Source/WebCore/html/LazyLoadImageObserver.h

/*
 * Copyright (C) 2020 Igalia S.L.
 *
 * 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 INC. AND ITS CONTRIBUTORS ``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 INC. OR ITS 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 "IntersectionObserver.h"

namespace WebCore {

class Document;
class Element;

class LazyLoadImageObserver {
    WTF_MAKE_FAST_ALLOCATED;
public:
    static void observe(Element&);
    static void unobserve(Element&, Document&);

private:
    friend class Document;

    static std::unique_ptr<LazyLoadImageObserver> create()
    {
        return std::unique_ptr<LazyLoadImageObserver>(new LazyLoadImageObserver());
    }
    LazyLoadImageObserver() = default;

    IntersectionObserver* intersectionObserver(Document&);
    bool isObserved(Element&) const;

    // The intersection observer responsible for loading the image once it's near the viewport.
    RefPtr<IntersectionObserver> m_lazyLoadIntersectionObserver;
};

} // namespace