Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1251 insertions, 0 deletions

diff --git a/dom/base/DirectionalityUtils.cpp b/dom/base/DirectionalityUtils.cpp
new file mode 100644
index 0000000000..40c2445431
--- /dev/null
+++ b/dom/base/DirectionalityUtils.cpp
@@ -0,0 +1,1251 @@
+/* -*- 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/. */
+
+/*
+  Implementation description from https://etherpad.mozilla.org/dir-auto
+
+  Static case
+  ===========
+  When we see a new content node with @dir=auto from the parser, we set the
+  NodeHasDirAuto flag on the node.  We won't have enough information to
+  decide the directionality of the node at this point.
+
+  When we bind a new content node to the document, if its parent has either of
+  the NodeAncestorHasDirAuto or NodeHasDirAuto flags, we set the
+  NodeAncestorHasDirAuto flag on the node.
+
+  When a new input with @type=text/search/tel/url/email and @dir=auto is added
+  from the parser, we resolve the directionality based on its @value.
+
+  When a new text node with non-neutral content is appended to a textarea
+  element with NodeHasDirAuto, if the directionality of the textarea element
+  is still unresolved, it is resolved based on the value of the text node.
+  Elements with unresolved directionality behave as LTR.
+
+  When a new text node with non-neutral content is appended to an element that
+  is not a textarea but has either of the NodeAncestorHasDirAuto or
+  NodeHasDirAuto flags, we walk up the parent chain while the
+  NodeAncestorHasDirAuto flag is present, and when we reach an element with
+  NodeHasDirAuto and no resolved directionality, we resolve the directionality
+  based on the contents of the text node and cease walking the parent chain.
+  Note that we should ignore elements with NodeHasDirAuto with resolved
+  directionality, so that the second text node in this example tree doesn't
+  affect the directionality of the div:
+
+  <div dir=auto>
+    <span>foo</span>
+    <span>بار</span>
+  </div>
+
+  The parent chain walk will be aborted if we hit a script or style element, or
+  if we hit an element with @dir=ltr or @dir=rtl.
+
+  I will call this algorithm "upward propagation".
+
+  Each text node should maintain a list of elements which have their
+  directionality determined by the first strong character of that text node.
+  This is useful to make dynamic changes more efficient.  One way to implement
+  this is to have a per-document hash table mapping a text node to a set of
+  elements.  I'll call this data structure TextNodeDirectionalityMap. The
+  algorithm for appending a new text node above needs to update this data
+  structure.
+
+  *IMPLEMENTATION NOTE*
+  In practice, the implementation uses two per-node properties:
+
+  dirAutoSetBy, which is set on a node with auto-directionality, and points to
+  the textnode that contains the strong character which determines the
+  directionality of the node.
+
+  textNodeDirectionalityMap, which is set on a text node and points to a hash
+  table listing the nodes whose directionality is determined by the text node.
+
+  Handling dynamic changes
+  ========================
+
+  We need to handle the following cases:
+
+  1. When the value of an input element with @type=text/search/tel/url/email is
+  changed, if it has NodeHasDirAuto, we update the resolved directionality.
+
+  2. When the dir attribute is changed from something else (including the case
+  where it doesn't exist) to auto on a textarea or an input element with
+  @type=text/search/tel/url/email, we set the NodeHasDirAuto flag and resolve
+  the directionality based on the value of the element.
+
+  3. When the dir attribute is changed from something else (including the case
+  where it doesn't exist) to auto on any element except case 1 above and the bdi
+  element, we run the following algorithm:
+  * We set the NodeHasDirAuto flag.
+  * If the element doesn't have the NodeAncestorHasDirAuto flag, we set the
+  NodeAncestorHasDirAuto flag on all of its child nodes.  (Note that if the
+  element does have NodeAncestorHasDirAuto, all of its children should
+  already have this flag too.  We can assert this in debug builds.)
+  * To resolve the directionality of the element, we run the algorithm explained
+  in
+  http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#the-dir-attribute
+  (I'll call this the "downward propagation algorithm".) by walking the child
+  subtree in tree order.  Note that an element with @dir=auto should not affect
+  other elements in its document with @dir=auto.  So there is no need to walk up
+  the parent chain in this case.  TextNodeDirectionalityMap needs to be updated
+  as appropriate.
+
+  3a. When the dir attribute is set to any valid value on an element that didn't
+  have a valid dir attribute before, this means that any descendant of that
+  element will not affect the directionality of any of its ancestors. So we need
+  to check whether any text node descendants of the element are listed in
+  TextNodeDirectionalityMap, and whether the elements whose direction they set
+  are ancestors of the element. If so, we need to rerun the downward propagation
+  algorithm for those ancestors.
+
+  4.  When the dir attribute is changed from auto to something else (including
+  the case where it gets removed) on a textarea or an input element with
+  @type=text/search/tel/url/email, we unset the NodeHasDirAuto flag and
+  resolve the directionality based on the directionality of the value of the
+  @dir attribute on element itself or its parent element.
+
+  5. When the dir attribute is changed from auto to something else (including
+  the case where it gets removed) on any element except case 4 above and the bdi
+  element, we run the following algorithm:
+  * We unset the NodeHasDirAuto flag.
+  * If the element does not have the NodeAncestorHasDirAuto flag, we unset
+  the NodeAncestorHasDirAuto flag on all of its child nodes, except those
+  who are a descendant of another element with NodeHasDirAuto.  (Note that if
+  the element has the NodeAncestorHasDirAuto flag, all of its child nodes
+  should still retain the same flag.)
+  * We resolve the directionality of the element based on the value of the @dir
+  attribute on the element itself or its parent element.
+  TextNodeDirectionalityMap needs to be updated as appropriate.
+
+  5a. When the dir attribute is removed or set to an invalid value on any
+  element (except a bdi element) with the NodeAncestorHasDirAuto flag which
+  previously had a valid dir attribute, it might have a text node descendant
+  that did not previously affect the directionality of any of its ancestors but
+  should now begin to affect them. We run the following algorithm:
+  * Walk up the parent chain from the element.
+  * For any element that appears in the TextNodeDirectionalityMap, remove the
+    element from the map and rerun the downward propagation algorithm
+    (see section 3).
+  * If we reach an element without either of the NodeHasDirAuto or
+    NodeAncestorHasDirAuto flags, abort the parent chain walk.
+
+  6. When an element with @dir=auto is added to the document, we should handle
+  it similar to the case 2/3 above.
