Source/WebCore/css/CSSImageSetValue.cpp

/*
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#include "config.h"
#include "CSSImageSetValue.h"

#if ENABLE(CSS_IMAGE_SET)

#include "CSSImageValue.h"
#include "CSSPrimitiveValue.h"
#include "CachedImage.h"
#include "CachedResourceLoader.h"
#include "CachedResourceRequest.h"
#include "CachedResourceRequestInitiators.h"
#include "CrossOriginAccessControl.h"
#include "Document.h"
#include "Page.h"
#include "StyleCachedImageSet.h"
#include "StylePendingImage.h"
#include <wtf/text/StringBuilder.h>

namespace WebCore {

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

inline void CSSImageSetValue::detachPendingImage()
{
    if (is<StylePendingImage>(m_imageSet.get()))
        downcast<StylePendingImage>(*m_imageSet).detachFromCSSValue();
}

CSSImageSetValue::~CSSImageSetValue()
{
    detachPendingImage();

    if (is<StyleCachedImageSet>(m_imageSet.get()))
        downcast<StyleCachedImageSet>(*m_imageSet).clearImageSetValue();
}

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

        ++i;
        ASSERT_WITH_SECURITY_IMPLICATION(i < length);
        CSSValue* scaleFactorValue = item(i);
        float scaleFactor = downcast<CSSPrimitiveValue>(*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;
}

StyleCachedImageSet* CSSImageSetValue::cachedImageSet(CachedResourceLoader& loader, const ResourceLoaderOptions& options)
{
    Document* document = loader.document();
    if (Page* page = document->page())
        m_scaleFactor = page->deviceScaleFactor();
    else
        m_scaleFactor = 1;

    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();
        CachedResourceRequest request(ResourceRequest(document->completeURL(image.imageURL)), options);
        request.setInitiator(cachedResourceRequestInitiators().css);
        if (options.requestOriginPolicy() == PotentiallyCrossOriginEnabled)
            updateRequestForAccessControl(request.mutableResourceRequest(), document->securityOrigin(), options.allowCredentials());
        if (CachedResourceHandle<CachedImage> cachedImage = loader.requestImage(request)) {
            detachPendingImage();
            m_imageSet = StyleCachedImageSet::create(cachedImage.get(), image.scaleFactor, this);
            m_accessedBestFitImage = true;
        }
    }

    return is<StyleCachedImageSet>(m_imageSet.get()) ? downcast<StyleCachedImageSet>(m_imageSet.get()) : nullptr;
}

StyleImage* CSSImageSetValue::cachedOrPendingImageSet(Document& document)
{
    if (!m_imageSet)
        m_imageSet = StylePendingImage::create(this);
    else if (!m_imageSet->isPendingImage()) {
        float deviceScaleFactor = 1;
        if (Page* page = document.page())
            deviceScaleFactor = page->deviceScaleFactor();

        // 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.appendLiteral("-webkit-image-set(");

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

        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::traverseSubresources(const std::function<bool (const CachedResource&)>& handler) const
{
    if (!is<StyleCachedImageSet>(m_imageSet.get()))
        return false;
    CachedImage* cachedResource = downcast<StyleCachedImageSet>(*m_imageSet).cachedImage();
    ASSERT(cachedResource);
    return handler(*cachedResource);
}

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.
}

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

} // namespace WebCore

#endif // ENABLE(CSS_IMAGE_SET)