Current work-in-progress crbug.com/567021

third_party/WebKit/Source/core/css/ActiveStyleSheets.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/css/ActiveStyleSheets.h"
+
+#include "core/css/CSSStyleSheet.h"
+#include "core/css/RuleSet.h"
+#include "core/css/resolver/ScopedStyleResolver.h"
+#include "core/dom/ContainerNode.h"
+#include "core/dom/StyleChangeReason.h"
+#include "core/dom/StyleEngine.h"
+#include "core/dom/TreeScope.h"
+#include "core/dom/shadow/ShadowRoot.h"
+#include "core/html/imports/HTMLImportsController.h"
+
+namespace blink {
+
+ActiveSheetsChange compareActiveStyleSheets(
+    const ActiveStyleSheetVector& oldStyleSheets,
+    const ActiveStyleSheetVector& newStyleSheets,
+    HeapVector<Member<RuleSet>>& changedRuleSets)
+{
+    unsigned newStyleSheetCount = newStyleSheets.size();
+    unsigned oldStyleSheetCount = oldStyleSheets.size();
+
+    unsigned minCount = std::min(newStyleSheetCount, oldStyleSheetCount);
+    unsigned index = 0;
+
+    // Walk the common prefix of stylesheets. If the stylesheet rules were
+    // modified since last time, add them to the list of changed rulesets.
+    for (; index < minCount && newStyleSheets[index].first == oldStyleSheets[index].first; index++) {
+        if (newStyleSheets[index].second == oldStyleSheets[index].second)
+            continue;
+
+        changedRuleSets.append(newStyleSheets[index].second);
+        changedRuleSets.append(oldStyleSheets[index].second);
+    }
+
+    if (index == oldStyleSheetCount) {
+        if (index == newStyleSheetCount)
+            return changedRuleSets.size() ? ActiveSheetsChanged : NoActiveSheetsChanged;
+
+        // Sheets added at the end.
+        for (; index < newStyleSheetCount; index++)
+            changedRuleSets.append(newStyleSheets[index].second);
+        return ActiveSheetsAppended;
+    }
+
+    if (index == newStyleSheetCount) {
+        // Sheets removed from the end.
+        for (; index < oldStyleSheetCount; index++)
+            changedRuleSets.append(oldStyleSheets[index].second);
+        return ActiveSheetsChanged;
+    }
+
+    DCHECK(index < oldStyleSheetCount && index < newStyleSheetCount);
+
+    // Both the new and old active stylesheet vectors have stylesheets following
+    // the common prefix. Figure out which were added or removed by sorting the
+    // merged vector of old and new sheets.
+
+    ActiveStyleSheetVector mergedSorted;
+    mergedSorted.reserveCapacity(oldStyleSheetCount + newStyleSheetCount - 2 * index);
+    mergedSorted.appendRange(oldStyleSheets.begin() + index, oldStyleSheets.end());
+    mergedSorted.appendRange(newStyleSheets.begin() + index, newStyleSheets.end());
+
+    std::sort(mergedSorted.begin(), mergedSorted.end());
+
+    auto mergedIterator = mergedSorted.begin();
+    while (mergedIterator != mergedSorted.end()) {
+
+        const auto& sheet1 = *mergedIterator++;
+        if (mergedIterator == mergedSorted.end() || (*mergedIterator).first != sheet1.first) {
+            // Sheet either removed or inserted.
+            changedRuleSets.append(sheet1.second);
+            continue;
+        }
+
+        // Sheet present in both old and new.
+        const auto& sheet2 = *mergedIterator++;
+
+        if (sheet1.second == sheet2.second) {
+            // TODO(rune@opera.com): HTML Imports keep document and stylesheets
+            // when removed from the parent document. The sorting does not detect
+            // such issues.
