root/Source/core/accessibility/AXTable.cpp

DEFINITIONS

1. m_isAXTable
2. init
3. create
4. hasARIARole
5. isAXTable
6. isDataTable
7. isTableExposableThroughAccessibility
8. clearChildren
9. addChildren
10. headerContainer
11. columns
12. rows
13. columnHeaders
14. cells
15. columnCount
16. rowCount
17. tableLevel
18. cellForColumnAndRow
19. roleValue
20. computeAccessibilityIsIgnored
21. title

/*
 * Copyright (C) 2008 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "core/accessibility/AXTable.h"

#include "core/accessibility/AXObjectCache.h"
#include "core/accessibility/AXTableCell.h"
#include "core/accessibility/AXTableColumn.h"
#include "core/accessibility/AXTableRow.h"
#include "core/html/HTMLTableCaptionElement.h"
#include "core/html/HTMLTableCellElement.h"
#include "core/html/HTMLTableColElement.h"
#include "core/html/HTMLTableElement.h"
#include "core/rendering/RenderTableCell.h"

namespace WebCore {

using namespace HTMLNames;

AXTable::AXTable(RenderObject* renderer)
    : AXRenderObject(renderer)
    , m_headerContainer(nullptr)
    , m_isAXTable(true)
{
}

AXTable::~AXTable()
{
}

void AXTable::init()
{
    AXRenderObject::init();
    m_isAXTable = isTableExposableThroughAccessibility();
}

PassRefPtr<AXTable> AXTable::create(RenderObject* renderer)
{
    return adoptRef(new AXTable(renderer));
}

bool AXTable::hasARIARole() const
{
    if (!m_renderer)
        return false;

    AccessibilityRole ariaRole = ariaRoleAttribute();
    if (ariaRole != UnknownRole)
        return true;

    return false;
}

bool AXTable::isAXTable() const
{
    if (!m_renderer)
        return false;

    return m_isAXTable;
}

bool AXTable::isDataTable() const
{
    if (!m_renderer)
        return false;

    // Do not consider it a data table is it has an ARIA role.
    if (hasARIARole())
        return false;

    // When a section of the document is contentEditable, all tables should be
    // treated as data tables, otherwise users may not be able to work with rich
    // text editors that allow creating and editing tables.
    if (node() && node()->rendererIsEditable())
        return true;

    // This employs a heuristic to determine if this table should appear.
    // Only "data" tables should be exposed as tables.
    // Unfortunately, there is no good way to determine the difference
    // between a "layout" table and a "data" table.

    RenderTable* table = toRenderTable(m_renderer);
    Node* tableNode = table->node();
    if (!isHTMLTableElement(tableNode))
        return false;

    // if there is a caption element, summary, THEAD, or TFOOT section, it's most certainly a data table
    HTMLTableElement* tableElement = toHTMLTableElement(tableNode);
    if (!tableElement->summary().isEmpty() || tableElement->tHead() || tableElement->tFoot() || tableElement->caption())
        return true;

    // if someone used "rules" attribute than the table should appear
    if (!tableElement->rules().isEmpty())
        return true;

    // if there's a colgroup or col element, it's probably a data table.
    if (Traversal<HTMLTableColElement>::firstChild(*tableElement))
        return true;

    // go through the cell's and check for tell-tale signs of "data" table status
    // cells have borders, or use attributes like headers, abbr, scope or axis
    table->recalcSectionsIfNeeded();
    RenderTableSection* firstBody = table->firstBody();
    if (!firstBody)
        return false;

    int numCols = firstBody->numColumns();
    int numRows = firstBody->numRows();

    // If there's only one cell, it's not a good AXTable candidate.
    if (numRows == 1 && numCols == 1)
        return false;

    // If there are at least 20 rows, we'll call it a data table.
    if (numRows >= 20)
        return true;

    // Store the background color of the table to check against cell's background colors.
    RenderStyle* tableStyle = table->style();
    if (!tableStyle)
        return false;
    Color tableBGColor = tableStyle->visitedDependentColor(CSSPropertyBackgroundColor);

