third_party/WebKit/Source/core/dom/StyleEngine.cpp

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2001 Dirk Mueller (mueller@kde.org)
 *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
 * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
 * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
 * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
 * Copyright (C) Research In Motion Limited 2010-2011. 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 "core/dom/StyleEngine.h"

#include "core/HTMLNames.h"
#include "core/css/CSSDefaultStyleSheets.h"
#include "core/css/CSSFontSelector.h"
#include "core/css/CSSStyleSheet.h"
#include "core/css/FontFaceCache.h"
#include "core/css/StyleSheetContents.h"
#include "core/css/invalidation/InvalidationSet.h"
#include "core/css/resolver/ScopedStyleResolver.h"
#include "core/dom/DocumentStyleSheetCollector.h"
#include "core/dom/Element.h"
#include "core/dom/ProcessingInstruction.h"
#include "core/dom/ShadowTreeStyleSheetCollection.h"
#include "core/dom/StyleChangeReason.h"
#include "core/dom/shadow/ShadowRoot.h"
#include "core/frame/Settings.h"
#include "core/html/HTMLIFrameElement.h"
#include "core/html/HTMLLinkElement.h"
#include "core/html/imports/HTMLImportsController.h"
#include "core/inspector/InspectorInstrumentation.h"
#include "core/page/Page.h"
#include "core/svg/SVGStyleElement.h"
#include "platform/TraceEvent.h"
#include "platform/fonts/FontCache.h"

namespace blink {

using namespace HTMLNames;

StyleEngine::StyleEngine(Document& document)
    : m_document(&document)
    , m_isMaster(!document.importsController() || document.importsController()->master() == &document)
    , m_documentStyleSheetCollection(DocumentStyleSheetCollection::create(document))
    // We don't need to create CSSFontSelector for imported document or
    // HTMLTemplateElement's document, because those documents have no frame.
    , m_fontSelector(document.frame() ? CSSFontSelector::create(&document) : nullptr)
{
    if (m_fontSelector)
        m_fontSelector->registerForInvalidationCallbacks(this);
}

StyleEngine::~StyleEngine()
{
}

static bool isStyleElement(Node& node)
{
    return isHTMLStyleElement(node) || isSVGStyleElement(node);
}

inline Document* StyleEngine::master()
{
    if (isMaster())
        return m_document;
    HTMLImportsController* import = document().importsController();
    if (!import) // Document::import() can return null while executing its destructor.
        return 0;
    return import->master();
}

TreeScopeStyleSheetCollection* StyleEngine::ensureStyleSheetCollectionFor(TreeScope& treeScope)
{
    if (treeScope == m_document)
        return documentStyleSheetCollection();

    StyleSheetCollectionMap::AddResult result = m_styleSheetCollectionMap.add(&treeScope, nullptr);
    if (result.isNewEntry)
        result.storedValue->value = new ShadowTreeStyleSheetCollection(toShadowRoot(treeScope));
    return result.storedValue->value.get();
}

TreeScopeStyleSheetCollection* StyleEngine::styleSheetCollectionFor(TreeScope& treeScope)
{
    if (treeScope == m_document)
        return documentStyleSheetCollection();

    StyleSheetCollectionMap::iterator it = m_styleSheetCollectionMap.find(&treeScope);
    if (it == m_styleSheetCollectionMap.end())
        return 0;
    return it->value.get();
}

const HeapVector<Member<StyleSheet>>& StyleEngine::styleSheetsForStyleSheetList(TreeScope& treeScope)
{
    if (treeScope == m_document)
        return documentStyleSheetCollection()->styleSheetsForStyleSheetList();

    return ensureStyleSheetCollectionFor(treeScope)->styleSheetsForStyleSheetList();
}

void StyleEngine::resetCSSFeatureFlags(const RuleFeatureSet& features)
{
    m_usesSiblingRules = features.usesSiblingRules();
    m_usesFirstLineRules = features.usesFirstLineRules();
    m_usesWindowInactiveSelector = features.usesWindowInactiveSelector();
    m_maxDirectAdjacentSelectors = features.maxDirectAdjacentSelectors();
}

void StyleEngine::injectAuthorSheet(StyleSheetContents* authorSheet)
{
    m_injectedAuthorStyleSheets.append(CSSStyleSheet::create(authorSheet, m_document));
    markDocumentDirty();
    resolverChanged(AnalyzedStyleUpdate);
}

void StyleEngine::addPendingSheet(StyleEngineContext &context)
{
    m_pendingScriptBlockingStylesheets++;

    context.addingPendingSheet(document());
    if (context.addedPendingSheetBeforeBody())
        m_pendingRenderBlockingStylesheets++;
}

