Source/WebCore/style/StyleSharingResolver.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2016 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "StyleSharingResolver.h"

 #include "ElementRuleCollector.h"
 #include "FullscreenManager.h"
 #include "HTMLInputElement.h"
 #include "HTMLNames.h"
 #include "NodeRenderStyle.h"
 #include "RenderStyle.h"
 #include "SVGElement.h"
 #include "ShadowRoot.h"
 #include "StyleResolver.h"
 #include "StyleScope.h"
 #include "StyleScopeRuleSets.h"
 #include "StyleUpdate.h"
 #include "StyledElement.h"
 #include "VisitedLinkState.h"
 #include "WebVTTElement.h"
 #include "XMLNames.h"

 namespace WebCore {
 namespace Style {

 static const unsigned cStyleSearchThreshold = 10;

 struct SharingResolver::Context {
     const Update& update;
     const StyledElement& element;
     bool elementAffectedByClassRules;
     InsideLink elementLinkState;
 };

 SharingResolver::SharingResolver(const Document& document, const ScopeRuleSets& ruleSets, const SelectorFilter& selectorFilter)
     : m_document(document)
     , m_ruleSets(ruleSets)
     , m_selectorFilter(selectorFilter)
 {
 }

 static inline bool parentElementPreventsSharing(const Element& parentElement)
 {
     return parentElement.hasFlagsSetDuringStylingOfChildren();
 }

 static inline bool elementHasDirectionAuto(const Element& element)
 {
     return is<HTMLElement>(element) && downcast<HTMLElement>(element).hasDirectionAuto();
 }

 std::unique_ptr<RenderStyle> SharingResolver::resolve(const Element& searchElement, const Update& update)
 {
     if (!is<StyledElement>(searchElement))
         return nullptr;
     auto& element = downcast<StyledElement>(searchElement);
     if (!element.parentElement())
         return nullptr;
     auto& parentElement = *element.parentElement();
     if (parentElement.shadowRoot())
         return nullptr;
     if (!update.elementStyle(parentElement))
         return nullptr;
     // If the element has inline style it is probably unique.
     if (element.inlineStyle())
         return nullptr;
     if (element.isSVGElement() && downcast<SVGElement>(element).animatedSMILStyleProperties())
         return nullptr;
     // Ids stop style sharing if they show up in the stylesheets.
     auto& id = element.idForStyleResolution();
     if (!id.isNull() && m_ruleSets.features().idsInRules.contains(id))
         return nullptr;
     if (parentElementPreventsSharing(parentElement))
         return nullptr;
     if (&element == m_document.cssTarget())
         return nullptr;
     if (elementHasDirectionAuto(element))
         return nullptr;
     if (element.shadowRoot() && !element.shadowRoot()->styleScope().resolver().ruleSets().authorStyle().hostPseudoClassRules().isEmpty())
         return nullptr;

     Context context {
         update,
         element,
         element.hasClass() && classNamesAffectedByRules(element.classNames()),
         m_document.visitedLinkState().determineLinkState(element)
     };

     // Check previous siblings and their cousins.
     unsigned count = 0;
     StyledElement* shareElement = nullptr;
     Node* cousinList = element.previousSibling();
     while (cousinList) {
         shareElement = findSibling(context, cousinList, count);
         if (shareElement)
             break;
         if (count >= cStyleSearchThreshold)
             break;
         cousinList = locateCousinList(cousinList->parentElement());
     }

     // If we have exhausted all our budget or our cousins.
     if (!shareElement)
         return nullptr;

     // Can't share if sibling rules apply. This is checked at the end as it should rarely fail.
     if (styleSharingCandidateMatchesRuleSet(element, m_ruleSets.sibling()))
         return nullptr;
     // Can't share if attribute rules apply.
     if (styleSharingCandidateMatchesRuleSet(element, m_ruleSets.uncommonAttribute()))
         return nullptr;
     // Tracking child index requires unique style for each node. This may get set by the sibling rule match above.
     if (parentElementPreventsSharing(parentElement))
         return nullptr;

     m_elementsSharingStyle.add(&element, shareElement);

     return RenderStyle::clonePtr(*update.elementStyle(*shareElement));
 }

 StyledElement* SharingResolver::findSibling(const Context& context, Node* node, unsigned& count) const
 {
     for (; node; node = node->previousSibling()) {
         if (!is<StyledElement>(*node))
             continue;
         if (canShareStyleWithElement(context, downcast<StyledElement>(*node)))
             break;
         if (count++ >= cStyleSearchThreshold)
             return nullptr;
     }
     return downcast<StyledElement>(node);
 }

