text/html/TableView.java

/*
 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package javax.swing.text.html;

import java.awt.*;
import java.util.BitSet;
import java.util.Vector;
import java.util.Arrays;
import javax.swing.SizeRequirements;
import javax.swing.event.DocumentEvent;

import javax.swing.text.*;

/**
 * HTML table view.
 *
 * @author  Timothy Prinzing
 * @see     View
 */
/*public*/ class TableView extends BoxView implements ViewFactory {

    /**
     * Constructs a TableView for the given element.
     *
     * @param elem the element that this view is responsible for
     */
    public TableView(Element elem) {
        super(elem, View.Y_AXIS);
        rows = new Vector<RowView>();
        gridValid = false;
        captionIndex = -1;
        totalColumnRequirements = new SizeRequirements();
    }

    /**
     * Creates a new table row.
     *
     * @param elem an element
     * @return the row
     */
    protected RowView createTableRow(Element elem) {
        // PENDING(prinz) need to add support for some of the other
        // elements, but for now just ignore anything that is not
        // a TR.
        Object o = elem.getAttributes().getAttribute(StyleConstants.NameAttribute);
        if (o == HTML.Tag.TR) {
            return new RowView(elem);
        }
        return null;
    }

    /**
     * The number of columns in the table.
     */
    public int getColumnCount() {
        return columnSpans.length;
    }

    /**
     * Fetches the span (width) of the given column.
     * This is used by the nested cells to query the
     * sizes of grid locations outside of themselves.
     */
    public int getColumnSpan(int col) {
        if (col < columnSpans.length) {
            return columnSpans[col];
        }
        return 0;
    }

    /**
     * The number of rows in the table.
     */
    public int getRowCount() {
        return rows.size();
    }

    /**
     * Fetch the span of multiple rows.  This includes
     * the border area.
     */
    public int getMultiRowSpan(int row0, int row1) {
        RowView rv0 = getRow(row0);
        RowView rv1 = getRow(row1);
        if ((rv0 != null) && (rv1 != null)) {
            int index0 = rv0.viewIndex;
            int index1 = rv1.viewIndex;
            int span = getOffset(Y_AXIS, index1) - getOffset(Y_AXIS, index0) +
                getSpan(Y_AXIS, index1);
            return span;
        }
        return 0;
    }

    /**
     * Fetches the span (height) of the given row.
     */
    public int getRowSpan(int row) {
        RowView rv = getRow(row);
        if (rv != null) {
            return getSpan(Y_AXIS, rv.viewIndex);
        }
        return 0;
    }

    RowView getRow(int row) {
        if (row < rows.size()) {
            return rows.elementAt(row);
        }
        return null;
    }

    protected View getViewAtPoint(int x, int y, Rectangle alloc) {
        int n = getViewCount();
        View v;
        Rectangle allocation = new Rectangle();
        for (int i = 0; i < n; i++) {
            allocation.setBounds(alloc);
            childAllocation(i, allocation);
            v = getView(i);
            if (v instanceof RowView) {
                v = ((RowView)v).findViewAtPoint(x, y, allocation);
                if (v != null) {
                    alloc.setBounds(allocation);
                    return v;
                }
            }
        }
        return super.getViewAtPoint(x, y, alloc);
    }

    /**
     * Determines the number of columns occupied by
     * the table cell represented by given element.
     */
    protected int getColumnsOccupied(View v) {
        AttributeSet a = v.getElement().getAttributes();

        if (a.isDefined(HTML.Attribute.COLSPAN)) {
            String s = (String) a.getAttribute(HTML.Attribute.COLSPAN);
            if (s != null) {
                try {
                    return Integer.parseInt(s);
                } catch (NumberFormatException nfe) {
                    // fall through to one column
                }
            }
        }

        return 1;
    }

    /**
     * Determines the number of rows occupied by
     * the table cell represented by given element.
     */
    protected int getRowsOccupied(View v) {
        AttributeSet a = v.getElement().getAttributes();

        if (a.isDefined(HTML.Attribute.ROWSPAN)) {
            String s = (String) a.getAttribute(HTML.Attribute.ROWSPAN);
            if (s != null) {
                try {
                    return Integer.parseInt(s);
                } catch (NumberFormatException nfe) {
                    // fall through to one row
                }
            }
        }

        return 1;
    }

    protected void invalidateGrid() {
        gridValid = false;
    }

    protected StyleSheet getStyleSheet() {
        HTMLDocument doc = (HTMLDocument) getDocument();
        return doc.getStyleSheet();
    }

    /**
     * Update the insets, which contain the caption if there
     * is a caption.
     */
    void updateInsets() {
        short top = (short) painter.getInset(TOP, this);
        short bottom = (short) painter.getInset(BOTTOM, this);
        if (captionIndex != -1) {
            View caption = getView(captionIndex);
            short h = (short) caption.getPreferredSpan(Y_AXIS);
            AttributeSet a = caption.getAttributes();
            Object align = a.getAttribute(CSS.Attribute.CAPTION_SIDE);
            if ((align != null) && (align.equals("bottom"))) {
                bottom += h;
            } else {
                top += h;
            }
        }
        setInsets(top, (short) painter.getInset(LEFT, this),
                  bottom, (short) painter.getInset(RIGHT, this));
    }

    /**
     * Update any cached values that come from attributes.
     */
    protected void setPropertiesFromAttributes() {
        StyleSheet sheet = getStyleSheet();
        attr = sheet.getViewAttributes(this);
        painter = sheet.getBoxPainter(attr);
        if (attr != null) {
            setInsets((short) painter.getInset(TOP, this),
                      (short) painter.getInset(LEFT, this),
                          (short) painter.getInset(BOTTOM, this),
                      (short) painter.getInset(RIGHT, this));

            CSS.LengthValue lv = (CSS.LengthValue)
                attr.getAttribute(CSS.Attribute.BORDER_SPACING);
            if (lv != null) {
                cellSpacing = (int) lv.getValue();
            } else {
                // Default cell spacing equals 2
                cellSpacing = 2;
            }
            lv = (CSS.LengthValue)
                    attr.getAttribute(CSS.Attribute.BORDER_TOP_WIDTH);
            if (lv != null) {
                    borderWidth = (int) lv.getValue();
            } else {
                    borderWidth = 0;
            }
        }
    }