    // check enough of the cells to find if the table matches our criteria
    // Criteria:
    //   1) must have at least one valid cell (and)
    //   2) at least half of cells have borders (or)
    //   3) at least half of cells have different bg colors than the table, and there is cell spacing
    unsigned validCellCount = 0;
    unsigned borderedCellCount = 0;
    unsigned backgroundDifferenceCellCount = 0;
    unsigned cellsWithTopBorder = 0;
    unsigned cellsWithBottomBorder = 0;
    unsigned cellsWithLeftBorder = 0;
    unsigned cellsWithRightBorder = 0;

    Color alternatingRowColors[5];
    int alternatingRowColorCount = 0;

    int headersInFirstColumnCount = 0;
    for (int row = 0; row < numRows; ++row) {

        int headersInFirstRowCount = 0;
        for (int col = 0; col < numCols; ++col) {
            RenderTableCell* cell = firstBody->primaryCellAt(row, col);
            if (!cell)
                continue;
            Node* cellNode = cell->node();
            if (!cellNode)
                continue;

            if (cell->width() < 1 || cell->height() < 1)
                continue;

            validCellCount++;

            bool isTHCell = cellNode->hasTagName(thTag);
            // If the first row is comprised of all <th> tags, assume it is a data table.
            if (!row && isTHCell)
                headersInFirstRowCount++;

            // If the first column is comprised of all <th> tags, assume it is a data table.
            if (!col && isTHCell)
                headersInFirstColumnCount++;

            // in this case, the developer explicitly assigned a "data" table attribute
            if (isHTMLTableCellElement(*cellNode)) {
                HTMLTableCellElement& cellElement = toHTMLTableCellElement(*cellNode);
                if (!cellElement.headers().isEmpty() || !cellElement.abbr().isEmpty()
                    || !cellElement.axis().isEmpty() || !cellElement.scope().isEmpty())
                    return true;
            }

            RenderStyle* renderStyle = cell->style();
            if (!renderStyle)
                continue;

            // If the empty-cells style is set, we'll call it a data table.
            if (renderStyle->emptyCells() == HIDE)
                return true;

            // If a cell has matching bordered sides, call it a (fully) bordered cell.
            if ((cell->borderTop() > 0 && cell->borderBottom() > 0)
                || (cell->borderLeft() > 0 && cell->borderRight() > 0))
                borderedCellCount++;

            // Also keep track of each individual border, so we can catch tables where most
            // cells have a bottom border, for example.
            if (cell->borderTop() > 0)
                cellsWithTopBorder++;
            if (cell->borderBottom() > 0)
                cellsWithBottomBorder++;
            if (cell->borderLeft() > 0)
                cellsWithLeftBorder++;
            if (cell->borderRight() > 0)
                cellsWithRightBorder++;

            // If the cell has a different color from the table and there is cell spacing,
            // then it is probably a data table cell (spacing and colors take the place of borders).
            Color cellColor = renderStyle->visitedDependentColor(CSSPropertyBackgroundColor);
            if (table->hBorderSpacing() > 0 && table->vBorderSpacing() > 0
                && tableBGColor != cellColor && cellColor.alpha() != 1)
                backgroundDifferenceCellCount++;

            // If we've found 10 "good" cells, we don't need to keep searching.
            if (borderedCellCount >= 10 || backgroundDifferenceCellCount >= 10)
                return true;

            // For the first 5 rows, cache the background color so we can check if this table has zebra-striped rows.
            if (row < 5 && row == alternatingRowColorCount) {
                RenderObject* renderRow = cell->parent();
                if (!renderRow || !renderRow->isBoxModelObject() || !toRenderBoxModelObject(renderRow)->isTableRow())
                    continue;
                RenderStyle* rowRenderStyle = renderRow->style();
                if (!rowRenderStyle)
                    continue;
                Color rowColor = rowRenderStyle->visitedDependentColor(CSSPropertyBackgroundColor);
                alternatingRowColors[alternatingRowColorCount] = rowColor;
                alternatingRowColorCount++;
            }
        }

        if (!row && headersInFirstRowCount == numCols && numCols > 1)
            return true;
    }

    if (headersInFirstColumnCount == numRows && numRows > 1)
        return true;

    // if there is less than two valid cells, it's not a data table
    if (validCellCount <= 1)
        return false;