 Node* SharingResolver::locateCousinList(const Element* parent) const
 {
     for (unsigned count = 0; count < cStyleSearchThreshold; ++count) {
         auto* elementSharingParentStyle = m_elementsSharingStyle.get(parent);
         if (!elementSharingParentStyle)
             return nullptr;
         if (!parentElementPreventsSharing(*elementSharingParentStyle)) {
             if (auto* cousin = elementSharingParentStyle->lastChild())
                 return cousin;
         }
         parent = elementSharingParentStyle;
     }

     return nullptr;
 }

 static bool canShareStyleWithControl(const HTMLFormControlElement& element, const HTMLFormControlElement& formElement)
 {
     if (!is<HTMLInputElement>(formElement) || !is<HTMLInputElement>(element))
         return false;

     auto& thisInputElement = downcast<HTMLInputElement>(formElement);
     auto& otherInputElement = downcast<HTMLInputElement>(element);

     if (thisInputElement.isAutoFilled() != otherInputElement.isAutoFilled())
         return false;
     if (thisInputElement.shouldAppearChecked() != otherInputElement.shouldAppearChecked())
         return false;
     if (thisInputElement.isRequired() != otherInputElement.isRequired())
         return false;

     if (formElement.isDisabledFormControl() != element.isDisabledFormControl())
         return false;

     if (formElement.isInRange() != element.isInRange())
         return false;

     if (formElement.isOutOfRange() != element.isOutOfRange())
         return false;

     return true;
 }

 bool SharingResolver::canShareStyleWithElement(const Context& context, const StyledElement& candidateElement) const
 {
     auto& element = context.element;
     auto* style = context.update.elementStyle(candidateElement);
     if (!style)
         return false;
     if (style->unique())
         return false;
     if (style->hasUniquePseudoStyle())
         return false;
     if (candidateElement.tagQName() != element.tagQName())
         return false;
     if (candidateElement.inlineStyle())
         return false;
     if (candidateElement.needsStyleRecalc())
         return false;
     if (candidateElement.isSVGElement() && downcast<SVGElement>(candidateElement).animatedSMILStyleProperties())
         return false;
     if (candidateElement.isLink() != element.isLink())
         return false;
     if (candidateElement.hovered() != element.hovered())
         return false;
     if (candidateElement.active() != element.active())
         return false;
     if (candidateElement.focused() != element.focused())
         return false;
     if (candidateElement.shadowPseudoId() != element.shadowPseudoId())
         return false;
     if (&candidateElement == m_document.cssTarget())
         return false;
     if (!sharingCandidateHasIdenticalStyleAffectingAttributes(context, candidateElement))
         return false;
     if (const_cast<StyledElement&>(candidateElement).additionalPresentationAttributeStyle() != const_cast<StyledElement&>(element).additionalPresentationAttributeStyle())
         return false;
     if (candidateElement.affectsNextSiblingElementStyle() || candidateElement.styleIsAffectedByPreviousSibling())
         return false;
     if (candidateElement.styleAffectedByFocusWithin() || element.styleAffectedByFocusWithin())
         return false;

     auto& candidateElementId = candidateElement.idForStyleResolution();
     if (!candidateElementId.isNull() && m_ruleSets.features().idsInRules.contains(candidateElementId))
         return false;

     bool isControl = is<HTMLFormControlElement>(candidateElement);

     if (isControl != is<HTMLFormControlElement>(element))
         return false;

     if (isControl && !canShareStyleWithControl(downcast<HTMLFormControlElement>(element), downcast<HTMLFormControlElement>(candidateElement)))
         return false;

     if (style->transitions() || style->animations())
         return false;

