CSSImageSetValue.cpp   [plain text]

/*
 * Copyright (C) 2012-2017 Apple Inc. All rights reserved.
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#include "config.h"
#include "CSSImageSetValue.h"

#include "CSSImageGeneratorValue.h"
#include "CSSImageValue.h"
#include "CSSPrimitiveValue.h"
#include "Document.h"
#include "Page.h"
#include "StyleBuilderState.h"
#include <wtf/text/StringBuilder.h>

namespace WebCore {

Ref<CSSImageSetValue> CSSImageSetValue::create()
{
    return adoptRef(*new CSSImageSetValue);
}

CSSImageSetValue::CSSImageSetValue()
    : CSSValueList(ImageSetClass, CommaSeparator)
{
}

CSSImageSetValue::~CSSImageSetValue() = default;

void CSSImageSetValue::fillImageSet()
{
    size_t length = this->length();
    for (size_t i = 0; i + 1 < length; i += 2) {
        CSSValue* imageValue = item(i);
        CSSValue* scaleFactorValue = item(i + 1);

        ASSERT(is<CSSImageValue>(imageValue) || is<CSSImageGeneratorValue>(imageValue));
        ASSERT(is<CSSPrimitiveValue>(scaleFactorValue));

        float scaleFactor = downcast<CSSPrimitiveValue>(scaleFactorValue)->floatValue(CSSUnitType::CSS_DPPX);
        m_imagesInSet.append({ imageValue, scaleFactor });
    }

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

ImageWithScale CSSImageSetValue::bestImageForScaleFactor()
{
    if (!m_imagesInSet.size())
        fillImageSet();

    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_deviceScaleFactor)
            return image;
    }
    return image;
}

CachedImage* CSSImageSetValue::cachedImage() const
{
    if (is<CSSImageValue>(m_selectedImageValue))
        return downcast<CSSImageValue>(*m_selectedImageValue).cachedImage();
    return nullptr;
}

ImageWithScale CSSImageSetValue::selectBestFitImage(const Document& document)
{
    updateDeviceScaleFactor(document);

    if (!m_accessedBestFitImage) {
        m_accessedBestFitImage = true;
        m_bestFitImage = bestImageForScaleFactor();
    }

    return m_bestFitImage;
}

void CSSImageSetValue::updateDeviceScaleFactor(const Document& document)
{
    // 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
    float deviceScaleFactor = document.page() ? document.page()->deviceScaleFactor() : 1;
    if (deviceScaleFactor == m_deviceScaleFactor)
        return;
    m_deviceScaleFactor = deviceScaleFactor;
    m_accessedBestFitImage = false;
    m_selectedImageValue = nullptr;
}

Ref<CSSImageSetValue> CSSImageSetValue::imageSetWithStylesResolved(Style::BuilderState& builderState)
{
    Ref<CSSImageSetValue> result = CSSImageSetValue::create();
    size_t length = this->length();
    for (size_t i = 0; i + 1 < length; i += 2) {
        result->append(builderState.resolveImageStyles(*itemWithoutBoundsCheck(i)));
        result->append(*itemWithoutBoundsCheck(i + 1));
    }

    return result;
}

String CSSImageSetValue::customCSSText() const
{
    StringBuilder result;
    result.appendLiteral("image-set(");

    size_t length = this->length();
    for (size_t i = 0; i + 1 < length; i += 2) {
        if (i > 0)
            result.appendLiteral(", ");

        result.append(item(i)->cssText(), ' ', item(i + 1)->cssText());
    }

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

bool CSSImageSetValue::traverseSubresources(const WTF::Function<bool (const CachedResource&)>& handler) const
{
    return m_selectedImageValue && m_selectedImageValue->traverseSubresources(handler);
}

} // namespace WebCore