+
+  7. When an element with NodeHasDirAuto or NodeAncestorHasDirAuto is
+  removed from the document, we should handle it similar to the case 4/5 above,
+  except that we don't need to handle anything in the child subtree.  We should
+  also remove all of the occurrences of that node and its descendants from
+  TextNodeDirectionalityMap. (This is the conceptual description of what needs
+  to happen but in the implementation UnbindFromTree is going to be called on
+  all of the descendants so we don't need to descend into the child subtree).
+
+  8. When the contents of a text node is changed either from script or by the
+  user, we need to run the following algorithm:
+  * If the change has happened after the first character with strong
+  directionality in the text node, do nothing.
+  * If the text node is a child of a bdi, script or style element, do nothing.
+  * If the text node belongs to a textarea with NodeHasDirAuto, we need to
+  update the directionality of the textarea.
+  * Grab a list of elements affected by this text node from
+  TextNodeDirectionalityMap and re-resolve the directionality of each one of
+  them based on the new contents of the text node.
+  * If the text node does not exist in TextNodeDirectionalityMap, and it has the
+  NodeAncestorHasDirAuto flag set, this could potentially be a text node
+  which is going to start affecting the directionality of its parent @dir=auto
+  elements. In this case, we need to fall back to the (potentially expensive)
+  "upward propagation algorithm".  The TextNodeDirectionalityMap data structure
+  needs to be update during this algorithm.
+  * If the new contents of the text node do not have any strong characters, and
+  the old contents used to, and the text node used to exist in
+  TextNodeDirectionalityMap and it has the NodeAncestorHasDirAuto flag set,
+  the elements associated with this text node inside TextNodeDirectionalityMap
+  will now get their directionality from another text node.  In this case, for
+  each element in the list retrieved from TextNodeDirectionalityMap, run the
+  downward propagation algorithm (section 3), and remove the text node from
+  TextNodeDirectionalityMap.
+
+  9. When a new text node is injected into a document, we need to run the
+  following algorithm:
+  * If the contents of the text node do not have any characters with strong
+  direction, do nothing.
+  * If the text node is a child of a bdi, script or style element, do nothing.
+  * If the text node is appended to a textarea element with NodeHasDirAuto, we
+  need to update the directionality of the textarea.
+  * If the text node has NodeAncestorHasDirAuto, we need to run the "upward
+  propagation algorithm".  The TextNodeDirectionalityMap data structure needs to
+  be update during this algorithm.
+
+  10. When a text node is removed from a document, we need to run the following
+  algorithm:
+  * If the contents of the text node do not have any characters with strong
+  direction, do nothing.
+  * If the text node is a child of a bdi, script or style element, do nothing.
+  * If the text node is removed from a textarea element with NodeHasDirAuto,
+  set the directionality to "ltr". (This is what the spec currently says, but
+  I'm filing a spec bug to get it fixed -- the directionality should depend on
+  the parent element here.)
+  * If the text node has NodeAncestorHasDirAuto, we need to look at the list
+  of elements being affected by this text node from TextNodeDirectionalityMap,
+  run the "downward propagation algorithm" (section 3) for each one of them,
+  while updating TextNodeDirectionalityMap along the way.
+
+  11. If the value of the @dir attribute on a bdi element is changed to an
+  invalid value (or if it's removed), determine the new directionality similar
+  to the case 3 above.
+
+  == Implemention Notes ==
+  When a new node gets bound to the tree, the BindToTree function gets called.
+  The reverse case is UnbindFromTree.
+  When the contents of a text node change, CharacterData::SetTextInternal
+  gets called.
+  */
+
+#include "mozilla/dom/DirectionalityUtils.h"
+
+#include "nsINode.h"
+#include "nsIContent.h"
+#include "nsIContentInlines.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/AutoRestore.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLSlotElement.h"
+#include "mozilla/dom/ShadowRoot.h"
+#include "nsUnicodeProperties.h"
+#include "nsTextFragment.h"
+#include "nsAttrValue.h"
+#include "nsTextNode.h"
+#include "nsCheapSets.h"
+
+namespace mozilla {
+
+using mozilla::dom::Element;
+using mozilla::dom::HTMLInputElement;
+using mozilla::dom::HTMLSlotElement;
+using mozilla::dom::ShadowRoot;
+
+static nsIContent* GetParentOrHostOrSlot(
+    nsIContent* aContent, bool* aCrossedShadowBoundary = nullptr) {
+  if (HTMLSlotElement* slot = aContent->GetAssignedSlot()) {
+    if (aCrossedShadowBoundary) {
+      *aCrossedShadowBoundary = true;
+    }
+    return slot;
+  }
+
+  nsIContent* parent = aContent->GetParent();
+  if (parent) {
+    return parent;
+  }
+
+  ShadowRoot* sr = ShadowRoot::FromNode(aContent);
+  if (sr) {
+    if (aCrossedShadowBoundary) {
+      *aCrossedShadowBoundary = true;
+    }
+    return sr->Host();
+  }
+
+  return nullptr;
+}
+
+static bool AncestorChainCrossesShadowBoundary(nsIContent* aDescendant,
+                                               nsIContent* aAncestor) {
+  bool crossedShadowBoundary = false;
+  nsIContent* content = aDescendant;
+  while (content && content != aAncestor) {
+    content = GetParentOrHostOrSlot(content, &crossedShadowBoundary);
+    if (crossedShadowBoundary) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/**
+ * Returns true if aElement is one of the elements whose text content should not
+ * affect its own direction, nor the direction of ancestors with dir=auto.
+ *
+ * Note that this does not include <bdi>, whose content does affect its own
+ * direction when it has dir=auto (which it has by default), so one needs to
+ * test for it separately, e.g. with DoesNotAffectDirectionOfAncestors.
+ * It *does* include textarea, because even if a textarea has dir=auto, it has
+ * unicode-bidi: plaintext and is handled automatically in bidi resolution.
+ * It also includes `input`, because it takes the `dir` value from its value
+ * attribute, instead of the child nodes.