     // Turn off style sharing for elements that can gain layers for reasons outside of the style system.
     // See comments in RenderObject::setStyle().
     if (candidateElement.hasTagName(HTMLNames::iframeTag) || candidateElement.hasTagName(HTMLNames::frameTag))
         return false;

     if (candidateElement.hasTagName(HTMLNames::embedTag) || candidateElement.hasTagName(HTMLNames::objectTag) || candidateElement.hasTagName(HTMLNames::appletTag) || candidateElement.hasTagName(HTMLNames::canvasTag))
         return false;

     if (elementHasDirectionAuto(candidateElement))
         return false;

     if (candidateElement.isLink() && context.elementLinkState != style->insideLink())
         return false;

     if (candidateElement.elementData() != element.elementData()) {
         if (candidateElement.attributeWithoutSynchronization(HTMLNames::readonlyAttr) != element.attributeWithoutSynchronization(HTMLNames::readonlyAttr))
             return false;
         if (candidateElement.isSVGElement()) {
             if (candidateElement.getAttribute(HTMLNames::typeAttr) != element.getAttribute(HTMLNames::typeAttr))
                 return false;
         } else {
             if (candidateElement.attributeWithoutSynchronization(HTMLNames::typeAttr) != element.attributeWithoutSynchronization(HTMLNames::typeAttr))
                 return false;
         }
     }

     if (candidateElement.matchesValidPseudoClass() != element.matchesValidPseudoClass())
         return false;

     if (element.matchesInvalidPseudoClass() != element.matchesValidPseudoClass())
         return false;

     if (candidateElement.matchesIndeterminatePseudoClass() != element.matchesIndeterminatePseudoClass())
         return false;

     if (candidateElement.matchesDefaultPseudoClass() != element.matchesDefaultPseudoClass())
         return false;

     if (candidateElement.shadowRoot() && !candidateElement.shadowRoot()->styleScope().resolver().ruleSets().authorStyle().hostPseudoClassRules().isEmpty())
         return false;

 #if ENABLE(FULLSCREEN_API)
     if (&candidateElement == m_document.fullscreenManager().currentFullscreenElement() || &element == m_document.fullscreenManager().currentFullscreenElement())
         return false;
 #endif
     return true;
 }

 bool SharingResolver::styleSharingCandidateMatchesRuleSet(const StyledElement& element, const RuleSet* ruleSet) const
 {
     if (!ruleSet)
         return false;

     ElementRuleCollector collector(const_cast<StyledElement&>(element), m_ruleSets, &m_selectorFilter);
     return collector.hasAnyMatchingRules(ruleSet);
 }

 bool SharingResolver::sharingCandidateHasIdenticalStyleAffectingAttributes(const Context& context, const StyledElement& sharingCandidate) const
 {
     auto& element = context.element;
     if (element.elementData() == sharingCandidate.elementData())
         return true;
     if (element.attributeWithoutSynchronization(XMLNames::langAttr) != sharingCandidate.attributeWithoutSynchronization(XMLNames::langAttr))
         return false;
     if (element.attributeWithoutSynchronization(HTMLNames::langAttr) != sharingCandidate.attributeWithoutSynchronization(HTMLNames::langAttr))
         return false;

     if (context.elementAffectedByClassRules) {
         if (!sharingCandidate.hasClass())
             return false;
         // SVG elements require a (slow!) getAttribute comparision because "class" is an animatable attribute for SVG.
         if (element.isSVGElement()) {
             if (element.getAttribute(HTMLNames::classAttr) != sharingCandidate.getAttribute(HTMLNames::classAttr))
                 return false;
         } else {
             if (element.classNames() != sharingCandidate.classNames())
                 return false;
         }
     } else if (sharingCandidate.hasClass() && classNamesAffectedByRules(sharingCandidate.classNames()))
         return false;

     if (const_cast<StyledElement&>(element).presentationAttributeStyle() != const_cast<StyledElement&>(sharingCandidate).presentationAttributeStyle())
         return false;

     return true;
 }

 bool SharingResolver::classNamesAffectedByRules(const SpaceSplitString& classNames) const
 {
     for (unsigned i = 0; i < classNames.size(); ++i) {
         if (m_ruleSets.features().classRules.contains(classNames[i]))
             return true;
     }
     return false;
 }


