root/Source/core/editing/VisiblePosition.cpp

DEFINITIONS

1. init
2. next
3. previous
4. leftVisuallyDistinctCandidate
5. left
6. rightVisuallyDistinctCandidate
7. right
8. honorEditingBoundaryAtOrBefore
9. honorEditingBoundaryAtOrAfter
10. skipToStartOfEditingBoundary
11. skipToEndOfEditingBoundary
12. canonicalizeCandidate
13. canonicalPosition
14. characterAfter
15. localCaretRect
16. absoluteCaretBounds
17. lineDirectionPointForBlockDirectionNavigation
18. debugPosition
19. formatForDebugger
20. showTreeForThis
21. makeRange
22. startVisiblePosition
23. setStart
24. setEnd
25. enclosingBlockFlowElement
26. isFirstVisiblePositionInNode
27. isLastVisiblePositionInNode
28. showTree
29. showTree

/*
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 * Portions Copyright (c) 2011 Motorola Mobility, 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.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``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 COMPUTER, INC. OR
 * 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/editing/VisiblePosition.h"

#include "HTMLNames.h"
#include "bindings/v8/ExceptionState.h"
#include "core/dom/Document.h"
#include "core/dom/Range.h"
#include "core/dom/Text.h"
#include "core/editing/VisibleUnits.h"
#include "core/editing/htmlediting.h"
#include "core/html/HTMLElement.h"
#include "core/rendering/RenderBlock.h"
#include "core/rendering/RootInlineBox.h"
#include "platform/geometry/FloatQuad.h"
#include "wtf/text/CString.h"

#ifndef NDEBUG
#include <stdio.h>
#endif

namespace WebCore {

using namespace HTMLNames;

VisiblePosition::VisiblePosition(const Position &pos, EAffinity affinity)
{
    init(pos, affinity);
}

VisiblePosition::VisiblePosition(const PositionWithAffinity& positionWithAffinity)
{
    init(positionWithAffinity.position(), positionWithAffinity.affinity());
}

void VisiblePosition::init(const Position& position, EAffinity affinity)
{
    m_affinity = affinity;

    m_deepPosition = canonicalPosition(position);

    // When not at a line wrap, make sure to end up with DOWNSTREAM affinity.
    if (m_affinity == UPSTREAM && (isNull() || inSameLine(VisiblePosition(position, DOWNSTREAM), *this)))
        m_affinity = DOWNSTREAM;
}

VisiblePosition VisiblePosition::next(EditingBoundaryCrossingRule rule) const
{
    VisiblePosition next(nextVisuallyDistinctCandidate(m_deepPosition), m_affinity);

    switch (rule) {
    case CanCrossEditingBoundary:
        return next;
    case CannotCrossEditingBoundary:
        return honorEditingBoundaryAtOrAfter(next);
    case CanSkipOverEditingBoundary:
        return skipToEndOfEditingBoundary(next);
    }
    ASSERT_NOT_REACHED();
    return honorEditingBoundaryAtOrAfter(next);
}

VisiblePosition VisiblePosition::previous(EditingBoundaryCrossingRule rule) const
{
    Position pos = previousVisuallyDistinctCandidate(m_deepPosition);

    // return null visible position if there is no previous visible position
    if (pos.atStartOfTree())
        return VisiblePosition();

    VisiblePosition prev = VisiblePosition(pos, DOWNSTREAM);
    ASSERT(prev != *this);

#ifndef NDEBUG
    // we should always be able to make the affinity DOWNSTREAM, because going previous from an
    // UPSTREAM position can never yield another UPSTREAM position (unless line wrap length is 0!).
    if (prev.isNotNull() && m_affinity == UPSTREAM) {
        VisiblePosition temp = prev;
        temp.setAffinity(UPSTREAM);
        ASSERT(inSameLine(temp, prev));
    }
#endif

    switch (rule) {
    case CanCrossEditingBoundary:
        return prev;
    case CannotCrossEditingBoundary:
        return honorEditingBoundaryAtOrBefore(prev);
    case CanSkipOverEditingBoundary:
        return skipToStartOfEditingBoundary(prev);
    }