+ */
+static bool DoesNotParticipateInAutoDirection(const nsIContent* aContent) {
+  mozilla::dom::NodeInfo* nodeInfo = aContent->NodeInfo();
+  return ((!aContent->IsHTMLElement() || nodeInfo->Equals(nsGkAtoms::script) ||
+           nodeInfo->Equals(nsGkAtoms::style) ||
+           nodeInfo->Equals(nsGkAtoms::input) ||
+           nodeInfo->Equals(nsGkAtoms::textarea) ||
+           aContent->IsInNativeAnonymousSubtree())) &&
+         !aContent->IsShadowRoot();
+}
+
+/**
+ * Returns true if aElement is one of the element whose text content should not
+ * affect the direction of ancestors with dir=auto (though it may affect its own
+ * direction, e.g. <bdi>)
+ */
+static bool DoesNotAffectDirectionOfAncestors(const Element* aElement) {
+  return (DoesNotParticipateInAutoDirection(aElement) ||
+          aElement->IsHTMLElement(nsGkAtoms::bdi) || aElement->HasFixedDir());
+}
+
+/**
+ * Returns the directionality of a Unicode character
+ */
+static Directionality GetDirectionFromChar(uint32_t ch) {
+  switch (mozilla::unicode::GetBidiCat(ch)) {
+    case eCharType_RightToLeft:
+    case eCharType_RightToLeftArabic:
+      return eDir_RTL;
+
+    case eCharType_LeftToRight:
+      return eDir_LTR;
+
+    default:
+      return eDir_NotSet;
+  }
+}
+
+inline static bool NodeAffectsDirAutoAncestor(nsIContent* aTextNode) {
+  nsIContent* parent = GetParentOrHostOrSlot(aTextNode);
+  return (parent && !DoesNotParticipateInAutoDirection(parent) &&
+          parent->NodeOrAncestorHasDirAuto() &&
+          !aTextNode->IsInNativeAnonymousSubtree());
+}
+
+Directionality GetDirectionFromText(const char16_t* aText,
+                                    const uint32_t aLength,
+                                    uint32_t* aFirstStrong) {
+  const char16_t* start = aText;
+  const char16_t* end = aText + aLength;
+
+  while (start < end) {
+    uint32_t current = start - aText;
+    uint32_t ch = *start++;
+
+    if (start < end && NS_IS_SURROGATE_PAIR(ch, *start)) {
+      ch = SURROGATE_TO_UCS4(ch, *start++);
+      current++;
+    }
+
+    // Just ignore lone surrogates
+    if (!IS_SURROGATE(ch)) {
+      Directionality dir = GetDirectionFromChar(ch);
+      if (dir != eDir_NotSet) {
+        if (aFirstStrong) {
+          *aFirstStrong = current;
+        }
+        return dir;
+      }
+    }
+  }
+
+  if (aFirstStrong) {
+    *aFirstStrong = UINT32_MAX;
+  }
+  return eDir_NotSet;
+}
+
+static Directionality GetDirectionFromText(const char* aText,
+                                           const uint32_t aLength,
+                                           uint32_t* aFirstStrong = nullptr) {
+  const char* start = aText;
+  const char* end = aText + aLength;
+
+  while (start < end) {
+    uint32_t current = start - aText;
+    unsigned char ch = (unsigned char)*start++;
+
+    Directionality dir = GetDirectionFromChar(ch);
+    if (dir != eDir_NotSet) {
+      if (aFirstStrong) {
+        *aFirstStrong = current;
+      }
+      return dir;
+    }
+  }
+
+  if (aFirstStrong) {
+    *aFirstStrong = UINT32_MAX;
+  }
+  return eDir_NotSet;
+}
+
+static Directionality GetDirectionFromText(const mozilla::dom::Text* aTextNode,
+                                           uint32_t* aFirstStrong = nullptr) {
+  const nsTextFragment* frag = &aTextNode->TextFragment();
+  if (frag->Is2b()) {
+    return GetDirectionFromText(frag->Get2b(), frag->GetLength(), aFirstStrong);
+  }
+
+  return GetDirectionFromText(frag->Get1b(), frag->GetLength(), aFirstStrong);
+}
+
+static nsTextNode* WalkDescendantsAndGetDirectionFromText(
+    nsINode* aRoot, nsINode* aSkip, Directionality* aDirectionality) {
+  nsIContent* child = aRoot->GetFirstChild();
+  while (child) {
+    if ((child->IsElement() &&
+         DoesNotAffectDirectionOfAncestors(child->AsElement())) ||
+        child->GetAssignedSlot()) {
+      child = child->GetNextNonChildNode(aRoot);
+      continue;
+    }
+
+    if (auto* slot = HTMLSlotElement::FromNode(child)) {
+      const nsTArray<RefPtr<nsINode>>& assignedNodes = slot->AssignedNodes();
+      for (uint32_t i = 0; i < assignedNodes.Length(); ++i) {
+        nsIContent* assignedNode = assignedNodes[i]->AsContent();
+        if (assignedNode->NodeType() == nsINode::TEXT_NODE) {
+          auto text = static_cast<nsTextNode*>(assignedNode);
+          if (assignedNode != aSkip) {
+            Directionality textNodeDir = GetDirectionFromText(text);
+            if (textNodeDir != eDir_NotSet) {
+              *aDirectionality = textNodeDir;
+              return text;
+            }
+          }
+        } else if (assignedNode->IsElement() &&
+                   !DoesNotAffectDirectionOfAncestors(
+                       assignedNode->AsElement())) {
+          nsTextNode* text = WalkDescendantsAndGetDirectionFromText(
+              assignedNode, aSkip, aDirectionality);
+          if (text) {
+            return text;
+          }
+        }
+      }
+    }
+
+    if (child->NodeType() == nsINode::TEXT_NODE && child != aSkip) {
+      auto text = static_cast<nsTextNode*>(child);
+      Directionality textNodeDir = GetDirectionFromText(text);
+      if (textNodeDir != eDir_NotSet) {
+        *aDirectionality = textNodeDir;
+        return text;
+      }
+    }
+    child = child->GetNextNode(aRoot);
+  }
+
+  return nullptr;
+}
+
+/**
+ * Set the directionality of a node with dir=auto as defined in
+ * http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#the-directionality
+ *
+ * @param[in] changedNode If we call this method because the content of a text
+ *            node is about to change, pass in the changed node, so that we
+ *            know not to return it
+ * @return the text node containing the character that determined the direction
+ */
+static nsTextNode* WalkDescendantsSetDirectionFromText(
+    Element* aElement, bool aNotify, nsINode* aChangedNode = nullptr) {
+  MOZ_ASSERT(aElement, "Must have an element");
+  MOZ_ASSERT(aElement->HasDirAuto(), "Element must have dir=auto");
+
+  if (DoesNotParticipateInAutoDirection(aElement)) {
+    return nullptr;
+  }
+
+  Directionality textNodeDir = eDir_NotSet;
+
+  // Check the text in Shadow DOM.
+  if (ShadowRoot* shadowRoot = aElement->GetShadowRoot()) {
+    nsTextNode* text = WalkDescendantsAndGetDirectionFromText(
+        shadowRoot, aChangedNode, &textNodeDir);
+    if (text) {
+      aElement->SetDirectionality(textNodeDir, aNotify);
+      return text;
+    }
+  }
+
+  // Check the text in light DOM.
