long offset = pos.offset();

    if (!node)
        return Position();
    
    if (isAtomicNode(node))
        return pos;

    if (offset >= (long)node->childNodeCount()) {
        do {
            NodeImpl *child = node->lastChild();
            if (!child)
                break;
            node = child;
        } while (!isAtomicNode(node));
        return Position(node, node->caretMaxOffset());
    }
    
    node = node->childNode(offset);
    ASSERT(node);
    while (!isAtomicNode(node)) {
        NodeImpl *child = node->firstChild();
        if (!child)
            break;
        node = child;
    }
    return Position(node, 0);
}

Position VisiblePosition::downstreamDeepEquivalent() const
{
    Position pos = m_deepPosition;
    
    if (pos.isNull() || atEnd(pos))
        return pos;

    Position downstreamTest = pos.downstream(StayInBlock);

    Position current = pos;
    while (!atEnd(current)) {
        current = nextPosition(current);
        if (isCandidate(current)) {
            if (downstreamTest != current.downstream(StayInBlock))
                break;
            pos = current;
        }
    }
    
    return pos;
}

Position VisiblePosition::rangeCompliantEquivalent(const Position &pos)
{
    NodeImpl *node = pos.node();
    if (!node)
        return Position();
    
    // FIXME: This clamps out-of-range values.
    // Instead we should probably assert, and not use such values.

    long offset = pos.offset();
    if (!offsetInCharacters(node->nodeType()) && isAtomicNode(node) && offset > 0)
        return Position(node->parentNode(), node->nodeIndex() + 1);

    return Position(node, kMax(0L, kMin(offset, maxOffset(node))));
}

long VisiblePosition::maxOffset(const NodeImpl *node)
{
    return offsetInCharacters(node->nodeType()) ? (long)static_cast<const CharacterDataImpl *>(node)->length() : (long)node->childNodeCount();
}

bool VisiblePosition::isAtomicNode(const NodeImpl *node)
{
    return node && (!node->hasChildNodes() || (node->id() == ID_OBJECT && node->renderer() && node->renderer()->isReplaced()));
}

QChar VisiblePosition::character() const
{
    Position pos = position();
    NodeImpl *node = pos.node();
    if (!node || !node->isTextNode()) {
        return QChar();
    }
    TextImpl *textNode = static_cast<TextImpl *>(pos.node());
    long offset = pos.offset();
    if ((unsigned)offset >= textNode->length()) {
        return QChar();
    }
    return textNode->data()[offset];
}

bool isEqualIgnoringAffinity(const VisiblePosition &a, const VisiblePosition &b)
{
    bool result = a.m_deepPosition == b.m_deepPosition;
    if (result) {
        // We want to catch cases where positions are equal, but affinities are not, since
        // this is very likely a bug, given the places where this call is used. The difference
        // is very likely due to code that set the affinity on a VisiblePosition "by hand" and 
        // did so incorrectly.
        ASSERT(a.m_affinity == b.m_affinity);
    }
    return result;
}

bool isNotEqualIgnoringAffinity(const VisiblePosition &a, const VisiblePosition &b)
{
    return !isEqualIgnoringAffinity(a, b);
}

void VisiblePosition::debugPosition(const char *msg) const
{
#if 0
    if (isNull())
        fprintf(stderr, "Position [%s]: null\n", msg);
    else
        fprintf(stderr, "Position [%s]: %s [%p] at %d\n", msg, m_deepPosition.node()->nodeName().string().latin1(), m_deepPosition.node(), m_deepPosition.offset());
#endif
}

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

Range makeRange(const VisiblePosition &start, const VisiblePosition &end)
{
    Position s = start.position();
    Position e = end.position();
    return Range(s.node(), s.offset(), e.node(), e.offset());
}

VisiblePosition startVisiblePosition(const Range &r, EAffinity affinity)
{
    return VisiblePosition(r.startContainer().handle(), r.startOffset(), affinity);
}

VisiblePosition endVisiblePosition(const Range &r, EAffinity affinity)
{
    return VisiblePosition(r.endContainer().handle(), r.endOffset(), affinity);
}

bool setStart(Range &r, const VisiblePosition &c)
{
    RangeImpl *ri = r.handle();
    if (!ri)
        return false;
    Position p = c.position();
    int code = 0;
    ri->setStart(p.node(), p.offset(), code);
    return code == 0;
}

bool setEnd(Range &r, const VisiblePosition &c)
{
    RangeImpl *ri = r.handle();
    if (!ri)
        return false;
    Position p = c.position();
    int code = 0;
    ri->setEnd(p.node(), p.offset(), code);
    return code == 0;
}

void setAffinityUsingLinePosition(VisiblePosition &pos)
{
    // When not moving across line wrap, make sure to end up with DOWNSTREAM affinity.  
    if (pos.isNotNull() && pos.affinity() == UPSTREAM) {
        VisiblePosition temp(pos);
        temp.setAffinity(DOWNSTREAM);
        if (!visiblePositionsOnDifferentLines(temp, pos))
            pos.setAffinity(DOWNSTREAM);
    }
}

bool visiblePositionsOnDifferentLines(const VisiblePosition &pos1, const VisiblePosition &pos2)
{
    if (pos1.isNull() || pos2.isNull())
        return false;
    if (pos1 == pos2)
        return false;
    