// This method is called whenever a top-level stylesheet has finished loading.
void StyleEngine::removePendingSheet(Node* styleSheetCandidateNode, const StyleEngineContext &context)
{
    DCHECK(styleSheetCandidateNode);
    TreeScope* treeScope = isStyleElement(*styleSheetCandidateNode) ? &styleSheetCandidateNode->treeScope() : m_document.get();
    if (styleSheetCandidateNode->inShadowIncludingDocument())
        markTreeScopeDirty(*treeScope);

    if (context.addedPendingSheetBeforeBody()) {
        DCHECK_GT(m_pendingRenderBlockingStylesheets, 0);
        m_pendingRenderBlockingStylesheets--;
    }

    // Make sure we knew this sheet was pending, and that our count isn't out of sync.
    DCHECK_GT(m_pendingScriptBlockingStylesheets, 0);

    m_pendingScriptBlockingStylesheets--;
    if (m_pendingScriptBlockingStylesheets)
        return;

    document().didRemoveAllPendingStylesheet();
}

void StyleEngine::setNeedsActiveStyleUpdate(StyleSheet* sheet, StyleResolverUpdateMode updateMode)
{
    // resolverChanged() is called for inactive non-master documents because
    // import documents are inactive documents. resolverChanged() for imports
    // will call resolverChanged() for the master document and update the active
    // stylesheets including the ones from the import.
    if (!document().isActive() && isMaster())
        return;

    if (sheet && document().isActive()) {
        Node* node = sheet->ownerNode();
        if (node && node->inShadowIncludingDocument()) {
            TreeScope& treeScope = isStyleElement(*node) ? node->treeScope() : *m_document;
            DCHECK(isStyleElement(*node) || node->treeScope() == m_document);
            markTreeScopeDirty(treeScope);
        }
    }

    resolverChanged(updateMode);
}

void StyleEngine::addStyleSheetCandidateNode(Node* node)
{
    if (!node->inShadowIncludingDocument() || document().isDetached())
        return;

    TreeScope& treeScope = isStyleElement(*node) ? node->treeScope() : *m_document;
    DCHECK(isStyleElement(*node) || treeScope == m_document);
    DCHECK(!isXSLStyleSheet(*node));
    TreeScopeStyleSheetCollection* collection = ensureStyleSheetCollectionFor(treeScope);
    DCHECK(collection);
    collection->addStyleSheetCandidateNode(node);

    markTreeScopeDirty(treeScope);
    if (treeScope != m_document)
        m_activeTreeScopes.add(&treeScope);
}

void StyleEngine::removeStyleSheetCandidateNode(Node* node)
{
    removeStyleSheetCandidateNode(node, *m_document);
}

void StyleEngine::removeStyleSheetCandidateNode(Node* node, TreeScope& treeScope)
{
    DCHECK(isStyleElement(*node) || treeScope == m_document);
    DCHECK(!isXSLStyleSheet(*node));

    TreeScopeStyleSheetCollection* collection = styleSheetCollectionFor(treeScope);
    // After detaching document, collection could be null. In the case,
    // we should not update anything. Instead, just return.
    if (!collection)
        return;
    collection->removeStyleSheetCandidateNode(node);

    markTreeScopeDirty(treeScope);
}

void StyleEngine::modifiedStyleSheetCandidateNode(Node* node)
{
    if (!node->inShadowIncludingDocument())
        return;

