document.cpp

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    int elapsed = elapsedTime();
    m_overMinimumLayoutThreshold = elapsed > cLayoutScheduleThreshold;
    
    // We'll want to schedule the timer to fire at the minimum layout threshold.
    return max(0, cLayoutScheduleThreshold - elapsed);
}

int Document::elapsedTime() const
{
    return static_cast<int>((currentTime() - m_startTime) * 1000);
}

void Document::write(const SegmentedString& text, Document* ownerDocument)
{
#ifdef INSTRUMENT_LAYOUT_SCHEDULING
    if (!ownerElement())
        printf("Beginning a document.write at %d\n", elapsedTime());
#endif

    if (!m_tokenizer) {
        open(ownerDocument);
        ASSERT(m_tokenizer);
        if (!m_tokenizer)
            return;
        UChar documentPrefix[] = { '<', 'h', 't', 'm', 'l', '>' };
        m_tokenizer->write(SegmentedString(documentPrefix, sizeof(documentPrefix) / sizeof(documentPrefix[0])), false);
    }

    m_tokenizer->write(text, false);

#ifdef INSTRUMENT_LAYOUT_SCHEDULING
    if (!ownerElement())
        printf("Ending a document.write at %d\n", elapsedTime());
#endif    
}

void Document::write(const String& text, Document* ownerDocument)
{
    write(SegmentedString(text), ownerDocument);
}

void Document::writeln(const String& text, Document* ownerDocument)
{
    write(text, ownerDocument);
    write("\n", ownerDocument);
}

void Document::finishParsing()
{
#ifdef INSTRUMENT_LAYOUT_SCHEDULING
    if (!ownerElement())
        printf("Received all data at %d\n", elapsedTime());
#endif
    
    // Let the tokenizer go through as much data as it can.  There will be three possible outcomes after
    // finish() is called:
    // (1) All remaining data is parsed, document isn't loaded yet
    // (2) All remaining data is parsed, document is loaded, tokenizer gets deleted
    // (3) Data is still remaining to be parsed.
    if (m_tokenizer)
        m_tokenizer->finish();
}

void Document::clear()
{
    delete m_tokenizer;
    m_tokenizer = 0;

    removeChildren();

    size_t size = m_windowEventListeners.size();
    for (size_t i = 0; i < size; ++i)
        m_windowEventListeners[i]->setRemoved(true);
    m_windowEventListeners.clear();
}

const KURL& Document::virtualURL() const
{
    return m_url;
}

KURL Document::virtualCompleteURL(const String& url) const
{
    return completeURL(url);
}

void Document::setURL(const KURL& url)
{
    const KURL& newURL = url.isEmpty() ? blankURL() : url;
    if (newURL == m_url)
        return;

    m_url = newURL;
    m_documentURI = m_url.string();
    updateBaseURL();
}

void Document::setBaseElementURL(const KURL& baseElementURL)
{ 
    m_baseElementURL = baseElementURL;
    updateBaseURL();
}

void Document::updateBaseURL()
{
    // DOM 3 Core: When the Document supports the feature "HTML" [DOM Level 2 HTML], the base URI is computed using
    // first the value of the href attribute of the HTML BASE element if any, and the value of the documentURI attribute
    // from the Document interface otherwise.
    if (m_baseElementURL.isEmpty()) {
        // The documentURI attribute is an arbitrary string. DOM 3 Core does not specify how it should be resolved,
        // so we use a null base URL.
        m_baseURL = KURL(KURL(), documentURI());
    } else
        m_baseURL = m_baseElementURL;
    if (!m_baseURL.isValid())
        m_baseURL = KURL();

    if (m_elemSheet)
        m_elemSheet->setHref(m_baseURL.string());
    if (m_mappedElementSheet)
        m_mappedElementSheet->setHref(m_baseURL.string());
}

String Document::userAgent(const KURL& url) const
{
    return frame() ? frame()->loader()->userAgent(url) : String();
}

void Document::setCSSStyleSheet(const String& url, const String& charset, const CachedCSSStyleSheet* sheet)
{
    m_sheet = CSSStyleSheet::create(this, url, charset);
    m_sheet->parseString(sheet->sheetText());

    updateStyleSelector();
}

#if FRAME_LOADS_USER_STYLESHEET
void Document::setUserStyleSheet(const String& sheet)
{
    if (m_usersheet != sheet) {
        m_usersheet = sheet;
        updateStyleSelector();
    }
}
#endif