    Position p1 = pos1.deepEquivalent();
    Position p2 = pos2.deepEquivalent();
    RenderObject *r1 = p1.node()->renderer();
    RenderObject *r2 = p2.node()->renderer();
    if (r1->isBlockFlow() || r2->isBlockFlow())
        return r1 == r2 ? false : true;
    InlineBox *b1 = r1 ? r1->inlineBox(p1.offset(), pos1.affinity()) : 0;
    InlineBox *b2 = r2 ? r2->inlineBox(p2.offset(), pos2.affinity()) : 0;
    return (b1 && b2 && b1->root() != b2->root());
}

enum EBlockRelationship { 
    NoBlockRelationship, 
    SameBlockRelationship, 
    PeerBlockRelationship, 
    AncestorBlockRelationship, 
    DescendantBlockRelationship, 
    OtherBlockRelationship 
};

static EBlockRelationship blockRelationship(const VisiblePosition &pos1, const VisiblePosition &pos2)
{
    if (pos1.isNull() || pos2.isNull())
        return NoBlockRelationship;
    if (pos1 == pos2)
        return SameBlockRelationship;

    Position p1 = pos1.deepEquivalent();
    Position p2 = pos2.deepEquivalent();
    NodeImpl *b1 = p1.node()->enclosingBlockFlowElement();
    NodeImpl *b2 = p2.node()->enclosingBlockFlowElement();
    if (!b1 || !b2)
        return NoBlockRelationship;
    if (b1 == b2) 
        return SameBlockRelationship;
    if (b1->parentNode() == b2->parentNode())
        return PeerBlockRelationship;
    if (b2->isAncestor(b1))
        return AncestorBlockRelationship;
    if (b1->isAncestor(b2))
        return DescendantBlockRelationship;
    return OtherBlockRelationship;
}

bool visiblePositionsInDifferentBlocks(const VisiblePosition &pos1, const VisiblePosition &pos2)
{
    switch (blockRelationship(pos1, pos2)) {
        case NoBlockRelationship:
        case SameBlockRelationship:
            return false;
        case PeerBlockRelationship:
        case AncestorBlockRelationship:
        case DescendantBlockRelationship:
        case OtherBlockRelationship:
            return true;
    }
    ASSERT_NOT_REACHED();
    return false;
}

bool isFirstVisiblePositionOnLine(const VisiblePosition &pos)
{
    if (pos.isNull())
        return false;
        
    VisiblePosition previous = pos.previous();
    return previous.isNull() || visiblePositionsOnDifferentLines(pos, previous);
}

bool isFirstVisiblePositionInParagraph(const VisiblePosition &pos)
{
    if (pos.isNull())
        return false;

    return pos.deepEquivalent().upstream(StayInBlock).node()->id() == ID_BR || isFirstVisiblePositionInBlock(pos);
}

bool isFirstVisiblePositionInBlock(const VisiblePosition &pos)
{
    if (pos.isNull())
        return false;

    Position upstream = pos.deepEquivalent().upstream(StayInBlock);
    return upstream.node()->isBlockFlow() && upstream.offset() == 0;
}

bool isFirstVisiblePositionInNode(const VisiblePosition &pos, const NodeImpl *node)
{
    if (pos.isNull())
        return false;
        
    VisiblePosition previous = pos.previous();
    return previous.isNull() || !previous.deepEquivalent().node()->isAncestor(node);
}

bool isLastVisiblePositionOnLine(const VisiblePosition &pos)
{
    if (pos.isNull())
        return false;
        
    VisiblePosition next = pos.next();
    return next.isNull() || visiblePositionsOnDifferentLines(pos, next);
}

bool isLastVisiblePositionInParagraph(const VisiblePosition &pos)
{
    if (pos.isNull())
        return false;

    return pos.deepEquivalent().downstream(StayInBlock).node()->id() == ID_BR || isLastVisiblePositionInBlock(pos);
}

bool isLastVisiblePositionInBlock(const VisiblePosition &pos)
{
    if (pos.isNull())
        return false;
        
    VisiblePosition next = pos.next();
    if (next.isNull())
        return true;
    
    switch (blockRelationship(pos, next)) {
        case NoBlockRelationship:
        case SameBlockRelationship:
        case AncestorBlockRelationship:
            return false;
        case OtherBlockRelationship:
        case PeerBlockRelationship:
        case DescendantBlockRelationship:
            return true;
    }
    ASSERT_NOT_REACHED();
    return false;
}

bool isLastVisiblePositionInNode(const VisiblePosition &pos, const NodeImpl *node)
{
    if (pos.isNull())
        return false;
        
    VisiblePosition next = pos.next();
    return next.isNull() || !next.deepEquivalent().node()->isAncestor(node);
}

}  // namespace DOM