+            if (Document* owner = sheet1.first->ownerDocument()) {
+                if (owner->importsController() && owner->importsController()->master() != owner)
+                    changedRuleSets.append(sheet1.second);
+            }
+            continue;
+        }
+
+        // Active rules for the given stylesheet changed.
+        // DOM, CSSOM, or media query changes.
+        changedRuleSets.append(sheet1.second);
+        changedRuleSets.append(sheet2.second);
+    }
+    return ActiveSheetsChanged;
+}
+
+namespace {
+
+enum RuleSetFlags {
+    FontFaceRules = 1 << 0,
+    KeyframesRules = 1 << 1,
+    ShadowBoundaryCrossingRules = 1 << 2,
+    UniversalRules = 1 << 3
+};
+
+unsigned getRuleFlags(const HeapVector<Member<RuleSet>> ruleSets)
+{
+    unsigned flags = 0;
+    for (auto& ruleSet : ruleSets) {
+        ruleSet->compactRulesIfNeeded();
+        if (!ruleSet->keyframesRules().isEmpty())
+            flags |= KeyframesRules;
+        if (!ruleSet->fontFaceRules().isEmpty())
+            flags |= FontFaceRules;
+        if (ruleSet->deepCombinatorOrShadowPseudoRules().size() || ruleSet->contentPseudoElementRules().size() || ruleSet->slottedPseudoElementRules().size())
+            flags |= ShadowBoundaryCrossingRules;
+        if (ruleSet->features().needsFullRecalcForRuleSetInvalidation())
+            flags |= UniversalRules;
+    }
+    return flags;
+}
+
+ContainerNode& invalidationRootForTreeScope(const TreeScope& treeScope)
+{
+    if (treeScope.rootNode().isDocumentNode())
+        return treeScope.rootNode();
+    return toShadowRoot(treeScope.rootNode()).host();
+}
+
+} // namespace
+
+void applyRuleSetChanges(StyleEngine& engine, TreeScope& treeScope,
+    const ActiveStyleSheetVector& oldStyleSheets,
+    const ActiveStyleSheetVector& newStyleSheets)
+{
+    HeapVector<Member<RuleSet>> changedRuleSets;
+
+    ActiveSheetsChange change = compareActiveStyleSheets(oldStyleSheets, newStyleSheets, changedRuleSets);
+    if (change == NoActiveSheetsChanged)
+        return;
+
+    engine.setNeedsGlobalRuleSetUpdate();
+
+    unsigned changedRuleFlags = getRuleFlags(changedRuleSets);
+    bool fontsChanged = treeScope.rootNode().isDocumentNode() && (changedRuleFlags & FontFaceRules);
+
+    if (change == ActiveSheetsChanged) {
+
+        if (fontsChanged)
+            engine.clearFontCache();
+
+        if (newStyleSheets.isEmpty()) {
+            treeScope.clearScopedStyleResolver();
+        } else {
+            if (treeScope.scopedStyleResolver())
+                treeScope.scopedStyleResolver()->resetAuthorStyle();
+            treeScope.ensureScopedStyleResolver().appendActiveStyleSheets(0, newStyleSheets);
+        }
+
+    } else {
+        treeScope.ensureScopedStyleResolver().appendActiveStyleSheets(oldStyleSheets.size(), newStyleSheets);
+    }
+
+    if (treeScope.document().hasPendingForcedStyleRecalc())
+        return;
+
+    if (!treeScope.document().body() || treeScope.document().hasNodesWithPlaceholderStyle()) {
+        treeScope.document().setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::CleanupPlaceholderStyles));
+        return;
+    }
+
+    if (fontsChanged || (changedRuleFlags & (KeyframesRules | ShadowBoundaryCrossingRules | UniversalRules))) {
+        invalidationRootForTreeScope(treeScope).setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::ActiveStylesheetsUpdate));
+        return;
+    }
+
+    engine.scheduleInvalidationsForRuleSets(treeScope, changedRuleSets);
+}
+
+} // namespace blink