position.cpp

linux下开源浏览器WebKit的源码,市面上的很多商用浏览器都是移植自WebKit

/*
 * Copyright (C) 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 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 "Position.h"

#include "CSSComputedStyleDeclaration.h"
#include "CString.h"
#include "CharacterNames.h"
#include "Logging.h"
#include "PositionIterator.h"
#include "RenderBlock.h"
#include "Text.h"
#include "TextIterator.h"
#include "VisiblePosition.h"
#include "htmlediting.h"
#include "visible_units.h"
#include <stdio.h>
  
namespace WebCore {

using namespace HTMLNames;

static Node* nextRenderedEditable(Node* node)
{
    while (1) {
        node = node->nextEditable();
        if (!node)
            return 0;
        RenderObject* renderer = node->renderer();
        if (!renderer)
            continue;
        if ((renderer->isBox() && toRenderBox(renderer)->inlineBoxWrapper()) || (renderer->isText() && toRenderText(renderer)->firstTextBox()))
            return node;
    }
    return 0;
}

static Node* previousRenderedEditable(Node* node)
{
    while (1) {
        node = node->previousEditable();
        if (!node)
            return 0;
        RenderObject* renderer = node->renderer();
        if (!renderer)
            continue;
        if ((renderer->isBox() && toRenderBox(renderer)->inlineBoxWrapper()) || (renderer->isText() && toRenderText(renderer)->firstTextBox()))
            return node;
    }
    return 0;
}

Element* Position::documentElement() const
{
    if (Node* n = node())
        if (Element* e = n->document()->documentElement())
            return e;
    return 0;
}

Element *Position::element() const
{
    Node *n;
    for (n = node(); n && !n->isElementNode(); n = n->parentNode())
        ; // empty loop body
    return static_cast<Element *>(n);
}

PassRefPtr<CSSComputedStyleDeclaration> Position::computedStyle() const
{
    Element* elem = element();
    if (!elem)
        return 0;
    return WebCore::computedStyle(elem);
}

Position Position::previous(PositionMoveType moveType) const
{
    Node* n = node();
    if (!n)
        return *this;
    
    int o = offset();
    // FIXME: Negative offsets shouldn't be allowed. We should catch this earlier.
    ASSERT(o >= 0);

    if (o > 0) {
        Node* child = n->childNode(o - 1);
        if (child)
            return Position(child, maxDeepOffset(child));

        // There are two reasons child might be 0:
        //   1) The node is node like a text node that is not an element, and therefore has no children.
        //      Going backward one character at a time is correct.
        //   2) The old offset was a bogus offset like (<br>, 1), and there is no child.
        //      Going from 1 to 0 is correct.
        switch (moveType) {
        case CodePoint:
            return Position(n, o - 1);
        case Character:
            return Position(n, uncheckedPreviousOffset(n, o));
        case BackwardDeletion:
            return Position(n, uncheckedPreviousOffsetForBackwardDeletion(n, o));
        }
    }

    Node* parent = n->parentNode();
    if (!parent)
        return *this;

    return Position(parent, n->nodeIndex());
}

Position Position::next(PositionMoveType moveType) const
{
    ASSERT(moveType != BackwardDeletion);

    Node* n = node();
    if (!n)
        return *this;
    
    int o = offset();
    // FIXME: Negative offsets shouldn't be allowed. We should catch this earlier.
    ASSERT(o >= 0);

    Node* child = n->childNode(o);
    if (child || !n->hasChildNodes() && o < maxDeepOffset(n)) {
        if (child)
            return Position(child, 0);
            
        // There are two reasons child might be 0:
        //   1) The node is node like a text node that is not an element, and therefore has no children.
        //      Going forward one character at a time is correct.
        //   2) The new offset is a bogus offset like (<br>, 1), and there is no child.
        //      Going from 0 to 1 is correct.
        return Position(n, (moveType == Character) ? uncheckedNextOffset(n, o) : o + 1);
    }