+  nsTextNode* text = WalkDescendantsAndGetDirectionFromText(
+      aElement, aChangedNode, &textNodeDir);
+  if (text) {
+    aElement->SetDirectionality(textNodeDir, aNotify);
+    return text;
+  }
+
+  // We walked all the descendants without finding a text node with strong
+  // directional characters. Set the directionality to LTR
+  aElement->SetDirectionality(eDir_LTR, aNotify);
+  return nullptr;
+}
+
+class nsTextNodeDirectionalityMap {
+  static void nsTextNodeDirectionalityMapDtor(void* aObject,
+                                              nsAtom* aPropertyName,
+                                              void* aPropertyValue,
+                                              void* aData) {
+    nsINode* textNode = static_cast<nsINode*>(aObject);
+    textNode->ClearHasTextNodeDirectionalityMap();
+
+    nsTextNodeDirectionalityMap* map =
+        reinterpret_cast<nsTextNodeDirectionalityMap*>(aPropertyValue);
+    map->EnsureMapIsClear();
+    delete map;
+  }
+
+ public:
+  explicit nsTextNodeDirectionalityMap(nsINode* aTextNode)
+      : mElementToBeRemoved(nullptr) {
+    MOZ_ASSERT(aTextNode, "Null text node");
+    MOZ_COUNT_CTOR(nsTextNodeDirectionalityMap);
+    aTextNode->SetProperty(nsGkAtoms::textNodeDirectionalityMap, this,
+                           nsTextNodeDirectionalityMapDtor);
+    aTextNode->SetHasTextNodeDirectionalityMap();
+  }
+
+  MOZ_COUNTED_DTOR(nsTextNodeDirectionalityMap)
+
+  static void nsTextNodeDirectionalityMapPropertyDestructor(
+      void* aObject, nsAtom* aProperty, void* aPropertyValue, void* aData) {
+    nsTextNode* textNode = static_cast<nsTextNode*>(aPropertyValue);
+    nsTextNodeDirectionalityMap* map = GetDirectionalityMap(textNode);
+    if (map) {
+      map->RemoveEntryForProperty(static_cast<Element*>(aObject));
+    }
+    NS_RELEASE(textNode);
+  }
+
+  void AddEntry(nsTextNode* aTextNode, Element* aElement) {
+    if (!mElements.Contains(aElement)) {
+      mElements.Put(aElement);
+      NS_ADDREF(aTextNode);
+      aElement->SetProperty(nsGkAtoms::dirAutoSetBy, aTextNode,
+                            nsTextNodeDirectionalityMapPropertyDestructor);
+      aElement->SetHasDirAutoSet();
+    }
+  }
+
+  void RemoveEntry(nsTextNode* aTextNode, Element* aElement) {
+    NS_ASSERTION(mElements.Contains(aElement),
+                 "element already removed from map");
+
+    mElements.Remove(aElement);
+    aElement->ClearHasDirAutoSet();
+    aElement->RemoveProperty(nsGkAtoms::dirAutoSetBy);
+  }
+
+  void RemoveEntryForProperty(Element* aElement) {
+    if (mElementToBeRemoved != aElement) {
+      mElements.Remove(aElement);
+    }
+    aElement->ClearHasDirAutoSet();
+  }
+
+ private:
+  nsCheapSet<nsPtrHashKey<Element>> mElements;
+  // Only used for comparison.
+  Element* mElementToBeRemoved;
+
+  static nsTextNodeDirectionalityMap* GetDirectionalityMap(nsINode* aTextNode) {
+    MOZ_ASSERT(aTextNode->NodeType() == nsINode::TEXT_NODE,
+               "Must be a text node");
+    nsTextNodeDirectionalityMap* map = nullptr;
+
+    if (aTextNode->HasTextNodeDirectionalityMap()) {
+      map = static_cast<nsTextNodeDirectionalityMap*>(
+          aTextNode->GetProperty(nsGkAtoms::textNodeDirectionalityMap));
+    }
+
+    return map;
+  }
+
+  static nsCheapSetOperator SetNodeDirection(nsPtrHashKey<Element>* aEntry,
+                                             void* aDir) {
+    aEntry->GetKey()->SetDirectionality(
+        *reinterpret_cast<Directionality*>(aDir), true);
+    return OpNext;
+  }
+
+  struct nsTextNodeDirectionalityMapAndElement {
+    nsTextNodeDirectionalityMap* mMap;
+    nsCOMPtr<nsINode> mNode;
+  };
+
+  static nsCheapSetOperator ResetNodeDirection(nsPtrHashKey<Element>* aEntry,
+                                               void* aData) {
+    // run the downward propagation algorithm
+    // and remove the text node from the map
+    nsTextNodeDirectionalityMapAndElement* data =
+        static_cast<nsTextNodeDirectionalityMapAndElement*>(aData);
+    nsINode* oldTextNode = data->mNode;
+    Element* rootNode = aEntry->GetKey();
+    nsTextNode* newTextNode = nullptr;
+    if (rootNode->GetParentNode() && rootNode->HasDirAuto()) {
+      newTextNode =
+          WalkDescendantsSetDirectionFromText(rootNode, true, oldTextNode);
+    }
+
+    AutoRestore<Element*> restore(data->mMap->mElementToBeRemoved);
+    data->mMap->mElementToBeRemoved = rootNode;
+    if (newTextNode) {
+      nsINode* oldDirAutoSetBy = static_cast<nsTextNode*>(
+          rootNode->GetProperty(nsGkAtoms::dirAutoSetBy));
+      if (oldDirAutoSetBy == newTextNode) {
+        // We're already registered.