    /**
     * Fill in the grid locations that are placeholders
     * for multi-column, multi-row, and missing grid
     * locations.
     */
    void updateGrid() {
        if (! gridValid) {
            relativeCells = false;
            multiRowCells = false;

            // determine which views are table rows and clear out
            // grid points marked filled.
            captionIndex = -1;
            rows.removeAllElements();
            int n = getViewCount();
            for (int i = 0; i < n; i++) {
                View v = getView(i);
                if (v instanceof RowView) {
                    rows.addElement((RowView) v);
                    RowView rv = (RowView) v;
                    rv.clearFilledColumns();
                    rv.rowIndex = rows.size() - 1;
                    rv.viewIndex = i;
                } else {
                    Object o = v.getElement().getAttributes().getAttribute(StyleConstants.NameAttribute);
                    if (o instanceof HTML.Tag) {
                        HTML.Tag kind = (HTML.Tag) o;
                        if (kind == HTML.Tag.CAPTION) {
                            captionIndex = i;
                        }
                    }
                }
            }

            int maxColumns = 0;
            int nrows = rows.size();
            for (int row = 0; row < nrows; row++) {
                RowView rv = getRow(row);
                int col = 0;
                for (int cell = 0; cell < rv.getViewCount(); cell++, col++) {
                    View cv = rv.getView(cell);
                    if (! relativeCells) {
                        AttributeSet a = cv.getAttributes();
                        CSS.LengthValue lv = (CSS.LengthValue)
                            a.getAttribute(CSS.Attribute.WIDTH);
                        if ((lv != null) && (lv.isPercentage())) {
                            relativeCells = true;
                        }
                    }
                    // advance to a free column
                    for (; rv.isFilled(col); col++);
                    int rowSpan = getRowsOccupied(cv);
                    if (rowSpan > 1) {
                        multiRowCells = true;
                    }
                    int colSpan = getColumnsOccupied(cv);
                    if ((colSpan > 1) || (rowSpan > 1)) {
                        // fill in the overflow entries for this cell
                        int rowLimit = row + rowSpan;
                        int colLimit = col + colSpan;
                        for (int i = row; i < rowLimit; i++) {
                            for (int j = col; j < colLimit; j++) {
                                if (i != row || j != col) {
                                    addFill(i, j);
                                }
                            }
                        }
                        if (colSpan > 1) {
                            col += colSpan - 1;
                        }
                    }
                }
                maxColumns = Math.max(maxColumns, col);
            }

            // setup the column layout/requirements
            columnSpans = new int[maxColumns];
            columnOffsets = new int[maxColumns];
            columnRequirements = new SizeRequirements[maxColumns];
            for (int i = 0; i < maxColumns; i++) {
                columnRequirements[i] = new SizeRequirements();
                columnRequirements[i].maximum = Integer.MAX_VALUE;
            }
            gridValid = true;
        }
    }

    /**
     * Mark a grid location as filled in for a cells overflow.
     */
    void addFill(int row, int col) {
        RowView rv = getRow(row);
        if (rv != null) {
            rv.fillColumn(col);
        }
    }

    /**
     * Layout the columns to fit within the given target span.
     *
     * @param targetSpan the given span for total of all the table
     *  columns
     * @param reqs the requirements desired for each column.  This
     *  is the column maximum of the cells minimum, preferred, and
     *  maximum requested span
     * @param spans the return value of how much to allocated to
     *  each column
     * @param offsets the return value of the offset from the
     *  origin for each column
     * @return the offset from the origin and the span for each column
     *  in the offsets and spans parameters
     */
    protected void layoutColumns(int targetSpan, int[] offsets, int[] spans,
                                 SizeRequirements[] reqs) {
        //clean offsets and spans
        Arrays.fill(offsets, 0);
        Arrays.fill(spans, 0);
        colIterator.setLayoutArrays(offsets, spans, targetSpan);
        CSS.calculateTiledLayout(colIterator, targetSpan);
    }

    /**
     * Calculate the requirements for each column.  The calculation
     * is done as two passes over the table.  The table cells that
     * occupy a single column are scanned first to determine the
     * maximum of minimum, preferred, and maximum spans along the
     * give axis.  Table cells that span multiple columns are excluded
     * from the first pass.  A second pass is made to determine if
     * the cells that span multiple columns are satisfied.  If the
     * column requirements are not satisified, the needs of the
     * multi-column cell is mixed into the existing column requirements.
     * The calculation of the multi-column distribution is based upon
     * the proportions of the existing column requirements and taking
     * into consideration any constraining maximums.
     */
    void calculateColumnRequirements(int axis) {
        // clean columnRequirements
        for (SizeRequirements req : columnRequirements) {
            req.minimum = 0;
            req.preferred = 0;
            req.maximum = Integer.MAX_VALUE;
        }
        Container host = getContainer();
        if (host != null) {
            if (host instanceof JTextComponent) {
                skipComments = !((JTextComponent)host).isEditable();
            } else {
                skipComments = true;
            }
        }
        // pass 1 - single column cells
        boolean hasMultiColumn = false;
        int nrows = getRowCount();
        for (int i = 0; i < nrows; i++) {
            RowView row = getRow(i);
            int col = 0;
            int ncells = row.getViewCount();
            for (int cell = 0; cell < ncells; cell++) {
                View cv = row.getView(cell);
                if (skipComments && !(cv instanceof CellView)) {
                    continue;
                }
                for (; row.isFilled(col); col++); // advance to a free column
                int rowSpan = getRowsOccupied(cv);
                int colSpan = getColumnsOccupied(cv);
                if (colSpan == 1) {
                    checkSingleColumnCell(axis, col, cv);
                } else {
                    hasMultiColumn = true;
                    col += colSpan - 1;
                }
                col++;
            }
        }

