bool isStartOfDocument(const VisiblePosition &p)
{
    return p.isNotNull() && p.previous().isNull();
}

VisiblePositionRange AccessibilityObject::rightLineVisiblePositionRange(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePositionRange();

    // make sure we move off of a line end
    VisiblePosition nextVisiblePos = visiblePos.next();
    if (nextVisiblePos.isNull())
        return VisiblePositionRange();

    VisiblePosition startPosition = startOfLine(nextVisiblePos);

    // fetch for a valid line start position
    if (startPosition.isNull()) {
        startPosition = visiblePos;
        nextVisiblePos = nextVisiblePos.next();
    } else
        startPosition = updateAXLineStartForVisiblePosition(startPosition);

    VisiblePosition endPosition = endOfLine(nextVisiblePos);

    // as long as the position hasn't reached the end of the doc,  keep searching for a valid line end position
    // Unless the VisiblePosition is at the very end, there should always be a valid line range.  However, endOfLine will
    // return null for position by a floating object, since floating object doesn't really belong to any line.
    // This check will reposition the marker after the floating object, to ensure we get a line end.
    while (endPosition.isNull() && nextVisiblePos.isNotNull()) {
        nextVisiblePos = nextVisiblePos.next();
        endPosition = endOfLine(nextVisiblePos);
    }

    return VisiblePositionRange(startPosition, endPosition);
}

void InsertListCommand::doApply()
{
    if (!endingSelection().isNonOrphanedCaretOrRange())
        return;

    if (!endingSelection().rootEditableElement())
        return;

    VisiblePosition visibleEnd = endingSelection().visibleEnd();
    VisiblePosition visibleStart = endingSelection().visibleStart();
    // When a selection ends at the start of a paragraph, we rarely paint
    // the selection gap before that paragraph, because there often is no gap.
    // In a case like this, it's not obvious to the user that the selection
    // ends "inside" that paragraph, so it would be confusing if InsertUn{Ordered}List
    // operated on that paragraph.
    // FIXME: We paint the gap before some paragraphs that are indented with left
    // margin/padding, but not others.  We should make the gap painting more consistent and
    // then use a left margin/padding rule here.
    if (visibleEnd.deepEquivalent() != visibleStart.deepEquivalent() && isStartOfParagraph(visibleEnd, CanSkipOverEditingBoundary)) {
        setEndingSelection(VisibleSelection(visibleStart, previousPositionOf(visibleEnd, CannotCrossEditingBoundary), endingSelection().isDirectional()));
        if (!endingSelection().rootEditableElement())
            return;
    }

    const HTMLQualifiedName& listTag = (m_type == OrderedList) ? olTag : ulTag;
    if (endingSelection().isRange()) {
        bool forceListCreation = false;
        VisibleSelection selection = selectionForParagraphIteration(endingSelection());
        ASSERT(selection.isRange());
        VisiblePosition startOfSelection = selection.visibleStart();
        VisiblePosition endOfSelection = selection.visibleEnd();
        VisiblePosition startOfLastParagraph = startOfParagraph(endOfSelection, CanSkipOverEditingBoundary);

        RefPtrWillBeRawPtr<Range> currentSelection = firstRangeOf(endingSelection());
        RefPtrWillBeRawPtr<ContainerNode> scopeForStartOfSelection = nullptr;
        RefPtrWillBeRawPtr<ContainerNode> scopeForEndOfSelection = nullptr;
        // FIXME: This is an inefficient way to keep selection alive because
        // indexForVisiblePosition walks from the beginning of the document to the
        // endOfSelection everytime this code is executed. But not using index is hard
        // because there are so many ways we can los eselection inside doApplyForSingleParagraph.
        int indexForStartOfSelection = indexForVisiblePosition(startOfSelection, scopeForStartOfSelection);
        int indexForEndOfSelection = indexForVisiblePosition(endOfSelection, scopeForEndOfSelection);

        if (startOfParagraph(startOfSelection, CanSkipOverEditingBoundary).deepEquivalent() != startOfLastParagraph.deepEquivalent()) {
            forceListCreation = !selectionHasListOfType(selection, listTag);

            VisiblePosition startOfCurrentParagraph = startOfSelection;
            while (inSameTreeAndOrdered(startOfCurrentParagraph, startOfLastParagraph) && !inSameParagraph(startOfCurrentParagraph, startOfLastParagraph, CanCrossEditingBoundary)) {
                // doApply() may operate on and remove the last paragraph of the selection from the document
                // if it's in the same list item as startOfCurrentParagraph.  Return early to avoid an
                // infinite loop and because there is no more work to be done.
                // FIXME(<rdar://problem/5983974>): The endingSelection() may be incorrect here.  Compute
                // the new location of endOfSelection and use it as the end of the new selection.
                if (!startOfLastParagraph.deepEquivalent().inDocument())
                    return;
                setEndingSelection(startOfCurrentParagraph);