    ASSERT_NOT_REACHED();
    return honorEditingBoundaryAtOrBefore(prev);
}

Position VisiblePosition::leftVisuallyDistinctCandidate() const
{
    Position p = m_deepPosition;
    if (p.isNull())
        return Position();

    Position downstreamStart = p.downstream();
    TextDirection primaryDirection = p.primaryDirection();

    while (true) {
        InlineBox* box;
        int offset;
        p.getInlineBoxAndOffset(m_affinity, primaryDirection, box, offset);
        if (!box)
            return primaryDirection == LTR ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);

        RenderObject* renderer = &box->renderer();

        while (true) {
            if ((renderer->isReplaced() || renderer->isBR()) && offset == box->caretRightmostOffset())
                return box->isLeftToRightDirection() ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);

            if (!renderer->node()) {
                box = box->prevLeafChild();
                if (!box)
                    return primaryDirection == LTR ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);
                renderer = &box->renderer();
                offset = box->caretRightmostOffset();
                continue;
            }

            offset = box->isLeftToRightDirection() ? renderer->previousOffset(offset) : renderer->nextOffset(offset);

            int caretMinOffset = box->caretMinOffset();
            int caretMaxOffset = box->caretMaxOffset();

            if (offset > caretMinOffset && offset < caretMaxOffset)
                break;

            if (box->isLeftToRightDirection() ? offset < caretMinOffset : offset > caretMaxOffset) {
                // Overshot to the left.
                InlineBox* prevBox = box->prevLeafChildIgnoringLineBreak();
                if (!prevBox) {
                    Position positionOnLeft = primaryDirection == LTR ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);
                    if (positionOnLeft.isNull())
                        return Position();

                    InlineBox* boxOnLeft;
                    int offsetOnLeft;
                    positionOnLeft.getInlineBoxAndOffset(m_affinity, primaryDirection, boxOnLeft, offsetOnLeft);
                    if (boxOnLeft && boxOnLeft->root() == box->root())
                        return Position();
                    return positionOnLeft;
                }

                // Reposition at the other logical position corresponding to our edge's visual position and go for another round.
                box = prevBox;
                renderer = &box->renderer();
                offset = prevBox->caretRightmostOffset();
                continue;
            }

            ASSERT(offset == box->caretLeftmostOffset());

            unsigned char level = box->bidiLevel();
            InlineBox* prevBox = box->prevLeafChild();

            if (box->direction() == primaryDirection) {
                if (!prevBox) {
                    InlineBox* logicalStart = 0;
                    if (primaryDirection == LTR ? box->root().getLogicalStartBoxWithNode(logicalStart) : box->root().getLogicalEndBoxWithNode(logicalStart)) {
                        box = logicalStart;
                        renderer = &box->renderer();
                        offset = primaryDirection == LTR ? box->caretMinOffset() : box->caretMaxOffset();
                    }
                    break;
                }
                if (prevBox->bidiLevel() >= level)
                    break;

                level = prevBox->bidiLevel();

                InlineBox* nextBox = box;
                do {
                    nextBox = nextBox->nextLeafChild();
                } while (nextBox && nextBox->bidiLevel() > level);

                if (nextBox && nextBox->bidiLevel() == level)
                    break;

                box = prevBox;
                renderer = &box->renderer();
                offset = box->caretRightmostOffset();
                if (box->direction() == primaryDirection)
                    break;
                continue;
            }

            while (prevBox && !prevBox->renderer().node())
                prevBox = prevBox->prevLeafChild();

            if (prevBox) {
                box = prevBox;
                renderer = &box->renderer();
                offset = box->caretRightmostOffset();
                if (box->bidiLevel() > level) {
                    do {
                        prevBox = prevBox->prevLeafChild();
                    } while (prevBox && prevBox->bidiLevel() > level);

