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 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ts=2 sw=2 et tw=78: */

 /* 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, nsGenericDOMDataNode::SetTextInternal

   gets called.

   */

 #include "mozilla/dom/DirectionalityUtils.h"

 #include "nsINode.h"

 #include "nsIContent.h"

 #include "nsIDocument.h"

 #include "mozilla/DebugOnly.h"

 #include "mozilla/dom/Element.h"

 #include "nsIDOMHTMLDocument.h"

 #include "nsUnicodeProperties.h"

 #include "nsTextFragment.h"

 #include "nsAttrValue.h"

 #include "nsTextNode.h"

 #include "nsCheapSets.h"

 namespace mozilla {

 using mozilla::dom::Element;

 /**

  * 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.

  */

 static bool

 DoesNotParticipateInAutoDirection(const Element* aElement)

 {

   nsINodeInfo* nodeInfo = aElement->NodeInfo();

   return (!aElement->IsHTML() ||

           nodeInfo->Equals(nsGkAtoms::script) ||

           nodeInfo->Equals(nsGkAtoms::style) ||

           nodeInfo->Equals(nsGkAtoms::textarea) ||

           aElement->IsInAnonymousSubtree());

 }

 static inline bool

 IsBdiWithoutDirAuto(const Element* aElement)

 {

   // We are testing for bdi elements without explicit dir="auto", so we can't

   // use the HasDirAuto() flag, since that will return true for bdi element with

   // no dir attribute or an invalid dir attribute

   return (aElement->IsHTML(nsGkAtoms::bdi) &&

           (!aElement->HasValidDir() || aElement->HasFixedDir()));

 }

 /**

  * 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) ||

           IsBdiWithoutDirAuto(aElement) ||

           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(nsINode* aTextNode)

 {

   Element* parent = aTextNode->GetParentElement();

   return (parent &&

           !DoesNotParticipateInAutoDirection(parent) &&

           parent->NodeOrAncestorHasDirAuto());

 }

 /**

  * Various methods for returning the directionality of a string using the

  * first-strong algorithm defined in http://unicode.org/reports/tr9/#P2

  *

  * @param[out] aFirstStrong the offset to the first character in the string with

  *             strong directionality, or UINT32_MAX if there is none (return

                value is eDir_NotSet).

  * @return the directionality of the string

  */

 static Directionality

 GetDirectionFromText(const char16_t* aText, const uint32_t aLength,

                      uint32_t* aFirstStrong = nullptr)

 {

   const char16_t* start = aText;

   const char16_t* end = aText + aLength;

   while (start < end) {

     uint32_t current = start - aText;

     uint32_t ch = *start++;

     if (NS_IS_HIGH_SURROGATE(ch) &&

         start < end &&

         NS_IS_LOW_SURROGATE(*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 nsTextFragment* aFrag,

                      uint32_t* aFirstStrong = nullptr)

 {

   if (aFrag->Is2b()) {

     return GetDirectionFromText(aFrag->Get2b(), aFrag->GetLength(),

                                    aFirstStrong);

   }

   return GetDirectionFromText(aFrag->Get1b(), aFrag->GetLength(),

                                  aFirstStrong);

 }

 /**

  * 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 nsINode*

 WalkDescendantsSetDirectionFromText(Element* aElement, bool aNotify = true,

                                     nsINode* aChangedNode = nullptr)

 {

   MOZ_ASSERT(aElement, "Must have an element");

   MOZ_ASSERT(aElement->HasDirAuto(), "Element must have dir=auto");

   if (DoesNotParticipateInAutoDirection(aElement)) {

     return nullptr;

   }

   nsIContent* child = aElement->GetFirstChild();

   while (child) {

     if (child->IsElement() &&

         DoesNotAffectDirectionOfAncestors(child->AsElement())) {

       child = child->GetNextNonChildNode(aElement);

       continue;

     }

     if (child->NodeType() == nsIDOMNode::TEXT_NODE &&

         child != aChangedNode) {

       Directionality textNodeDir = GetDirectionFromText(child->GetText());

       if (textNodeDir != eDir_NotSet) {

         // We found a descendant text node with strong directional characters.