    TreeScope& treeScope = isStyleElement(*node) ? node->treeScope() : *m_document;
    DCHECK(isStyleElement(*node) || treeScope == m_document);
    markTreeScopeDirty(treeScope);
    resolverChanged(FullStyleUpdate);
}

void StyleEngine::watchedSelectorsChanged()
{
    if (m_resolver) {
        m_resolver->initWatchedSelectorRules();
        m_resolver->resetRuleFeatures();
    }
    document().setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::DeclarativeContent));
}

bool StyleEngine::shouldUpdateDocumentStyleSheetCollection(StyleResolverUpdateMode updateMode) const
{
    return m_documentScopeDirty || updateMode == FullStyleUpdate;
}

bool StyleEngine::shouldUpdateShadowTreeStyleSheetCollection(StyleResolverUpdateMode updateMode) const
{
    return !m_dirtyTreeScopes.isEmpty() || updateMode == FullStyleUpdate;
}

void StyleEngine::clearMediaQueryRuleSetOnTreeScopeStyleSheets(UnorderedTreeScopeSet& treeScopes)
{
    for (TreeScope* treeScope : treeScopes) {
        DCHECK(treeScope != m_document);
        ShadowTreeStyleSheetCollection* collection = toShadowTreeStyleSheetCollection(styleSheetCollectionFor(*treeScope));
        DCHECK(collection);
        collection->clearMediaQueryRuleSetStyleSheets();
    }
}

void StyleEngine::clearMediaQueryRuleSetStyleSheets()
{
    resolverChanged(FullStyleUpdate);
    documentStyleSheetCollection()->clearMediaQueryRuleSetStyleSheets();
    clearMediaQueryRuleSetOnTreeScopeStyleSheets(m_activeTreeScopes);
}

void StyleEngine::updateStyleSheetsInImport(DocumentStyleSheetCollector& parentCollector)
{
    DCHECK(!isMaster());
    HeapVector<Member<StyleSheet>> sheetsForList;
    ImportedDocumentStyleSheetCollector subcollector(parentCollector, sheetsForList);
    documentStyleSheetCollection()->collectStyleSheets(*this, subcollector);
    documentStyleSheetCollection()->swapSheetsForSheetList(sheetsForList);
}

void StyleEngine::updateActiveStyleSheetsInShadow(StyleResolverUpdateMode updateMode, TreeScope* treeScope, UnorderedTreeScopeSet& treeScopesRemoved)
{
    DCHECK_NE(treeScope, m_document);
    ShadowTreeStyleSheetCollection* collection = toShadowTreeStyleSheetCollection(styleSheetCollectionFor(*treeScope));
    DCHECK(collection);
    collection->updateActiveStyleSheets(*this, updateMode);
    if (!collection->hasStyleSheetCandidateNodes()) {
        treeScopesRemoved.add(treeScope);
        // When removing TreeScope from ActiveTreeScopes,
        // its resolver should be destroyed by invoking resetAuthorStyle.
        DCHECK(!treeScope->scopedStyleResolver());
    }
}

void StyleEngine::updateActiveStyleSheets(StyleResolverUpdateMode updateMode)
{
    DCHECK(isMaster());
    DCHECK(!document().inStyleRecalc());

    if (!document().isActive())
        return;

    TRACE_EVENT0("blink,blink_style", "StyleEngine::updateActiveStyleSheets");

    if (shouldUpdateDocumentStyleSheetCollection(updateMode))
        documentStyleSheetCollection()->updateActiveStyleSheets(*this, updateMode);

    if (shouldUpdateShadowTreeStyleSheetCollection(updateMode)) {
        UnorderedTreeScopeSet treeScopesRemoved;

        if (updateMode == FullStyleUpdate) {
            for (TreeScope* treeScope : m_activeTreeScopes)
                updateActiveStyleSheetsInShadow(updateMode, treeScope, treeScopesRemoved);
        } else {
            for (TreeScope* treeScope : m_dirtyTreeScopes)
                updateActiveStyleSheetsInShadow(updateMode, treeScope, treeScopesRemoved);
        }
        for (TreeScope* treeScope : treeScopesRemoved)
            m_activeTreeScopes.remove(treeScope);
    }

    InspectorInstrumentation::activeStyleSheetsUpdated(m_document);

    m_dirtyTreeScopes.clear();
    m_documentScopeDirty = false;
}

const HeapVector<Member<CSSStyleSheet>> StyleEngine::activeStyleSheetsForInspector() const
{
    if (m_activeTreeScopes.isEmpty())
        return documentStyleSheetCollection()->activeAuthorStyleSheets();