                // Save and restore endOfSelection and startOfLastParagraph when necessary
                // since moveParagraph and movePragraphWithClones can remove nodes.
                if (!doApplyForSingleParagraph(forceListCreation, listTag, *currentSelection))
                    break;
                if (endOfSelection.isNull() || endOfSelection.isOrphan() || startOfLastParagraph.isNull() || startOfLastParagraph.isOrphan()) {
                    endOfSelection = visiblePositionForIndex(indexForEndOfSelection, scopeForEndOfSelection.get());
                    // If endOfSelection is null, then some contents have been deleted from the document.
                    // This should never happen and if it did, exit early immediately because we've lost the loop invariant.
                    ASSERT(endOfSelection.isNotNull());
                    if (endOfSelection.isNull() || !rootEditableElementOf(endOfSelection))
                        return;
                    startOfLastParagraph = startOfParagraph(endOfSelection, CanSkipOverEditingBoundary);
                }

                startOfCurrentParagraph = startOfNextParagraph(endingSelection().visibleStart());
            }
            setEndingSelection(endOfSelection);
        }
        doApplyForSingleParagraph(forceListCreation, listTag, *currentSelection);
        // Fetch the end of the selection, for the reason mentioned above.
        if (endOfSelection.isNull() || endOfSelection.isOrphan()) {
            endOfSelection = visiblePositionForIndex(indexForEndOfSelection, scopeForEndOfSelection.get());
            if (endOfSelection.isNull())
                return;
        }
        if (startOfSelection.isNull() || startOfSelection.isOrphan()) {
            startOfSelection = visiblePositionForIndex(indexForStartOfSelection, scopeForStartOfSelection.get());
            if (startOfSelection.isNull())
                return;
        }
        setEndingSelection(VisibleSelection(startOfSelection, endOfSelection, endingSelection().isDirectional()));
        return;
    }

    ASSERT(firstRangeOf(endingSelection()));
    doApplyForSingleParagraph(false, listTag, *firstRangeOf(endingSelection()));
}

void Selection::setBase(const VisiblePosition& visiblePosition)
{
    m_base = visiblePosition.deepEquivalent();
    validate();
}

void Selection::validate()
{
    // Move the selection to rendered positions, if possible.
    bool baseAndExtentEqual = m_base == m_extent;
    if (m_base.isNotNull()) {
        m_base = VisiblePosition(m_base, m_affinity).deepEquivalent();
        if (baseAndExtentEqual)
            m_extent = m_base;
    }
    if (m_extent.isNotNull() && !baseAndExtentEqual)
        m_extent = VisiblePosition(m_extent, m_affinity).deepEquivalent();

    // Make sure we do not have a dangling base or extent.
    if (m_base.isNull() && m_extent.isNull())
        m_baseIsFirst = true;
    else if (m_base.isNull()) {
        m_base = m_extent;
        m_baseIsFirst = true;
    } else if (m_extent.isNull()) {
        m_extent = m_base;
        m_baseIsFirst = true;
    } else {
        m_baseIsFirst = comparePositions(m_base, m_extent) <= 0;
    }

    if (m_baseIsFirst) {
        m_start = m_base;
        m_end = m_extent;
    } else {
        m_start = m_extent;
        m_end = m_base;
    }

    // Expand the selection if requested.
    switch (m_granularity) {
        case CharacterGranularity:
            // Don't do any expansion.
            break;
        case WordGranularity: {
            // General case: Select the word the caret is positioned inside of, or at the start of (RightWordIfOnBoundary).
            // Edge case: If the caret is after the last word in a soft-wrapped line or the last word in
            // the document, select that last word (LeftWordIfOnBoundary).
            // Edge case: If the caret is after the last word in a paragraph, select from the the end of the
            // last word to the line break (also RightWordIfOnBoundary);
            VisiblePosition start = VisiblePosition(m_start, m_affinity);
            VisiblePosition originalEnd(m_end, m_affinity);
            EWordSide side = RightWordIfOnBoundary;
            if (isEndOfDocument(start) || (isEndOfLine(start) && !isStartOfLine(start) && !isEndOfParagraph(start)))
                side = LeftWordIfOnBoundary;
            m_start = startOfWord(start, side).deepEquivalent();
            side = RightWordIfOnBoundary;
            if (isEndOfDocument(originalEnd) || (isEndOfLine(originalEnd) && !isStartOfLine(originalEnd) && !isEndOfParagraph(originalEnd)))
                side = LeftWordIfOnBoundary;
                
            VisiblePosition wordEnd(endOfWord(originalEnd, side));
            VisiblePosition end(wordEnd);
            
            if (isEndOfParagraph(originalEnd)) {
                // Select the paragraph break (the space from the end of a paragraph to the start of 
                // the next one) to match TextEdit.
                end = wordEnd.next();
                
                if (Node* table = isFirstPositionAfterTable(end)) {
                    // The paragraph break after the last paragraph in the last cell of a block table ends
                    // at the start of the paragraph after the table.
                    if (isBlock(table))
                        end = end.next(true);
                    else
                        end = wordEnd;
                }
                
                if (end.isNull())
                    end = wordEnd;
                    
