root/Source/core/loader/ImageLoader.cpp

DEFINITIONS

1. loadEventSender
2. errorEventSender
3. pageIsBeingDismissed
4. m_highPriorityClientCount
5. setImage
6. setImageWithoutConsideringPendingLoadEvent
7. updateFromElement
8. updateFromElementIgnoringPreviousError
9. notifyFinished
10. renderImageResource
11. updateRenderer
12. updatedHasPendingEvent
13. timerFired
14. dispatchPendingEvent
15. dispatchPendingLoadEvent
16. dispatchPendingErrorEvent
17. addClient
18. removeClient
19. dispatchPendingLoadEvents
20. dispatchPendingErrorEvents
21. elementDidMoveToNewDocument
22. sourceImageChanged
23. clearFailedLoadURL

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010 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.
 */

#include "config.h"
#include "core/loader/ImageLoader.h"

#include "core/dom/Document.h"
#include "core/dom/Element.h"
#include "core/events/Event.h"
#include "core/events/EventSender.h"
#include "core/fetch/CrossOriginAccessControl.h"
#include "core/fetch/FetchRequest.h"
#include "core/fetch/ResourceFetcher.h"
#include "core/html/HTMLObjectElement.h"
#include "core/html/parser/HTMLParserIdioms.h"
#include "core/rendering/RenderImage.h"
#include "core/rendering/RenderVideo.h"
#include "core/rendering/svg/RenderSVGImage.h"
#include "platform/weborigin/SecurityOrigin.h"

namespace WebCore {

static ImageEventSender& loadEventSender()
{
    DEFINE_STATIC_LOCAL(ImageEventSender, sender, (EventTypeNames::load));
    return sender;
}

static ImageEventSender& errorEventSender()
{
    DEFINE_STATIC_LOCAL(ImageEventSender, sender, (EventTypeNames::error));
    return sender;
}

static inline bool pageIsBeingDismissed(Document* document)
{
    return document->pageDismissalEventBeingDispatched() != Document::NoDismissal;
}

ImageLoader::ImageLoader(Element* element)
    : m_element(element)
    , m_image(0)
    , m_derefElementTimer(this, &ImageLoader::timerFired)
    , m_hasPendingLoadEvent(false)
    , m_hasPendingErrorEvent(false)
    , m_imageComplete(true)
    , m_loadManually(false)
    , m_elementIsProtected(false)
    , m_highPriorityClientCount(0)
{
}

ImageLoader::~ImageLoader()
{
    if (m_image)
        m_image->removeClient(this);

    ASSERT(m_hasPendingLoadEvent || !loadEventSender().hasPendingEvents(this));
    if (m_hasPendingLoadEvent)
        loadEventSender().cancelEvent(this);

    ASSERT(m_hasPendingErrorEvent || !errorEventSender().hasPendingEvents(this));
    if (m_hasPendingErrorEvent)
        errorEventSender().cancelEvent(this);

    // If the ImageLoader is being destroyed but it is still protecting its image-loading Element,
    // remove that protection here.
    if (m_elementIsProtected)
        m_element->deref();
}

void ImageLoader::setImage(ImageResource* newImage)
{
    setImageWithoutConsideringPendingLoadEvent(newImage);

    // Only consider updating the protection ref-count of the Element immediately before returning
    // from this function as doing so might result in the destruction of this ImageLoader.
    updatedHasPendingEvent();
}

void ImageLoader::setImageWithoutConsideringPendingLoadEvent(ImageResource* newImage)
{
    ASSERT(m_failedLoadURL.isEmpty());
    ImageResource* oldImage = m_image.get();
    if (newImage != oldImage) {
        sourceImageChanged();
        m_image = newImage;
        if (m_hasPendingLoadEvent) {
            loadEventSender().cancelEvent(this);
            m_hasPendingLoadEvent = false;
        }
        if (m_hasPendingErrorEvent) {
            errorEventSender().cancelEvent(this);
            m_hasPendingErrorEvent = false;
        }
        m_imageComplete = true;
        if (newImage)
            newImage->addClient(this);
        if (oldImage)
            oldImage->removeClient(this);
    }

    if (RenderImageResource* imageResource = renderImageResource())
        imageResource->resetAnimation();
}

void ImageLoader::updateFromElement()
{
    // Don't load images for inactive documents. We don't want to slow down the
    // raw HTML parsing case by loading images we don't intend to display.
    Document& document = m_element->document();
    if (!document.isActive())
        return;

    AtomicString attr = m_element->imageSourceURL();

    if (!m_failedLoadURL.isEmpty() && attr == m_failedLoadURL)
        return;