        // pass 2 - multi-column cells
        if (hasMultiColumn) {
            for (int i = 0; i < nrows; i++) {
                RowView row = getRow(i);
                int col = 0;
                int ncells = row.getViewCount();
                for (int cell = 0; cell < ncells; cell++) {
                    View cv = row.getView(cell);
                    if (skipComments && !(cv instanceof CellView)) {
                        continue;
                    }
                    for (; row.isFilled(col); col++); // advance to a free column
                    int colSpan = getColumnsOccupied(cv);
                    if (colSpan > 1) {
                        checkMultiColumnCell(axis, col, colSpan, cv);
                        col += colSpan - 1;
                    }
                    col++;
                }
            }
        }
    }

    /**
     * check the requirements of a table cell that spans a single column.
     */
    void checkSingleColumnCell(int axis, int col, View v) {
        SizeRequirements req = columnRequirements[col];
        req.minimum = Math.max((int) v.getMinimumSpan(axis), req.minimum);
        req.preferred = Math.max((int) v.getPreferredSpan(axis), req.preferred);
    }

    /**
     * check the requirements of a table cell that spans multiple
     * columns.
     */
    void checkMultiColumnCell(int axis, int col, int ncols, View v) {
        // calculate the totals
        long min = 0;
        long pref = 0;
        long max = 0;
        for (int i = 0; i < ncols; i++) {
            SizeRequirements req = columnRequirements[col + i];
            min += req.minimum;
            pref += req.preferred;
            max += req.maximum;
        }

        // check if the minimum size needs adjustment.
        int cmin = (int) v.getMinimumSpan(axis);
        if (cmin > min) {
            /*
             * the columns that this cell spans need adjustment to fit
             * this table cell.... calculate the adjustments.
             */
            SizeRequirements[] reqs = new SizeRequirements[ncols];
            for (int i = 0; i < ncols; i++) {
                reqs[i] = columnRequirements[col + i];
            }
            int[] spans = new int[ncols];
            int[] offsets = new int[ncols];
            SizeRequirements.calculateTiledPositions(cmin, null, reqs,
                                                     offsets, spans);
            // apply the adjustments
            for (int i = 0; i < ncols; i++) {
                SizeRequirements req = reqs[i];
                req.minimum = Math.max(spans[i], req.minimum);
                req.preferred = Math.max(req.minimum, req.preferred);
                req.maximum = Math.max(req.preferred, req.maximum);
            }
        }

        // check if the preferred size needs adjustment.
        int cpref = (int) v.getPreferredSpan(axis);
        if (cpref > pref) {
            /*
             * the columns that this cell spans need adjustment to fit
             * this table cell.... calculate the adjustments.
             */
            SizeRequirements[] reqs = new SizeRequirements[ncols];
            for (int i = 0; i < ncols; i++) {
                reqs[i] = columnRequirements[col + i];
            }
            int[] spans = new int[ncols];
            int[] offsets = new int[ncols];
            SizeRequirements.calculateTiledPositions(cpref, null, reqs,
                                                     offsets, spans);
            // apply the adjustments
            for (int i = 0; i < ncols; i++) {
                SizeRequirements req = reqs[i];
                req.preferred = Math.max(spans[i], req.preferred);
                req.maximum = Math.max(req.preferred, req.maximum);
            }
        }

    }

    // --- BoxView methods -----------------------------------------

    /**
     * Calculate the requirements for the minor axis.  This is called by
     * the superclass whenever the requirements need to be updated (i.e.
     * a preferenceChanged was messaged through this view).
     * <p>
     * This is implemented to calculate the requirements as the sum of the
     * requirements of the columns and then adjust it if the
     * CSS width or height attribute is specified and applicable to
     * the axis.
     */
    protected SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r) {
        updateGrid();

        // calculate column requirements for each column
        calculateColumnRequirements(axis);


        // the requirements are the sum of the columns.
        if (r == null) {
            r = new SizeRequirements();
        }
        long min = 0;
        long pref = 0;
        int n = columnRequirements.length;
        for (int i = 0; i < n; i++) {
            SizeRequirements req = columnRequirements[i];
            min += req.minimum;
            pref += req.preferred;
        }
        int adjust = (n + 1) * cellSpacing + 2 * borderWidth;
        min += adjust;
        pref += adjust;
        r.minimum = (int) min;
        r.preferred = (int) pref;
        r.maximum = (int) pref;


        AttributeSet attr = getAttributes();
        CSS.LengthValue cssWidth = (CSS.LengthValue)attr.getAttribute(
                                                    CSS.Attribute.WIDTH);

        if (BlockView.spanSetFromAttributes(axis, r, cssWidth, null)) {
            if (r.minimum < (int)min) {
                // The user has requested a smaller size than is needed to
                // show the table, override it.
                r.maximum = r.minimum = r.preferred = (int) min;
            }
        }
        totalColumnRequirements.minimum = r.minimum;
        totalColumnRequirements.preferred = r.preferred;
        totalColumnRequirements.maximum = r.maximum;

        // set the alignment
        Object o = attr.getAttribute(CSS.Attribute.TEXT_ALIGN);
        if (o != null) {
            // set horizontal alignment
            String ta = o.toString();
            if (ta.equals("left")) {
                r.alignment = 0;
            } else if (ta.equals("center")) {
                r.alignment = 0.5f;
            } else if (ta.equals("right")) {
                r.alignment = 1;
            } else {
                r.alignment = 0;
            }
        } else {
            r.alignment = 0;
        }

        return r;
    }

    /**
     * Calculate the requirements for the major axis.  This is called by
     * the superclass whenever the requirements need to be updated (i.e.
     * a preferenceChanged was messaged through this view).
     * <p>
     * This is implemented to provide the superclass behavior adjusted for
     * multi-row table cells.
     */
    protected SizeRequirements calculateMajorAxisRequirements(int axis, SizeRequirements r) {
        updateInsets();
        rowIterator.updateAdjustments();
        r = CSS.calculateTiledRequirements(rowIterator, r);
        r.maximum = r.preferred;
        return r;
    }

