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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
tree10027f336435511475e392454359edea8e25895d /layout/style/StyleContextSource.h
parent49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff)
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Add m-esr52 at 52.6.0
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-rw-r--r--layout/style/StyleContextSource.h161
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diff --git a/layout/style/StyleContextSource.h b/layout/style/StyleContextSource.h
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_StyleContextSource_h
+#define mozilla_StyleContextSource_h
+
+#include "mozilla/ServoBindingTypes.h"
+#include "nsRuleNode.h"
+
+namespace mozilla {
+
+// Tagged union between Gecko Rule Nodes and Servo Computed Values.
+//
+// The rule node is the node in the lexicographic tree of rule nodes
+// (the "rule tree") that indicates which style rules are used to
+// compute the style data, and in what cascading order. The least
+// specific rule matched is the one whose rule node is a child of the
+// root of the rule tree, and the most specific rule matched is the
+// |mRule| member of the rule node.
+//
+// In the Servo case, we hold an atomically-refcounted handle to a
+// Servo ComputedValues struct, which is more or less the Servo equivalent
+// of an nsStyleContext.
+
+// Underlying pointer without any strong ownership semantics.
+struct NonOwningStyleContextSource
+{
+ MOZ_IMPLICIT NonOwningStyleContextSource(nsRuleNode* aRuleNode)
+ : mBits(reinterpret_cast<uintptr_t>(aRuleNode)) {}
+ explicit NonOwningStyleContextSource(const ServoComputedValues* aComputedValues)
+ : mBits(reinterpret_cast<uintptr_t>(aComputedValues) | 1) {}
+
+ bool operator==(const NonOwningStyleContextSource& aOther) const {
+ MOZ_ASSERT(IsServoComputedValues() == aOther.IsServoComputedValues(),
+ "Comparing Servo to Gecko - probably a bug");
+ return mBits == aOther.mBits;
+ }
+ bool operator!=(const NonOwningStyleContextSource& aOther) const {
+ return !(*this == aOther);
+ }
+
+ // We intentionally avoid exposing IsGeckoRuleNode() here, because that would
+ // encourage callers to do:
+ //
+ // if (source.IsGeckoRuleNode()) {
+ // // Code that we would run unconditionally if it weren't for Servo.
+ // }
+ //
+ // We want these branches to compile away when MOZ_STYLO is disabled, but that
+ // won't happen if there's an implicit null-check.
+ bool IsNull() const { return !mBits; }
+ bool IsGeckoRuleNodeOrNull() const { return !IsServoComputedValues(); }
+ bool IsServoComputedValues() const {
+#ifdef MOZ_STYLO
+ return mBits & 1;
+#else
+ return false;
+#endif
+ }
+
+ nsRuleNode* AsGeckoRuleNode() const {
+ MOZ_ASSERT(IsGeckoRuleNodeOrNull() && !IsNull());
+ return reinterpret_cast<nsRuleNode*>(mBits);
+ }
+
+ const ServoComputedValues* AsServoComputedValues() const {
+ MOZ_ASSERT(IsServoComputedValues());
+ return reinterpret_cast<ServoComputedValues*>(mBits & ~1);
+ }
+
+ bool MatchesNoRules() const {
+ if (IsGeckoRuleNodeOrNull()) {
+ return AsGeckoRuleNode()->IsRoot();
+ }
+
+ // Just assume a Servo-backed StyleContextSource always matches some rules.
+ //
+ // MatchesNoRules is used to ensure style contexts that match no rules
+ // go into a separate mEmptyChild list on their parent. This is only used
+ // as an optimization so that calling FindChildWithRules for style context
+ // sharing is faster for text nodes (which match no rules, and are common).
+ // Since Servo will handle sharing for us, there's no need to split children
+ // into two lists.
+ return false;
+ }
+
+private:
+ uintptr_t mBits;
+};
+
+// Higher-level struct that owns a strong reference to the source. The source
+// is never null.
+struct OwningStyleContextSource
+{
+ explicit OwningStyleContextSource(already_AddRefed<nsRuleNode> aRuleNode)
+ : mRaw(aRuleNode.take())
+ {
+ MOZ_COUNT_CTOR(OwningStyleContextSource);
+ MOZ_ASSERT(!mRaw.IsNull());
+ };
+
+ explicit OwningStyleContextSource(already_AddRefed<ServoComputedValues> aComputedValues)
+ : mRaw(aComputedValues.take())
+ {
+ MOZ_COUNT_CTOR(OwningStyleContextSource);
+ MOZ_ASSERT(!mRaw.IsNull());
+ }
+
+ OwningStyleContextSource(OwningStyleContextSource&& aOther)
+ : mRaw(aOther.mRaw)
+ {
+ MOZ_COUNT_CTOR(OwningStyleContextSource);
+ aOther.mRaw = nullptr;
+ }
+
+ OwningStyleContextSource& operator=(OwningStyleContextSource&) = delete;
+ OwningStyleContextSource(OwningStyleContextSource&) = delete;
+
+ ~OwningStyleContextSource() {
+ MOZ_COUNT_DTOR(OwningStyleContextSource);
+ if (mRaw.IsNull()) {
+ // We must have invoked the move constructor.
+ } else if (IsGeckoRuleNode()) {
+ RefPtr<nsRuleNode> releaseme = dont_AddRef(AsGeckoRuleNode());
+ } else {
+ MOZ_ASSERT(IsServoComputedValues());
+ RefPtr<ServoComputedValues> releaseme =
+ dont_AddRef(AsServoComputedValues());
+ }
+ }
+
+ bool operator==(const OwningStyleContextSource& aOther) const {
+ return mRaw == aOther.mRaw;
+ }
+ bool operator!=(const OwningStyleContextSource& aOther) const {
+ return !(*this == aOther);
+ }
+ bool IsNull() const { return mRaw.IsNull(); }
+ bool IsGeckoRuleNode() const {
+ MOZ_ASSERT(!mRaw.IsNull());
+ return mRaw.IsGeckoRuleNodeOrNull();
+ }
+ bool IsServoComputedValues() const { return mRaw.IsServoComputedValues(); }
+
+ NonOwningStyleContextSource AsRaw() const { return mRaw; }
+ nsRuleNode* AsGeckoRuleNode() const { return mRaw.AsGeckoRuleNode(); }
+ ServoComputedValues* AsServoComputedValues() const {
+ return const_cast<ServoComputedValues*>(mRaw.AsServoComputedValues());
+ }
+
+ bool MatchesNoRules() const { return mRaw.MatchesNoRules(); }
+
+private:
+ NonOwningStyleContextSource mRaw;
+};
+
+} // namespace mozilla
+
+#endif // mozilla_StyleContextSource_h