+        return OpNext;
+      }
+      nsTextNodeDirectionalityMap::AddEntryToMap(newTextNode, rootNode);
+    } else {
+      rootNode->ClearHasDirAutoSet();
+      rootNode->RemoveProperty(nsGkAtoms::dirAutoSetBy);
+    }
+    return OpRemove;
+  }
+
+  static nsCheapSetOperator TakeEntries(nsPtrHashKey<Element>* aEntry,
+                                        void* aData) {
+    AutoTArray<Element*, 8>* entries =
+        static_cast<AutoTArray<Element*, 8>*>(aData);
+    entries->AppendElement(aEntry->GetKey());
+    return OpRemove;
+  }
+
+ public:
+  uint32_t UpdateAutoDirection(Directionality aDir) {
+    return mElements.EnumerateEntries(SetNodeDirection, &aDir);
+  }
+
+  void ResetAutoDirection(nsINode* aTextNode) {
+    nsTextNodeDirectionalityMapAndElement data = {this, aTextNode};
+    mElements.EnumerateEntries(ResetNodeDirection, &data);
+  }
+
+  void EnsureMapIsClear() {
+    AutoRestore<Element*> restore(mElementToBeRemoved);
+    AutoTArray<Element*, 8> entries;
+    mElements.EnumerateEntries(TakeEntries, &entries);
+    for (Element* el : entries) {
+      el->ClearHasDirAutoSet();
+      el->RemoveProperty(nsGkAtoms::dirAutoSetBy);
+    }
+  }
+
+  static void RemoveElementFromMap(nsTextNode* aTextNode, Element* aElement) {
+    if (aTextNode->HasTextNodeDirectionalityMap()) {
+      GetDirectionalityMap(aTextNode)->RemoveEntry(aTextNode, aElement);
+    }
+  }
+
+  static void AddEntryToMap(nsTextNode* aTextNode, Element* aElement) {
+    nsTextNodeDirectionalityMap* map = GetDirectionalityMap(aTextNode);
+    if (!map) {
+      map = new nsTextNodeDirectionalityMap(aTextNode);
+    }
+
+    map->AddEntry(aTextNode, aElement);
+  }
+
+  static uint32_t UpdateTextNodeDirection(nsINode* aTextNode,
+                                          Directionality aDir) {
+    MOZ_ASSERT(aTextNode->HasTextNodeDirectionalityMap(),
+               "Map missing in UpdateTextNodeDirection");
+    return GetDirectionalityMap(aTextNode)->UpdateAutoDirection(aDir);
+  }
+
+  static void ResetTextNodeDirection(nsTextNode* aTextNode,
+                                     nsTextNode* aChangedTextNode) {
+    MOZ_ASSERT(aTextNode->HasTextNodeDirectionalityMap(),
+               "Map missing in ResetTextNodeDirection");
+    RefPtr<nsTextNode> textNode = aTextNode;
+    GetDirectionalityMap(textNode)->ResetAutoDirection(aChangedTextNode);
+  }
+
+  static void EnsureMapIsClearFor(nsINode* aTextNode) {
+    if (aTextNode->HasTextNodeDirectionalityMap()) {
+      GetDirectionalityMap(aTextNode)->EnsureMapIsClear();
+    }
+  }
+};
+
+Directionality RecomputeDirectionality(Element* aElement, bool aNotify) {
+  MOZ_ASSERT(!aElement->HasDirAuto(),
+             "RecomputeDirectionality called with dir=auto");
+
+  if (aElement->HasValidDir()) {
+    return aElement->GetDirectionality();
+  }
+
+  Directionality dir = eDir_LTR;
+  if (nsIContent* parent = GetParentOrHostOrSlot(aElement)) {
+    if (ShadowRoot* shadow = ShadowRoot::FromNode(parent)) {
+      parent = shadow->GetHost();
+    }
+
+    if (parent && parent->IsElement()) {
+      // If the node doesn't have an explicit dir attribute with a valid value,
+      // the directionality is the same as the parent element (but don't
+      // propagate the parent directionality if it isn't set yet).
+      Directionality parentDir = parent->AsElement()->GetDirectionality();
+      if (parentDir != eDir_NotSet) {
+        dir = parentDir;
+      }
+    }
+  }
+
+  aElement->SetDirectionality(dir, aNotify);
+  return dir;
+}
+
+static void SetDirectionalityOnDescendantsInternal(nsINode* aNode,
+                                                   Directionality aDir,
+                                                   bool aNotify) {
+  if (Element* element = Element::FromNode(aNode)) {
+    if (ShadowRoot* shadow = element->GetShadowRoot()) {
+      SetDirectionalityOnDescendantsInternal(shadow, aDir, aNotify);
+    }
+  }
+
+  for (nsIContent* child = aNode->GetFirstChild(); child;) {
+    if (!child->IsElement()) {
+      child = child->GetNextNode(aNode);
+      continue;
+    }
+
+    Element* element = child->AsElement();
+    if (element->HasValidDir() || element->HasDirAuto() ||
+        element->GetAssignedSlot()) {
+      child = child->GetNextNonChildNode(aNode);
+      continue;
+    }
+    if (ShadowRoot* shadow = element->GetShadowRoot()) {
+      SetDirectionalityOnDescendantsInternal(shadow, aDir, aNotify);
+    }
+
+    if (auto* slot = HTMLSlotElement::FromNode(child)) {
+      const nsTArray<RefPtr<nsINode>>& assignedNodes = slot->AssignedNodes();
+      for (uint32_t i = 0; i < assignedNodes.Length(); ++i) {
+        nsINode* node = assignedNodes[i];
+        Element* assignedElement =
+            node->IsElement() ? node->AsElement() : nullptr;
+        if (assignedElement && !assignedElement->HasValidDir() &&
+            !assignedElement->HasDirAuto()) {
+          assignedElement->SetDirectionality(aDir, aNotify);
+          SetDirectionalityOnDescendantsInternal(assignedElement, aDir,
+                                                 aNotify);
+        }
+      }
+    }
+
+    element->SetDirectionality(aDir, aNotify);
+
+    child = child->GetNextNode(aNode);
+  }
+}
+
+// We want the public version of this only to acc
+void SetDirectionalityOnDescendants(Element* aElement, Directionality aDir,
+                                    bool aNotify) {
+  return SetDirectionalityOnDescendantsInternal(aElement, aDir, aNotify);
+}
+
+static void ResetAutoDirection(Element* aElement, bool aNotify) {
+  if (aElement->HasDirAutoSet()) {
+    // If the parent has the DirAutoSet flag, its direction is determined by
+    // some text node descendant.
+    // Remove it from the map and reset its direction by the downward
+    // propagation algorithm
+    nsTextNode* setByNode = static_cast<nsTextNode*>(
+        aElement->GetProperty(nsGkAtoms::dirAutoSetBy));
+    if (setByNode) {
+      nsTextNodeDirectionalityMap::RemoveElementFromMap(setByNode, aElement);
+    }
+  }
+
+  if (aElement->HasDirAuto()) {
+    nsTextNode* setByNode =
+        WalkDescendantsSetDirectionFromText(aElement, aNotify);
+    if (setByNode) {
+      nsTextNodeDirectionalityMap::AddEntryToMap(setByNode, aElement);
+    }
+    SetDirectionalityOnDescendants(aElement, aElement->GetDirectionality(),
+                                   aNotify);
+  }
+}
+
+/**
+ * Walk the parent chain of a text node whose dir attribute has been removed and
+ * reset the direction of any of its ancestors which have dir=auto and whose
+ * directionality is determined by a text node descendant.