String Document::userStyleSheet() const
{
#if FRAME_LOADS_USER_STYLESHEET
    return m_usersheet;
#else
    Page* page = this->page();
    if (!page)
        return String();
    return page->userStyleSheet();
#endif
}

CSSStyleSheet* Document::elementSheet()
{
    if (!m_elemSheet)
        m_elemSheet = CSSStyleSheet::create(this, m_baseURL.string());
    return m_elemSheet.get();
}

CSSStyleSheet* Document::mappedElementSheet()
{
    if (!m_mappedElementSheet)
        m_mappedElementSheet = CSSStyleSheet::create(this, m_baseURL.string());
    return m_mappedElementSheet.get();
}

static Node* nextNodeWithExactTabIndex(Node* start, int tabIndex, KeyboardEvent* event)
{
    // Search is inclusive of start
    for (Node* n = start; n; n = n->traverseNextNode())
        if (n->isKeyboardFocusable(event) && n->tabIndex() == tabIndex)
            return n;
    
    return 0;
}

static Node* previousNodeWithExactTabIndex(Node* start, int tabIndex, KeyboardEvent* event)
{
    // Search is inclusive of start
    for (Node* n = start; n; n = n->traversePreviousNode())
        if (n->isKeyboardFocusable(event) && n->tabIndex() == tabIndex)
            return n;
    
    return 0;
}

static Node* nextNodeWithGreaterTabIndex(Node* start, int tabIndex, KeyboardEvent* event)
{
    // Search is inclusive of start
    int winningTabIndex = SHRT_MAX + 1;
    Node* winner = 0;
    for (Node* n = start; n; n = n->traverseNextNode())
        if (n->isKeyboardFocusable(event) && n->tabIndex() > tabIndex && n->tabIndex() < winningTabIndex) {
            winner = n;
            winningTabIndex = n->tabIndex();
        }
    
    return winner;
}

static Node* previousNodeWithLowerTabIndex(Node* start, int tabIndex, KeyboardEvent* event)
{
    // Search is inclusive of start
    int winningTabIndex = 0;
    Node* winner = 0;
    for (Node* n = start; n; n = n->traversePreviousNode())
        if (n->isKeyboardFocusable(event) && n->tabIndex() < tabIndex && n->tabIndex() > winningTabIndex) {
            winner = n;
            winningTabIndex = n->tabIndex();
        }
    
    return winner;
}

Node* Document::nextFocusableNode(Node* start, KeyboardEvent* event)
{
    if (start) {
        // If a node is excluded from the normal tabbing cycle, the next focusable node is determined by tree order
        if (start->tabIndex() < 0) {
            for (Node* n = start->traverseNextNode(); n; n = n->traverseNextNode())
                if (n->isKeyboardFocusable(event) && n->tabIndex() >= 0)
                    return n;
        }
    
        // First try to find a node with the same tabindex as start that comes after start in the document.
        if (Node* winner = nextNodeWithExactTabIndex(start->traverseNextNode(), start->tabIndex(), event))
            return winner;

        if (start->tabIndex() == 0)
            // We've reached the last node in the document with a tabindex of 0. This is the end of the tabbing order.
            return 0;
    }

    // Look for the first node in the document that:
    // 1) has the lowest tabindex that is higher than start's tabindex (or 0, if start is null), and
    // 2) comes first in the document, if there's a tie.
    if (Node* winner = nextNodeWithGreaterTabIndex(this, start ? start->tabIndex() : 0, event))
        return winner;

    // There are no nodes with a tabindex greater than start's tabindex,
    // so find the first node with a tabindex of 0.
    return nextNodeWithExactTabIndex(this, 0, event);
}

Node* Document::previousFocusableNode(Node* start, KeyboardEvent* event)
{
    Node* last;
    for (last = this; last->lastChild(); last = last->lastChild())
        ; // Empty loop.

    // First try to find the last node in the document that comes before start and has the same tabindex as start.
    // If start is null, find the last node in the document with a tabindex of 0.
    Node* startingNode;
    int startingTabIndex;
    if (start) {
        startingNode = start->traversePreviousNode();
        startingTabIndex = start->tabIndex();
    } else {
        startingNode = last;
        startingTabIndex = 0;
    }
    
    // However, if a node is excluded from the normal tabbing cycle, the previous focusable node is determined by tree order
    if (startingTabIndex < 0) {
        for (Node* n = startingNode; n; n = n->traversePreviousNode())
            if (n->isKeyboardFocusable(event) && n->tabIndex() >= 0)
                return n;        
    }

    if (Node* winner = previousNodeWithExactTabIndex(startingNode, startingTabIndex, event))
        return winner;