         // Set the directionality of aElement to the corresponding value.

         aElement->SetDirectionality(textNodeDir, aNotify);

         return child;

       }

     }

     child = child->GetNextNode(aElement);

   }

   // 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, nsIAtom* aPropertyName,

                                   void *aPropertyValue, void* aData)

   {

     nsINode* textNode = static_cast<nsINode * >(aObject);

     textNode->ClearHasTextNodeDirectionalityMap();

     nsTextNodeDirectionalityMap* map =

       reinterpret_cast<nsTextNodeDirectionalityMap * >(aPropertyValue);

     map->EnsureMapIsClear(textNode);

     delete map;

   }

 public:

   nsTextNodeDirectionalityMap(nsINode* aTextNode)

   {

     MOZ_ASSERT(aTextNode, "Null text node");

     MOZ_COUNT_CTOR(nsTextNodeDirectionalityMap);

     aTextNode->SetProperty(nsGkAtoms::textNodeDirectionalityMap, this,

                            nsTextNodeDirectionalityMapDtor);

     aTextNode->SetHasTextNodeDirectionalityMap();

   }

   ~nsTextNodeDirectionalityMap()

   {

     MOZ_COUNT_DTOR(nsTextNodeDirectionalityMap);

   }

   void AddEntry(nsINode* aTextNode, Element* aElement)

   {

     if (!mElements.Contains(aElement)) {

       mElements.Put(aElement);

       aElement->SetProperty(nsGkAtoms::dirAutoSetBy, aTextNode);

       aElement->SetHasDirAutoSet();

     }

   }

   void RemoveEntry(nsINode* aTextNode, Element* aElement)

   {

     NS_ASSERTION(mElements.Contains(aElement),

                  "element already removed from map");

     mElements.Remove(aElement);

     aElement->ClearHasDirAutoSet();

     aElement->UnsetProperty(nsGkAtoms::dirAutoSetBy);

   }

 private:

   nsCheapSet<nsPtrHashKey<Element> > mElements;

   static nsTextNodeDirectionalityMap* GetDirectionalityMap(nsINode* aTextNode)

   {

     MOZ_ASSERT(aTextNode->NodeType() == nsIDOMNode::TEXT_NODE,

                "Must be a text node");

     nsTextNodeDirectionalityMap* map = nullptr;

     if (aTextNode->HasTextNodeDirectionalityMap()) {

       map = static_cast<nsTextNodeDirectionalityMap * >

         (aTextNode->GetProperty(nsGkAtoms::textNodeDirectionalityMap));

     }

     return map;

   }

   static PLDHashOperator SetNodeDirection(nsPtrHashKey<Element>* aEntry, void* aDir)

   {

     MOZ_ASSERT(aEntry->GetKey()->IsElement(), "Must be an Element");

     aEntry->GetKey()->SetDirectionality(*reinterpret_cast<Directionality*>(aDir),

                                         true);

     return PL_DHASH_NEXT;

   }

   static PLDHashOperator ResetNodeDirection(nsPtrHashKey<Element>* aEntry, void* aData)

   {

     MOZ_ASSERT(aEntry->GetKey()->IsElement(), "Must be an Element");

     // run the downward propagation algorithm

     // and remove the text node from the map

     nsINode* oldTextNode = static_cast<Element*>(aData);

     Element* rootNode = aEntry->GetKey();

     nsINode* newTextNode = nullptr;

     if (oldTextNode && rootNode->HasDirAuto()) {

       newTextNode = WalkDescendantsSetDirectionFromText(rootNode, true,

                                                         oldTextNode);

     }

     if (newTextNode) {

       nsTextNodeDirectionalityMap::AddEntryToMap(newTextNode, rootNode);

     } else {

       rootNode->ClearHasDirAutoSet();

       rootNode->UnsetProperty(nsGkAtoms::dirAutoSetBy);

     }

     return PL_DHASH_REMOVE;

   }

   static PLDHashOperator ClearEntry(nsPtrHashKey<Element>* aEntry, void* aData)

   {

     Element* rootNode = aEntry->GetKey();

     rootNode->ClearHasDirAutoSet();

     rootNode->UnsetProperty(nsGkAtoms::dirAutoSetBy);

     return PL_DHASH_REMOVE;

   }

 public:

   void UpdateAutoDirection(Directionality aDir)

   {

     mElements.EnumerateEntries(SetNodeDirection, &aDir);

   }

   void ClearAutoDirection()

   {

     mElements.EnumerateEntries(ResetNodeDirection, nullptr);

   }

   void ResetAutoDirection(nsINode* aTextNode)

   {

     mElements.EnumerateEntries(ResetNodeDirection, aTextNode);

   }

   void EnsureMapIsClear(nsINode* aTextNode)

   {

     DebugOnly<uint32_t> clearedEntries =

       mElements.EnumerateEntries(ClearEntry, aTextNode);