            }
                
            m_end = end.deepEquivalent();
            break;
        }
        case SentenceGranularity: {
            m_start = startOfSentence(VisiblePosition(m_start, m_affinity)).deepEquivalent();
            m_end = endOfSentence(VisiblePosition(m_end, m_affinity)).deepEquivalent();
            break;
        }
        case LineGranularity: {
            m_start = startOfLine(VisiblePosition(m_start, m_affinity)).deepEquivalent();
            VisiblePosition end = endOfLine(VisiblePosition(m_end, m_affinity));
            // If the end of this line is at the end of a paragraph, include the space 
            // after the end of the line in the selection.
            if (isEndOfParagraph(end)) {
                VisiblePosition next = end.next();
                if (next.isNotNull())
                    end = next;
            }
            m_end = end.deepEquivalent();
            break;
        }
        case LineBoundary:
            m_start = startOfLine(VisiblePosition(m_start, m_affinity)).deepEquivalent();
            m_end = endOfLine(VisiblePosition(m_end, m_affinity)).deepEquivalent();
//.........这里部分代码省略.........

// If a selection starts in one block and ends in another, we have to merge to bring content before the
// start together with content after the end.
void DeleteSelectionCommand::mergeParagraphs()
{
    if (!m_mergeBlocksAfterDelete) {
        if (m_pruneStartBlockIfNecessary) {
            // We aren't going to merge into the start block, so remove it if it's empty.
            prune(m_startBlock);
            // Removing the start block during a deletion is usually an indication that we need
            // a placeholder, but not in this case.
            m_needPlaceholder = false;
        }
        return;
    }
    
    // It shouldn't have been asked to both try and merge content into the start block and prune it.
    ASSERT(!m_pruneStartBlockIfNecessary);

    // FIXME: Deletion should adjust selection endpoints as it removes nodes so that we never get into this state (4099839).
    if (!m_downstreamEnd.anchorNode()->inDocument() || !m_upstreamStart.anchorNode()->inDocument())
         return;
         
    // FIXME: The deletion algorithm shouldn't let this happen.
    if (comparePositions(m_upstreamStart, m_downstreamEnd) > 0)
        return;
        
    // There's nothing to merge.
    if (m_upstreamStart == m_downstreamEnd)
        return;
        
    VisiblePosition startOfParagraphToMove(m_downstreamEnd);
    VisiblePosition mergeDestination(m_upstreamStart);
    
    // m_downstreamEnd's block has been emptied out by deletion.  There is no content inside of it to
    // move, so just remove it.
    Element* endBlock = static_cast<Element*>(enclosingBlock(m_downstreamEnd.deprecatedNode()));
    if (!endBlock || !endBlock->contains(startOfParagraphToMove.deepEquivalent().deprecatedNode()) || !startOfParagraphToMove.deepEquivalent().deprecatedNode()) {
        removeNode(enclosingBlock(m_downstreamEnd.deprecatedNode()));
        return;
    }
    
    // We need to merge into m_upstreamStart's block, but it's been emptied out and collapsed by deletion.
    if (!mergeDestination.deepEquivalent().deprecatedNode() || !mergeDestination.deepEquivalent().deprecatedNode()->isDescendantOf(enclosingBlock(m_upstreamStart.containerNode())) || m_startsAtEmptyLine) {
        insertNodeAt(createBreakElement(document()).get(), m_upstreamStart);
        mergeDestination = VisiblePosition(m_upstreamStart);
    }
    
    if (mergeDestination == startOfParagraphToMove)
        return;
        
    VisiblePosition endOfParagraphToMove = endOfParagraph(startOfParagraphToMove);
    
    if (mergeDestination == endOfParagraphToMove)
        return;
    
    // The rule for merging into an empty block is: only do so if its farther to the right.
    // FIXME: Consider RTL.
    if (!m_startsAtEmptyLine && isStartOfParagraph(mergeDestination) && startOfParagraphToMove.absoluteCaretBounds().x() > mergeDestination.absoluteCaretBounds().x()) {
        if (mergeDestination.deepEquivalent().downstream().deprecatedNode()->hasTagName(brTag)) {
            removeNodeAndPruneAncestors(mergeDestination.deepEquivalent().downstream().deprecatedNode());
            m_endingPosition = startOfParagraphToMove.deepEquivalent();
            return;
        }
    }
    
    // Block images, tables and horizontal rules cannot be made inline with content at mergeDestination.  If there is 
    // any (!isStartOfParagraph(mergeDestination)), don't merge, just move the caret to just before the selection we deleted.
    // See https://bugs.webkit.org/show_bug.cgi?id=25439
    if (isRenderedAsNonInlineTableImageOrHR(startOfParagraphToMove.deepEquivalent().deprecatedNode()) && !isStartOfParagraph(mergeDestination)) {
        m_endingPosition = m_upstreamStart;
        return;
    }
    
    RefPtr<Range> range = Range::create(document(), startOfParagraphToMove.deepEquivalent().parentAnchoredEquivalent(), endOfParagraphToMove.deepEquivalent().parentAnchoredEquivalent());
    RefPtr<Range> rangeToBeReplaced = Range::create(document(), mergeDestination.deepEquivalent().parentAnchoredEquivalent(), mergeDestination.deepEquivalent().parentAnchoredEquivalent());
    if (!document()->frame()->editor()->client()->shouldMoveRangeAfterDelete(range.get(), rangeToBeReplaced.get()))
        return;
    