    // half of the cells had borders, it's a data table
    unsigned neededCellCount = validCellCount / 2;
    if (borderedCellCount >= neededCellCount
        || cellsWithTopBorder >= neededCellCount
        || cellsWithBottomBorder >= neededCellCount
        || cellsWithLeftBorder >= neededCellCount
        || cellsWithRightBorder >= neededCellCount)
        return true;

    // half had different background colors, it's a data table
    if (backgroundDifferenceCellCount >= neededCellCount)
        return true;

    // Check if there is an alternating row background color indicating a zebra striped style pattern.
    if (alternatingRowColorCount > 2) {
        Color firstColor = alternatingRowColors[0];
        for (int k = 1; k < alternatingRowColorCount; k++) {
            // If an odd row was the same color as the first row, its not alternating.
            if (k % 2 == 1 && alternatingRowColors[k] == firstColor)
                return false;
            // If an even row is not the same as the first row, its not alternating.
            if (!(k % 2) && alternatingRowColors[k] != firstColor)
                return false;
        }
        return true;
    }

    return false;
}

bool AXTable::isTableExposableThroughAccessibility() const
{
    // The following is a heuristic used to determine if a
    // <table> should be exposed as an AXTable. The goal
    // is to only show "data" tables.

    if (!m_renderer)
        return false;

    // If the developer assigned an aria role to this, then we
    // shouldn't expose it as a table, unless, of course, the aria
    // role is a table.
    if (hasARIARole())
        return false;

    return isDataTable();
}

void AXTable::clearChildren()
{
    AXRenderObject::clearChildren();
    m_rows.clear();
    m_columns.clear();

    if (m_headerContainer) {
        m_headerContainer->detachFromParent();
        m_headerContainer = nullptr;
    }
}

void AXTable::addChildren()
{
    if (!isAXTable()) {
        AXRenderObject::addChildren();
        return;
    }

    ASSERT(!m_haveChildren);

    m_haveChildren = true;
    if (!m_renderer || !m_renderer->isTable())
        return;

    RenderTable* table = toRenderTable(m_renderer);
    AXObjectCache* axCache = m_renderer->document().axObjectCache();

    // Go through all the available sections to pull out the rows and add them as children.
    table->recalcSectionsIfNeeded();
    RenderTableSection* tableSection = table->topSection();
    if (!tableSection)
        return;

    RenderTableSection* initialTableSection = tableSection;
    while (tableSection) {

        HashSet<AXObject*> appendedRows;
        unsigned numRows = tableSection->numRows();
        for (unsigned rowIndex = 0; rowIndex < numRows; ++rowIndex) {

            RenderTableRow* renderRow = tableSection->rowRendererAt(rowIndex);
            if (!renderRow)
                continue;

            AXObject* rowObject = axCache->getOrCreate(renderRow);
            if (!rowObject->isTableRow())
                continue;

            AXTableRow* row = toAXTableRow(rowObject);
            // We need to check every cell for a new row, because cell spans
            // can cause us to miss rows if we just check the first column.
            if (appendedRows.contains(row))
                continue;

            row->setRowIndex(static_cast<int>(m_rows.size()));
            m_rows.append(row);
            if (!row->accessibilityIsIgnored())
                m_children.append(row);
            appendedRows.add(row);
        }

        tableSection = table->sectionBelow(tableSection, SkipEmptySections);
    }

    // make the columns based on the number of columns in the first body
    unsigned length = initialTableSection->numColumns();
    for (unsigned i = 0; i < length; ++i) {
        AXTableColumn* column = toAXTableColumn(axCache->getOrCreate(ColumnRole));
        column->setColumnIndex((int)i);
        column->setParent(this);
        m_columns.append(column);
        if (!column->accessibilityIsIgnored())
            m_children.append(column);
    }

    AXObject* headerContainerObject = headerContainer();
    if (headerContainerObject && !headerContainerObject->accessibilityIsIgnored())
        m_children.append(headerContainerObject);
}

AXObject* AXTable::headerContainer()
{
    if (m_headerContainer)
        return m_headerContainer.get();