    HeapVector<Member<CSSStyleSheet>> activeStyleSheets;

    activeStyleSheets.appendVector(documentStyleSheetCollection()->activeAuthorStyleSheets());
    for (TreeScope* treeScope : m_activeTreeScopes) {
        if (TreeScopeStyleSheetCollection* collection = m_styleSheetCollectionMap.get(treeScope))
            activeStyleSheets.appendVector(collection->activeAuthorStyleSheets());
    }

    // FIXME: Inspector needs a vector which has all active stylesheets.
    // However, creating such a large vector might cause performance regression.
    // Need to implement some smarter solution.
    return activeStyleSheets;
}

void StyleEngine::didRemoveShadowRoot(ShadowRoot* shadowRoot)
{
    m_styleSheetCollectionMap.remove(shadowRoot);
    m_activeTreeScopes.remove(shadowRoot);
    m_dirtyTreeScopes.remove(shadowRoot);
}

void StyleEngine::shadowRootRemovedFromDocument(ShadowRoot* shadowRoot)
{
    if (StyleResolver* styleResolver = resolver()) {
        styleResolver->resetAuthorStyle(*shadowRoot);

        if (TreeScopeStyleSheetCollection* collection = styleSheetCollectionFor(*shadowRoot))
            styleResolver->removePendingAuthorStyleSheets(collection->activeAuthorStyleSheets());
    }
    m_styleSheetCollectionMap.remove(shadowRoot);
    m_activeTreeScopes.remove(shadowRoot);
    m_dirtyTreeScopes.remove(shadowRoot);
}

void StyleEngine::appendActiveAuthorStyleSheets()
{
    DCHECK(isMaster());

    m_resolver->appendAuthorStyleSheets(documentStyleSheetCollection()->activeAuthorStyleSheets());
    for (TreeScope* treeScope : m_activeTreeScopes) {
        if (TreeScopeStyleSheetCollection* collection = m_styleSheetCollectionMap.get(treeScope))
            m_resolver->appendAuthorStyleSheets(collection->activeAuthorStyleSheets());
    }
    m_resolver->finishAppendAuthorStyleSheets();
}

void StyleEngine::createResolver()
{
    TRACE_EVENT1("blink", "StyleEngine::createResolver", "frame", document().frame());
    // It is a programming error to attempt to resolve style on a Document
    // which is not in a frame. Code which hits this should have checked
    // Document::isActive() before calling into code which could get here.

    DCHECK(document().frame());

    m_resolver = StyleResolver::create(*m_document);

    // A scoped style resolver for document will be created during
    // appendActiveAuthorStyleSheets if needed.
    appendActiveAuthorStyleSheets();
}

void StyleEngine::clearResolver()
{
    DCHECK(!document().inStyleRecalc());
    DCHECK(isMaster() || !m_resolver);

    document().clearScopedStyleResolver();
    // StyleEngine::shadowRootRemovedFromDocument removes not-in-document
    // treescopes from activeTreeScopes. StyleEngine::didRemoveShadowRoot
    // removes treescopes which are being destroyed from activeTreeScopes.
    // So we need to clearScopedStyleResolver for treescopes which have been
    // just removed from document. If document is destroyed before invoking
    // updateActiveStyleSheets, the treescope has a scopedStyleResolver which
    // has destroyed StyleSheetContents.
    for (TreeScope* treeScope : m_activeTreeScopes)
        treeScope->clearScopedStyleResolver();

    if (m_resolver) {
        TRACE_EVENT1("blink", "StyleEngine::clearResolver", "frame", document().frame());
        m_resolver->dispose();
        m_resolver.clear();
    }
}

void StyleEngine::clearMasterResolver()
{
    if (Document* master = this->master())
        master->styleEngine().clearResolver();
}

void StyleEngine::didDetach()
{
    clearResolver();
}

bool StyleEngine::shouldClearResolver() const
{
    return !m_didCalculateResolver && !haveScriptBlockingStylesheetsLoaded();
}

void StyleEngine::resolverChanged(StyleResolverUpdateMode mode)
{
    if (!isMaster()) {
        if (Document* master = this->master())
            master->styleEngine().resolverChanged(mode);
        return;
    }

