visible_units.cpp

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    VisiblePosition visPos = VisiblePosition(startNode, startOffset, DOWNSTREAM);
    return positionAvoidingFirstPositionInTable(visPos);
}

VisiblePosition startOfLine(const VisiblePosition& c)
{
    VisiblePosition visPos = startPositionForLine(c);
    
    if (visPos.isNotNull()) {
        // Make sure the start of line is not greater than the given input position.  Else use the previous position to 
        // obtain start of line.  This condition happens when the input position is before the space character at the end 
        // of a soft-wrapped non-editable line. In this scenario, startPositionForLine would incorrectly hand back a position
        // greater than the input position.  This fix is to account for the discrepancy between lines with webkit-line-break:after-white-space 
        // style versus lines without that style, which would break before a space by default. 
        Position p = visPos.deepEquivalent();
        if (p.offset() > c.deepEquivalent().offset() && p.node()->isSameNode(c.deepEquivalent().node())) {
            visPos = c.previous();
            if (visPos.isNull())
                return VisiblePosition();
            visPos = startPositionForLine(visPos);
        }
    }

    return c.honorEditableBoundaryAtOrAfter(visPos);
}

static VisiblePosition endPositionForLine(const VisiblePosition& c)
{
    if (c.isNull())
        return VisiblePosition();

    RootInlineBox *rootBox = rootBoxForLine(c);
    if (!rootBox) {
        // There are VisiblePositions at offset 0 in blocks without
        // RootInlineBoxes, like empty editable blocks and bordered blocks.
        Position p = c.deepEquivalent();
        if (p.node()->renderer() && p.node()->renderer()->isRenderBlock() && p.offset() == 0)
            return c;
        return VisiblePosition();
    }
    
    // Generated content (e.g. list markers and CSS :before and :after
    // pseudoelements) have no corresponding DOM element, and so cannot be
    // represented by a VisiblePosition.  Use whatever precedes instead.
    Node *endNode;
    InlineBox *endBox = rootBox->lastLeafChild();
    while (1) {
        if (!endBox)
            return VisiblePosition();

        RenderObject *endRenderer = endBox->renderer();
        if (!endRenderer)
            return VisiblePosition();

        endNode = endRenderer->node();
        if (endNode)
            break;
        
        endBox = endBox->prevLeafChild();
    }
    
    int endOffset = 1;
    if (endNode->hasTagName(brTag)) {
        endOffset = 0;
    } else if (endBox->isInlineTextBox()) {
        InlineTextBox *endTextBox = static_cast<InlineTextBox *>(endBox);
        endOffset = endTextBox->start();
        if (!endTextBox->isLineBreak())
            endOffset += endTextBox->len();
    }
    
    return VisiblePosition(endNode, endOffset, VP_UPSTREAM_IF_POSSIBLE);
}

VisiblePosition endOfLine(const VisiblePosition& c)
{
    VisiblePosition visPos = endPositionForLine(c);
    
    // Make sure the end of line is at the same line as the given input position.  Else use the previous position to 
    // obtain end of line.  This condition happens when the input position is before the space character at the end 
    // of a soft-wrapped non-editable line. In this scenario, endPositionForLine would incorrectly hand back a position
    // in the next line instead. This fix is to account for the discrepancy between lines with webkit-line-break:after-white-space style
    // versus lines without that style, which would break before a space by default. 
    if (!inSameLine(c, visPos)) {
        visPos = c.previous();
        if (visPos.isNull())
            return VisiblePosition();
        visPos = endPositionForLine(visPos);
    }
    
    return c.honorEditableBoundaryAtOrBefore(visPos);
}

bool inSameLine(const VisiblePosition &a, const VisiblePosition &b)
{
    return a.isNotNull() && startOfLine(a) == startOfLine(b);
}

bool isStartOfLine(const VisiblePosition &p)
{
    return p.isNotNull() && p == startOfLine(p);
}

bool isEndOfLine(const VisiblePosition &p)
{
    return p.isNotNull() && p == endOfLine(p);
}

// The first leaf before node that has the same editability as node.
static Node* previousLeafWithSameEditability(Node* node)
{
    bool editable = node->isContentEditable();
    Node* n = node->previousLeafNode();
    while (n) {
        if (editable == n->isContentEditable())
            return n;
        n = n->previousLeafNode();
    }
    return 0;
}

VisiblePosition previousLinePosition(const VisiblePosition &visiblePosition, int x)
{
    Position p = visiblePosition.deepEquivalent();
    Node *node = p.node();
    Node* highestRoot = highestEditableRoot(p);
    if (!node)
        return VisiblePosition();
    
    node->document()->updateLayoutIgnorePendingStylesheets();
    
    RenderObject *renderer = node->renderer();
    if (!renderer)
        return VisiblePosition();

    RenderBlock *containingBlock = 0;
    RootInlineBox *root = 0;
    InlineBox* box;
    int ignoredCaretOffset;
    visiblePosition.getInlineBoxAndOffset(box, ignoredCaretOffset);
    if (box) {
        root = box->root()->prevRootBox();
        if (root)
            containingBlock = renderer->containingBlock();
    }

    if (!root) {
        // This containing editable block does not have a previous line.
        // Need to move back to previous containing editable block in this root editable
        // block and find the last root line box in that block.
        Node* startBlock = enclosingBlock(node);
        Node* n = previousLeafWithSameEditability(node);
        while (n && startBlock == enclosingBlock(n))
            n = previousLeafWithSameEditability(n);
        while (n) {
            if (highestEditableRoot(Position(n, 0)) != highestRoot)
                break;
            Position pos(n, caretMinOffset(n));
            if (pos.isCandidate()) {
                ASSERT(n->renderer());
                Position maxPos(n, caretMaxOffset(n));
                maxPos.getInlineBoxAndOffset(DOWNSTREAM, box, ignoredCaretOffset);
                if (box) {
                    // previous root line box found
                    root = box->root();
                    containingBlock = n->renderer()->containingBlock();
                    break;
                }