 }
 }
	/*
	* Copyright (C) 2016 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "StyleSharingResolver.h"

	#include "ElementRuleCollector.h"
	#include "FullscreenManager.h"
	#include "HTMLInputElement.h"
	#include "HTMLNames.h"
	#include "NodeRenderStyle.h"
	#include "RenderStyle.h"
	#include "SVGElement.h"
	#include "ShadowRoot.h"
	#include "StyleResolver.h"
	#include "StyleScope.h"
	#include "StyleScopeRuleSets.h"
	#include "StyleUpdate.h"
	#include "StyledElement.h"
	#include "VisitedLinkState.h"
	#include "WebVTTElement.h"
	#include "XMLNames.h"

	namespace WebCore {
	namespace Style {

	static const unsigned cStyleSearchThreshold = 10;

	struct SharingResolver::Context {
	const Update& update;
	const StyledElement& element;
	bool elementAffectedByClassRules;
	InsideLink elementLinkState;
	};

	SharingResolver::SharingResolver(const Document& document, const ScopeRuleSets& ruleSets, const SelectorFilter& selectorFilter)
	: m_document(document)
	, m_ruleSets(ruleSets)
	, m_selectorFilter(selectorFilter)
	{
	}

	static inline bool parentElementPreventsSharing(const Element& parentElement)
	{
	return parentElement.hasFlagsSetDuringStylingOfChildren();
	}

	static inline bool elementHasDirectionAuto(const Element& element)
	{
	return is<HTMLElement>(element) && downcast<HTMLElement>(element).hasDirectionAuto();
	}

	std::unique_ptr<RenderStyle> SharingResolver::resolve(const Element& searchElement, const Update& update)
	{
	if (!is<StyledElement>(searchElement))
	return nullptr;
	auto& element = downcast<StyledElement>(searchElement);
	if (!element.parentElement())
	return nullptr;
	auto& parentElement = *element.parentElement();
	if (parentElement.shadowRoot())
	return nullptr;
	if (!update.elementStyle(parentElement))
	return nullptr;
	// If the element has inline style it is probably unique.
	if (element.inlineStyle())
	return nullptr;
	if (element.isSVGElement() && downcast<SVGElement>(element).animatedSMILStyleProperties())
	return nullptr;
	// Ids stop style sharing if they show up in the stylesheets.
	auto& id = element.idForStyleResolution();
	if (!id.isNull() && m_ruleSets.features().idsInRules.contains(id))
	return nullptr;
	if (parentElementPreventsSharing(parentElement))
	return nullptr;
	if (&element == m_document.cssTarget())
	return nullptr;
	if (elementHasDirectionAuto(element))
	return nullptr;
	if (element.shadowRoot() && !element.shadowRoot()->styleScope().resolver().ruleSets().authorStyle().hostPseudoClassRules().isEmpty())
	return nullptr;

	Context context {
	update,
	element,
	element.hasClass() && classNamesAffectedByRules(element.classNames()),
	m_document.visitedLinkState().determineLinkState(element)
	};

	// Check previous siblings and their cousins.
	unsigned count = 0;
	StyledElement* shareElement = nullptr;
	Node* cousinList = element.previousSibling();
	while (cousinList) {
	shareElement = findSibling(context, cousinList, count);
	if (shareElement)
	break;
	if (count >= cStyleSearchThreshold)
	break;
	cousinList = locateCousinList(cousinList->parentElement());
	}

	// If we have exhausted all our budget or our cousins.
	if (!shareElement)
	return nullptr;

	// Can't share if sibling rules apply. This is checked at the end as it should rarely fail.
	if (styleSharingCandidateMatchesRuleSet(element, m_ruleSets.sibling()))
	return nullptr;
	// Can't share if attribute rules apply.
	if (styleSharingCandidateMatchesRuleSet(element, m_ruleSets.uncommonAttribute()))
	return nullptr;
	// Tracking child index requires unique style for each node. This may get set by the sibling rule match above.
	if (parentElementPreventsSharing(parentElement))
	return nullptr;

	m_elementsSharingStyle.add(&element, shareElement);

	return RenderStyle::clonePtr(update.elementStyle(shareElement));
	}

	StyledElement* SharingResolver::findSibling(const Context& context, Node* node, unsigned& count) const
	{
	for (; node; node = node->previousSibling()) {
	if (!is<StyledElement>(*node))
	continue;
	if (canShareStyleWithElement(context, downcast<StyledElement>(*node)))
	break;
	if (count++ >= cStyleSearchThreshold)
	return nullptr;
	}
	return downcast<StyledElement>(node);
	}