    // Don't bother updating, since we haven't loaded all our style info yet
    // and haven't calculated the style selector for the first time.
    if (!document().isActive() || shouldClearResolver()) {
        clearResolver();
        return;
    }

    m_didCalculateResolver = true;
    updateActiveStyleSheets(mode);
}

void StyleEngine::clearFontCache()
{
    if (m_fontSelector)
        m_fontSelector->fontFaceCache()->clearCSSConnected();
    if (m_resolver)
        m_resolver->invalidateMatchedPropertiesCache();
}

void StyleEngine::updateGenericFontFamilySettings()
{
    // FIXME: we should not update generic font family settings when
    // document is inactive.
    DCHECK(document().isActive());

    if (!m_fontSelector)
        return;

    m_fontSelector->updateGenericFontFamilySettings(*m_document);
    if (m_resolver)
        m_resolver->invalidateMatchedPropertiesCache();
    FontCache::fontCache()->invalidateShapeCache();
}

void StyleEngine::removeFontFaceRules(const HeapVector<Member<const StyleRuleFontFace>>& fontFaceRules)
{
    if (!m_fontSelector)
        return;

    FontFaceCache* cache = m_fontSelector->fontFaceCache();
    for (unsigned i = 0; i < fontFaceRules.size(); ++i)
        cache->remove(fontFaceRules[i]);
    if (m_resolver)
        m_resolver->invalidateMatchedPropertiesCache();
}

void StyleEngine::markTreeScopeDirty(TreeScope& scope)
{
    if (scope == m_document) {
        markDocumentDirty();
        return;
    }

    DCHECK(m_styleSheetCollectionMap.contains(&scope));
    m_dirtyTreeScopes.add(&scope);
}

void StyleEngine::markDocumentDirty()
{
    m_documentScopeDirty = true;
    if (document().importLoader())
        document().importsController()->master()->styleEngine().markDocumentDirty();
}

CSSStyleSheet* StyleEngine::createSheet(Element* e, const String& text, TextPosition startPosition, StyleEngineContext &context)
{
    CSSStyleSheet* styleSheet = nullptr;

    e->document().styleEngine().addPendingSheet(context);

    AtomicString textContent(text);

    HeapHashMap<AtomicString, Member<StyleSheetContents>>::AddResult result = m_textToSheetCache.add(textContent, nullptr);
    if (result.isNewEntry || !result.storedValue->value) {
        styleSheet = StyleEngine::parseSheet(e, text, startPosition);
        if (result.isNewEntry && styleSheet->contents()->isCacheableForStyleElement()) {
            result.storedValue->value = styleSheet->contents();
            m_sheetToTextCache.add(styleSheet->contents(), textContent);
        }
    } else {
        StyleSheetContents* contents = result.storedValue->value;
        DCHECK(contents);
        DCHECK(contents->isCacheableForStyleElement());
        DCHECK_EQ(contents->singleOwnerDocument(), e->document());
        styleSheet = CSSStyleSheet::createInline(contents, e, startPosition);
    }

    DCHECK(styleSheet);
    styleSheet->setTitle(e->title());
    if (!e->isInShadowTree())
        setPreferredStylesheetSetNameIfNotSet(e->title());
    return styleSheet;
}

CSSStyleSheet* StyleEngine::parseSheet(Element* e, const String& text, TextPosition startPosition)
{
    CSSStyleSheet* styleSheet = nullptr;
    styleSheet = CSSStyleSheet::createInline(e, KURL(), startPosition, e->document().characterSet());
    styleSheet->contents()->parseStringAtPosition(text, startPosition);
    return styleSheet;
}

void StyleEngine::removeSheet(StyleSheetContents* contents)
{
    HeapHashMap<Member<StyleSheetContents>, AtomicString>::iterator it = m_sheetToTextCache.find(contents);
    if (it == m_sheetToTextCache.end())
        return;