    Node* parent = n->parentNode();
    if (!parent)
        return *this;

    return Position(parent, n->nodeIndex() + 1);
}

int Position::uncheckedPreviousOffset(const Node* n, int current)
{
    return n->renderer() ? n->renderer()->previousOffset(current) : current - 1;
}

int Position::uncheckedPreviousOffsetForBackwardDeletion(const Node* n, int current)
{
    return n->renderer() ? n->renderer()->previousOffsetForBackwardDeletion(current) : current - 1;
}

int Position::uncheckedNextOffset(const Node* n, int current)
{
    return n->renderer() ? n->renderer()->nextOffset(current) : current + 1;
}

bool Position::atStart() const
{
    Node *n = node();
    if (!n)
        return true;
    
    return offset() <= 0 && n->parent() == 0;
}

bool Position::atEnd() const
{
    Node *n = node();
    if (!n)
        return true;
    
    return n->parent() == 0 && offset() >= maxDeepOffset(n);
}

int Position::renderedOffset() const
{
    if (!node()->isTextNode())
        return offset();
   
    if (!node()->renderer())
        return offset();
                    
    int result = 0;
    RenderText *textRenderer = toRenderText(node()->renderer());
    for (InlineTextBox *box = textRenderer->firstTextBox(); box; box = box->nextTextBox()) {
        int start = box->start();
        int end = box->start() + box->len();
        if (offset() < start)
            return result;
        if (offset() <= end) {
            result += offset() - start;
            return result;
        }
        result += box->len();
    }
    return result;
}

// return first preceding DOM position rendered at a different location, or "this"
Position Position::previousCharacterPosition(EAffinity affinity) const
{
    if (isNull())
        return Position();

    Node *fromRootEditableElement = node()->rootEditableElement();

    bool atStartOfLine = isStartOfLine(VisiblePosition(*this, affinity));
    bool rendered = isCandidate();
    
    Position currentPos = *this;
    while (!currentPos.atStart()) {
        currentPos = currentPos.previous();

        if (currentPos.node()->rootEditableElement() != fromRootEditableElement)
            return *this;

        if (atStartOfLine || !rendered) {
            if (currentPos.isCandidate())
                return currentPos;
        } else if (rendersInDifferentPosition(currentPos))
            return currentPos;
    }
    
    return *this;
}

// return first following position rendered at a different location, or "this"
Position Position::nextCharacterPosition(EAffinity affinity) const
{
    if (isNull())
        return Position();

    Node *fromRootEditableElement = node()->rootEditableElement();

    bool atEndOfLine = isEndOfLine(VisiblePosition(*this, affinity));
    bool rendered = isCandidate();
    
    Position currentPos = *this;
    while (!currentPos.atEnd()) {
        currentPos = currentPos.next();

        if (currentPos.node()->rootEditableElement() != fromRootEditableElement)
            return *this;

        if (atEndOfLine || !rendered) {
            if (currentPos.isCandidate())
                return currentPos;
        } else if (rendersInDifferentPosition(currentPos))
            return currentPos;
    }
    
    return *this;
}

// Whether or not [node, 0] and [node, maxDeepOffset(node)] are their own VisiblePositions.
// If true, adjacent candidates are visually distinct.
// FIXME: Disregard nodes with renderers that have no height, as we do in isCandidate.
// FIXME: Share code with isCandidate, if possible.
static bool endsOfNodeAreVisuallyDistinctPositions(Node* node)
{
    if (!node || !node->renderer())
        return false;
        
    if (!node->renderer()->isInline())
        return true;
        
    // Don't include inline tables.
    if (node->hasTagName(tableTag))
        return false;
    
    // There is a VisiblePosition inside an empty inline-block container.
    return node->renderer()->isReplaced() && canHaveChildrenForEditing(node) && toRenderBox(node->renderer())->height() != 0 && !node->firstChild();
}

static Node* enclosingVisualBoundary(Node* node)
{
    while (node && !endsOfNodeAreVisuallyDistinctPositions(node))
        node = node->parentNode();
        
    return node;
}

// upstream() and downstream() want to return positions that are either in a
// text node or at just before a non-text node.  This method checks for that.
static bool isStreamer(const PositionIterator& pos)
{
    if (!pos.node())
        return true;
        
    if (isAtomicNode(pos.node()))
        return true;
        
    return pos.atStartOfNode();
}

// This function and downstream() are used for moving back and forth between visually equivalent candidates.
// For example, for the text node "foo     bar" where whitespace is collapsible, there are two candidates 
// that map to the VisiblePosition between 'b' and the space.  This function will return the left candidate 
// and downstream() will return the right one.
// Also, upstream() will return [boundary, 0] for any of the positions from [boundary, 0] to the first candidate
// in boundary, where endsOfNodeAreVisuallyDistinctPositions(boundary) is true.
Position Position::upstream() const
{
    Node* startNode = node();
    if (!startNode)
        return Position();
    
    // iterate backward from there, looking for a qualified position
    Node* boundary = enclosingVisualBoundary(startNode);
    PositionIterator lastVisible = *this;
    PositionIterator currentPos = lastVisible;
    bool startEditable = startNode->isContentEditable();