                return VisiblePosition(pos, DOWNSTREAM);
            }
            n = previousLeafWithSameEditability(n);
        }
    }
    
    if (root) {
        // FIXME: Can be wrong for multi-column layout and with transforms.
        FloatPoint absPos = containingBlock->localToAbsolute(FloatPoint());
        if (containingBlock->hasOverflowClip())
            absPos -= containingBlock->layer()->scrolledContentOffset();
        RenderObject* renderer = root->closestLeafChildForXPos(x - absPos.x(), isEditablePosition(p))->renderer();
        Node* node = renderer->node();
        if (editingIgnoresContent(node))
            return Position(node->parent(), node->nodeIndex());
        return renderer->positionForCoordinates(x - absPos.x(), root->topOverflow());
    }
    
    // Could not find a previous line. This means we must already be on the first line.
    // Move to the start of the content in this block, which effectively moves us
    // to the start of the line we're on.
    Node* rootElement = node->isContentEditable() ? node->rootEditableElement() : node->document()->documentElement();
    return VisiblePosition(rootElement, 0, DOWNSTREAM);
}

static Node* nextLeafWithSameEditability(Node* node, int offset)
{
    bool editable = node->isContentEditable();
    ASSERT(offset >= 0);
    Node* child = node->childNode(offset);
    Node* n = child ? child->nextLeafNode() : node->nextLeafNode();
    while (n) {
        if (editable == n->isContentEditable())
            return n;
        n = n->nextLeafNode();
    }
    return 0;
}

static Node* nextLeafWithSameEditability(Node* node)
{
    if (!node)
        return 0;
    
    bool editable = node->isContentEditable();
    Node* n = node->nextLeafNode();
    while (n) {
        if (editable == n->isContentEditable())
            return n;
        n = n->nextLeafNode();
    }
    return 0;
}

VisiblePosition nextLinePosition(const VisiblePosition &visiblePosition, int x)
{
    Position p = visiblePosition.deepEquivalent();
    Node *node = p.node();
    Node* highestRoot = highestEditableRoot(p);
    if (!node)
        return VisiblePosition();
    
    node->document()->updateLayoutIgnorePendingStylesheets();

    RenderObject *renderer = node->renderer();
    if (!renderer)
        return VisiblePosition();

    RenderBlock *containingBlock = 0;
    RootInlineBox *root = 0;
    InlineBox* box;
    int ignoredCaretOffset;
    visiblePosition.getInlineBoxAndOffset(box, ignoredCaretOffset);
    if (box) {
        root = box->root()->nextRootBox();
        if (root)
            containingBlock = renderer->containingBlock();
    }

    if (!root) {
        // This containing editable block does not have a next line.
        // Need to move forward to next containing editable block in this root editable
        // block and find the first root line box in that block.
        Node* startBlock = enclosingBlock(node);
        Node* n = nextLeafWithSameEditability(node, p.offset());
        while (n && startBlock == enclosingBlock(n))
            n = nextLeafWithSameEditability(n);
        while (n) {
            if (highestEditableRoot(Position(n, 0)) != highestRoot)
                break;
            Position pos(n, caretMinOffset(n));
            if (pos.isCandidate()) {
                ASSERT(n->renderer());
                pos.getInlineBoxAndOffset(DOWNSTREAM, box, ignoredCaretOffset);
                if (box) {
                    // next root line box found
                    root = box->root();
                    containingBlock = n->renderer()->containingBlock();
                    break;
                }

                return VisiblePosition(pos, DOWNSTREAM);
            }
            n = nextLeafWithSameEditability(n);
        }
    }
    
    if (root) {
        // FIXME: Can be wrong for multi-column layout and with transforms.
        FloatPoint absPos = containingBlock->localToAbsolute(FloatPoint());
        if (containingBlock->hasOverflowClip())
            absPos -= containingBlock->layer()->scrolledContentOffset();
        RenderObject* renderer = root->closestLeafChildForXPos(x - absPos.x(), isEditablePosition(p))->renderer();
        Node* node = renderer->node();
        if (editingIgnoresContent(node))
            return Position(node->parent(), node->nodeIndex());
        return renderer->positionForCoordinates(x - absPos.x(), root->topOverflow());
    }    

    // Could not find a next line. This means we must already be on the last line.
    // Move to the end of the content in this block, which effectively moves us
    // to the end of the line we're on.
    Element* rootElement = node->isContentEditable() ? node->rootEditableElement() : node->document()->documentElement();
    return VisiblePosition(rootElement, rootElement ? rootElement->childNodeCount() : 0, DOWNSTREAM);
}

// ---------

static unsigned startSentenceBoundary(const UChar* characters, unsigned length)
{
    TextBreakIterator* iterator = sentenceBreakIterator(characters, length);
    // FIXME: The following function can return -1; we don't handle that.
    return textBreakPreceding(iterator, length);
}

VisiblePosition startOfSentence(const VisiblePosition &c)
{
    return previousBoundary(c, startSentenceBoundary);
}

static unsigned endSentenceBoundary(const UChar* characters, unsigned length)
{
    TextBreakIterator* iterator = sentenceBreakIterator(characters, length);
    return textBreakNext(iterator);
}

// FIXME: This includes the space after the punctuation that marks the end of the sentence.
VisiblePosition endOfSentence(const VisiblePosition &c)
{
    return nextBoundary(c, endSentenceBoundary);
}