    m_textToSheetCache.remove(it->value);
    m_sheetToTextCache.remove(contents);
}

void StyleEngine::collectScopedStyleFeaturesTo(RuleFeatureSet& features) const
{
    HeapHashSet<Member<const StyleSheetContents>> visitedSharedStyleSheetContents;
    if (document().scopedStyleResolver())
        document().scopedStyleResolver()->collectFeaturesTo(features, visitedSharedStyleSheetContents);
    for (TreeScope* treeScope : m_activeTreeScopes) {
        // When creating StyleResolver, dirty treescopes might not be processed.
        // So some active treescopes might not have a scoped style resolver.
        // In this case, we should skip collectFeatures for the treescopes without
        // scoped style resolvers. When invoking updateActiveStyleSheets,
        // the treescope's features will be processed.
        if (ScopedStyleResolver* resolver = treeScope->scopedStyleResolver())
            resolver->collectFeaturesTo(features, visitedSharedStyleSheetContents);
    }
}

void StyleEngine::fontsNeedUpdate(CSSFontSelector*)
{
    if (!document().isActive())
        return;

    if (m_resolver)
        m_resolver->invalidateMatchedPropertiesCache();
    document().setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::Fonts));
}

void StyleEngine::setFontSelector(CSSFontSelector* fontSelector)
{
    if (m_fontSelector)
        m_fontSelector->unregisterForInvalidationCallbacks(this);
    m_fontSelector = fontSelector;
    if (m_fontSelector)
        m_fontSelector->registerForInvalidationCallbacks(this);
}

void StyleEngine::platformColorsChanged()
{
    if (m_resolver)
        m_resolver->invalidateMatchedPropertiesCache();
    document().setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::PlatformColorChange));
}

bool StyleEngine::shouldSkipInvalidationFor(const Element& element) const
{
    if (!resolver())
        return true;
    if (!element.inActiveDocument())
        return true;
    if (!element.parentNode())
        return true;
    return element.parentNode()->getStyleChangeType() >= SubtreeStyleChange;
}

void StyleEngine::classChangedForElement(const SpaceSplitString& changedClasses, Element& element)
{
    if (shouldSkipInvalidationFor(element))
        return;
    InvalidationLists invalidationLists;
    unsigned changedSize = changedClasses.size();
    RuleFeatureSet& ruleFeatureSet = ensureResolver().ensureUpdatedRuleFeatureSet();
    for (unsigned i = 0; i < changedSize; ++i)
        ruleFeatureSet.collectInvalidationSetsForClass(invalidationLists, element, changedClasses[i]);
    m_styleInvalidator.scheduleInvalidationSetsForElement(invalidationLists, element);
}

void StyleEngine::classChangedForElement(const SpaceSplitString& oldClasses, const SpaceSplitString& newClasses, Element& element)
{
    if (shouldSkipInvalidationFor(element))
        return;

    if (!oldClasses.size()) {
        classChangedForElement(newClasses, element);
        return;
    }

    // Class vectors tend to be very short. This is faster than using a hash table.
    BitVector remainingClassBits;
    remainingClassBits.ensureSize(oldClasses.size());

    InvalidationLists invalidationLists;
    RuleFeatureSet& ruleFeatureSet = ensureResolver().ensureUpdatedRuleFeatureSet();

    for (unsigned i = 0; i < newClasses.size(); ++i) {
        bool found = false;
        for (unsigned j = 0; j < oldClasses.size(); ++j) {
            if (newClasses[i] == oldClasses[j]) {
                // Mark each class that is still in the newClasses so we can skip doing
                // an n^2 search below when looking for removals. We can't break from
                // this loop early since a class can appear more than once.
                remainingClassBits.quickSet(j);
                found = true;
            }
        }
        // Class was added.
        if (!found)
            ruleFeatureSet.collectInvalidationSetsForClass(invalidationLists, element, newClasses[i]);
    }

    for (unsigned i = 0; i < oldClasses.size(); ++i) {
        if (remainingClassBits.quickGet(i))
            continue;
        // Class was removed.
        ruleFeatureSet.collectInvalidationSetsForClass(invalidationLists, element, oldClasses[i]);
    }

    m_styleInvalidator.scheduleInvalidationSetsForElement(invalidationLists, element);
}

void StyleEngine::attributeChangedForElement(const QualifiedName& attributeName, Element& element)
{
    if (shouldSkipInvalidationFor(element))
        return;