	Node* SharingResolver::locateCousinList(const Element* parent) const
	{
	for (unsigned count = 0; count < cStyleSearchThreshold; ++count) {
	auto* elementSharingParentStyle = m_elementsSharingStyle.get(parent);
	if (!elementSharingParentStyle)
	return nullptr;
	if (!parentElementPreventsSharing(*elementSharingParentStyle)) {
	if (auto* cousin = elementSharingParentStyle->lastChild())
	return cousin;
	}
	parent = elementSharingParentStyle;
	}

	return nullptr;
	}

	static bool canShareStyleWithControl(const HTMLFormControlElement& element, const HTMLFormControlElement& formElement)
	{
	if (!is<HTMLInputElement>(formElement) \|\| !is<HTMLInputElement>(element))
	return false;

	auto& thisInputElement = downcast<HTMLInputElement>(formElement);
	auto& otherInputElement = downcast<HTMLInputElement>(element);

	if (thisInputElement.isAutoFilled() != otherInputElement.isAutoFilled())
	return false;
	if (thisInputElement.shouldAppearChecked() != otherInputElement.shouldAppearChecked())
	return false;
	if (thisInputElement.isRequired() != otherInputElement.isRequired())
	return false;

	if (formElement.isDisabledFormControl() != element.isDisabledFormControl())
	return false;

	if (formElement.isInRange() != element.isInRange())
	return false;

	if (formElement.isOutOfRange() != element.isOutOfRange())
	return false;

	return true;
	}

	bool SharingResolver::canShareStyleWithElement(const Context& context, const StyledElement& candidateElement) const
	{
	auto& element = context.element;
	auto* style = context.update.elementStyle(candidateElement);
	if (!style)
	return false;
	if (style->unique())
	return false;
	if (style->hasUniquePseudoStyle())
	return false;
	if (candidateElement.tagQName() != element.tagQName())
	return false;
	if (candidateElement.inlineStyle())
	return false;
	if (candidateElement.needsStyleRecalc())
	return false;
	if (candidateElement.isSVGElement() && downcast<SVGElement>(candidateElement).animatedSMILStyleProperties())
	return false;
	if (candidateElement.isLink() != element.isLink())
	return false;
	if (candidateElement.hovered() != element.hovered())
	return false;
	if (candidateElement.active() != element.active())
	return false;
	if (candidateElement.focused() != element.focused())
	return false;
	if (candidateElement.shadowPseudoId() != element.shadowPseudoId())
	return false;
	if (&candidateElement == m_document.cssTarget())
	return false;
	if (!sharingCandidateHasIdenticalStyleAffectingAttributes(context, candidateElement))
	return false;
	if (const_cast<StyledElement&>(candidateElement).additionalPresentationAttributeStyle() != const_cast<StyledElement&>(element).additionalPresentationAttributeStyle())
	return false;
	if (candidateElement.affectsNextSiblingElementStyle() \|\| candidateElement.styleIsAffectedByPreviousSibling())
	return false;
	if (candidateElement.styleAffectedByFocusWithin() \|\| element.styleAffectedByFocusWithin())
	return false;

	auto& candidateElementId = candidateElement.idForStyleResolution();
	if (!candidateElementId.isNull() && m_ruleSets.features().idsInRules.contains(candidateElementId))
	return false;

	bool isControl = is<HTMLFormControlElement>(candidateElement);

	if (isControl != is<HTMLFormControlElement>(element))
	return false;

	if (isControl && !canShareStyleWithControl(downcast<HTMLFormControlElement>(element), downcast<HTMLFormControlElement>(candidateElement)))
	return false;

	if (style->transitions() \|\| style->animations())
	return false;