    /**
     * Perform layout for the minor axis of the box (i.e. the
     * axis orthogonal 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.  This
     * is called by the superclass whenever the layout needs to be
     * updated along the minor axis.
     * <p>
     * This is implemented to call the
     * <a href="#layoutColumns">layoutColumns</a> method, and then
     * forward to the superclass to actually carry out the layout
     * of the tables rows.
     *
     * @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) {
        // make grid is properly represented
        updateGrid();

        // all of the row layouts are invalid, so mark them that way
        int n = getRowCount();
        for (int i = 0; i < n; i++) {
            RowView row = getRow(i);
            row.layoutChanged(axis);
        }

        // calculate column spans
        layoutColumns(targetSpan, columnOffsets, columnSpans, columnRequirements);

        // continue normal layout
        super.layoutMinorAxis(targetSpan, axis, offsets, spans);
    }


    /**
     * Perform 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 minor axis.  This
     * is called by the superclass whenever the layout needs to be
     * updated along the minor axis.
     * <p>
     * This method is where the layout of the table rows within the
     * table takes place.  This method is implemented to call the use
     * the RowIterator and the CSS collapsing tile to layout
     * with border spacing and border collapsing capabilities.
     *
     * @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) {
        rowIterator.setLayoutArrays(offsets, spans);
        CSS.calculateTiledLayout(rowIterator, targetSpan);

        if (captionIndex != -1) {
            // place the caption
            View caption = getView(captionIndex);
            int h = (int) caption.getPreferredSpan(Y_AXIS);
            spans[captionIndex] = h;
            short boxBottom = (short) painter.getInset(BOTTOM, this);
            if (boxBottom != getBottomInset()) {
                offsets[captionIndex] = targetSpan + boxBottom;
            } else {
                offsets[captionIndex] = - getTopInset();
            }
        }
    }

    /**
     * Fetches the child view that represents the given position in
     * the model.  This is implemented to walk through the children
     * looking for a range that contains the given position.  In this
     * view the children do not necessarily have a one to one mapping
     * with the child elements.
     *
     * @param pos  the search position >= 0
     * @param a  the allocation to the table on entry, and the
     *   allocation of the view containing the position on exit
     * @return  the view representing the given position, or
     *   null if there isn't one
     */
    protected View getViewAtPosition(int pos, Rectangle a) {
        int n = getViewCount();
        for (int i = 0; i < n; i++) {
            View v = getView(i);
            int p0 = v.getStartOffset();
            int p1 = v.getEndOffset();
            if ((pos >= p0) && (pos < p1)) {
                // it's in this view.
                if (a != null) {
                    childAllocation(i, a);
                }
                return v;
            }
        }
        if (pos == getEndOffset()) {
            View v = getView(n - 1);
            if (a != null) {
                this.childAllocation(n - 1, a);
            }
            return v;
        }
        return null;
    }

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

    /**
     * Fetches the attributes to use when rendering.  This is
     * implemented to multiplex the attributes specified in the
     * model with a StyleSheet.
     */
    public AttributeSet getAttributes() {
        if (attr == null) {
            StyleSheet sheet = getStyleSheet();
            attr = sheet.getViewAttributes(this);
        }
        return attr;
    }

    /**
     * Renders using the given rendering surface and area on that
     * surface.  This is implemented to delegate to the css box
     * painter to paint the border and background prior to the
     * interior.  The superclass culls rendering the children
     * that don't directly intersect the clip and the row may
     * have cells hanging from a row above in it.  The table
     * does not use the superclass rendering behavior and instead
     * paints all of the rows and lets the rows cull those
     * cells not intersecting the clip region.
     *
     * @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) {
        // paint the border
        Rectangle a = allocation.getBounds();
        setSize(a.width, a.height);
        if (captionIndex != -1) {
            // adjust the border for the caption
            short top = (short) painter.getInset(TOP, this);
            short bottom = (short) painter.getInset(BOTTOM, this);
            if (top != getTopInset()) {
                int h = getTopInset() - top;
                a.y += h;
                a.height -= h;
            } else {
                a.height -= getBottomInset() - bottom;
            }
        }
        painter.paint(g, a.x, a.y, a.width, a.height, this);
        // paint interior
        int n = getViewCount();
        for (int i = 0; i < n; i++) {
            View v = getView(i);
            v.paint(g, getChildAllocation(i, allocation));
        }
        //super.paint(g, a);
    }

    /**
     * Establishes the parent view for this view.  This is
     * guaranteed to be called before any other methods if the
     * parent view is functioning properly.
     * <p>
     * This is implemented
     * to forward to the superclass as well as call the
     * <a href="#setPropertiesFromAttributes">setPropertiesFromAttributes</a>
     * method to set the paragraph properties from the css
     * attributes.  The call is made at this time to ensure
     * the ability to resolve upward through the parents
     * view attributes.
     *
     * @param parent the new parent, or null if the view is
     *  being removed from a parent it was previously added
     *  to
     */
    public void setParent(View parent) {
        super.setParent(parent);
        if (parent != null) {
            setPropertiesFromAttributes();
        }
    }

    /**
     * Fetches the ViewFactory implementation that is feeding
     * the view hierarchy.
     * This replaces the ViewFactory with an implementation that
     * calls through to the createTableRow and createTableCell
     * methods.   If the element given to the factory isn't a
     * table row or cell, the request is delegated to the factory
     * produced by the superclass behavior.
     *
     * @return the factory, null if none
     */
    public ViewFactory getViewFactory() {
        return this;
    }

    /**
     * Gives notification that something was inserted into
     * the document in a location that this view is responsible for.
     * This replaces the ViewFactory with an implementation that
     * calls through to the createTableRow and createTableCell
     * methods.   If the element given to the factory isn't a
     * table row or cell, the request is delegated to the factory
     * passed as an argument.
     *
     * @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 View#insertUpdate
     */
    public void insertUpdate(DocumentEvent e, Shape a, ViewFactory f) {
        super.insertUpdate(e, a, this);
    }