    // moveParagraphs will insert placeholders if it removes blocks that would require their use, don't let block
    // removals that it does cause the insertion of *another* placeholder.
    bool needPlaceholder = m_needPlaceholder;
    bool paragraphToMergeIsEmpty = (startOfParagraphToMove == endOfParagraphToMove);
    moveParagraph(startOfParagraphToMove, endOfParagraphToMove, mergeDestination, false, !paragraphToMergeIsEmpty);
    m_needPlaceholder = needPlaceholder;
    // The endingPosition was likely clobbered by the move, so recompute it (moveParagraph selects the moved paragraph).
    m_endingPosition = endingSelection().start();
}

AccessibilityObject* objectFocusedAndCaretOffsetUnignored(AccessibilityObject* referenceObject, int& offset)
{
    // Indication that something bogus has transpired.
    offset = -1;

    Document* document = referenceObject->document();
    if (!document)
        return 0;

    Node* focusedNode = referenceObject->selection().end().containerNode();
    if (!focusedNode)
        return 0;

    RenderObject* focusedRenderer = focusedNode->renderer();
    if (!focusedRenderer)
        return 0;

    AccessibilityObject* focusedObject = document->axObjectCache()->getOrCreate(focusedRenderer);
    if (!focusedObject)
        return 0;

    // Look for the actual (not ignoring accessibility) selected object.
    AccessibilityObject* firstUnignoredParent = focusedObject;
    if (firstUnignoredParent->accessibilityIsIgnored())
        firstUnignoredParent = firstUnignoredParent->parentObjectUnignored();
    if (!firstUnignoredParent)
        return 0;

    // Don't ignore links if the offset is being requested for a link.
    if (!referenceObject->isLink() && firstUnignoredParent->isLink())
        firstUnignoredParent = firstUnignoredParent->parentObjectUnignored();
    if (!firstUnignoredParent)
        return 0;

    // The reference object must either coincide with the focused
    // object being considered, or be a descendant of it.
    if (referenceObject->isDescendantOfObject(firstUnignoredParent))
        referenceObject = firstUnignoredParent;

    Node* startNode = 0;
    if (firstUnignoredParent != referenceObject || firstUnignoredParent->isTextControl()) {
        // We need to use the first child's node of the reference
        // object as the start point to calculate the caret offset
        // because we want it to be relative to the object of
        // reference, not just to the focused object (which could have
        // previous siblings which should be taken into account too).
        AccessibilityObject* axFirstChild = referenceObject->firstChild();
        if (axFirstChild)
            startNode = axFirstChild->node();
    }
    if (!startNode)
        startNode = firstUnignoredParent->node();

    // Check if the node for the first parent object not ignoring
    // accessibility is null again before using it. This might happen
    // with certain kind of accessibility objects, such as the root
    // one (the scroller containing the webArea object).
    if (!startNode)
        return 0;

    VisiblePosition startPosition = VisiblePosition(positionBeforeNode(startNode), DOWNSTREAM);
    VisiblePosition endPosition = firstUnignoredParent->selection().visibleEnd();

    if (startPosition == endPosition)
        offset = 0;
    else if (!isStartOfLine(endPosition)) {
        RefPtr<Range> range = makeRange(startPosition, endPosition.previous());
        offset = TextIterator::rangeLength(range.get(), true) + 1;
    } else {
        RefPtr<Range> range = makeRange(startPosition, endPosition);
        offset = TextIterator::rangeLength(range.get(), true);
    }

    return firstUnignoredParent;
}

// FIXME: We should merge this function with ApplyBlockElementCommand::formatSelection
void IndentOutdentCommand::outdentRegion(const VisiblePosition& startOfSelection, const VisiblePosition& endOfSelection)
{
    VisiblePosition endOfCurrentParagraph = endOfParagraph(startOfSelection);
    VisiblePosition endOfLastParagraph = endOfParagraph(endOfSelection);

    if (endOfCurrentParagraph == endOfLastParagraph) {
        outdentParagraph();
        return;
    }

    Position originalSelectionEnd = endingSelection().end();
    VisiblePosition endAfterSelection = endOfParagraph(endOfLastParagraph.next());

    while (endOfCurrentParagraph != endAfterSelection) {
        VisiblePosition endOfNextParagraph = endOfParagraph(endOfCurrentParagraph.next());
        if (endOfCurrentParagraph == endOfLastParagraph)
            setEndingSelection(VisibleSelection(originalSelectionEnd, DOWNSTREAM));
        else
            setEndingSelection(endOfCurrentParagraph);

        outdentParagraph();

        // outdentParagraph could move more than one paragraph if the paragraph
        // is in a list item. As a result, endAfterSelection and endOfNextParagraph
        // could refer to positions no longer in the document.
        if (endAfterSelection.isNotNull() && !endAfterSelection.deepEquivalent().inDocument())
            break;

        if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().inDocument()) {
            endOfCurrentParagraph = VisiblePosition(endingSelection().end());
            endOfNextParagraph = endOfParagraph(endOfCurrentParagraph.next());
        }
        endOfCurrentParagraph = endOfNextParagraph;
    }
}

void ApplyBlockElementCommand::doApply()
{
    if (!endingSelection().rootEditableElement())
        return;