+ */
+void WalkAncestorsResetAutoDirection(Element* aElement, bool aNotify) {
+  nsTextNode* setByNode;
+  nsIContent* parent = GetParentOrHostOrSlot(aElement);
+  while (parent && parent->NodeOrAncestorHasDirAuto()) {
+    if (!parent->IsElement()) {
+      parent = GetParentOrHostOrSlot(parent);
+      continue;
+    }
+
+    Element* parentElement = parent->AsElement();
+    if (parent->HasDirAutoSet()) {
+      // If the parent has the DirAutoSet flag, its direction is determined by
+      // some text node descendant.
+      // Remove it from the map and reset its direction by the downward
+      // propagation algorithm
+      setByNode = static_cast<nsTextNode*>(
+          parent->GetProperty(nsGkAtoms::dirAutoSetBy));
+      if (setByNode) {
+        nsTextNodeDirectionalityMap::RemoveElementFromMap(setByNode,
+                                                          parentElement);
+      }
+    }
+    if (parentElement->HasDirAuto()) {
+      setByNode = WalkDescendantsSetDirectionFromText(parentElement, aNotify);
+      if (setByNode) {
+        nsTextNodeDirectionalityMap::AddEntryToMap(setByNode, parentElement);
+      }
+      SetDirectionalityOnDescendants(
+          parentElement, parentElement->GetDirectionality(), aNotify);
+      break;
+    }
+    parent = GetParentOrHostOrSlot(parent);
+  }
+}
+
+static void RecomputeSlottedNodeDirection(HTMLSlotElement& aSlot,
+                                          nsINode& aNode) {
+  auto* assignedElement = Element::FromNode(aNode);
+  if (!assignedElement) {
+    return;
+  }
+
+  if (assignedElement->HasValidDir() || assignedElement->HasDirAuto()) {
+    return;
+  }
+
+  // Try to optimize out state changes when possible.
+  if (assignedElement->GetDirectionality() == aSlot.GetDirectionality()) {
+    return;
+  }
+
+  assignedElement->SetDirectionality(aSlot.GetDirectionality(), true);
+  SetDirectionalityOnDescendantsInternal(assignedElement,
+                                         aSlot.GetDirectionality(), true);
+}
+
+void SlotAssignedNodeChanged(HTMLSlotElement* aSlot,
+                             nsIContent& aAssignedNode) {
+  if (!aSlot) {
+    return;
+  }
+
+  if (aSlot->NodeOrAncestorHasDirAuto()) {
+    // The directionality of the assigned node may impact the directionality of
+    // the slot. So recompute everything.
+    SlotStateChanged(aSlot, /* aAllAssignedNodesChanged = */ false);
+  }
+
+  if (aAssignedNode.GetAssignedSlot() == aSlot) {
+    RecomputeSlottedNodeDirection(*aSlot, aAssignedNode);
+  }
+}
+
+void SlotStateChanged(HTMLSlotElement* aSlot, bool aAllAssignedNodesChanged) {
+  if (!aSlot) {
+    return;
+  }
+
+  Directionality oldDir = aSlot->GetDirectionality();
+
+  if (aSlot->HasDirAuto()) {
+    ResetAutoDirection(aSlot, true);
+  }
+
+  if (aSlot->NodeOrAncestorHasDirAuto()) {
+    WalkAncestorsResetAutoDirection(aSlot, true);
+  }
+
+  if (aAllAssignedNodesChanged || oldDir != aSlot->GetDirectionality()) {
+    for (nsINode* node : aSlot->AssignedNodes()) {
+      RecomputeSlottedNodeDirection(*aSlot, *node);
+    }
+  }
+}
+
+void WalkDescendantsResetAutoDirection(Element* aElement) {
+  nsIContent* child = aElement->GetFirstChild();
+  while (child) {
+    if (child->IsElement() && child->AsElement()->HasDirAuto()) {
+      child = child->GetNextNonChildNode(aElement);
+      continue;
+    }
+
+    if (child->NodeType() == nsINode::TEXT_NODE &&
+        child->HasTextNodeDirectionalityMap()) {
+      nsTextNodeDirectionalityMap::ResetTextNodeDirection(
+          static_cast<nsTextNode*>(child), nullptr);
+      // Don't call nsTextNodeDirectionalityMap::EnsureMapIsClearFor(child)
+      // since ResetTextNodeDirection may have kept elements in child's
+      // DirectionalityMap.
+    }
+    child = child->GetNextNode(aElement);
+  }
+}
+
+static void SetAncestorHasDirAutoOnDescendants(nsINode* aRoot);
+
+static void MaybeSetAncestorHasDirAutoOnShadowDOM(nsINode* aNode) {
+  if (aNode->IsElement()) {
+    if (ShadowRoot* sr = aNode->AsElement()->GetShadowRoot()) {
+      sr->SetAncestorHasDirAuto();
+      SetAncestorHasDirAutoOnDescendants(sr);
+    }
+  }
+}
+
+static void SetAncestorHasDirAutoOnDescendants(nsINode* aRoot) {
+  MaybeSetAncestorHasDirAutoOnShadowDOM(aRoot);
+
+  nsIContent* child = aRoot->GetFirstChild();
+  while (child) {
+    if (child->IsElement() &&
+        DoesNotAffectDirectionOfAncestors(child->AsElement())) {
+      child = child->GetNextNonChildNode(aRoot);
+      continue;
+    }
+
+    // If the child is assigned to a slot, it should inherit the state from
+    // that.
+    if (!child->GetAssignedSlot()) {
+      MaybeSetAncestorHasDirAutoOnShadowDOM(child);
+      child->SetAncestorHasDirAuto();
+      if (auto* slot = HTMLSlotElement::FromNode(child)) {
+        const nsTArray<RefPtr<nsINode>>& assignedNodes = slot->AssignedNodes();
+        for (uint32_t i = 0; i < assignedNodes.Length(); ++i) {
+          assignedNodes[i]->SetAncestorHasDirAuto();
+          SetAncestorHasDirAutoOnDescendants(assignedNodes[i]);
+        }
+      }
+    }
+    child = child->GetNextNode(aRoot);
+  }
+}
+
+void WalkDescendantsSetDirAuto(Element* aElement, bool aNotify) {
+  // Only test for DoesNotParticipateInAutoDirection -- in other words, if
+  // aElement is a <bdi> which is having its dir attribute set to auto (or
+  // removed or set to an invalid value, which are equivalent to dir=auto for
+  // <bdi>, we *do* want to set AncestorHasDirAuto on its descendants, unlike
+  // in SetDirOnBind where we don't propagate AncestorHasDirAuto to a <bdi>
+  // being bound to an existing node with dir=auto.