    /**
     * Gives notification that something was removed from the document
     * in a location that this view is responsible for.
     * This replaces the ViewFactory with an implementation that
     * calls through to the createTableRow and createTableCell
     * methods.   If the element given to the factory isn't a
     * table row or cell, the request is delegated to the factory
     * passed as an argument.
     *
     * @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 View#removeUpdate
     */
    public void removeUpdate(DocumentEvent e, Shape a, ViewFactory f) {
        super.removeUpdate(e, a, this);
    }

    /**
     * Gives notification from the document that attributes were changed
     * in a location that this view is responsible for.
     * This replaces the ViewFactory with an implementation that
     * calls through to the createTableRow and createTableCell
     * methods.   If the element given to the factory isn't a
     * table row or cell, the request is delegated to the factory
     * passed as an argument.
     *
     * @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 View#changedUpdate
     */
    public void changedUpdate(DocumentEvent e, Shape a, ViewFactory f) {
        super.changedUpdate(e, a, this);
    }

    protected void forwardUpdate(DocumentEvent.ElementChange ec,
                                 DocumentEvent e, Shape a, ViewFactory f) {
        super.forwardUpdate(ec, e, a, f);
        // A change in any of the table cells usually effects the whole table,
        // so redraw it all!
        if (a != null) {
            Component c = getContainer();
            if (c != null) {
                Rectangle alloc = (a instanceof Rectangle) ? (Rectangle)a :
                                   a.getBounds();
                c.repaint(alloc.x, alloc.y, alloc.width, alloc.height);
            }
        }
    }

    /**
     * Change the child views.  This is implemented to
     * provide the superclass behavior and invalidate the
     * grid so that rows and columns will be recalculated.
     */
    public void replace(int offset, int length, View[] views) {
        super.replace(offset, length, views);
        invalidateGrid();
    }

    // --- ViewFactory methods ------------------------------------------

    /**
     * The table itself acts as a factory for the various
     * views that actually represent pieces of the table.
     * All other factory activity is delegated to the factory
     * returned by the parent of the table.
     */
    public View create(Element elem) {
        Object o = elem.getAttributes().getAttribute(StyleConstants.NameAttribute);
        if (o instanceof HTML.Tag) {
            HTML.Tag kind = (HTML.Tag) o;
            if (kind == HTML.Tag.TR) {
                return createTableRow(elem);
            } else if ((kind == HTML.Tag.TD) || (kind == HTML.Tag.TH)) {
                return new CellView(elem);
            } else if (kind == HTML.Tag.CAPTION) {
                return new javax.swing.text.html.ParagraphView(elem);
            }
        }
        // default is to delegate to the normal factory
        View p = getParent();
        if (p != null) {
            ViewFactory f = p.getViewFactory();
            if (f != null) {
                return f.create(elem);
            }
        }
        return null;
    }

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

    private AttributeSet attr;
    private StyleSheet.BoxPainter painter;

    private int cellSpacing;
    private int borderWidth;

    /**
     * The index of the caption view if there is a caption.
     * This has a value of -1 if there is no caption.  The
     * caption lives in the inset area of the table, and is
     * updated with each time the grid is recalculated.
     */
    private int captionIndex;

    /**
     * Do any of the table cells contain a relative size
     * specification?  This is updated with each call to
     * updateGrid().  If this is true, the ColumnIterator
     * will do extra work to calculate relative cell
     * specifications.
     */
    private boolean relativeCells;

    /**
     * Do any of the table cells span multiple rows?  If
     * true, the RowRequirementIterator will do additional
     * work to adjust the requirements of rows spanned by
     * a single table cell.  This is updated with each call to
     * updateGrid().
     */
    private boolean multiRowCells;

    int[] columnSpans;
    int[] columnOffsets;
    /**
     * SizeRequirements for all the columns.
     */
    SizeRequirements totalColumnRequirements;
    SizeRequirements[] columnRequirements;

    RowIterator rowIterator = new RowIterator();
    ColumnIterator colIterator = new ColumnIterator();

    Vector<RowView> rows;

    // whether to display comments inside table or not.
    boolean skipComments = false;

    boolean gridValid;
    static final private BitSet EMPTY = new BitSet();

    class ColumnIterator implements CSS.LayoutIterator {

        /**
         * Disable percentage adjustments which should only apply
         * when calculating layout, not requirements.
         */
        void disablePercentages() {
            percentages = null;
        }

        /**
         * Update percentage adjustments if they are needed.
         */
        private void updatePercentagesAndAdjustmentWeights(int span) {
            adjustmentWeights = new int[columnRequirements.length];
            for (int i = 0; i < columnRequirements.length; i++) {
                adjustmentWeights[i] = 0;
            }
            if (relativeCells) {
                percentages = new int[columnRequirements.length];
            } else {
                percentages = null;
            }
            int nrows = getRowCount();
            for (int rowIndex = 0; rowIndex < nrows; rowIndex++) {
                RowView row = getRow(rowIndex);
                int col = 0;
                int ncells = row.getViewCount();
                for (int cell = 0; cell < ncells; cell++, col++) {
                    View cv = row.getView(cell);
                    for (; row.isFilled(col); col++); // advance to a free column
                    int rowSpan = getRowsOccupied(cv);
                    int colSpan = getColumnsOccupied(cv);
                    AttributeSet a = cv.getAttributes();
                    CSS.LengthValue lv = (CSS.LengthValue)
                        a.getAttribute(CSS.Attribute.WIDTH);
                    if ( lv != null ) {
                        int len = (int) (lv.getValue(span) / colSpan + 0.5f);
                        for (int i = 0; i < colSpan; i++) {
                            if (lv.isPercentage()) {
                                // add a percentage requirement
                                percentages[col+i] = Math.max(percentages[col+i], len);
                                adjustmentWeights[col + i] = Math.max(adjustmentWeights[col + i], WorstAdjustmentWeight);
                            } else {
                                adjustmentWeights[col + i] = Math.max(adjustmentWeights[col + i], WorstAdjustmentWeight - 1);
                            }
                        }
                    }
                    col += colSpan - 1;
                }
            }
        }