    InvalidationLists invalidationLists;
    ensureResolver().ensureUpdatedRuleFeatureSet().collectInvalidationSetsForAttribute(invalidationLists, element, attributeName);
    m_styleInvalidator.scheduleInvalidationSetsForElement(invalidationLists, element);
}

void StyleEngine::idChangedForElement(const AtomicString& oldId, const AtomicString& newId, Element& element)
{
    if (shouldSkipInvalidationFor(element))
        return;

    InvalidationLists invalidationLists;
    RuleFeatureSet& ruleFeatureSet = ensureResolver().ensureUpdatedRuleFeatureSet();
    if (!oldId.isEmpty())
        ruleFeatureSet.collectInvalidationSetsForId(invalidationLists, element, oldId);
    if (!newId.isEmpty())
        ruleFeatureSet.collectInvalidationSetsForId(invalidationLists, element, newId);
    m_styleInvalidator.scheduleInvalidationSetsForElement(invalidationLists, element);
}

void StyleEngine::pseudoStateChangedForElement(CSSSelector::PseudoType pseudoType, Element& element)
{
    if (shouldSkipInvalidationFor(element))
        return;

    InvalidationLists invalidationLists;
    ensureResolver().ensureUpdatedRuleFeatureSet().collectInvalidationSetsForPseudoClass(invalidationLists, element, pseudoType);
    m_styleInvalidator.scheduleInvalidationSetsForElement(invalidationLists, element);
}

void StyleEngine::setStatsEnabled(bool enabled)
{
    if (!enabled) {
        m_styleResolverStats = nullptr;
        return;
    }
    if (!m_styleResolverStats)
        m_styleResolverStats = StyleResolverStats::create();
    else
        m_styleResolverStats->reset();
}

void StyleEngine::setPreferredStylesheetSetNameIfNotSet(const String& name)
{
    if (!m_preferredStylesheetSetName.isEmpty())
        return;
    m_preferredStylesheetSetName = name;
    // TODO(rune@opera.com): Setting the selected set here is wrong if the set
    // has been previously set by through Document.selectedStylesheetSet. Our
    // current implementation ignores the effect of Document.selectedStylesheetSet
    // and either only collects persistent style, or additionally preferred
    // style when present. We are currently not marking the document scope dirty
    // because preferred style is updated during active stylesheet update which
    // would make this method re-entrant. Will need to change for async update.
    m_selectedStylesheetSetName = name;
}

void StyleEngine::setSelectedStylesheetSetName(const String& name)
{
    m_selectedStylesheetSetName = name;
    // TODO(rune@opera.com): Setting Document.selectedStylesheetSet currently
    // has no other effect than the ability to read back the set value using
    // the same api. If it did have an effect, we should have marked the
    // document scope dirty and triggered an update of the active stylesheets
    // from here.
}

void StyleEngine::setHttpDefaultStyle(const String& content)
{
    setPreferredStylesheetSetNameIfNotSet(content);
    markDocumentDirty();
    resolverChanged(FullStyleUpdate);
}

void StyleEngine::ensureFullscreenUAStyle()
{
    CSSDefaultStyleSheets::instance().ensureDefaultStyleSheetForFullscreen();
    if (!m_resolver)
        return;
    if (!m_resolver->hasFullscreenUAStyle())
        m_resolver->resetRuleFeatures();
}

DEFINE_TRACE(StyleEngine)
{
    visitor->trace(m_document);
    visitor->trace(m_injectedAuthorStyleSheets);
    visitor->trace(m_documentStyleSheetCollection);
    visitor->trace(m_styleSheetCollectionMap);
    visitor->trace(m_resolver);
    visitor->trace(m_styleInvalidator);
    visitor->trace(m_dirtyTreeScopes);
    visitor->trace(m_activeTreeScopes);
    visitor->trace(m_fontSelector);
    visitor->trace(m_textToSheetCache);
    visitor->trace(m_sheetToTextCache);
    CSSFontSelectorClient::trace(visitor);
}

DEFINE_TRACE_WRAPPERS(StyleEngine)
{
    for (auto sheet : m_injectedAuthorStyleSheets) {
        visitor->traceWrappers(sheet);
    }
    visitor->traceWrappers(m_documentStyleSheetCollection);
}

} // namespace blink