1 files changed, 266 insertions, 0 deletions
diff --git a/layout/style/DeclarationBlock.h b/layout/style/DeclarationBlock.h
new file mode 100644
index 0000000000..57bfd6f1bc
--- /dev/null
+++ b/layout/style/DeclarationBlock.h
@@ -0,0 +1,266 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/*
+ * representation of a declaration block in a CSS stylesheet, or of
+ * a style attribute
+ */
+
+#ifndef mozilla_DeclarationBlock_h
+#define mozilla_DeclarationBlock_h
+
+#include "mozilla/Atomics.h"
+#include "mozilla/ServoBindings.h"
+
+#include "nsCSSPropertyID.h"
+#include "nsString.h"
+
+class nsHTMLCSSStyleSheet;
+
+namespace mozilla {
+
+namespace css {
+class Declaration;
+class Rule;
+}  // namespace css
+
+class DeclarationBlock final {
+  DeclarationBlock(const DeclarationBlock& aCopy)
+      : mRaw(Servo_DeclarationBlock_Clone(aCopy.mRaw).Consume()),
+        mImmutable(false),
+        mIsDirty(false) {
+    mContainer.mRaw = 0;
+  }
+
+ public:
+  explicit DeclarationBlock(already_AddRefed<RawServoDeclarationBlock> aRaw)
+      : mRaw(aRaw), mImmutable(false), mIsDirty(false) {
+    mContainer.mRaw = 0;
+  }
+
+  DeclarationBlock()
+      : DeclarationBlock(Servo_DeclarationBlock_CreateEmpty().Consume()) {}
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DeclarationBlock)
+
+  already_AddRefed<DeclarationBlock> Clone() const {
+    return do_AddRef(new DeclarationBlock(*this));
+  }
+
+  /**
+   * Return whether |this| may be modified.
+   */
+  bool IsMutable() const { return !mImmutable; }
+
+  /**
+   * Crash in debug builds if |this| cannot be modified.
+   */
+  void AssertMutable() const {
+    MOZ_ASSERT(IsMutable(), "someone forgot to call EnsureMutable");
+    MOZ_ASSERT(!OwnerIsReadOnly(), "User Agent sheets shouldn't be modified");
+  }
+
+  /**
+   * Mark this declaration as unmodifiable.
+   */
+  void SetImmutable() { mImmutable = true; }
+
+  /**
+   * Return whether |this| has been restyled after modified.
+   */
+  bool IsDirty() const { return mIsDirty; }
+
+  /**
+   * Mark this declaration as dirty.
+   */
+  void SetDirty() { mIsDirty = true; }
+
+  /**
+   * Mark this declaration as not dirty.
+   */
+  void UnsetDirty() { mIsDirty = false; }
+
+  /**
+   * Copy |this|, if necessary to ensure that it can be modified.
+   */
+  already_AddRefed<DeclarationBlock> EnsureMutable() {
+    MOZ_ASSERT(!OwnerIsReadOnly());
+
+    if (!IsDirty()) {
+      // In stylo, the old DeclarationBlock is stored in element's rule node
+      // tree directly, to avoid new values replacing the DeclarationBlock in
+      // the tree directly, we need to copy the old one here if we haven't yet
+      // copied. As a result the new value does not replace rule node tree until
+      // traversal happens.
+      //
+      // FIXME(emilio, bug 1606413): This is a hack for ::first-line and
+      // transitions starting due to CSSOM changes when other transitions are
+      // already running. Try to simplify this setup, so that rule tree updates
+      // find the mutated declaration block properly rather than having to
+      // insert the cloned declaration in the tree.
+      return Clone();
+    }
+
+    if (!IsMutable()) {
+      return Clone();
+    }
+
+    return do_AddRef(this);
+  }
+
+  void SetOwningRule(css::Rule* aRule) {
+    MOZ_ASSERT(!mContainer.mOwningRule || !aRule,
+               "should never overwrite one rule with another");
+    mContainer.mOwningRule = aRule;
+  }
+
+  css::Rule* GetOwningRule() const {
+    if (mContainer.mRaw & 0x1) {
+      return nullptr;
+    }
+    return mContainer.mOwningRule;
+  }
+
+  void SetHTMLCSSStyleSheet(nsHTMLCSSStyleSheet* aHTMLCSSStyleSheet) {
+    MOZ_ASSERT(!mContainer.mHTMLCSSStyleSheet || !aHTMLCSSStyleSheet,
+               "should never overwrite one sheet with another");
+    mContainer.mHTMLCSSStyleSheet = aHTMLCSSStyleSheet;
+    if (aHTMLCSSStyleSheet) {
+      mContainer.mRaw |= uintptr_t(1);
+    }
+  }
+
+  nsHTMLCSSStyleSheet* GetHTMLCSSStyleSheet() const {
+    if (!(mContainer.mRaw & 0x1)) {
+      return nullptr;
+    }
+    auto c = mContainer;
+    c.mRaw &= ~uintptr_t(1);
+    return c.mHTMLCSSStyleSheet;
+  }
+
+  bool IsReadOnly() const;
+
+  size_t SizeofIncludingThis(MallocSizeOf);
+
+  static already_AddRefed<DeclarationBlock> FromCssText(
+      const nsACString& aCssText, URLExtraData* aExtraData,
+      nsCompatibility aMode, css::Loader* aLoader, uint16_t aRuleType) {