    // Do not load any image if the 'src' attribute is missing or if it is
    // an empty string.
    ResourcePtr<ImageResource> newImage = 0;
    if (!attr.isNull() && !stripLeadingAndTrailingHTMLSpaces(attr).isEmpty()) {
        FetchRequest request(ResourceRequest(document.completeURL(sourceURI(attr))), element()->localName());

        AtomicString crossOriginMode = m_element->fastGetAttribute(HTMLNames::crossoriginAttr);
        if (!crossOriginMode.isNull())
            request.setCrossOriginAccessControl(document.securityOrigin(), crossOriginMode);

        if (m_loadManually) {
            bool autoLoadOtherImages = document.fetcher()->autoLoadImages();
            document.fetcher()->setAutoLoadImages(false);
            newImage = new ImageResource(request.resourceRequest());
            newImage->setLoading(true);
            document.fetcher()->m_documentResources.set(newImage->url(), newImage.get());
            document.fetcher()->setAutoLoadImages(autoLoadOtherImages);
        } else {
            newImage = document.fetcher()->fetchImage(request);
        }

        // If we do not have an image here, it means that a cross-site
        // violation occurred, or that the image was blocked via Content
        // Security Policy, or the page is being dismissed. Trigger an
        // error event if the page is not being dismissed.
        if (!newImage && !pageIsBeingDismissed(&document)) {
            m_failedLoadURL = attr;
            m_hasPendingErrorEvent = true;
            errorEventSender().dispatchEventSoon(this);
        } else
            clearFailedLoadURL();
    } else if (!attr.isNull()) {
        // Fire an error event if the url is empty.
        m_hasPendingErrorEvent = true;
        errorEventSender().dispatchEventSoon(this);
    }

    ImageResource* oldImage = m_image.get();
    if (newImage != oldImage) {
        sourceImageChanged();

        if (m_hasPendingLoadEvent) {
            loadEventSender().cancelEvent(this);
            m_hasPendingLoadEvent = false;
        }

        // Cancel error events that belong to the previous load, which is now cancelled by changing the src attribute.
        // If newImage is null and m_hasPendingErrorEvent is true, we know the error event has been just posted by
        // this load and we should not cancel the event.
        // FIXME: If both previous load and this one got blocked with an error, we can receive one error event instead of two.
        if (m_hasPendingErrorEvent && newImage) {
            errorEventSender().cancelEvent(this);
            m_hasPendingErrorEvent = false;
        }

        m_image = newImage;
        m_hasPendingLoadEvent = newImage;
        m_imageComplete = !newImage;

        if (newImage) {
            updateRenderer();

            // If newImage is cached, addClient() will result in the load event
            // being queued to fire. Ensure this happens after beforeload is
            // dispatched.
            newImage->addClient(this);
        } else {
            updateRenderer();
        }

        if (oldImage)
            oldImage->removeClient(this);
    }

    if (RenderImageResource* imageResource = renderImageResource())
        imageResource->resetAnimation();

    // Only consider updating the protection ref-count of the Element immediately before returning
    // from this function as doing so might result in the destruction of this ImageLoader.
    updatedHasPendingEvent();
}

void ImageLoader::updateFromElementIgnoringPreviousError()
{
    clearFailedLoadURL();
    updateFromElement();
}

void ImageLoader::notifyFinished(Resource* resource)
{
    ASSERT(m_failedLoadURL.isEmpty());
    ASSERT(resource == m_image.get());

    m_imageComplete = true;
    updateRenderer();

    if (!m_hasPendingLoadEvent)
        return;

    if (resource->errorOccurred()) {
        loadEventSender().cancelEvent(this);
        m_hasPendingLoadEvent = false;

        m_hasPendingErrorEvent = true;
        errorEventSender().dispatchEventSoon(this);

        // Only consider updating the protection ref-count of the Element immediately before returning
        // from this function as doing so might result in the destruction of this ImageLoader.
        updatedHasPendingEvent();
        return;
    }
    if (resource->wasCanceled()) {
        m_hasPendingLoadEvent = false;
        // Only consider updating the protection ref-count of the Element immediately before returning
        // from this function as doing so might result in the destruction of this ImageLoader.
        updatedHasPendingEvent();
        return;
    }
    loadEventSender().dispatchEventSoon(this);
}

RenderImageResource* ImageLoader::renderImageResource()
{
    RenderObject* renderer = m_element->renderer();

    if (!renderer)
        return 0;

