1 files changed, 171 insertions, 0 deletions
diff --git a/layout/style/ServoElementSnapshot.h b/layout/style/ServoElementSnapshot.h
new file mode 100644
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+++ b/layout/style/ServoElementSnapshot.h
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+/* -*- 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/. */
+
+#ifndef mozilla_ServoElementSnapshot_h
+#define mozilla_ServoElementSnapshot_h
+
+#include "AttrArray.h"
+#include "mozilla/TypedEnumBits.h"
+#include "mozilla/dom/BorrowedAttrInfo.h"
+#include "mozilla/dom/RustTypes.h"
+#include "nsAttrName.h"
+#include "nsAttrValue.h"
+#include "nsChangeHint.h"
+#include "nsGkAtoms.h"
+#include "nsAtom.h"
+#include "MainThreadUtils.h"
+
+namespace mozilla {
+namespace dom {
+class Element;
+}
+
+/**
+ * A bitflags enum class used to determine what data does a ServoElementSnapshot
+ * contains.
+ */
+enum class ServoElementSnapshotFlags : uint8_t {
+  State = 1 << 0,
+  Attributes = 1 << 1,
+  Id = 1 << 2,
+  MaybeClass = 1 << 3,
+  OtherPseudoClassState = 1 << 4,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(ServoElementSnapshotFlags)
+
+/**
+ * This class holds all non-tree-structural state of an element that might be
+ * used for selector matching eventually.
+ *
+ * This means the attributes, and the element state, such as :hover, :active,
+ * etc...
+ */
+class ServoElementSnapshot {
+  typedef dom::BorrowedAttrInfo BorrowedAttrInfo;
+  typedef dom::Element Element;
+
+  // TODO: Now that the element state shares a representation with rust we
+  // should be able to do better and not use the internal type.
+  typedef dom::ElementState::InternalType ServoStateType;
+
+ public:
+  typedef ServoElementSnapshotFlags Flags;
+
+  explicit ServoElementSnapshot(const Element&);
+
+  ~ServoElementSnapshot() {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_COUNT_DTOR(ServoElementSnapshot);
+  }
+
+  bool HasAttrs() const { return HasAny(Flags::Attributes); }
+
+  bool HasState() const { return HasAny(Flags::State); }
+
+  bool HasOtherPseudoClassState() const {
+    return HasAny(Flags::OtherPseudoClassState);
+  }
+
+  /**
+   * Captures the given state (if not previously captured).
+   */
+  void AddState(dom::ElementState aState) {
+    if (!HasAny(Flags::State)) {
+      mState = aState.GetInternalValue();
+      mContains |= Flags::State;
+    }
+  }
+
+  /**
+   * Captures the given element attributes (if not previously captured).
+   *
+   * The attribute name and namespace are used to note which kind of attribute
+   * has changed.
+   */
+  void AddAttrs(const Element&, int32_t aNameSpaceID, nsAtom* aAttribute);
+
+  /**
+   * Captures some other pseudo-class matching state not included in
+   * ElementState.
+   */
+  void AddOtherPseudoClassState(const Element&);
+
+  /**
+   * Needed methods for attribute matching.
+   */
+  BorrowedAttrInfo GetAttrInfoAt(uint32_t aIndex) const {
+    MOZ_ASSERT(HasAttrs());
+    if (aIndex >= mAttrs.Length()) {
+      return BorrowedAttrInfo(nullptr, nullptr);
+    }
+    return BorrowedAttrInfo(&mAttrs[aIndex].mName, &mAttrs[aIndex].mValue);
+  }
+
+  const nsAttrValue* GetParsedAttr(nsAtom* aLocalName) const {
+    return GetParsedAttr(aLocalName, kNameSpaceID_None);
+  }
+
+  const nsAttrValue* GetParsedAttr(nsAtom* aLocalName,
+                                   int32_t aNamespaceID) const {
+    MOZ_ASSERT(HasAttrs());
+    uint32_t i, len = mAttrs.Length();
+    if (aNamespaceID == kNameSpaceID_None) {
+      // This should be the common case so lets make an optimized loop
+      for (i = 0; i < len; ++i) {
+        if (mAttrs[i].mName.Equals(aLocalName)) {
+          return &mAttrs[i].mValue;
+        }
+      }
+
+      return nullptr;
+    }
+
+    for (i = 0; i < len; ++i) {
+      if (mAttrs[i].mName.Equals(aLocalName, aNamespaceID)) {
+        return &mAttrs[i].mValue;
+      }
+    }
+
+    return nullptr;
+  }
+
+  bool IsInChromeDocument() const { return mIsInChromeDocument; }
+  bool SupportsLangAttr() const { return mSupportsLangAttr; }
+
+  bool HasAny(Flags aFlags) const { return bool(mContains & aFlags); }
+
+  bool IsTableBorderNonzero() const {
+    MOZ_ASSERT(HasOtherPseudoClassState());
+    return mIsTableBorderNonzero;
+  }
+
+  bool IsSelectListBox() const {
+    MOZ_ASSERT(HasOtherPseudoClassState());
+    return mIsSelectListBox;
+  }
+
+ private:
+  // TODO: Profile, a 1 or 2 element AutoTArray could be worth it, given we know
+  // we're dealing with attribute changes when we take snapshots of attributes,
+  // though it can be wasted space if we deal with a lot of state-only
+  // snapshots.
+  nsTArray<AttrArray::InternalAttr> mAttrs;
+  nsTArray<RefPtr<nsAtom>> mChangedAttrNames;
+  nsAttrValue mClass;
+  ServoStateType mState;
+  Flags mContains;
+  bool mIsInChromeDocument : 1;
+  bool mSupportsLangAttr : 1;
+  bool mIsTableBorderNonzero : 1;
+  bool mIsSelectListBox : 1;
+  bool mClassAttributeChanged : 1;
+  bool mIdAttributeChanged : 1;
+};
+
+}  // namespace mozilla
+
+#endif