third_party/WebKit/Source/core/fetch/ImageResourceObserver.h

/*
    Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
    Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
    Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
    Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
*/

#ifndef ImageResourceObserver_h
#define ImageResourceObserver_h

#include "core/CoreExport.h"
#include "platform/graphics/ImageAnimationPolicy.h"
#include "platform/network/ResourceLoadPriority.h"
#include "wtf/Forward.h"

namespace blink {

class ImageResource;
class IntRect;

class CORE_EXPORT ImageResourceObserver {
public:
    virtual ~ImageResourceObserver() {}

    // Called whenever a frame of an image changes, either because we got more data from the network or
    // because we are animating. If not null, the IntRect is the changed rect of the image.
    virtual void imageChanged(ImageResource*, const IntRect* = 0) { }

    // Called just before ResourceClient::notifyFinished() would be called.
    // This is to avoid an ImageResourceObserver from being
    // also a ResourceClient just to be notified for load finish.
    virtual void imageNotifyFinished(ImageResource*) { }

    // Called to find out if this client wants to actually display the image. Used to tell when we
    // can halt animation. Content nodes that hold image refs for example would not render the image,
    // but LayoutImages would (assuming they have visibility: visible and their layout tree isn't hidden
    // e.g., in the b/f cache or in a background tab).
    virtual bool willRenderImage() { return false; }

    // Called to get imageAnimation policy from settings
    virtual bool getImageAnimationPolicy(ImageAnimationPolicy&) { return false; }

    virtual ResourcePriority computeResourcePriority() const { return ResourcePriority(); }

    // Name for debugging, e.g. shown in memory-infra.
    virtual String debugName() const = 0;

    static bool isExpectedType(ImageResourceObserver*) { return true; }
};

} // namespace blink

#endif