    AXMockObject* tableHeader = toAXMockObject(axObjectCache()->getOrCreate(TableHeaderContainerRole));
    tableHeader->setParent(this);

    m_headerContainer = tableHeader;
    return m_headerContainer.get();
}

AXObject::AccessibilityChildrenVector& AXTable::columns()
{
    updateChildrenIfNecessary();

    return m_columns;
}

AXObject::AccessibilityChildrenVector& AXTable::rows()
{
    updateChildrenIfNecessary();

    return m_rows;
}

void AXTable::columnHeaders(AccessibilityChildrenVector& headers)
{
    if (!m_renderer)
        return;

    updateChildrenIfNecessary();

    unsigned colCount = m_columns.size();
    for (unsigned k = 0; k < colCount; ++k) {
        AXObject* header = toAXTableColumn(m_columns[k].get())->headerObject();
        if (!header)
            continue;
        headers.append(header);
    }
}

void AXTable::cells(AXObject::AccessibilityChildrenVector& cells)
{
    if (!m_renderer)
        return;

    updateChildrenIfNecessary();

    int numRows = m_rows.size();
    for (int row = 0; row < numRows; ++row) {
        AccessibilityChildrenVector rowChildren = m_rows[row]->children();
        cells.appendVector(rowChildren);
    }
}

unsigned AXTable::columnCount()
{
    updateChildrenIfNecessary();

    return m_columns.size();
}

unsigned AXTable::rowCount()
{
    updateChildrenIfNecessary();

    return m_rows.size();
}

int AXTable::tableLevel() const
{
    int level = 0;
    for (AXObject* obj = static_cast<AXObject*>(const_cast<AXTable*>(this)); obj; obj = obj->parentObject()) {
        if (obj->isAXTable())
            ++level;
    }

    return level;
}

AXTableCell* AXTable::cellForColumnAndRow(unsigned column, unsigned row)
{
    updateChildrenIfNecessary();
    if (column >= columnCount() || row >= rowCount())
        return 0;

    // Iterate backwards through the rows in case the desired cell has a rowspan and exists in a previous row.
    for (unsigned rowIndexCounter = row + 1; rowIndexCounter > 0; --rowIndexCounter) {
        unsigned rowIndex = rowIndexCounter - 1;
        AccessibilityChildrenVector children = m_rows[rowIndex]->children();
        // Since some cells may have colspans, we have to check the actual range of each
        // cell to determine which is the right one.
        for (unsigned colIndexCounter = std::min(static_cast<unsigned>(children.size()), column + 1); colIndexCounter > 0; --colIndexCounter) {
            unsigned colIndex = colIndexCounter - 1;
            AXObject* child = children[colIndex].get();
            ASSERT(child->isTableCell());
            if (!child->isTableCell())
                continue;

            pair<unsigned, unsigned> columnRange;
            pair<unsigned, unsigned> rowRange;
            AXTableCell* tableCellChild = toAXTableCell(child);
            tableCellChild->columnIndexRange(columnRange);
            tableCellChild->rowIndexRange(rowRange);

            if ((column >= columnRange.first && column < (columnRange.first + columnRange.second))
                && (row >= rowRange.first && row < (rowRange.first + rowRange.second)))
                return tableCellChild;
        }
    }

    return 0;
}

AccessibilityRole AXTable::roleValue() const
{
    if (!isAXTable())
        return AXRenderObject::roleValue();

    return TableRole;
}

bool AXTable::computeAccessibilityIsIgnored() const
{
    AXObjectInclusion decision = defaultObjectInclusion();
    if (decision == IncludeObject)
        return false;
    if (decision == IgnoreObject)
        return true;

    if (!isAXTable())
        return AXRenderObject::computeAccessibilityIsIgnored();

    return false;
}

String AXTable::title() const
{
    if (!isAXTable())
        return AXRenderObject::title();

    String title;
    if (!m_renderer)
        return title;

    // see if there is a caption
    Node* tableElement = m_renderer->node();
    if (isHTMLTableElement(tableElement)) {
        HTMLTableCaptionElement* caption = toHTMLTableElement(tableElement)->caption();
        if (caption)
            title = caption->innerText();
    }

    // try the standard
    if (title.isEmpty())
        title = AXRenderObject::title();

    return title;
}

} // namespace WebCore