                    if (!prevBox || prevBox->bidiLevel() < level)
                        continue;
                }
            } else {
                // Trailing edge of a secondary run. Set to the leading edge of the entire run.
                while (true) {
                    while (InlineBox* nextBox = box->nextLeafChild()) {
                        if (nextBox->bidiLevel() < level)
                            break;
                        box = nextBox;
                    }
                    if (box->bidiLevel() == level)
                        break;
                    level = box->bidiLevel();
                    while (InlineBox* prevBox = box->prevLeafChild()) {
                        if (prevBox->bidiLevel() < level)
                            break;
                        box = prevBox;
                    }
                    if (box->bidiLevel() == level)
                        break;
                    level = box->bidiLevel();
                }
                renderer = &box->renderer();
                offset = primaryDirection == LTR ? box->caretMinOffset() : box->caretMaxOffset();
            }
            break;
        }

        p = createLegacyEditingPosition(renderer->node(), offset);

        if ((p.isCandidate() && p.downstream() != downstreamStart) || p.atStartOfTree() || p.atEndOfTree())
            return p;

        ASSERT(p != m_deepPosition);
    }
}

VisiblePosition VisiblePosition::left(bool stayInEditableContent) const
{
    Position pos = leftVisuallyDistinctCandidate();
    // FIXME: Why can't we move left from the last position in a tree?
    if (pos.atStartOfTree() || pos.atEndOfTree())
        return VisiblePosition();

    VisiblePosition left = VisiblePosition(pos, DOWNSTREAM);
    ASSERT(left != *this);

    if (!stayInEditableContent)
        return left;

    // FIXME: This may need to do something different from "before".
    return honorEditingBoundaryAtOrBefore(left);
}

Position VisiblePosition::rightVisuallyDistinctCandidate() const
{
    Position p = m_deepPosition;
    if (p.isNull())
        return Position();

    Position downstreamStart = p.downstream();
    TextDirection primaryDirection = p.primaryDirection();

    while (true) {
        InlineBox* box;
        int offset;
        p.getInlineBoxAndOffset(m_affinity, primaryDirection, box, offset);
        if (!box)
            return primaryDirection == LTR ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);

        RenderObject* renderer = &box->renderer();

        while (true) {
            if ((renderer->isReplaced() || renderer->isBR()) && offset == box->caretLeftmostOffset())
                return box->isLeftToRightDirection() ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);

            if (!renderer->node()) {
                box = box->nextLeafChild();
                if (!box)
                    return primaryDirection == LTR ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);
                renderer = &box->renderer();
                offset = box->caretLeftmostOffset();
                continue;
            }

            offset = box->isLeftToRightDirection() ? renderer->nextOffset(offset) : renderer->previousOffset(offset);

            int caretMinOffset = box->caretMinOffset();
            int caretMaxOffset = box->caretMaxOffset();

            if (offset > caretMinOffset && offset < caretMaxOffset)
                break;

            if (box->isLeftToRightDirection() ? offset > caretMaxOffset : offset < caretMinOffset) {
                // Overshot to the right.
                InlineBox* nextBox = box->nextLeafChildIgnoringLineBreak();
                if (!nextBox) {
                    Position positionOnRight = primaryDirection == LTR ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);
                    if (positionOnRight.isNull())
                        return Position();

                    InlineBox* boxOnRight;
                    int offsetOnRight;
                    positionOnRight.getInlineBoxAndOffset(m_affinity, primaryDirection, boxOnRight, offsetOnRight);
                    if (boxOnRight && boxOnRight->root() == box->root())
                        return Position();
                    return positionOnRight;
                }

                // Reposition at the other logical position corresponding to our edge's visual position and go for another round.
                box = nextBox;
                renderer = &box->renderer();
                offset = nextBox->caretLeftmostOffset();
                continue;
            }

            ASSERT(offset == box->caretRightmostOffset());

            unsigned char level = box->bidiLevel();
            InlineBox* nextBox = box->nextLeafChild();

            if (box->direction() == primaryDirection) {
                if (!nextBox) {
                    InlineBox* logicalEnd = 0;
                    if (primaryDirection == LTR ? box->root().getLogicalEndBoxWithNode(logicalEnd) : box->root().getLogicalStartBoxWithNode(logicalEnd)) {
                        box = logicalEnd;
                        renderer = &box->renderer();
                        offset = primaryDirection == LTR ? box->caretMaxOffset() : box->caretMinOffset();
                    }
                    break;
                }

                if (nextBox->bidiLevel() >= level)
                    break;

                level = nextBox->bidiLevel();

