Current work-in-progress crbug.com/567021

third_party/WebKit/Source/core/css/invalidation/StyleSheetInvalidationAnalysis.cpp

-/*
- * Copyright (C) 2012 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 COMPUTER, 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 COMPUTER, 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 "core/css/invalidation/StyleSheetInvalidationAnalysis.h"
-
-#include "core/css/CSSSelectorList.h"
-#include "core/css/StyleRuleImport.h"
-#include "core/css/StyleSheetContents.h"
-#include "core/dom/ContainerNode.h"
-#include "core/dom/Document.h"
-#include "core/dom/ElementTraversal.h"
-#include "core/dom/StyleChangeReason.h"
-#include "core/dom/TreeScope.h"
-#include "core/dom/shadow/ShadowRoot.h"
-#include "core/html/HTMLStyleElement.h"
-
-namespace blink {
-
-StyleSheetInvalidationAnalysis::StyleSheetInvalidationAnalysis(const TreeScope& treeScope, const HeapVector<Member<StyleSheetContents>>& sheets)
-    : m_treeScope(&treeScope)
-{
-    for (unsigned i = 0; i < sheets.size() && !m_dirtiesAllStyle; ++i)
-        analyzeStyleSheet(sheets[i]);
-}
-
-static bool determineSelectorScopes(const CSSSelectorList& selectorList, HashSet<StringImpl*>& idScopes, HashSet<StringImpl*>& classScopes)
-{
-    for (const CSSSelector* selector = selectorList.first(); selector; selector = CSSSelectorList::next(*selector)) {
-        const CSSSelector* scopeSelector = 0;
-        // This picks the widest scope, not the narrowest, to minimize the number of found scopes.
-        for (const CSSSelector* current = selector; current; current = current->tagHistory()) {
-            // Prefer ids over classes.
-            if (current->match() == CSSSelector::Id)
-                scopeSelector = current;
-            else if (current->match() == CSSSelector::Class && (!scopeSelector || scopeSelector->match() != CSSSelector::Id))
-                scopeSelector = current;
-            CSSSelector::RelationType relation = current->relation();
-            // FIXME: it would be better to use setNeedsStyleRecalc for all shadow hosts matching
-            // scopeSelector. Currently requests full style recalc.
-            if (relation == CSSSelector::ShadowDeep || relation == CSSSelector::ShadowPseudo)
-                return false;
-            if (relation != CSSSelector::Descendant && relation != CSSSelector::Child && relation != CSSSelector::SubSelector)
-                break;
-        }
-        if (!scopeSelector)
-            return false;
-        ASSERT(scopeSelector->match() == CSSSelector::Class || scopeSelector->match() == CSSSelector::Id);
-        if (scopeSelector->match() == CSSSelector::Id)
-            idScopes.add(scopeSelector->value().impl());
-        else
-            classScopes.add(scopeSelector->value().impl());
-    }
-    return true;
-}
-
-static bool ruleAdditionMightRequireDocumentStyleRecalc(StyleRuleBase* rule)
-{
-    // This funciton is conservative. We only return false when we know that
-    // the added @rule can't require style recalcs.
-    switch (rule->type()) {
-    case StyleRule::Import: // Whatever we import should do its own analysis, we don't need to invalidate the document here!
-    case StyleRule::Page: // Page rules apply only during printing, we force a full-recalc before printing.
-        return false;
-
-    case StyleRule::Media: // If the media rule doesn't apply, we could avoid recalc.
-    case StyleRule::FontFace: // If the fonts aren't in use, we could avoid recalc.
-    case StyleRule::Supports: // If we evaluated the supports-clause we could avoid recalc.
-    case StyleRule::Viewport: // If the viewport doesn't match, we could avoid recalcing.
-    case StyleRule::Keyframes: // If the animation doesn't match an element, we could avoid recalc.
-        return true;
-
-    // These should all be impossible to reach:
-    case StyleRule::Charset:
-    case StyleRule::Keyframe:
-    case StyleRule::Namespace:
-    case StyleRule::Style:
-        break;
-    }
-    ASSERT_NOT_REACHED();
-    return true;
-}
-
-void StyleSheetInvalidationAnalysis::analyzeStyleSheet(StyleSheetContents* styleSheetContents)
-{
-    // Updating the style on the shadow DOM for image fallback content can bring us here when imports
-    // are still getting loaded in the main document. Just need to exit early as we will return here
-    // when the imports finish loading.
-    if (styleSheetContents->isLoading())
-        return;
-
-    // See if all rules on the sheet are scoped to some specific ids or classes.
-    // Then test if we actually have any of those in the tree at the moment.
-    const HeapVector<Member<StyleRuleImport>>& importRules = styleSheetContents->importRules();
-    for (unsigned i = 0; i < importRules.size(); ++i) {
-        if (!importRules[i]->styleSheet())
-            continue;
-        analyzeStyleSheet(importRules[i]->styleSheet());
-        if (m_dirtiesAllStyle)
-            return;
-    }
-
-    if (m_treeScope->rootNode().isShadowRoot())
-        return;
-
-    const HeapVector<Member<StyleRuleBase>>& rules = styleSheetContents->childRules();
-    for (unsigned i = 0; i < rules.size(); i++) {
-        StyleRuleBase* rule = rules[i].get();
-        if (!rule->isStyleRule()) {
-            if (ruleAdditionMightRequireDocumentStyleRecalc(rule)) {
-                m_dirtiesAllStyle = true;
-                return;
-            }
-            continue;
-        }
-        StyleRule* styleRule = toStyleRule(rule);
-        if (!determineSelectorScopes(styleRule->selectorList(), m_idScopes, m_classScopes)) {
-            m_dirtiesAllStyle = true;
-            return;
-        }
-    }
-}
-
-static bool elementMatchesSelectorScopes(const Element* element, const HashSet<StringImpl*>& idScopes, const HashSet<StringImpl*>& classScopes)
-{
-    if (!idScopes.isEmpty() && element->hasID() && idScopes.contains(element->idForStyleResolution().impl()))
-        return true;
-    if (classScopes.isEmpty() || !element->hasClass())
-        return false;
-    const SpaceSplitString& classNames = element->classNames();
-    for (unsigned i = 0; i < classNames.size(); ++i) {
-        if (classScopes.contains(classNames[i].impl()))
-            return true;
-    }
-    return false;
-}
-
-void StyleSheetInvalidationAnalysis::invalidateStyle()
-{
-    ASSERT(!m_dirtiesAllStyle);
-
-    if (m_treeScope->rootNode().isShadowRoot()) {
-        ContainerNode& shadowHost = toShadowRoot(m_treeScope->rootNode()).host();
-        shadowHost.setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::StyleSheetChange));
-        return;
-    }
-
-    if (m_idScopes.isEmpty() && m_classScopes.isEmpty())
-        return;
-    Element* element = ElementTraversal::firstWithin(m_treeScope->document());
-    while (element) {
-        if (elementMatchesSelectorScopes(element, m_idScopes, m_classScopes)) {
-            element->setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::StyleSheetChange));
-            // The whole subtree is now invalidated, we can skip to the next sibling.
-            element = ElementTraversal::nextSkippingChildren(*element);
-            continue;
-        }
-        element = ElementTraversal::next(*element);
-    }
-}
-
-} // namespace blink