    // We don't return style generated image because it doesn't belong to the ImageLoader.
    // See <https://bugs.webkit.org/show_bug.cgi?id=42840>
    if (renderer->isImage() && !static_cast<RenderImage*>(renderer)->isGeneratedContent())
        return toRenderImage(renderer)->imageResource();

    if (renderer->isSVGImage())
        return toRenderSVGImage(renderer)->imageResource();

    if (renderer->isVideo())
        return toRenderVideo(renderer)->imageResource();

    return 0;
}

void ImageLoader::updateRenderer()
{
    RenderImageResource* imageResource = renderImageResource();

    if (!imageResource)
        return;

    // Only update the renderer if it doesn't have an image or if what we have
    // is a complete image.  This prevents flickering in the case where a dynamic
    // change is happening between two images.
    ImageResource* cachedImage = imageResource->cachedImage();
    if (m_image != cachedImage && (m_imageComplete || !cachedImage))
        imageResource->setImageResource(m_image.get());
}

void ImageLoader::updatedHasPendingEvent()
{
    // If an Element that does image loading is removed from the DOM the load/error event for the image is still observable.
    // As long as the ImageLoader is actively loading, the Element itself needs to be ref'ed to keep it from being
    // destroyed by DOM manipulation or garbage collection.
    // If such an Element wishes for the load to stop when removed from the DOM it needs to stop the ImageLoader explicitly.
    bool wasProtected = m_elementIsProtected;
    m_elementIsProtected = m_hasPendingLoadEvent || m_hasPendingErrorEvent;
    if (wasProtected == m_elementIsProtected)
        return;

    if (m_elementIsProtected) {
        if (m_derefElementTimer.isActive())
            m_derefElementTimer.stop();
        else
            m_element->ref();
    } else {
        ASSERT(!m_derefElementTimer.isActive());
        m_derefElementTimer.startOneShot(0, FROM_HERE);
    }
}

void ImageLoader::timerFired(Timer<ImageLoader>*)
{
    m_element->deref();
}

void ImageLoader::dispatchPendingEvent(ImageEventSender* eventSender)
{
    ASSERT(eventSender == &loadEventSender() || eventSender == &errorEventSender());
    const AtomicString& eventType = eventSender->eventType();
    if (eventType == EventTypeNames::load)
        dispatchPendingLoadEvent();
    if (eventType == EventTypeNames::error)
        dispatchPendingErrorEvent();
}

void ImageLoader::dispatchPendingLoadEvent()
{
    if (!m_hasPendingLoadEvent)
        return;
    if (!m_image)
        return;
    m_hasPendingLoadEvent = false;
    if (element()->document().frame())
        dispatchLoadEvent();

    // Only consider updating the protection ref-count of the Element immediately before returning
    // from this function as doing so might result in the destruction of this ImageLoader.
    updatedHasPendingEvent();
}

void ImageLoader::dispatchPendingErrorEvent()
{
    if (!m_hasPendingErrorEvent)
        return;
    m_hasPendingErrorEvent = false;
    if (element()->document().frame())
        element()->dispatchEvent(Event::create(EventTypeNames::error));

    // Only consider updating the protection ref-count of the Element immediately before returning
    // from this function as doing so might result in the destruction of this ImageLoader.
    updatedHasPendingEvent();
}

void ImageLoader::addClient(ImageLoaderClient* client)
{
    if (client->requestsHighLiveResourceCachePriority()) {
        if (m_image && !m_highPriorityClientCount++)
            m_image->setCacheLiveResourcePriority(Resource::CacheLiveResourcePriorityHigh);
    }
    m_clients.add(client);
}
void ImageLoader::removeClient(ImageLoaderClient* client)
{
    if (client->requestsHighLiveResourceCachePriority()) {
        ASSERT(m_highPriorityClientCount);
        m_highPriorityClientCount--;
        if (m_image && !m_highPriorityClientCount)
            m_image->setCacheLiveResourcePriority(Resource::CacheLiveResourcePriorityLow);
    }
    m_clients.remove(client);
}

void ImageLoader::dispatchPendingLoadEvents()
{
    loadEventSender().dispatchPendingEvents();
}

void ImageLoader::dispatchPendingErrorEvents()
{
    errorEventSender().dispatchPendingEvents();
}

void ImageLoader::elementDidMoveToNewDocument()
{
    clearFailedLoadURL();
    setImage(0);
}

void ImageLoader::sourceImageChanged()
{
    ImageLoaderClientSet::iterator end = m_clients.end();
    for (ImageLoaderClientSet::iterator it = m_clients.begin(); it != end; ++it) {
        ImageLoaderClient* handle = *it;
        handle->notifyImageSourceChanged();
    }
}

inline void ImageLoader::clearFailedLoadURL()
{
    m_failedLoadURL = AtomicString();
}

}