                InlineBox* prevBox = box;
                do {
                    prevBox = prevBox->prevLeafChild();
                } while (prevBox && prevBox->bidiLevel() > level);

                if (prevBox && prevBox->bidiLevel() == level)   // For example, abc FED 123 ^ CBA
                    break;

                // For example, abc 123 ^ CBA or 123 ^ CBA abc
                box = nextBox;
                renderer = &box->renderer();
                offset = box->caretLeftmostOffset();
                if (box->direction() == primaryDirection)
                    break;
                continue;
            }

            while (nextBox && !nextBox->renderer().node())
                nextBox = nextBox->nextLeafChild();

            if (nextBox) {
                box = nextBox;
                renderer = &box->renderer();
                offset = box->caretLeftmostOffset();

                if (box->bidiLevel() > level) {
                    do {
                        nextBox = nextBox->nextLeafChild();
                    } while (nextBox && nextBox->bidiLevel() > level);

                    if (!nextBox || nextBox->bidiLevel() < level)
                        continue;
                }
            } else {
                // Trailing edge of a secondary run. Set to the leading edge of the entire run.
                while (true) {
                    while (InlineBox* prevBox = box->prevLeafChild()) {
                        if (prevBox->bidiLevel() < level)
                            break;
                        box = prevBox;
                    }
                    if (box->bidiLevel() == level)
                        break;
                    level = box->bidiLevel();
                    while (InlineBox* nextBox = box->nextLeafChild()) {
                        if (nextBox->bidiLevel() < level)
                            break;
                        box = nextBox;
                    }
                    if (box->bidiLevel() == level)
                        break;
                    level = box->bidiLevel();
                }
                renderer = &box->renderer();
                offset = primaryDirection == LTR ? box->caretMaxOffset() : box->caretMinOffset();
            }
            break;
        }

        p = createLegacyEditingPosition(renderer->node(), offset);

        if ((p.isCandidate() && p.downstream() != downstreamStart) || p.atStartOfTree() || p.atEndOfTree())
            return p;

        ASSERT(p != m_deepPosition);
    }
}

VisiblePosition VisiblePosition::right(bool stayInEditableContent) const
{
    Position pos = rightVisuallyDistinctCandidate();
    // FIXME: Why can't we move left from the last position in a tree?
    if (pos.atStartOfTree() || pos.atEndOfTree())
        return VisiblePosition();

    VisiblePosition right = VisiblePosition(pos, DOWNSTREAM);
    ASSERT(right != *this);

    if (!stayInEditableContent)
        return right;

    // FIXME: This may need to do something different from "after".
    return honorEditingBoundaryAtOrAfter(right);
}

VisiblePosition VisiblePosition::honorEditingBoundaryAtOrBefore(const VisiblePosition &pos) const
{
    if (pos.isNull())
        return pos;

    Node* highestRoot = highestEditableRoot(deepEquivalent());

    // Return empty position if pos is not somewhere inside the editable region containing this position
    if (highestRoot && !pos.deepEquivalent().deprecatedNode()->isDescendantOf(highestRoot))
        return VisiblePosition();

    // Return pos itself if the two are from the very same editable region, or both are non-editable
    // FIXME: In the non-editable case, just because the new position is non-editable doesn't mean movement
    // to it is allowed.  VisibleSelection::adjustForEditableContent has this problem too.
    if (highestEditableRoot(pos.deepEquivalent()) == highestRoot)
        return pos;

    // Return empty position if this position is non-editable, but pos is editable
    // FIXME: Move to the previous non-editable region.
    if (!highestRoot)
        return VisiblePosition();

    // Return the last position before pos that is in the same editable region as this position
    return lastEditablePositionBeforePositionInRoot(pos.deepEquivalent(), highestRoot);
}