	// Turn off style sharing for elements that can gain layers for reasons outside of the style system.
	// See comments in RenderObject::setStyle().
	if (candidateElement.hasTagName(HTMLNames::iframeTag) \|\| candidateElement.hasTagName(HTMLNames::frameTag))
	return false;

	if (candidateElement.hasTagName(HTMLNames::embedTag) \|\| candidateElement.hasTagName(HTMLNames::objectTag) \|\| candidateElement.hasTagName(HTMLNames::appletTag) \|\| candidateElement.hasTagName(HTMLNames::canvasTag))
	return false;

	if (elementHasDirectionAuto(candidateElement))
	return false;

	if (candidateElement.isLink() && context.elementLinkState != style->insideLink())
	return false;

	if (candidateElement.elementData() != element.elementData()) {
	if (candidateElement.attributeWithoutSynchronization(HTMLNames::readonlyAttr) != element.attributeWithoutSynchronization(HTMLNames::readonlyAttr))
	return false;
	if (candidateElement.isSVGElement()) {
	if (candidateElement.getAttribute(HTMLNames::typeAttr) != element.getAttribute(HTMLNames::typeAttr))
	return false;
	} else {
	if (candidateElement.attributeWithoutSynchronization(HTMLNames::typeAttr) != element.attributeWithoutSynchronization(HTMLNames::typeAttr))
	return false;
	}
	}

	if (candidateElement.matchesValidPseudoClass() != element.matchesValidPseudoClass())
	return false;

	if (element.matchesInvalidPseudoClass() != element.matchesValidPseudoClass())
	return false;

	if (candidateElement.matchesIndeterminatePseudoClass() != element.matchesIndeterminatePseudoClass())
	return false;

	if (candidateElement.matchesDefaultPseudoClass() != element.matchesDefaultPseudoClass())
	return false;

	if (candidateElement.shadowRoot() && !candidateElement.shadowRoot()->styleScope().resolver().ruleSets().authorStyle().hostPseudoClassRules().isEmpty())
	return false;

	#if ENABLE(FULLSCREEN_API)
	if (&candidateElement == m_document.fullscreenManager().currentFullscreenElement() \|\| &element == m_document.fullscreenManager().currentFullscreenElement())
	return false;
	#endif
	return true;
	}

	bool SharingResolver::styleSharingCandidateMatchesRuleSet(const StyledElement& element, const RuleSet* ruleSet) const
	{
	if (!ruleSet)
	return false;

	ElementRuleCollector collector(const_cast<StyledElement&>(element), m_ruleSets, &m_selectorFilter);
	return collector.hasAnyMatchingRules(ruleSet);
	}

	bool SharingResolver::sharingCandidateHasIdenticalStyleAffectingAttributes(const Context& context, const StyledElement& sharingCandidate) const
	{
	auto& element = context.element;
	if (element.elementData() == sharingCandidate.elementData())
	return true;
	if (element.attributeWithoutSynchronization(XMLNames::langAttr) != sharingCandidate.attributeWithoutSynchronization(XMLNames::langAttr))
	return false;
	if (element.attributeWithoutSynchronization(HTMLNames::langAttr) != sharingCandidate.attributeWithoutSynchronization(HTMLNames::langAttr))
	return false;

	if (context.elementAffectedByClassRules) {
	if (!sharingCandidate.hasClass())
	return false;
	// SVG elements require a (slow!) getAttribute comparision because "class" is an animatable attribute for SVG.
	if (element.isSVGElement()) {
	if (element.getAttribute(HTMLNames::classAttr) != sharingCandidate.getAttribute(HTMLNames::classAttr))
	return false;
	} else {
	if (element.classNames() != sharingCandidate.classNames())
	return false;
	}
	} else if (sharingCandidate.hasClass() && classNamesAffectedByRules(sharingCandidate.classNames()))
	return false;

	if (const_cast<StyledElement&>(element).presentationAttributeStyle() != const_cast<StyledElement&>(sharingCandidate).presentationAttributeStyle())
	return false;

	return true;
	}

	bool SharingResolver::classNamesAffectedByRules(const SpaceSplitString& classNames) const
	{
	for (unsigned i = 0; i < classNames.size(); ++i) {
	if (m_ruleSets.features().classRules.contains(classNames[i]))
	return true;
	}
	return false;
	}


	}
	}