Source/WebCore/html/parser/HTMLFormattingElementList.h

/*
 * Copyright (C) 2010 Google, 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 GOOGLE 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 GOOGLE 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. 
 */

#pragma once

#include "HTMLStackItem.h"
#include <wtf/Forward.h>
#include <wtf/RefPtr.h>
#include <wtf/Vector.h>

namespace WebCore {

class Element;

// This may end up merged into HTMLElementStack.
class HTMLFormattingElementList {
    WTF_MAKE_NONCOPYABLE(HTMLFormattingElementList);
public:
    HTMLFormattingElementList();
    ~HTMLFormattingElementList();

    // Ideally Entry would be private, but HTMLTreeBuilder has to coordinate
    // between the HTMLFormattingElementList and HTMLElementStack and needs
    // access to Entry::isMarker() and Entry::replaceElement() to do so.
    class Entry {
    public:
        // Inline because they're hot and Vector<T> uses them.
        explicit Entry(Ref<HTMLStackItem>&& item)
            : m_item(WTFMove(item))
        {
        }
        enum MarkerEntryType { MarkerEntry };
        Entry(MarkerEntryType)
        {
        }

        bool isMarker() const { return !m_item; }

        HTMLStackItem* stackItem() const { return m_item.get(); }
        Element& element() const
        {
            // The fact that !m_item == isMarker() is an implementation detail
            // callers should check isMarker() before calling element().
            ASSERT(m_item);
            return m_item->element();
        }
        void replaceElement(Ref<HTMLStackItem>&& item) { m_item = WTFMove(item); }

        // Needed for use with Vector.  These are super-hot and must be inline.
        bool operator==(Element* element) const { return !m_item ? !element : &m_item->element() == element; }
        bool operator!=(Element* element) const { return !m_item ? !!element : &m_item->element() != element; }

    private:
        RefPtr<HTMLStackItem> m_item;
    };

    class Bookmark {
    public:
        explicit Bookmark(Entry& entry)
            : m_hasBeenMoved(false)
            , m_mark(&entry)
        {
        }

        void moveToAfter(Entry& before)
        {
            m_hasBeenMoved = true;
            m_mark = &before;
        }

        bool hasBeenMoved() const { return m_hasBeenMoved; }
        Entry& mark() const { ASSERT(m_mark); return *m_mark; }

    private:
        bool m_hasBeenMoved;
        Entry* m_mark;
    };

    bool isEmpty() const { return !size(); }
    size_t size() const { return m_entries.size(); }

    Element* closestElementInScopeWithName(const AtomString&);

    Entry* find(Element&);
    bool contains(Element&);
    void append(Ref<HTMLStackItem>&&);
    void remove(Element&);

    Bookmark bookmarkFor(Element&);
    void swapTo(Element& oldElement, Ref<HTMLStackItem>&& newItem, const Bookmark&);

    void appendMarker();
    // clearToLastMarker also clears the marker (per the HTML5 spec).
    void clearToLastMarker();

    const Entry& at(size_t i) const { return m_entries[i]; }
    Entry& at(size_t i) { return m_entries[i]; }

#if ENABLE(TREE_DEBUGGING)
    void show();
#endif

private:
    Entry& first() { return at(0); }

    // http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#list-of-active-formatting-elements
    // These functions enforce the "Noah's Ark" condition, which removes redundant mis-nested elements.
    void tryToEnsureNoahsArkConditionQuickly(HTMLStackItem&, Vector<HTMLStackItem*>& remainingCandidates);
    void ensureNoahsArkCondition(HTMLStackItem&);

    Vector<Entry> m_entries;
};

} // namespace WebCore