VisiblePosition VisiblePosition::honorEditingBoundaryAtOrAfter(const VisiblePosition &pos) const
{
    if (pos.isNull())
        return pos;

    Node* highestRoot = highestEditableRoot(deepEquivalent());

    // Return empty position if pos is not somewhere inside the editable region containing this position
    if (highestRoot && !pos.deepEquivalent().deprecatedNode()->isDescendantOf(highestRoot))
        return VisiblePosition();

    // Return pos itself if the two are from the very same editable region, or both are non-editable
    // FIXME: In the non-editable case, just because the new position is non-editable doesn't mean movement
    // to it is allowed.  VisibleSelection::adjustForEditableContent has this problem too.
    if (highestEditableRoot(pos.deepEquivalent()) == highestRoot)
        return pos;

    // Return empty position if this position is non-editable, but pos is editable
    // FIXME: Move to the next non-editable region.
    if (!highestRoot)
        return VisiblePosition();

    // Return the next position after pos that is in the same editable region as this position
    return firstEditablePositionAfterPositionInRoot(pos.deepEquivalent(), highestRoot);
}

VisiblePosition VisiblePosition::skipToStartOfEditingBoundary(const VisiblePosition &pos) const
{
    if (pos.isNull())
        return pos;

    Node* highestRoot = highestEditableRoot(deepEquivalent());
    Node* highestRootOfPos = highestEditableRoot(pos.deepEquivalent());

    // Return pos itself if the two are from the very same editable region, or both are non-editable.
    if (highestRootOfPos == highestRoot)
        return pos;

    // If |pos| has an editable root, skip to the start
    if (highestRootOfPos)
        return VisiblePosition(previousVisuallyDistinctCandidate(Position(highestRootOfPos, Position::PositionIsBeforeAnchor).parentAnchoredEquivalent()));

    // That must mean that |pos| is not editable. Return the last position before pos that is in the same editable region as this position
    return lastEditablePositionBeforePositionInRoot(pos.deepEquivalent(), highestRoot);
}

VisiblePosition VisiblePosition::skipToEndOfEditingBoundary(const VisiblePosition &pos) const
{
    if (pos.isNull())
        return pos;

    Node* highestRoot = highestEditableRoot(deepEquivalent());
    Node* highestRootOfPos = highestEditableRoot(pos.deepEquivalent());

    // Return pos itself if the two are from the very same editable region, or both are non-editable.
    if (highestRootOfPos == highestRoot)
        return pos;

    // If |pos| has an editable root, skip to the end
    if (highestRootOfPos)
        return VisiblePosition(Position(highestRootOfPos, Position::PositionIsAfterAnchor).parentAnchoredEquivalent());

    // That must mean that |pos| is not editable. Return the next position after pos that is in the same editable region as this position
    return firstEditablePositionAfterPositionInRoot(pos.deepEquivalent(), highestRoot);
}

static Position canonicalizeCandidate(const Position& candidate)
{
    if (candidate.isNull())
        return Position();
    ASSERT(candidate.isCandidate());
    Position upstream = candidate.upstream();
    if (upstream.isCandidate())
        return upstream;
    return candidate;
}

Position VisiblePosition::canonicalPosition(const Position& passedPosition)
{
    // The updateLayout call below can do so much that even the position passed
    // in to us might get changed as a side effect. Specifically, there are code
    // paths that pass selection endpoints, and updateLayout can change the selection.
    Position position = passedPosition;

    // FIXME (9535):  Canonicalizing to the leftmost candidate means that if we're at a line wrap, we will
    // ask renderers to paint downstream carets for other renderers.
    // To fix this, we need to either a) add code to all paintCarets to pass the responsibility off to
    // the appropriate renderer for VisiblePosition's like these, or b) canonicalize to the rightmost candidate
    // unless the affinity is upstream.
    if (position.isNull())
        return Position();

    ASSERT(position.document());
    position.document()->updateLayoutIgnorePendingStylesheets();

    Node* node = position.containerNode();

    Position candidate = position.upstream();
    if (candidate.isCandidate())
        return candidate;
    candidate = position.downstream();
    if (candidate.isCandidate())
        return candidate;