+    RefPtr<RawServoDeclarationBlock> raw =
+        Servo_ParseStyleAttribute(&aCssText, aExtraData, aMode, aLoader,
+                                  aRuleType)
+            .Consume();
+    return MakeAndAddRef<DeclarationBlock>(raw.forget());
+  }
+
+  static already_AddRefed<DeclarationBlock> FromCssText(
+      const nsAString& aCssText, URLExtraData* aExtraData,
+      nsCompatibility aMode, css::Loader* aLoader, uint16_t aRuleType) {
+    NS_ConvertUTF16toUTF8 value(aCssText);
+    return FromCssText(value, aExtraData, aMode, aLoader, aRuleType);
+  }
+
+  RawServoDeclarationBlock* Raw() const { return mRaw; }
+  RawServoDeclarationBlock* const* RefRaw() const {
+    static_assert(sizeof(RefPtr<RawServoDeclarationBlock>) ==
+                      sizeof(RawServoDeclarationBlock*),
+                  "RefPtr should just be a pointer");
+    return reinterpret_cast<RawServoDeclarationBlock* const*>(&mRaw);
+  }
+
+  const StyleStrong<RawServoDeclarationBlock>* RefRawStrong() const {
+    static_assert(sizeof(RefPtr<RawServoDeclarationBlock>) ==
+                      sizeof(RawServoDeclarationBlock*),
+                  "RefPtr should just be a pointer");
+    static_assert(
+        sizeof(RefPtr<RawServoDeclarationBlock>) ==
+            sizeof(StyleStrong<RawServoDeclarationBlock>),
+        "RawServoDeclarationBlockStrong should be the same as RefPtr");
+    return reinterpret_cast<const StyleStrong<RawServoDeclarationBlock>*>(
+        &mRaw);
+  }
+
+  void ToString(nsACString& aResult) const {
+    Servo_DeclarationBlock_GetCssText(mRaw, &aResult);
+  }
+
+  uint32_t Count() const { return Servo_DeclarationBlock_Count(mRaw); }
+
+  bool GetNthProperty(uint32_t aIndex, nsACString& aReturn) const {
+    aReturn.Truncate();
+    return Servo_DeclarationBlock_GetNthProperty(mRaw, aIndex, &aReturn);
+  }
+
+  void GetPropertyValue(const nsACString& aProperty, nsACString& aValue) const {
+    Servo_DeclarationBlock_GetPropertyValue(mRaw, &aProperty, &aValue);
+  }
+
+  void GetPropertyValueByID(nsCSSPropertyID aPropID, nsACString& aValue) const {
+    Servo_DeclarationBlock_GetPropertyValueById(mRaw, aPropID, &aValue);
+  }
+
+  bool GetPropertyIsImportant(const nsACString& aProperty) const {
+    return Servo_DeclarationBlock_GetPropertyIsImportant(mRaw, &aProperty);
+  }
+
+  // Returns whether the property was removed.
+  bool RemoveProperty(const nsACString& aProperty,
+                      DeclarationBlockMutationClosure aClosure = {}) {
+    AssertMutable();
+    return Servo_DeclarationBlock_RemoveProperty(mRaw, &aProperty, aClosure);
+  }
+
+  // Returns whether the property was removed.
+  bool RemovePropertyByID(nsCSSPropertyID aProperty,
+                          DeclarationBlockMutationClosure aClosure = {}) {
+    AssertMutable();
+    return Servo_DeclarationBlock_RemovePropertyById(mRaw, aProperty, aClosure);
+  }
+
+ private:
+  ~DeclarationBlock() = default;
+
+  bool OwnerIsReadOnly() const;
+
+  union {
+    // We only ever have one of these since we have an
+    // nsHTMLCSSStyleSheet only for style attributes, and style
+    // attributes never have an owning rule.
+
+    // It's an nsHTMLCSSStyleSheet if the low bit is set.
+
+    uintptr_t mRaw;
+
+    // The style rule that owns this declaration.  May be null.
+    css::Rule* mOwningRule;
+
+    // The nsHTMLCSSStyleSheet that is responsible for this declaration.
+    // Only non-null for style attributes.
+    nsHTMLCSSStyleSheet* mHTMLCSSStyleSheet;
+  } mContainer;
+
+  RefPtr<RawServoDeclarationBlock> mRaw;
+
+  // set when declaration put in the rule tree;
+  bool mImmutable;
+
+  // True if this declaration has not been restyled after modified.
+  //
+  // Since we can clear this flag from style worker threads, we use an Atomic.
+  //
+  // Note that although a single DeclarationBlock can be shared between
+  // different rule nodes (due to the style="" attribute cache), whenever a
+  // DeclarationBlock has its mIsDirty flag set to true, we always clone it to
+  // a unique object first. So when we clear this flag during Servo traversal,
+  // we know that we are clearing it on a DeclarationBlock that has a single
+  // reference, and there is no problem with another user of the same
+  // DeclarationBlock thinking that it is not dirty.
+  Atomic<bool, MemoryOrdering::Relaxed> mIsDirty;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_DeclarationBlock_h