        /**
         * Set the layout arrays to use for holding layout results
         */
        public void setLayoutArrays(int offsets[], int spans[], int targetSpan) {
            this.offsets = offsets;
            this.spans = spans;
            updatePercentagesAndAdjustmentWeights(targetSpan);
        }

        // --- RequirementIterator methods -------------------

        public int getCount() {
            return columnRequirements.length;
        }

        public void setIndex(int i) {
            col = i;
        }

        public void setOffset(int offs) {
            offsets[col] = offs;
        }

        public int getOffset() {
            return offsets[col];
        }

        public void setSpan(int span) {
            spans[col] = span;
        }

        public int getSpan() {
            return spans[col];
        }

        public float getMinimumSpan(float parentSpan) {
            // do not care for percentages, since min span can't
            // be less than columnRequirements[col].minimum,
            // but can be less than percentage value.
            return columnRequirements[col].minimum;
        }

        public float getPreferredSpan(float parentSpan) {
            if ((percentages != null) && (percentages[col] != 0)) {
                return Math.max(percentages[col], columnRequirements[col].minimum);
            }
            return columnRequirements[col].preferred;
        }

        public float getMaximumSpan(float parentSpan) {
            return columnRequirements[col].maximum;
        }

        public float getBorderWidth() {
            return borderWidth;
        }


        public float getLeadingCollapseSpan() {
            return cellSpacing;
        }

        public float getTrailingCollapseSpan() {
            return cellSpacing;
        }

        public int getAdjustmentWeight() {
            return adjustmentWeights[col];
        }

        /**
         * Current column index
         */
        private int col;

        /**
         * percentage values (may be null since there
         * might not be any).
         */
        private int[] percentages;

        private int[] adjustmentWeights;

        private int[] offsets;
        private int[] spans;
    }

    class RowIterator implements CSS.LayoutIterator {

        RowIterator() {
        }

        void updateAdjustments() {
            int axis = Y_AXIS;
            if (multiRowCells) {
                // adjust requirements of multi-row cells
                int n = getRowCount();
                adjustments = new int[n];
                for (int i = 0; i < n; i++) {
                    RowView rv = getRow(i);
                    if (rv.multiRowCells == true) {
                        int ncells = rv.getViewCount();
                        for (int j = 0; j < ncells; j++) {
                            View v = rv.getView(j);
                            int nrows = getRowsOccupied(v);
                            if (nrows > 1) {
                                int spanNeeded = (int) v.getPreferredSpan(axis);
                                adjustMultiRowSpan(spanNeeded, nrows, i);
                            }
                        }
                    }
                }
            } else {
                adjustments = null;
            }
        }

        /**
         * Fixup preferences to accommodate a multi-row table cell
         * if not already covered by existing preferences.  This is
         * a no-op if not all of the rows needed (to do this check/fixup)
         * have arrived yet.
         */
        void adjustMultiRowSpan(int spanNeeded, int nrows, int rowIndex) {
            if ((rowIndex + nrows) > getCount()) {
                // rows are missing (could be a bad rowspan specification)
                // or not all the rows have arrived.  Do the best we can with
                // the current set of rows.
                nrows = getCount() - rowIndex;
                if (nrows < 1) {
                    return;
                }
            }
            int span = 0;
            for (int i = 0; i < nrows; i++) {
                RowView rv = getRow(rowIndex + i);
                span += rv.getPreferredSpan(Y_AXIS);
            }
            if (spanNeeded > span) {
                int adjust = (spanNeeded - span);
                int rowAdjust = adjust / nrows;
                int firstAdjust = rowAdjust + (adjust - (rowAdjust * nrows));
                RowView rv = getRow(rowIndex);
                adjustments[rowIndex] = Math.max(adjustments[rowIndex],
                                                 firstAdjust);
                for (int i = 1; i < nrows; i++) {
                    adjustments[rowIndex + i] = Math.max(
                        adjustments[rowIndex + i], rowAdjust);
                }
            }
        }

        void setLayoutArrays(int[] offsets, int[] spans) {
            this.offsets = offsets;
            this.spans = spans;
        }

        // --- RequirementIterator methods -------------------

        public void setOffset(int offs) {
            RowView rv = getRow(row);
            if (rv != null) {
                offsets[rv.viewIndex] = offs;
            }
        }

        public int getOffset() {
            RowView rv = getRow(row);
            if (rv != null) {
                return offsets[rv.viewIndex];
            }
            return 0;
        }

        public void setSpan(int span) {
            RowView rv = getRow(row);
            if (rv != null) {
                spans[rv.viewIndex] = span;
            }
        }

        public int getSpan() {
            RowView rv = getRow(row);
            if (rv != null) {
                return spans[rv.viewIndex];
            }
            return 0;
        }

        public int getCount() {
            return rows.size();
        }

        public void setIndex(int i) {
            row = i;
        }

        public float getMinimumSpan(float parentSpan) {
            return getPreferredSpan(parentSpan);
        }

        public float getPreferredSpan(float parentSpan) {
            RowView rv = getRow(row);
            if (rv != null) {
                int adjust = (adjustments != null) ? adjustments[row] : 0;
                return rv.getPreferredSpan(TableView.this.getAxis()) + adjust;
            }
            return 0;
        }

        public float getMaximumSpan(float parentSpan) {
            return getPreferredSpan(parentSpan);
        }

        public float getBorderWidth() {
            return borderWidth;
        }

        public float getLeadingCollapseSpan() {
            return cellSpacing;
        }

        public float getTrailingCollapseSpan() {
            return cellSpacing;
        }

        public int getAdjustmentWeight() {
            return 0;
        }

        /**
         * Current row index
         */
        private int row;

        /**
         * Adjustments to the row requirements to handle multi-row
         * table cells.
         */
        private int[] adjustments;

        private int[] offsets;
        private int[] spans;
    }

    /**
     * View of a row in a row-centric table.
     */
    public class RowView extends BoxView {