    VisiblePosition visibleEnd = endingSelection().visibleEnd();
    VisiblePosition visibleStart = endingSelection().visibleStart();
    if (visibleStart.isNull() || visibleStart.isOrphan() || visibleEnd.isNull() || visibleEnd.isOrphan())
        return;

    // When a selection ends at the start of a paragraph, we rarely paint
    // the selection gap before that paragraph, because there often is no gap.
    // In a case like this, it's not obvious to the user that the selection
    // ends "inside" that paragraph, so it would be confusing if Indent/Outdent
    // operated on that paragraph.
    // FIXME: We paint the gap before some paragraphs that are indented with left
    // margin/padding, but not others.  We should make the gap painting more consistent and
    // then use a left margin/padding rule here.
    if (visibleEnd != visibleStart && isStartOfParagraph(visibleEnd))
        setEndingSelection(VisibleSelection(visibleStart, visibleEnd.previous(CannotCrossEditingBoundary), endingSelection().isDirectional()));

    VisibleSelection selection = selectionForParagraphIteration(endingSelection());
    VisiblePosition startOfSelection = selection.visibleStart();
    VisiblePosition endOfSelection = selection.visibleEnd();
    ASSERT(!startOfSelection.isNull());
    ASSERT(!endOfSelection.isNull());
    RefPtr<ContainerNode> startScope;
    int startIndex = indexForVisiblePosition(startOfSelection, startScope);
    RefPtr<ContainerNode> endScope;
    int endIndex = indexForVisiblePosition(endOfSelection, endScope);

    formatSelection(startOfSelection, endOfSelection);

    document()->updateLayoutIgnorePendingStylesheets();

    ASSERT(startScope == endScope);
    ASSERT(startIndex >= 0);
    ASSERT(startIndex <= endIndex);
    if (startScope == endScope && startIndex >= 0 && startIndex <= endIndex) {
        VisiblePosition start(visiblePositionForIndex(startIndex, startScope.get()));
        VisiblePosition end(visiblePositionForIndex(endIndex, endScope.get()));
        if (start.isNotNull() && end.isNotNull())
            setEndingSelection(VisibleSelection(start, end, endingSelection().isDirectional()));
    }
}

void FormatBlockCommand::doApply()
{
    if (!endingSelection().isNonOrphanedCaretOrRange())
        return;
    
    if (!endingSelection().rootEditableElement())
        return;

    VisiblePosition visibleEnd = endingSelection().visibleEnd();
    VisiblePosition visibleStart = endingSelection().visibleStart();
    // When a selection ends at the start of a paragraph, we rarely paint 
    // the selection gap before that paragraph, because there often is no gap.  
    // In a case like this, it's not obvious to the user that the selection 
    // ends "inside" that paragraph, so it would be confusing if FormatBlock
    // operated on that paragraph.
    // FIXME: We paint the gap before some paragraphs that are indented with left 
    // margin/padding, but not others.  We should make the gap painting more consistent and 
    // then use a left margin/padding rule here.
    if (visibleEnd != visibleStart && isStartOfParagraph(visibleEnd))
        setEndingSelection(VisibleSelection(visibleStart, visibleEnd.previous(true)));

    if (endingSelection().isRange() && modifyRange())
        return;

    ExceptionCode ec;
    String localName, prefix;
    if (!Document::parseQualifiedName(m_tagName, prefix, localName, ec))
        return;
    QualifiedName qTypeOfBlock(prefix, localName, xhtmlNamespaceURI);

    Node* refNode = enclosingBlockFlowElement(endingSelection().visibleStart());
    if (refNode->hasTagName(qTypeOfBlock))
        // We're already in a block with the format we want, so we don't have to do anything
        return;
    
    VisiblePosition paragraphStart = startOfParagraph(endingSelection().visibleStart());
    VisiblePosition paragraphEnd = endOfParagraph(endingSelection().visibleStart());
    VisiblePosition blockStart = startOfBlock(endingSelection().visibleStart());
    VisiblePosition blockEnd = endOfBlock(endingSelection().visibleStart());
    RefPtr<Element> blockNode = createHTMLElement(document(), m_tagName);
    RefPtr<Element> placeholder = createBreakElement(document());
    
    Node* root = endingSelection().start().node()->rootEditableElement();
    if (validBlockTag(refNode->nodeName().lower()) && 
        paragraphStart == blockStart && paragraphEnd == blockEnd && 
        refNode != root && !root->isDescendantOf(refNode))
        // Already in a valid block tag that only contains the current paragraph, so we can swap with the new tag
        insertNodeBefore(blockNode, refNode);
    else {
        // Avoid inserting inside inline elements that surround paragraphStart with upstream().
        // This is only to avoid creating bloated markup.
        insertNodeAt(blockNode, paragraphStart.deepEquivalent().upstream());
    }
    appendNode(placeholder, blockNode);
    