+  if (!DoesNotParticipateInAutoDirection(aElement) &&
+      !aElement->AncestorHasDirAuto()) {
+    SetAncestorHasDirAutoOnDescendants(aElement);
+  }
+
+  nsTextNode* textNode = WalkDescendantsSetDirectionFromText(aElement, aNotify);
+  if (textNode) {
+    nsTextNodeDirectionalityMap::AddEntryToMap(textNode, aElement);
+  }
+}
+
+void WalkDescendantsClearAncestorDirAuto(nsIContent* aContent) {
+  if (aContent->IsElement()) {
+    if (ShadowRoot* shadowRoot = aContent->AsElement()->GetShadowRoot()) {
+      shadowRoot->ClearAncestorHasDirAuto();
+      WalkDescendantsClearAncestorDirAuto(shadowRoot);
+    }
+  }
+
+  nsIContent* child = aContent->GetFirstChild();
+  while (child) {
+    if (child->GetAssignedSlot()) {
+      // If the child node is assigned to a slot, nodes state is inherited from
+      // the slot, not from element's parent.
+      child = child->GetNextNonChildNode(aContent);
+      continue;
+    }
+    if (child->IsElement()) {
+      if (child->AsElement()->HasDirAuto()) {
+        child = child->GetNextNonChildNode(aContent);
+        continue;
+      }
+
+      if (auto* slot = HTMLSlotElement::FromNode(child)) {
+        const nsTArray<RefPtr<nsINode>>& assignedNodes = slot->AssignedNodes();
+        for (uint32_t i = 0; i < assignedNodes.Length(); ++i) {
+          if (assignedNodes[i]->IsElement()) {
+            Element* slottedElement = assignedNodes[i]->AsElement();
+            if (slottedElement->HasDirAuto()) {
+              continue;
+            }
+          }
+
+          nsIContent* content = assignedNodes[i]->AsContent();
+          content->ClearAncestorHasDirAuto();
+          WalkDescendantsClearAncestorDirAuto(content);
+        }
+      }
+    }
+
+    child->ClearAncestorHasDirAuto();
+    child = child->GetNextNode(aContent);
+  }
+}
+
+void SetAncestorDirectionIfAuto(nsTextNode* aTextNode, Directionality aDir,
+                                bool aNotify = true) {
+  MOZ_ASSERT(aTextNode->NodeType() == nsINode::TEXT_NODE,
+             "Must be a text node");
+
+  bool crossedShadowBoundary = false;
+  nsIContent* parent = GetParentOrHostOrSlot(aTextNode, &crossedShadowBoundary);
+  while (parent && parent->NodeOrAncestorHasDirAuto()) {
+    if (!parent->IsElement()) {
+      parent = GetParentOrHostOrSlot(parent, &crossedShadowBoundary);
+      continue;
+    }
+
+    Element* parentElement = parent->AsElement();
+    if (DoesNotParticipateInAutoDirection(parentElement) ||
+        parentElement->HasFixedDir()) {
+      break;
+    }
+
+    if (parentElement->HasDirAuto()) {
+      bool resetDirection = false;
+      nsTextNode* directionWasSetByTextNode = static_cast<nsTextNode*>(
+          parent->GetProperty(nsGkAtoms::dirAutoSetBy));
+
+      if (!parent->HasDirAutoSet()) {
+        // Fast path if parent's direction is not yet set by any descendant
+        MOZ_ASSERT(!directionWasSetByTextNode,
+                   "dirAutoSetBy property should be null");
+        resetDirection = true;
+      } else {
+        // If parent's direction is already set, we need to know if
+        // aTextNode is before or after the text node that had set it.
+        // We will walk parent's descendants in tree order starting from
+        // aTextNode to optimize for the most common case where text nodes are
+        // being appended to tree.
+        if (!directionWasSetByTextNode) {
+          resetDirection = true;
+        } else if (directionWasSetByTextNode != aTextNode) {
+          if (crossedShadowBoundary || AncestorChainCrossesShadowBoundary(
+                                           directionWasSetByTextNode, parent)) {
+            // Need to take the slow path when the path from either the old or
+            // new text node to the dir=auto element crosses shadow boundary.
+            ResetAutoDirection(parentElement, aNotify);
+            return;
+          }
+
+          nsIContent* child = aTextNode->GetNextNode(parent);
+          while (child) {
+            if (child->IsElement() &&
+                DoesNotAffectDirectionOfAncestors(child->AsElement())) {
+              child = child->GetNextNonChildNode(parent);
+              continue;
+            }
+
+            if (child == directionWasSetByTextNode) {
+              // we found the node that set the element's direction after our
+              // text node, so we need to reset the direction
+              resetDirection = true;
+              break;
+            }
+
+            child = child->GetNextNode(parent);
+          }
+        }
+      }
+
+      if (resetDirection) {
+        if (directionWasSetByTextNode) {
+          nsTextNodeDirectionalityMap::RemoveElementFromMap(
+              directionWasSetByTextNode, parentElement);
+        }
+        parentElement->SetDirectionality(aDir, aNotify);
+        nsTextNodeDirectionalityMap::AddEntryToMap(aTextNode, parentElement);
+        SetDirectionalityOnDescendants(parentElement, aDir, aNotify);
+      }
+
+      // Since we found an element with dir=auto, we can stop walking the
+      // parent chain: none of its ancestors will have their direction set by
+      // any of its descendants.
+      return;
+    }
+    parent = GetParentOrHostOrSlot(parent, &crossedShadowBoundary);
+  }
+}
+
+bool TextNodeWillChangeDirection(nsTextNode* aTextNode, Directionality* aOldDir,
+                                 uint32_t aOffset) {
+  if (!NodeAffectsDirAutoAncestor(aTextNode)) {
+    nsTextNodeDirectionalityMap::EnsureMapIsClearFor(aTextNode);
+    return false;
+  }
+
+  uint32_t firstStrong;
+  *aOldDir = GetDirectionFromText(aTextNode, &firstStrong);
+  return (aOffset <= firstStrong);
+}
+
+void TextNodeChangedDirection(nsTextNode* aTextNode, Directionality aOldDir,
+                              bool aNotify) {
+  Directionality newDir = GetDirectionFromText(aTextNode);
+  if (newDir == eDir_NotSet) {
+    if (aOldDir != eDir_NotSet && aTextNode->HasTextNodeDirectionalityMap()) {
+      // This node used to have a strong directional character but no
+      // longer does. ResetTextNodeDirection() will re-resolve the
+      // directionality of any elements whose directionality was
+      // determined by this node.