        /**
         * Constructs a TableView for the given element.
         *
         * @param elem the element that this view is responsible for
         */
        public RowView(Element elem) {
            super(elem, View.X_AXIS);
            fillColumns = new BitSet();
            RowView.this.setPropertiesFromAttributes();
        }

        void clearFilledColumns() {
            fillColumns.and(EMPTY);
        }

        void fillColumn(int col) {
            fillColumns.set(col);
        }

        boolean isFilled(int col) {
            return fillColumns.get(col);
        }

        /**
         * The number of columns present in this row.
         */
        int getColumnCount() {
            int nfill = 0;
            int n = fillColumns.size();
            for (int i = 0; i < n; i++) {
                if (fillColumns.get(i)) {
                    nfill ++;
                }
            }
            return getViewCount() + nfill;
        }

        /**
         * Fetches the attributes to use when rendering.  This is
         * implemented to multiplex the attributes specified in the
         * model with a StyleSheet.
         */
        public AttributeSet getAttributes() {
            return attr;
        }

        View findViewAtPoint(int x, int y, Rectangle alloc) {
            int n = getViewCount();
            for (int i = 0; i < n; i++) {
                if (getChildAllocation(i, alloc).contains(x, y)) {
                    childAllocation(i, alloc);
                    return getView(i);
                }
            }
            return null;
        }

        protected StyleSheet getStyleSheet() {
            HTMLDocument doc = (HTMLDocument) getDocument();
            return doc.getStyleSheet();
        }

        /**
         * This is called by a child to indicate its
         * preferred span has changed.  This is implemented to
         * execute the superclass behavior and well as try to
         * determine if a row with a multi-row cell hangs across
         * this row.  If a multi-row cell covers this row it also
         * needs to propagate a preferenceChanged so that it will
         * recalculate the multi-row cell.
         *
         * @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) {
            super.preferenceChanged(child, width, height);
            if (TableView.this.multiRowCells && height) {
                for (int i = rowIndex  - 1; i >= 0; i--) {
                    RowView rv = TableView.this.getRow(i);
                    if (rv.multiRowCells) {
                        rv.preferenceChanged(null, false, true);
                        break;
                    }
                }
            }
        }

        // The major axis requirements for a row are dictated by the column
        // requirements. These methods use the value calculated by
        // TableView.
        protected SizeRequirements calculateMajorAxisRequirements(int axis, SizeRequirements r) {
            SizeRequirements req = new SizeRequirements();
            req.minimum = totalColumnRequirements.minimum;
            req.maximum = totalColumnRequirements.maximum;
            req.preferred = totalColumnRequirements.preferred;
            req.alignment = 0f;
            return req;
        }

        public float getMinimumSpan(int axis) {
            float value;

            if (axis == View.X_AXIS) {
                value = totalColumnRequirements.minimum + getLeftInset() +
                        getRightInset();
            }
            else {
                value = super.getMinimumSpan(axis);
            }
            return value;
        }

        public float getMaximumSpan(int axis) {
            float value;

            if (axis == View.X_AXIS) {
                // We're flexible.
                value = (float)Integer.MAX_VALUE;
            }
            else {
                value = super.getMaximumSpan(axis);
            }
            return value;
        }

        public float getPreferredSpan(int axis) {
            float value;

            if (axis == View.X_AXIS) {
                value = totalColumnRequirements.preferred + getLeftInset() +
                        getRightInset();
            }
            else {
                value = super.getPreferredSpan(axis);
            }
            return value;
        }

        public void changedUpdate(DocumentEvent e, Shape a, ViewFactory f) {
            super.changedUpdate(e, a, f);
            int pos = e.getOffset();
            if (pos <= getStartOffset() && (pos + e.getLength()) >=
                getEndOffset()) {
                RowView.this.setPropertiesFromAttributes();
            }
        }

        /**
         * Renders using the given rendering surface and area on that
         * surface.  This is implemented to delegate to the css box
         * painter to paint the border and background prior to the
         * interior.
         *
         * @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 a = (Rectangle) allocation;
            painter.paint(g, a.x, a.y, a.width, a.height, this);
            super.paint(g, a);
        }

        /**
         * Change the child views.  This is implemented to
         * provide the superclass behavior and invalidate the
         * grid so that rows and columns will be recalculated.
         */
        public void replace(int offset, int length, View[] views) {
            super.replace(offset, length, views);
            invalidateGrid();
        }

        /**
         * Calculate the height requirements of the table row.  The
         * requirements of multi-row cells are not considered for this
         * calculation.  The table itself will check and adjust the row
         * requirements for all the rows that have multi-row cells spanning
         * them.  This method updates the multi-row flag that indicates that
         * this row and rows below need additional consideration.
         */
        protected SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r) {
//          return super.calculateMinorAxisRequirements(axis, r);
            long min = 0;
            long pref = 0;
            long max = 0;
            multiRowCells = false;
            int n = getViewCount();
            for (int i = 0; i < n; i++) {
                View v = getView(i);
                if (getRowsOccupied(v) > 1) {
                    multiRowCells = true;
                    max = Math.max((int) v.getMaximumSpan(axis), max);
                } else {
                    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 = (int) min;
            r.maximum = (int) max;
            return r;
        }

        /**
         * Perform 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.
         * <p>
         * This is re-implemented to give each child the span of the column
         * width for the table, and to give cells that span multiple columns
         * the multi-column span.
         *
         * @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) {
            int col = 0;
            int ncells = getViewCount();
            for (int cell = 0; cell < ncells; cell++) {
                View cv = getView(cell);
                if (skipComments && !(cv instanceof CellView)) {
                    continue;
                }
                for (; isFilled(col); col++); // advance to a free column
                int colSpan = getColumnsOccupied(cv);
                spans[cell] = columnSpans[col];
                offsets[cell] = columnOffsets[col];
                if (colSpan > 1) {
                    int n = columnSpans.length;
                    for (int j = 1; j < colSpan; j++) {
                        // Because the table may be only partially formed, some
                        // of the columns may not yet exist.  Therefore we check
                        // the bounds.
                        if ((col+j) < n) {
                            spans[cell] += columnSpans[col+j];
                            spans[cell] += cellSpacing;
                        }
                    }
                    col += colSpan - 1;
                }
                col++;
            }
        }