    // There are no nodes before start with the same tabindex as start, so look for a node that:
    // 1) has the highest non-zero tabindex (that is less than start's tabindex), and
    // 2) comes last in the document, if there's a tie.
    startingTabIndex = (start && start->tabIndex()) ? start->tabIndex() : SHRT_MAX;
    return previousNodeWithLowerTabIndex(last, startingTabIndex, event);
}

int Document::nodeAbsIndex(Node *node)
{
    ASSERT(node->document() == this);

    int absIndex = 0;
    for (Node *n = node; n && n != this; n = n->traversePreviousNode())
        absIndex++;
    return absIndex;
}

Node *Document::nodeWithAbsIndex(int absIndex)
{
    Node *n = this;
    for (int i = 0; n && (i < absIndex); i++) {
        n = n->traverseNextNode();
    }
    return n;
}

void Document::processHttpEquiv(const String &equiv, const String &content)
{
    ASSERT(!equiv.isNull() && !content.isNull());

    Frame *frame = this->frame();

    if (equalIgnoringCase(equiv, "default-style")) {
        // The preferred style set has been overridden as per section 
        // 14.3.2 of the HTML4.0 specification.  We need to update the
        // sheet used variable and then update our style selector. 
        // For more info, see the test at:
        // http://www.hixie.ch/tests/evil/css/import/main/preferred.html
        // -dwh
        m_selectedStylesheetSet = content;
        m_preferredStylesheetSet = content;
        updateStyleSelector();
    } else if (equalIgnoringCase(equiv, "refresh")) {
        double delay;
        String url;
        if (frame && parseHTTPRefresh(content, true, delay, url)) {
            if (url.isEmpty())
                url = frame->loader()->url().string();
            else
                url = completeURL(url).string();
            frame->loader()->scheduleHTTPRedirection(delay, url);
        }
    } else if (equalIgnoringCase(equiv, "set-cookie")) {
        // FIXME: make setCookie work on XML documents too; e.g. in case of <html:meta .....>
        if (isHTMLDocument())
            static_cast<HTMLDocument*>(this)->setCookie(content);
    } else if (equalIgnoringCase(equiv, "content-language"))
        setContentLanguage(content);
    else if (equalIgnoringCase(equiv, "x-dns-prefetch-control"))
        parseDNSPrefetchControlHeader(content);
}

MouseEventWithHitTestResults Document::prepareMouseEvent(const HitTestRequest& request, const IntPoint& documentPoint, const PlatformMouseEvent& event)
{
    ASSERT(!renderer() || renderer()->isRenderView());

    if (!renderer())
        return MouseEventWithHitTestResults(event, HitTestResult(IntPoint()));

    HitTestResult result(documentPoint);
    renderView()->layer()->hitTest(request, result);

    if (!request.readOnly())
        updateRendering();

    return MouseEventWithHitTestResults(event, result);
}

// DOM Section 1.1.1
bool Document::childTypeAllowed(NodeType type)
{
    switch (type) {
        case ATTRIBUTE_NODE:
        case CDATA_SECTION_NODE:
        case DOCUMENT_FRAGMENT_NODE:
        case DOCUMENT_NODE:
        case ENTITY_NODE:
        case ENTITY_REFERENCE_NODE:
        case NOTATION_NODE:
        case TEXT_NODE:
        case XPATH_NAMESPACE_NODE:
            return false;
        case COMMENT_NODE:
        case PROCESSING_INSTRUCTION_NODE:
            return true;
        case DOCUMENT_TYPE_NODE:
        case ELEMENT_NODE:
            // Documents may contain no more than one of each of these.
            // (One Element and one DocumentType.)
            for (Node* c = firstChild(); c; c = c->nextSibling())
                if (c->nodeType() == type)
                    return false;
            return true;
    }
    return false;
}

bool Document::canReplaceChild(Node* newChild, Node* oldChild)
{
    if (!oldChild)
        // ContainerNode::replaceChild will raise a NOT_FOUND_ERR.
        return true;

    if (oldChild->nodeType() == newChild->nodeType())
        return true;

    int numDoctypes = 0;
    int numElements = 0;

    // First, check how many doctypes and elements we have, not counting
    // the child we're about to remove.
    for (Node* c = firstChild(); c; c = c->nextSibling()) {
        if (c == oldChild)
            continue;
        
        switch (c->nodeType()) {
            case DOCUMENT_TYPE_NODE:
                numDoctypes++;
                break;
            case ELEMENT_NODE:
                numElements++;
                break;
            default:
                break;
        }
    }
    
    // Then