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diff --git a/dom/base/DirectionalityUtils.h b/dom/base/DirectionalityUtils.h
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+++ b/dom/base/DirectionalityUtils.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 DirectionalityUtils_h___
+#define DirectionalityUtils_h___
+
+#include "nscore.h"
+
+class nsIContent;
+class nsAString;
+class nsAttrValue;
+class nsTextNode;
+
+namespace mozilla {
+namespace dom {
+class Element;
+} // namespace dom
+} // namespace mozilla
+
+namespace mozilla {
+
+enum Directionality : uint8_t {
+  eDir_NotSet,
+  eDir_RTL,
+  eDir_LTR,
+  eDir_Auto
+};
+
+/**
+ * Set the directionality of an element according to the algorithm defined at
+ * http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#the-directionality,
+ * not including elements with auto direction.
+ *
+ * @return the directionality that the element was set to
+ */
+Directionality RecomputeDirectionality(mozilla::dom::Element* aElement,
+                                       bool aNotify = true);
+
+/**
+ * Set the directionality of any descendants of a node that do not themselves
+ * have a dir attribute.
+ * For performance reasons we walk down the descendant tree in the rare case
+ * of setting the dir attribute, rather than walking up the ancestor tree in
+ * the much more common case of getting the element's directionality.
+ */
+void SetDirectionalityOnDescendants(mozilla::dom::Element* aElement,
+                                    Directionality aDir,
+                                    bool aNotify = true);
+
+/**
+ * Walk the descendants of a node in tree order and, for any text node
+ * descendant that determines the directionality of some element and is not a
+ * descendant of another descendant of the original node with dir=auto,
+ * redetermine that element's directionality
+  */
+void WalkDescendantsResetAutoDirection(mozilla::dom::Element* aElement);
+
+/**
+ * After setting dir=auto on an element, walk its descendants in tree order.
+ * If the node doesn't have the NODE_ANCESTOR_HAS_DIR_AUTO flag, set the
+ * NODE_ANCESTOR_HAS_DIR_AUTO flag on all of its descendants.
+ * Resolve the directionality of the element by the "downward propagation
+ * algorithm" (defined in section 3 in the comments at the beginning of
+ * DirectionalityUtils.cpp)
+ */
+void WalkDescendantsSetDirAuto(mozilla::dom::Element* aElement,
+                               bool aNotify = true);
+
+/**
+ * After unsetting dir=auto on an element, walk its descendants in tree order,
+ * skipping any that have dir=auto themselves, and unset the
+ * NODE_ANCESTOR_HAS_DIR_AUTO flag
+ */
+void WalkDescendantsClearAncestorDirAuto(mozilla::dom::Element* aElement);
+
+/**
+ * When the contents of a text node are about to change, retrieve the current
+ * directionality of the text
+ *
+ * @return whether the text node affects the directionality of any element
+ */
+bool TextNodeWillChangeDirection(nsIContent* aTextNode, Directionality* aOldDir,
+                                 uint32_t aOffset);
+
+/**
+ * After the contents of a text node have changed, change the directionality
+ * of any elements whose directionality is determined by that node
+ */
+void TextNodeChangedDirection(nsTextNode* aTextNode, Directionality aOldDir,
+                              bool aNotify);
+
+/**
+ * When a text node is appended to an element, find any ancestors with dir=auto
+ * whose directionality will be determined by the text node
+ */
+void SetDirectionFromNewTextNode(nsTextNode* aTextNode);
+
+/**
+ * When a text node is removed from a document, find any ancestors whose
+ * directionality it determined and redetermine their directionality
+ *
+ * @param aTextNode the text node
+ */
+void ResetDirectionSetByTextNode(nsTextNode* aTextNode);
+
+/**
+ * Set the directionality of an element according to the directionality of the
+ * text in aValue
+ */
+void SetDirectionalityFromValue(mozilla::dom::Element* aElement,
+                                const nsAString& aValue,
+                                bool aNotify);
+
+/**
+ * Called when setting the dir attribute on an element, immediately after
+ * AfterSetAttr. This is instead of using BeforeSetAttr or AfterSetAttr, because
+ * in AfterSetAttr we don't know the old value, so we can't identify all cases
+ * where we need to walk up or down the document tree and reset the direction;
+ * and in BeforeSetAttr we can't do the walk because this element hasn't had the
+ * value set yet so the results will be wrong.
+ */
+void OnSetDirAttr(mozilla::dom::Element* aElement,
+                  const nsAttrValue* aNewValue,
+                  bool hadValidDir,
+                  bool hadDirAuto,
+                  bool aNotify);
+
+/**
+ * Called when binding a new element to the tree, to set the
+ * NodeAncestorHasDirAuto flag and set the direction of the element and its
+ * ancestors if necessary
+ */
+void SetDirOnBind(mozilla::dom::Element* aElement, nsIContent* aParent);
+
+/**
+ * Called when unbinding an element from the tree, to recompute the
+ * directionality of the element if it doesn't have autodirection, and to
+ * clean up any entries in nsTextDirectionalityMap that refer to it.
+ */
+void ResetDir(mozilla::dom::Element* aElement);
+} // end namespace mozilla
+
+#endif /* DirectionalityUtils_h___ */