flutter_flutter/engine/core/loader/ImageLoader.h

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 * Copyright (C) 2004, 2009 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 ImageLoader_h
#define ImageLoader_h

#include "core/fetch/ImageResource.h"
#include "core/fetch/ImageResourceClient.h"
#include "core/fetch/ResourcePtr.h"
#include "platform/heap/Handle.h"
#include "wtf/HashSet.h"
#include "wtf/WeakPtr.h"
#include "wtf/text/AtomicString.h"

namespace blink {

class IncrementLoadEventDelayCount;
class FetchRequest;
class Document;

class ImageLoaderClient : public DummyBase<void> {
public:
    virtual void notifyImageSourceChanged() = 0;

    // Determines whether the observed ImageResource should have higher priority in the decoded resources cache.
    virtual bool requestsHighLiveResourceCachePriority() { return false; }

    virtual void trace(Visitor*) { }

protected:
    ImageLoaderClient() { }
};

class Element;
class ImageLoader;
class RenderImageResource;

template<typename T> class EventSender;
typedef EventSender<ImageLoader> ImageEventSender;

class ImageLoader : public DummyBase<ImageLoader>, public ImageResourceClient {
public:
    explicit ImageLoader(Element*);
    virtual ~ImageLoader();
    void trace(Visitor*);

    enum LoadType {
        LoadNormally,
        ForceLoadImmediately
    };

    enum UpdateFromElementBehavior {
        // This should be the update behavior when the element is attached to a document, or when DOM mutations trigger a new load.
        // Starts loading if a load hasn't already been started.
        UpdateNormal,
        // This should be the update behavior when the resource was changed (via 'src', 'srcset' or 'sizes').
        // Starts a new load even if a previous load of the same resource have failed, to match Firefox's behavior.
        // FIXME - Verify that this is the right behavior according to the spec.
        UpdateIgnorePreviousError,
        // This forces the image to update its intrinsic size, even if the image source has not changed.
        UpdateSizeChanged
    };

    void updateFromElement(UpdateFromElementBehavior = UpdateNormal, LoadType = LoadNormally);

    void elementDidMoveToNewDocument();

    Element* element() const { return m_element; }
    bool imageComplete() const
    {
        return m_imageComplete && !m_pendingTask;
    }

    ImageResource* image() const { return m_image.get(); }
    void setImage(ImageResource*); // Cancels pending load events, and doesn't dispatch new ones.

    bool hasPendingActivity() const
    {
        return m_hasPendingLoadEvent || m_hasPendingErrorEvent || m_pendingTask;
    }

    void dispatchPendingEvent(ImageEventSender*);

    static void dispatchPendingLoadEvents();
    static void dispatchPendingErrorEvents();

    void addClient(ImageLoaderClient*);
    void removeClient(ImageLoaderClient*);

protected:
    virtual void notifyFinished(Resource*) override;

private:
    class Task;

    // Called from the task or from updateFromElement to initiate the load.
    void doUpdateFromElement(UpdateFromElementBehavior);

    virtual void dispatchLoadEvent() = 0;
    virtual String sourceURI(const AtomicString&) const = 0;

    void updatedHasPendingEvent();

    void dispatchPendingLoadEvent();
    void dispatchPendingErrorEvent();

    RenderImageResource* renderImageResource();
    void updateRenderer();

    void setImageWithoutConsideringPendingLoadEvent(ImageResource*);
    void sourceImageChanged();
    void clearFailedLoadURL();
    void crossSiteOrCSPViolationOccured(AtomicString);
    void enqueueImageLoadingMicroTask(UpdateFromElementBehavior);

    void timerFired(Timer<ImageLoader>*);

    KURL imageSourceToKURL(AtomicString) const;

    // Used to determine whether to immediately initiate the load
    // or to schedule a microtask.
    bool shouldLoadImmediately(const KURL&, LoadType) const;

    void willRemoveClient(ImageLoaderClient&);

    RawPtr<Element> m_element;
    ResourcePtr<ImageResource> m_image;
    RefPtr<Element> m_keepAlive;
    HashSet<ImageLoaderClient*> m_clients;
    Timer<ImageLoader> m_derefElementTimer;
    AtomicString m_failedLoadURL;
    WeakPtr<Task> m_pendingTask; // owned by Microtask
    OwnPtr<IncrementLoadEventDelayCount> m_loadDelayCounter;
    bool m_hasPendingLoadEvent : 1;
    bool m_hasPendingErrorEvent : 1;
    bool m_imageComplete : 1;
    bool m_elementIsProtected : 1;
    unsigned m_highPriorityClientCount;
};

}

#endif