    // When neither upstream or downstream gets us to a candidate (upstream/downstream won't leave
    // blocks or enter new ones), we search forward and backward until we find one.
    Position next = canonicalizeCandidate(nextCandidate(position));
    Position prev = canonicalizeCandidate(previousCandidate(position));
    Node* nextNode = next.deprecatedNode();
    Node* prevNode = prev.deprecatedNode();

    // The new position must be in the same editable element. Enforce that first.
    // Unless the descent is from a non-editable html element to an editable body.
    if (isHTMLHtmlElement(node) && !node->rendererIsEditable() && node->document().body() && node->document().body()->rendererIsEditable())
        return next.isNotNull() ? next : prev;

    Node* editingRoot = editableRootForPosition(position);

    // If the html element is editable, descending into its body will look like a descent
    // from non-editable to editable content since rootEditableElement() always stops at the body.
    if (isHTMLHtmlElement(editingRoot) || position.deprecatedNode()->isDocumentNode())
        return next.isNotNull() ? next : prev;

    bool prevIsInSameEditableElement = prevNode && editableRootForPosition(prev) == editingRoot;
    bool nextIsInSameEditableElement = nextNode && editableRootForPosition(next) == editingRoot;
    if (prevIsInSameEditableElement && !nextIsInSameEditableElement)
        return prev;

    if (nextIsInSameEditableElement && !prevIsInSameEditableElement)
        return next;

    if (!nextIsInSameEditableElement && !prevIsInSameEditableElement)
        return Position();

    // The new position should be in the same block flow element. Favor that.
    Node* originalBlock = node ? node->enclosingBlockFlowElement() : 0;
    bool nextIsOutsideOriginalBlock = !nextNode->isDescendantOf(originalBlock) && nextNode != originalBlock;
    bool prevIsOutsideOriginalBlock = !prevNode->isDescendantOf(originalBlock) && prevNode != originalBlock;
    if (nextIsOutsideOriginalBlock && !prevIsOutsideOriginalBlock)
        return prev;

    return next;
}

UChar32 VisiblePosition::characterAfter() const
{
    // We canonicalize to the first of two equivalent candidates, but the second of the two candidates
    // is the one that will be inside the text node containing the character after this visible position.
    Position pos = m_deepPosition.downstream();
    if (!pos.containerNode() || !pos.containerNode()->isTextNode())
        return 0;
    switch (pos.anchorType()) {
    case Position::PositionIsAfterChildren:
    case Position::PositionIsAfterAnchor:
    case Position::PositionIsBeforeAnchor:
    case Position::PositionIsBeforeChildren:
        return 0;
    case Position::PositionIsOffsetInAnchor:
        break;
    }
    unsigned offset = static_cast<unsigned>(pos.offsetInContainerNode());
    Text* textNode = pos.containerText();
    unsigned length = textNode->length();
    if (offset >= length)
        return 0;

    return textNode->data().characterStartingAt(offset);
}

LayoutRect VisiblePosition::localCaretRect(RenderObject*& renderer) const
{
    if (m_deepPosition.isNull()) {
        renderer = 0;
        return IntRect();
    }
    Node* node = m_deepPosition.anchorNode();

    renderer = node->renderer();
    if (!renderer)
        return LayoutRect();

    InlineBox* inlineBox;
    int caretOffset;
    getInlineBoxAndOffset(inlineBox, caretOffset);

    if (inlineBox)
        renderer = &inlineBox->renderer();

    return renderer->localCaretRect(inlineBox, caretOffset);
}

IntRect VisiblePosition::absoluteCaretBounds() const
{
    RenderObject* renderer;
    LayoutRect localRect = localCaretRect(renderer);
    if (localRect.isEmpty() || !renderer)
        return IntRect();

    return renderer->localToAbsoluteQuad(FloatRect(localRect)).enclosingBoundingBox();
}

int VisiblePosition::lineDirectionPointForBlockDirectionNavigation() const
{
    RenderObject* renderer;
    LayoutRect localRect = localCaretRect(renderer);
    if (localRect.isEmpty() || !renderer)
        return 0;