+      nsTextNodeDirectionalityMap::ResetTextNodeDirection(aTextNode, aTextNode);
+    }
+  } else {
+    // This node has a strong directional character. If it has a
+    // TextNodeDirectionalityMap property, it already determines the
+    // directionality of some element(s), so call UpdateTextNodeDirection to
+    // reresolve their directionality. If it has no map, or if
+    // UpdateTextNodeDirection returns zero, indicating that the map is
+    // empty, call SetAncestorDirectionIfAuto to find ancestor elements
+    // which should have their directionality determined by this node.
+    if (aTextNode->HasTextNodeDirectionalityMap() &&
+        nsTextNodeDirectionalityMap::UpdateTextNodeDirection(aTextNode,
+                                                             newDir)) {
+      return;
+    }
+    SetAncestorDirectionIfAuto(aTextNode, newDir, aNotify);
+  }
+}
+
+void SetDirectionFromNewTextNode(nsTextNode* aTextNode) {
+  if (!NodeAffectsDirAutoAncestor(aTextNode)) {
+    return;
+  }
+
+  nsIContent* parent = GetParentOrHostOrSlot(aTextNode);
+  if (parent && parent->NodeOrAncestorHasDirAuto()) {
+    aTextNode->SetAncestorHasDirAuto();
+  }
+
+  Directionality dir = GetDirectionFromText(aTextNode);
+  if (dir != eDir_NotSet) {
+    SetAncestorDirectionIfAuto(aTextNode, dir);
+  }
+}
+
+void ResetDirectionSetByTextNode(nsTextNode* aTextNode) {
+  if (!NodeAffectsDirAutoAncestor(aTextNode)) {
+    nsTextNodeDirectionalityMap::EnsureMapIsClearFor(aTextNode);
+    return;
+  }
+
+  Directionality dir = GetDirectionFromText(aTextNode);
+  if (dir != eDir_NotSet && aTextNode->HasTextNodeDirectionalityMap()) {
+    nsTextNodeDirectionalityMap::ResetTextNodeDirection(aTextNode, aTextNode);
+  }
+}
+
+void SetDirectionalityFromValue(Element* aElement, const nsAString& value,
+                                bool aNotify) {
+  Directionality dir =
+      GetDirectionFromText(value.BeginReading(), value.Length());
+  if (dir == eDir_NotSet) {
+    dir = eDir_LTR;
+  }
+
+  aElement->SetDirectionality(dir, aNotify);
+}
+
+void OnSetDirAttr(Element* aElement, const nsAttrValue* aNewValue,
+                  bool hadValidDir, bool hadDirAuto, bool aNotify) {
+  if (aElement->IsHTMLElement(nsGkAtoms::input)) {
+    return;
+  }
+
+  if (aElement->AncestorHasDirAuto()) {
+    if (!hadValidDir) {
+      // The element is a descendant of an element with dir = auto, is
+      // having its dir attribute set, and previously didn't have a valid dir
+      // attribute.
+      // Check whether any of its text node descendants determine the
+      // direction of any of its ancestors, and redetermine their direction
+      WalkDescendantsResetAutoDirection(aElement);
+    } else if (!aElement->HasValidDir()) {
+      // The element is a descendant of an element with dir = auto and is
+      // having its dir attribute removed or set to an invalid value.
+      // Reset the direction of any of its ancestors whose direction is
+      // determined by a text node descendant
+      WalkAncestorsResetAutoDirection(aElement, aNotify);
+    }
+  } else if (hadDirAuto && !aElement->HasDirAuto()) {
+    // The element isn't a descendant of an element with dir = auto, and is
+    // having its dir attribute set to something other than auto.
+    // Walk the descendant tree and clear the AncestorHasDirAuto flag.
+    //
+    // N.B: For elements other than <bdi> it would be enough to test that the
+    //      current value of dir was "auto" in BeforeSetAttr to know that we
+    //      were unsetting dir="auto". For <bdi> things are more complicated,
+    //      since it behaves like dir="auto" whenever the dir attribute is
+    //      empty or invalid, so we would have to check whether the old value
+    //      was not either "ltr" or "rtl", and the new value was either "ltr"
+    //      or "rtl". Element::HasDirAuto() encapsulates all that, so doing it
+    //      here is simpler.
+    WalkDescendantsClearAncestorDirAuto(aElement);
+  }
+
+  if (aElement->HasDirAuto()) {
+    WalkDescendantsSetDirAuto(aElement, aNotify);
+  } else {
+    if (aElement->HasDirAutoSet()) {
+      nsTextNode* setByNode = static_cast<nsTextNode*>(
+          aElement->GetProperty(nsGkAtoms::dirAutoSetBy));
+      nsTextNodeDirectionalityMap::RemoveElementFromMap(setByNode, aElement);
+    }
+    SetDirectionalityOnDescendants(
+        aElement, RecomputeDirectionality(aElement, aNotify), aNotify);
+  }
+}
+
+void SetDirOnBind(Element* aElement, nsIContent* aParent) {
+  // Set the AncestorHasDirAuto flag, unless this element shouldn't affect
+  // ancestors that have dir=auto
+  if (!DoesNotParticipateInAutoDirection(aElement) &&
+      !aElement->IsHTMLElement(nsGkAtoms::bdi) && aParent &&
+      aParent->NodeOrAncestorHasDirAuto()) {
+    aElement->SetAncestorHasDirAuto();
+
+    SetAncestorHasDirAutoOnDescendants(aElement);
+
+    if (aElement->GetFirstChild() || aElement->GetShadowRoot()) {
+      // We may also need to reset the direction of an ancestor with dir=auto
+      WalkAncestorsResetAutoDirection(aElement, true);
+    }
+  }
+
+  if (!aElement->HasDirAuto()) {
+    // if the element doesn't have dir=auto, set its own directionality from
+    // the dir attribute or by inheriting from its ancestors.
+    RecomputeDirectionality(aElement, false);
+  }
+}
+
+void ResetDir(Element* aElement) {
+  if (aElement->HasDirAutoSet()) {
+    nsTextNode* setByNode = static_cast<nsTextNode*>(
+        aElement->GetProperty(nsGkAtoms::dirAutoSetBy));
+    nsTextNodeDirectionalityMap::RemoveElementFromMap(setByNode, aElement);
+  }
+
+  if (!aElement->HasDirAuto()) {
+    RecomputeDirectionality(aElement, false);
+  }
+}
+
+}  // end namespace mozilla