     MOZ_ASSERT(clearedEntries == 0, "Map should be empty already");

   }

   static void RemoveElementFromMap(nsINode* aTextNode, Element* aElement)

   {

     if (aTextNode->HasTextNodeDirectionalityMap()) {

       GetDirectionalityMap(aTextNode)->RemoveEntry(aTextNode, aElement);

     }

   }

   static void AddEntryToMap(nsINode* aTextNode, Element* aElement)

   {

     nsTextNodeDirectionalityMap* map = GetDirectionalityMap(aTextNode);

     if (!map) {

       map = new nsTextNodeDirectionalityMap(aTextNode);

     }

     map->AddEntry(aTextNode, aElement);

   }

   static void UpdateTextNodeDirection(nsINode* aTextNode, Directionality aDir)

   {

     MOZ_ASSERT(aTextNode->HasTextNodeDirectionalityMap(),

                "Map missing in UpdateTextNodeDirection");

     GetDirectionalityMap(aTextNode)->UpdateAutoDirection(aDir);

   }

   static void ClearTextNodeDirection(nsINode* aTextNode)

   {

     MOZ_ASSERT(aTextNode->HasTextNodeDirectionalityMap(),

                "Map missing in ResetTextNodeDirection");

     GetDirectionalityMap(aTextNode)->ClearAutoDirection();

   }

   static void ResetTextNodeDirection(nsINode* aTextNode)

   {

     MOZ_ASSERT(aTextNode->HasTextNodeDirectionalityMap(),

                "Map missing in ResetTextNodeDirection");

     GetDirectionalityMap(aTextNode)->ResetAutoDirection(aTextNode);

   }

   static void EnsureMapIsClearFor(nsINode* aTextNode)

   {

     if (aTextNode->HasTextNodeDirectionalityMap()) {

       GetDirectionalityMap(aTextNode)->EnsureMapIsClear(aTextNode);

     }

   }

 };

 Directionality

 RecomputeDirectionality(Element* aElement, bool aNotify)

 {

   MOZ_ASSERT(!aElement->HasDirAuto(),

              "RecomputeDirectionality called with dir=auto");

   Directionality dir = eDir_LTR;

   if (aElement->HasValidDir()) {

     dir = aElement->GetDirectionality();

   } else {

     Element* parent = aElement->GetParentElement();

     if (parent) {

       // If the element 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->GetDirectionality();

       if (parentDir != eDir_NotSet) {

         dir = parentDir;

       }

     } else {

       // If there is no parent element and no dir attribute, the directionality

       // is LTR.

       dir = eDir_LTR;

     }

     aElement->SetDirectionality(dir, aNotify);

   }

   return dir;

 }

 void

 SetDirectionalityOnDescendants(Element* aElement, Directionality aDir,

                                bool aNotify)

 {

   for (nsIContent* child = aElement->GetFirstChild(); child; ) {

     if (!child->IsElement()) {

       child = child->GetNextNode(aElement);

       continue;

     }

     Element* element = child->AsElement();

     if (element->HasValidDir() || element->HasDirAuto()) {

       child = child->GetNextNonChildNode(aElement);

       continue;

     }

     element->SetDirectionality(aDir, aNotify);

     child = child->GetNextNode(aElement);

   }

 }

 /**

  * 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)

 {

   nsINode* setByNode;

   Element* parent = aElement->GetParentElement();

   while (parent && parent->NodeOrAncestorHasDirAuto()) {

     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<nsINode*>(parent->GetProperty(nsGkAtoms::dirAutoSetBy));

       if (setByNode) {

         nsTextNodeDirectionalityMap::RemoveElementFromMap(setByNode, parent);

       }

     }

     if (parent->HasDirAuto()) {

       setByNode = WalkDescendantsSetDirectionFromText(parent, aNotify);

       if (setByNode) {

         nsTextNodeDirectionalityMap::AddEntryToMap(setByNode, parent);

       }

       break;

     }

     parent = parent->GetParentElement();

   }

 }

 void

 WalkDescendantsResetAutoDirection(Element* aElement)

 {

   nsIContent* child = aElement->GetFirstChild();

   while (child) {

     if (child->HasDirAuto()) {

       child = child->GetNextNonChildNode(aElement);

       continue;

     }

     if (child->HasTextNodeDirectionalityMap()) {

       nsTextNodeDirectionalityMap::ResetTextNodeDirection(child);

       nsTextNodeDirectionalityMap::EnsureMapIsClearFor(child);

