Source/core/css/CSSImageSetValue.cpp

/*
 * Copyright (C) 2012 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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#include "config.h"
#include "core/css/CSSImageSetValue.h"

#include "FetchInitiatorTypeNames.h"
#include "core/css/CSSImageValue.h"
#include "core/css/CSSPrimitiveValue.h"
#include "core/dom/Document.h"
#include "core/fetch/FetchRequest.h"
#include "core/fetch/ImageResource.h"
#include "core/fetch/ResourceFetcher.h"
#include "core/rendering/style/StyleFetchedImageSet.h"
#include "core/rendering/style/StylePendingImage.h"
#include "wtf/text/StringBuilder.h"

namespace WebCore {

CSSImageSetValue::CSSImageSetValue()
    : CSSValueList(ImageSetClass, CommaSeparator)
    , m_accessedBestFitImage(false)
    , m_scaleFactor(1)
{
}

CSSImageSetValue::~CSSImageSetValue()
{
    if (m_imageSet && m_imageSet->isImageResourceSet())
        static_cast<StyleFetchedImageSet*>(m_imageSet.get())->clearImageSetValue();
}

void CSSImageSetValue::fillImageSet()
{
    size_t length = this->length();
    size_t i = 0;
    while (i < length) {
        CSSValue* imageValue = item(i);
        String imageURL = toCSSImageValue(imageValue)->url();

        ++i;
        ASSERT_WITH_SECURITY_IMPLICATION(i < length);
        CSSValue* scaleFactorValue = item(i);
        float scaleFactor = toCSSPrimitiveValue(scaleFactorValue)->getFloatValue();

        ImageWithScale image;
        image.imageURL = imageURL;
        image.scaleFactor = scaleFactor;
        m_imagesInSet.append(image);
        ++i;
    }

    // Sort the images so that they are stored in order from lowest resolution to highest.
    std::sort(m_imagesInSet.begin(), m_imagesInSet.end(), CSSImageSetValue::compareByScaleFactor);
}

CSSImageSetValue::ImageWithScale CSSImageSetValue::bestImageForScaleFactor()
{
    ImageWithScale image;
    size_t numberOfImages = m_imagesInSet.size();
    for (size_t i = 0; i < numberOfImages; ++i) {
        image = m_imagesInSet.at(i);
        if (image.scaleFactor >= m_scaleFactor)
            return image;
    }
    return image;
}

StyleFetchedImageSet* CSSImageSetValue::cachedImageSet(ResourceFetcher* loader, float deviceScaleFactor)
{
    ASSERT(loader);

    m_scaleFactor = deviceScaleFactor;

    if (!m_imagesInSet.size())
        fillImageSet();

    if (!m_accessedBestFitImage) {
        // FIXME: In the future, we want to take much more than deviceScaleFactor into acount here.
        // All forms of scale should be included: Page::pageScaleFactor(), Frame::pageZoomFactor(),
        // and any CSS transforms. https://bugs.webkit.org/show_bug.cgi?id=81698
        ImageWithScale image = bestImageForScaleFactor();
        if (Document* document = loader->document()) {
            FetchRequest request(ResourceRequest(document->completeURL(image.imageURL)), FetchInitiatorTypeNames::css);
            if (ResourcePtr<ImageResource> cachedImage = loader->fetchImage(request)) {
                m_imageSet = StyleFetchedImageSet::create(cachedImage.get(), image.scaleFactor, this);
                m_accessedBestFitImage = true;
            }
        }
    }

    return (m_imageSet && m_imageSet->isImageResourceSet()) ? static_cast<StyleFetchedImageSet*>(m_imageSet.get()) : 0;
}

StyleImage* CSSImageSetValue::cachedOrPendingImageSet(float deviceScaleFactor)
{
    if (!m_imageSet) {
        m_imageSet = StylePendingImage::create(this);
    } else if (!m_imageSet->isPendingImage()) {
        // If the deviceScaleFactor has changed, we may not have the best image loaded, so we have to re-assess.
        if (deviceScaleFactor != m_scaleFactor) {
            m_accessedBestFitImage = false;
            m_imageSet = StylePendingImage::create(this);
        }
    }

    return m_imageSet.get();
}

String CSSImageSetValue::customCssText() const
{
    StringBuilder result;
    result.append("-webkit-image-set(");

    size_t length = this->length();
    size_t i = 0;
    while (i < length) {
        if (i > 0)
            result.append(", ");

        const CSSValue* imageValue = item(i);
        result.append(imageValue->cssText());
        result.append(' ');

        ++i;
        ASSERT_WITH_SECURITY_IMPLICATION(i < length);
        const CSSValue* scaleFactorValue = item(i);
        result.append(scaleFactorValue->cssText());
        // FIXME: Eventually the scale factor should contain it's own unit http://wkb.ug/100120.
        // For now 'x' is hard-coded in the parser, so we hard-code it here too.
        result.append('x');

        ++i;
    }

    result.append(")");
    return result.toString();
}

bool CSSImageSetValue::hasFailedOrCanceledSubresources() const
{
    if (!m_imageSet || !m_imageSet->isImageResourceSet())
        return false;
    Resource* cachedResource = static_cast<StyleFetchedImageSet*>(m_imageSet.get())->cachedImage();
    if (!cachedResource)
        return true;
    return cachedResource->loadFailedOrCanceled();
}

CSSImageSetValue::CSSImageSetValue(const CSSImageSetValue& cloneFrom)
    : CSSValueList(cloneFrom)
    , m_accessedBestFitImage(false)
    , m_scaleFactor(1)
{
    // Non-CSSValueList data is not accessible through CSS OM, no need to clone.
}

PassRefPtr<CSSImageSetValue> CSSImageSetValue::cloneForCSSOM() const
{
    return adoptRef(new CSSImageSetValue(*this));
}

} // namespace WebCore