    VisiblePosition destination(Position(placeholder.get(), 0));
    if (paragraphStart == paragraphEnd && !lineBreakExistsAtVisiblePosition(paragraphStart)) {
        setEndingSelection(destination);
        return;
    }
    moveParagraph(paragraphStart, paragraphEnd, destination, true, false);
}

void IndentOutdentCommand::outdentParagraph()
{
    VisiblePosition visibleStartOfParagraph = startOfParagraph(endingSelection().visibleStart());
    VisiblePosition visibleEndOfParagraph = endOfParagraph(visibleStartOfParagraph);

    HTMLElement* enclosingElement = toHTMLElement(enclosingNodeOfType(visibleStartOfParagraph.deepEquivalent(), &isHTMLListOrBlockquoteElement));
    if (!enclosingElement || !enclosingElement->parentNode()->hasEditableStyle()) // We can't outdent if there is no place to go!
        return;

    // Use InsertListCommand to remove the selection from the list
    if (isHTMLOListElement(*enclosingElement)) {
        applyCommandToComposite(InsertListCommand::create(document(), InsertListCommand::OrderedList));
        return;
    }
    if (isHTMLUListElement(*enclosingElement)) {
        applyCommandToComposite(InsertListCommand::create(document(), InsertListCommand::UnorderedList));
        return;
    }

    // The selection is inside a blockquote i.e. enclosingNode is a blockquote
    VisiblePosition positionInEnclosingBlock = VisiblePosition(firstPositionInNode(enclosingElement));
    // If the blockquote is inline, the start of the enclosing block coincides with
    // positionInEnclosingBlock.
    VisiblePosition startOfEnclosingBlock = (enclosingElement->layoutObject() && enclosingElement->layoutObject()->isInline()) ? positionInEnclosingBlock : startOfBlock(positionInEnclosingBlock);
    VisiblePosition lastPositionInEnclosingBlock = VisiblePosition(lastPositionInNode(enclosingElement));
    VisiblePosition endOfEnclosingBlock = endOfBlock(lastPositionInEnclosingBlock);
    if (visibleStartOfParagraph == startOfEnclosingBlock &&
        visibleEndOfParagraph == endOfEnclosingBlock) {
        // The blockquote doesn't contain anything outside the paragraph, so it can be totally removed.
        Node* splitPoint = enclosingElement->nextSibling();
        removeNodePreservingChildren(enclosingElement);
        // outdentRegion() assumes it is operating on the first paragraph of an enclosing blockquote, but if there are multiply nested blockquotes and we've
        // just removed one, then this assumption isn't true. By splitting the next containing blockquote after this node, we keep this assumption true
        if (splitPoint) {
            if (Element* splitPointParent = splitPoint->parentElement()) {
                if (splitPointParent->hasTagName(blockquoteTag)
                    && !splitPoint->hasTagName(blockquoteTag)
                    && splitPointParent->parentNode()->hasEditableStyle()) // We can't outdent if there is no place to go!
                    splitElement(splitPointParent, splitPoint);
            }
        }

        document().updateLayoutIgnorePendingStylesheets();
        visibleStartOfParagraph = VisiblePosition(visibleStartOfParagraph.deepEquivalent());
        visibleEndOfParagraph = VisiblePosition(visibleEndOfParagraph.deepEquivalent());
        if (visibleStartOfParagraph.isNotNull() && !isStartOfParagraph(visibleStartOfParagraph))
            insertNodeAt(createBreakElement(document()), visibleStartOfParagraph.deepEquivalent());
        if (visibleEndOfParagraph.isNotNull() && !isEndOfParagraph(visibleEndOfParagraph))
            insertNodeAt(createBreakElement(document()), visibleEndOfParagraph.deepEquivalent());

        return;
    }
    RefPtrWillBeRawPtr<Node> splitBlockquoteNode = enclosingElement;
    if (Element* enclosingBlockFlow = enclosingBlock(visibleStartOfParagraph.deepEquivalent().deprecatedNode())) {
        if (enclosingBlockFlow != enclosingElement) {
            splitBlockquoteNode = splitTreeToNode(enclosingBlockFlow, enclosingElement, true);
        } else {
            // We split the blockquote at where we start outdenting.
            Node* highestInlineNode = highestEnclosingNodeOfType(visibleStartOfParagraph.deepEquivalent(), isInline, CannotCrossEditingBoundary, enclosingBlockFlow);
            splitElement(enclosingElement, highestInlineNode ? highestInlineNode : visibleStartOfParagraph.deepEquivalent().deprecatedNode());
        }
    }
    VisiblePosition startOfParagraphToMove(startOfParagraph(visibleStartOfParagraph));
    VisiblePosition endOfParagraphToMove(endOfParagraph(visibleEndOfParagraph));
    if (startOfParagraphToMove.isNull() || endOfParagraphToMove.isNull())
        return;
    RefPtrWillBeRawPtr<HTMLBRElement> placeholder = createBreakElement(document());
    insertNodeBefore(placeholder, splitBlockquoteNode);
    moveParagraph(startOfParagraphToMove, endOfParagraphToMove, VisiblePosition(positionBeforeNode(placeholder.get())), true);
}

bool SelectionModifier::modifyWithPageGranularity(EAlteration alter,
                                                  unsigned verticalDistance,
                                                  VerticalDirection direction) {
  if (!verticalDistance)
    return false;