        /**
         * Perform layout for the minor axis of the box (i.e. the
         * axis orthogonal 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.  This
         * is called by the superclass whenever the layout needs to be
         * updated along the minor axis.
         * <p>
         * This is implemented to delegate to the superclass, then adjust
         * the span for any cell that spans multiple rows.
         *
         * @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) {
            super.layoutMinorAxis(targetSpan, axis, offsets, spans);
            int col = 0;
            int ncells = getViewCount();
            for (int cell = 0; cell < ncells; cell++, col++) {
                View cv = getView(cell);
                for (; isFilled(col); col++); // advance to a free column
                int colSpan = getColumnsOccupied(cv);
                int rowSpan = getRowsOccupied(cv);
                if (rowSpan > 1) {

                    int row0 = rowIndex;
                    int row1 = Math.min(rowIndex + rowSpan - 1, getRowCount()-1);
                    spans[cell] = getMultiRowSpan(row0, row1);
                }
                if (colSpan > 1) {
                    col += colSpan - 1;
                }
            }
        }

        /**
         * Determines the resizability of the view along the
         * given axis.  A value of 0 or less is not resizable.
         *
         * @param axis may be either View.X_AXIS or View.Y_AXIS
         * @return the resize weight
         * @exception IllegalArgumentException for an invalid axis
         */
        public int getResizeWeight(int axis) {
            return 1;
        }

        /**
         * Fetches the child view that represents the given position in
         * the model.  This is implemented to walk through the children
         * looking for a range that contains the given position.  In this
         * view the children do not necessarily have a one to one mapping
         * with the child elements.
         *
         * @param pos  the search position >= 0
         * @param a  the allocation to the table on entry, and the
         *   allocation of the view containing the position on exit
         * @return  the view representing the given position, or
         *   null if there isn't one
         */
        protected View getViewAtPosition(int pos, Rectangle a) {
            int n = getViewCount();
            for (int i = 0; i < n; i++) {
                View v = getView(i);
                int p0 = v.getStartOffset();
                int p1 = v.getEndOffset();
                if ((pos >= p0) && (pos < p1)) {
                    // it's in this view.
                    if (a != null) {
                        childAllocation(i, a);
                    }
                    return v;
                }
            }
            if (pos == getEndOffset()) {
                View v = getView(n - 1);
                if (a != null) {
                    this.childAllocation(n - 1, a);
                }
                return v;
            }
            return null;
        }

        /**
         * Update any cached values that come from attributes.
         */
        void setPropertiesFromAttributes() {
            StyleSheet sheet = getStyleSheet();
            attr = sheet.getViewAttributes(this);
            painter = sheet.getBoxPainter(attr);
        }

        private StyleSheet.BoxPainter painter;
        private AttributeSet attr;

        /** columns filled by multi-column or multi-row cells */
        BitSet fillColumns;

        /**
         * The row index within the overall grid
         */
        int rowIndex;

        /**
         * The view index (for row index to view index conversion).
         * This is set by the updateGrid method.
         */
        int viewIndex;

        /**
         * Does this table row have cells that span multiple rows?
         */
        boolean multiRowCells;

    }

    /**
     * Default view of an html table cell.  This needs to be moved
     * somewhere else.
     */
    class CellView extends BlockView {

        /**
         * Constructs a TableCell for the given element.
         *
         * @param elem the element that this view is responsible for
         */
        public CellView(Element elem) {
            super(elem, Y_AXIS);
        }

        /**
         * Perform 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.  This is called by the
         * superclass to recalculate the positions of the child views
         * when the layout might have changed.
         * <p>
         * This is implemented to delegate to the superclass to
         * tile the children.  If the target span is greater than
         * was needed, the offsets are adjusted to align the children
         * (i.e. position according to the html valign attribute).
         *
         * @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) {
            super.layoutMajorAxis(targetSpan, axis, offsets, spans);
            // calculate usage
            int used = 0;
            int n = spans.length;
            for (int i = 0; i < n; i++) {
                used += spans[i];
            }

            // calculate adjustments
            int adjust = 0;
            if (used < targetSpan) {
                // PENDING(prinz) change to use the css alignment.
                String valign = (String) getElement().getAttributes().getAttribute(
                    HTML.Attribute.VALIGN);
                if (valign == null) {
                    AttributeSet rowAttr = getElement().getParentElement().getAttributes();
                    valign = (String) rowAttr.getAttribute(HTML.Attribute.VALIGN);
                }
                if ((valign == null) || valign.equals("middle")) {
                    adjust = (targetSpan - used) / 2;
                } else if (valign.equals("bottom")) {
                    adjust = targetSpan - used;
                }
            }

            // make adjustments.
            if (adjust != 0) {
                for (int i = 0; i < n; i++) {
                    offsets[i] += adjust;
                }
            }
        }

        /**
         * Calculate the requirements needed along the major axis.
         * This is called by the superclass whenever the requirements
         * need to be updated (i.e. a preferenceChanged was messaged
         * through this view).
         * <p>
         * This is implemented to delegate to the superclass, but
         * indicate the maximum size is very large (i.e. the cell
         * is willing to expend to occupy the full height of the row).
         *
         * @param axis the axis being layed out.
         * @param r the requirements to fill in.  If null, a new one
         *  should be allocated.
         */
        protected SizeRequirements calculateMajorAxisRequirements(int axis,
                                                                  SizeRequirements r) {
            SizeRequirements req = super.calculateMajorAxisRequirements(axis, r);
            req.maximum = Integer.MAX_VALUE;
            return req;
        }

        @Override
        protected SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r) {
            SizeRequirements rv = super.calculateMinorAxisRequirements(axis, r);
            //for the cell the minimum should be derived from the child views
            //the parent behaviour is to use CSS for that
            int n = getViewCount();
            int min = 0;
            for (int i = 0; i < n; i++) {
                View v = getView(i);
                min = Math.max((int) v.getMinimumSpan(axis), min);
            }
            rv.minimum = Math.min(rv.minimum, min);
            return rv;
        }
    }


}