     * Determines in which direction the next view lays.
     * Consider the View at index n. Typically the <code>View</code>s
     * are layed out from left to right, so that the <code>View</code>
     * to the EAST will be at index n + 1, and the <code>View</code>
     * to the WEST will be at index n - 1. In certain situations,
     * such as with bidirectional text, it is possible
     * that the <code>View</code> to EAST is not at index n + 1,
     * but rather at index n - 1, or that the <code>View</code>
     * to the WEST is not at index n - 1, but index n + 1.
     * In this case this method would return true,
     * indicating the <code>View</code>s are layed out in
     * descending order. Otherwise the method would return false
     * indicating the <code>View</code>s are layed out in ascending order.
     * <p>
     * If the receiver is laying its <code>View</code>s along the 
     * <code>Y_AXIS</code>, this will will return the value from
     * invoking the same method on the <code>View</code>
     * responsible for rendering <code>position</code> and
     * <code>bias</code>. Otherwise this will return false.
     *
     * @param position position into the model
     * @param bias either <code>Position.Bias.Forward</code> or
     *          <code>Position.Bias.Backward</code>
     * @return true if the <code>View</code>s surrounding the 
     *		<code>View</code> responding for rendering
     *         	<code>position</code> and <code>bias</code>
     *		are layed out in descending order; otherwise false
     */
    protected boolean flipEastAndWestAtEnds(int position,
					    Position.Bias bias) {
	if(majorAxis == Y_AXIS) {
	    int testPos = (bias == Position.Bias.Backward) ?
		          Math.max(0, position - 1) : position;
	    int index = getViewIndexAtPosition(testPos);
	    if(index != -1) {
		View v = getView(index);
		if(v != null && v instanceof CompositeView) {
		    return ((CompositeView)v).flipEastAndWestAtEnds(position,
								    bias);
		}
	    }
	}
	return false;
    }

    // --- variables ------------------------------------------------

    int majorAxis;

    int majorSpan;
    int minorSpan;

    /*
     * Request cache
     */
    boolean majorReqValid;
    boolean minorReqValid;
    SizeRequirements majorRequest;
    SizeRequirements minorRequest;

    /*
     * Allocation cache
     */
    boolean majorAllocValid;
    int[] majorOffsets;
    int[] majorSpans;
    boolean minorAllocValid;
    int[] minorOffsets;
    int[] minorSpans;

    /** used in paint. */
    Rectangle tempRect;
}