    // This ignores transforms on purpose, for now. Vertical navigation is done
    // without consulting transforms, so that 'up' in transformed text is 'up'
    // relative to the text, not absolute 'up'.
    FloatPoint caretPoint = renderer->localToAbsolute(localRect.location());
    RenderObject* containingBlock = renderer->containingBlock();
    if (!containingBlock)
        containingBlock = renderer; // Just use ourselves to determine the writing mode if we have no containing block.
    return containingBlock->isHorizontalWritingMode() ? caretPoint.x() : caretPoint.y();
}

#ifndef NDEBUG

void VisiblePosition::debugPosition(const char* msg) const
{
    if (isNull())
        fprintf(stderr, "Position [%s]: null\n", msg);
    else {
        fprintf(stderr, "Position [%s]: %s, ", msg, m_deepPosition.deprecatedNode()->nodeName().utf8().data());
        m_deepPosition.showAnchorTypeAndOffset();
    }
}

void VisiblePosition::formatForDebugger(char* buffer, unsigned length) const
{
    m_deepPosition.formatForDebugger(buffer, length);
}

void VisiblePosition::showTreeForThis() const
{
    m_deepPosition.showTreeForThis();
}

#endif

PassRefPtrWillBeRawPtr<Range> makeRange(const VisiblePosition &start, const VisiblePosition &end)
{
    if (start.isNull() || end.isNull())
        return nullptr;

    Position s = start.deepEquivalent().parentAnchoredEquivalent();
    Position e = end.deepEquivalent().parentAnchoredEquivalent();
    if (s.isNull() || e.isNull())
        return nullptr;

    return Range::create(s.containerNode()->document(), s.containerNode(), s.offsetInContainerNode(), e.containerNode(), e.offsetInContainerNode());
}

VisiblePosition startVisiblePosition(const Range *r, EAffinity affinity)
{
    return VisiblePosition(r->startPosition(), affinity);
}

bool setStart(Range *r, const VisiblePosition &visiblePosition)
{
    if (!r)
        return false;
    Position p = visiblePosition.deepEquivalent().parentAnchoredEquivalent();
    TrackExceptionState exceptionState;
    r->setStart(p.containerNode(), p.offsetInContainerNode(), exceptionState);
    return !exceptionState.hadException();
}

bool setEnd(Range *r, const VisiblePosition &visiblePosition)
{
    if (!r)
        return false;
    Position p = visiblePosition.deepEquivalent().parentAnchoredEquivalent();
    TrackExceptionState exceptionState;
    r->setEnd(p.containerNode(), p.offsetInContainerNode(), exceptionState);
    return !exceptionState.hadException();
}

Element* enclosingBlockFlowElement(const VisiblePosition &visiblePosition)
{
    if (visiblePosition.isNull())
        return NULL;

    return visiblePosition.deepEquivalent().deprecatedNode()->enclosingBlockFlowElement();
}

bool isFirstVisiblePositionInNode(const VisiblePosition &visiblePosition, const Node *node)
{
    if (visiblePosition.isNull())
        return false;

    if (!visiblePosition.deepEquivalent().containerNode()->isDescendantOf(node))
        return false;

    VisiblePosition previous = visiblePosition.previous();
    return previous.isNull() || !previous.deepEquivalent().deprecatedNode()->isDescendantOf(node);
}

bool isLastVisiblePositionInNode(const VisiblePosition &visiblePosition, const Node *node)
{
    if (visiblePosition.isNull())
        return false;

    if (!visiblePosition.deepEquivalent().containerNode()->isDescendantOf(node))
        return false;

    VisiblePosition next = visiblePosition.next();
    return next.isNull() || !next.deepEquivalent().deprecatedNode()->isDescendantOf(node);
}

}  // namespace WebCore

#ifndef NDEBUG

void showTree(const WebCore::VisiblePosition* vpos)
{
    if (vpos)
        vpos->showTreeForThis();
}

void showTree(const WebCore::VisiblePosition& vpos)
{
    vpos.showTreeForThis();
}

#endif