  DCHECK(!frame()->document()->needsLayoutTreeUpdate());
  DocumentLifecycle::DisallowTransitionScope disallowTransition(
      frame()->document()->lifecycle());

  willBeModified(alter, direction == FrameSelection::DirectionUp
                            ? DirectionBackward
                            : DirectionForward);

  VisiblePosition pos;
  LayoutUnit xPos;
  switch (alter) {
    case FrameSelection::AlterationMove:
      pos = createVisiblePosition(direction == FrameSelection::DirectionUp
                                      ? m_selection.start()
                                      : m_selection.end(),
                                  m_selection.affinity());
      xPos = lineDirectionPointForBlockDirectionNavigation(
          direction == FrameSelection::DirectionUp ? START : END);
      m_selection.setAffinity(direction == FrameSelection::DirectionUp
                                  ? TextAffinity::Upstream
                                  : TextAffinity::Downstream);
      break;
    case FrameSelection::AlterationExtend:
      pos = createVisiblePosition(m_selection.extent(), m_selection.affinity());
      xPos = lineDirectionPointForBlockDirectionNavigation(EXTENT);
      m_selection.setAffinity(TextAffinity::Downstream);
      break;
  }

  int startY;
  if (!absoluteCaretY(pos, startY))
    return false;
  if (direction == FrameSelection::DirectionUp)
    startY = -startY;
  int lastY = startY;

  VisiblePosition result;
  VisiblePosition next;
  for (VisiblePosition p = pos;; p = next) {
    if (direction == FrameSelection::DirectionUp)
      next = previousLinePosition(p, xPos);
    else
      next = nextLinePosition(p, xPos);

    if (next.isNull() || next.deepEquivalent() == p.deepEquivalent())
      break;
    int nextY;
    if (!absoluteCaretY(next, nextY))
      break;
    if (direction == FrameSelection::DirectionUp)
      nextY = -nextY;
    if (nextY - startY > static_cast<int>(verticalDistance))
      break;
    if (nextY >= lastY) {
      lastY = nextY;
      result = next;
    }
  }

  if (result.isNull())
    return false;

  switch (alter) {
    case FrameSelection::AlterationMove:
      m_selection = createVisibleSelection(
          SelectionInDOMTree::Builder()
              .collapse(result.toPositionWithAffinity())
              .setIsDirectional(m_selection.isDirectional())
              .build());
      break;
    case FrameSelection::AlterationExtend:
      m_selection.setExtent(result);
      break;
  }

  m_selection.setIsDirectional(shouldAlwaysUseDirectionalSelection(frame()) ||
                               alter == FrameSelection::AlterationExtend);

  return true;
}

bool isEndOfDocument(const VisiblePosition &p)
{
    return p.isNotNull() && p.next().isNull();
}

void TypingCommand::forwardDeleteKeyPressed(TextGranularity granularity, bool killRing)
{
    LocalFrame* frame = document().frame();
    if (!frame)
        return;

    frame->spellChecker().updateMarkersForWordsAffectedByEditing(false);

    VisibleSelection selectionToDelete;
    VisibleSelection selectionAfterUndo;

    switch (endingSelection().selectionType()) {
    case RangeSelection:
        selectionToDelete = endingSelection();
        selectionAfterUndo = selectionToDelete;
        break;
    case CaretSelection: {
        m_smartDelete = false;

        // Handle delete at beginning-of-block case.
        // Do nothing in the case that the caret is at the start of a
        // root editable element or at the start of a document.
        OwnPtrWillBeRawPtr<FrameSelection> selection = FrameSelection::create();
        selection->setSelection(endingSelection());
        selection->modify(FrameSelection::AlterationExtend, DirectionForward, granularity);
        if (killRing && selection->isCaret() && granularity != CharacterGranularity)
            selection->modify(FrameSelection::AlterationExtend, DirectionForward, CharacterGranularity);

        Position downstreamEnd = endingSelection().end().downstream();
        VisiblePosition visibleEnd = endingSelection().visibleEnd();
        Node* enclosingTableCell = enclosingNodeOfType(visibleEnd.deepEquivalent(), &isTableCell);
        if (enclosingTableCell && visibleEnd == VisiblePosition(lastPositionInNode(enclosingTableCell)))
            return;
        if (visibleEnd == endOfParagraph(visibleEnd))
            downstreamEnd = visibleEnd.next(CannotCrossEditingBoundary).deepEquivalent().downstream();
        // When deleting tables: Select the table first, then perform the deletion
        if (isRenderedTableElement(downstreamEnd.containerNode()) && downstreamEnd.computeOffsetInContainerNode() <= caretMinOffset(downstreamEnd.containerNode())) {
            setEndingSelection(VisibleSelection(endingSelection().end(), positionAfterNode(downstreamEnd.containerNode()), DOWNSTREAM, endingSelection().isDirectional()));
            typingAddedToOpenCommand(ForwardDeleteKey);
            return;
        }

        // deleting to end of paragraph when at end of paragraph needs to merge the next paragraph (if any)
        if (granularity == ParagraphBoundary && selection->selection().isCaret() && isEndOfParagraph(selection->selection().visibleEnd()))
            selection->modify(FrameSelection::AlterationExtend, DirectionForward, CharacterGranularity);

        selectionToDelete = selection->selection();
        if (!startingSelection().isRange() || selectionToDelete.base() != startingSelection().start())
            selectionAfterUndo = selectionToDelete;
        else {
            // It's a little tricky to compute what the starting selection would have been in the original document.
            // We can't let the VisibleSelection class's validation kick in or it'll adjust for us based on
            // the current state of the document and we'll get the wrong result.
            Position extent = startingSelection().end();
            if (extent.containerNode() != selectionToDelete.end().containerNode())
                extent = selectionToDelete.extent();
            else {
                int extraCharacters;
                if (selectionToDelete.start().containerNode() == selectionToDelete.end().containerNode())
                    extraCharacters = selectionToDelete.end().computeOffsetInContainerNode() - selectionToDelete.start().computeOffsetInContainerNode();
                else
                    extraCharacters = selectionToDelete.end().computeOffsetInContainerNode();
                extent = Position(extent.containerNode(), extent.computeOffsetInContainerNode() + extraCharacters, Position::PositionIsOffsetInAnchor);
            }
            selectionAfterUndo.setWithoutValidation(startingSelection().start(), extent);
        }
        break;
    }
    case NoSelection:
        ASSERT_NOT_REACHED();
        break;
    }

    ASSERT(!selectionToDelete.isNone());
    if (selectionToDelete.isNone())
        return;

    if (selectionToDelete.isCaret())
        return;

    if (killRing)
        frame->editor().addToKillRing(selectionToDelete.toNormalizedRange().get(), false);
    // Make undo select what was deleted on Mac alone
    if (frame->editor().behavior().shouldUndoOfDeleteSelectText())
        setStartingSelection(selectionAfterUndo);
    CompositeEditCommand::deleteSelection(selectionToDelete, m_smartDelete);
    setSmartDelete(false);
    typingAddedToOpenCommand(ForwardDeleteKey);
}

void TypingCommand::forwardDeleteKeyPressed(TextGranularity granularity, bool shouldAddToKillRing)
{
    Frame& frame = this->frame();

    frame.editor().updateMarkersForWordsAffectedByEditing(false);

    VisibleSelection selectionToDelete;
    VisibleSelection selectionAfterUndo;

    switch (endingSelection().selectionType()) {
    case VisibleSelection::RangeSelection:
        selectionToDelete = endingSelection();
        selectionAfterUndo = selectionToDelete;
        break;
    case VisibleSelection::CaretSelection: {
        m_smartDelete = false;

        // Handle delete at beginning-of-block case.
        // Do nothing in the case that the caret is at the start of a
        // root editable element or at the start of a document.
        FrameSelection selection;
        selection.setSelection(endingSelection());
        selection.modify(FrameSelection::AlterationExtend, DirectionForward, granularity);
        if (shouldAddToKillRing && selection.isCaret() && granularity != CharacterGranularity)
            selection.modify(FrameSelection::AlterationExtend, DirectionForward, CharacterGranularity);

        Position downstreamEnd = endingSelection().end().downstream();
        VisiblePosition visibleEnd = endingSelection().visibleEnd();
        Node* enclosingTableCell = enclosingNodeOfType(visibleEnd.deepEquivalent(), &isTableCell);
        if (enclosingTableCell && visibleEnd == lastPositionInNode(enclosingTableCell))
            return;
        if (visibleEnd == endOfParagraph(visibleEnd))
            downstreamEnd = visibleEnd.next(CannotCrossEditingBoundary).deepEquivalent().downstream();
        // When deleting tables: Select the table first, then perform the deletion
        if (downstreamEnd.containerNode() && downstreamEnd.containerNode()->renderer() && downstreamEnd.containerNode()->renderer()->isTable()
            && downstreamEnd.computeOffsetInContainerNode() <= caretMinOffset(downstreamEnd.containerNode())) {
            setEndingSelection(VisibleSelection(endingSelection().end(), positionAfterNode(downstreamEnd.containerNode()), DOWNSTREAM, endingSelection().isDirectional()));
            typingAddedToOpenCommand(ForwardDeleteKey);
            return;
        }

        // deleting to end of paragraph when at end of paragraph needs to merge the next paragraph (if any)
        if (granularity == ParagraphBoundary && selection.selection().isCaret() && isEndOfParagraph(selection.selection().visibleEnd()))
            selection.modify(FrameSelection::AlterationExtend, DirectionForward, CharacterGranularity);

        selectionToDelete = selection.selection();
        if (!startingSelection().isRange() || selectionToDelete.base() != startingSelection().start())
            selectionAfterUndo = selectionToDelete;
        else {
            // It's a little tricky to compute what the starting selection would have been in the original document.
            // We can't let the VisibleSelection class's validation kick in or it'll adjust for us based on
            // the current state of the document and we'll get the wrong result.
            Position extent = startingSelection().end();
            if (extent.containerNode() != selectionToDelete.end().containerNode())
                extent = selectionToDelete.extent();