     }

     child = child->GetNextNode(aElement);

   }

 }

 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)) {

     bool setAncestorDirAutoFlag =

 #ifdef DEBUG

       true;

 #else

       !aElement->AncestorHasDirAuto();

 #endif

     if (setAncestorDirAutoFlag) {

       nsIContent* child = aElement->GetFirstChild();

       while (child) {

         if (child->IsElement() &&

             DoesNotAffectDirectionOfAncestors(child->AsElement())) {

           child = child->GetNextNonChildNode(aElement);

           continue;

         }

         MOZ_ASSERT(!aElement->AncestorHasDirAuto() ||

                    child->AncestorHasDirAuto(),

                    "AncestorHasDirAuto set on node but not its children");

         child->SetAncestorHasDirAuto();

         child = child->GetNextNode(aElement);

       }

     }

   }

   nsINode* textNode = WalkDescendantsSetDirectionFromText(aElement, aNotify);

   if (textNode) {

     nsTextNodeDirectionalityMap::AddEntryToMap(textNode, aElement);

   }

 }

 void

 WalkDescendantsClearAncestorDirAuto(Element* aElement)

 {

   nsIContent* child = aElement->GetFirstChild();

   while (child) {

     if (child->HasDirAuto()) {

       child = child->GetNextNonChildNode(aElement);

       continue;

     }

     child->ClearAncestorHasDirAuto();

     child = child->GetNextNode(aElement);

   }

 }

 void SetAncestorDirectionIfAuto(nsINode* aTextNode, Directionality aDir,

                                 bool aNotify = true)

 {

   MOZ_ASSERT(aTextNode->NodeType() == nsIDOMNode::TEXT_NODE,

              "Must be a text node");

   Element* parent = aTextNode->GetParentElement();

   while (parent && parent->NodeOrAncestorHasDirAuto()) {

     if (DoesNotParticipateInAutoDirection(parent) || parent->HasFixedDir()) {

       break;

     }

     if (parent->HasDirAuto()) {

       bool resetDirection = false;

       nsINode* directionWasSetByTextNode =

         static_cast<nsINode*>(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) {

           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, parent

           );

         }

         parent->SetDirectionality(aDir, aNotify);

         nsTextNodeDirectionalityMap::AddEntryToMap(aTextNode, parent);

         SetDirectionalityOnDescendants(parent, 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 = parent->GetParentElement();

   }

 }

 bool

 TextNodeWillChangeDirection(nsIContent* aTextNode, Directionality* aOldDir,

                             uint32_t aOffset)

 {

   if (!NodeAffectsDirAutoAncestor(aTextNode)) {

     nsTextNodeDirectionalityMap::EnsureMapIsClearFor(aTextNode);

     return false;

   }

   uint32_t firstStrong;

   *aOldDir = GetDirectionFromText(aTextNode->GetText(), &firstStrong);

   return (aOffset <= firstStrong);

 }

 void

 TextNodeChangedDirection(nsIContent* aTextNode, Directionality aOldDir,

                          bool aNotify)

 {

   Directionality newDir = GetDirectionFromText(aTextNode->GetText());

   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);

     }

   } 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. Otherwise call

     // SetAncestorDirectionIfAuto to find ancestor elements which should

     // have their directionality determined by this node.

     if (aTextNode->HasTextNodeDirectionalityMap()) {

       nsTextNodeDirectionalityMap::UpdateTextNodeDirection(aTextNode, newDir);

     } else {

       SetAncestorDirectionIfAuto(aTextNode, newDir, aNotify);

     }

   }

 }

 void

 SetDirectionFromNewTextNode(nsIContent* aTextNode)

 {

   if (!NodeAffectsDirAutoAncestor(aTextNode)) {

     return;

   }

   Element* parent = aTextNode->GetParentElement();

   if (parent && parent->NodeOrAncestorHasDirAuto()) {

     aTextNode->SetAncestorHasDirAuto();

   }

   Directionality dir = GetDirectionFromText(aTextNode->GetText());

   if (dir != eDir_NotSet) {

     SetAncestorDirectionIfAuto(aTextNode, dir);

   }

 }

 void

 ResetDirectionSetByTextNode(nsTextNode* aTextNode, bool aNullParent)

 {

   if (!NodeAffectsDirAutoAncestor(aTextNode)) {

     nsTextNodeDirectionalityMap::EnsureMapIsClearFor(aTextNode);

     return;

   }

   Directionality dir = GetDirectionFromText(aTextNode->GetText());

   if (dir != eDir_NotSet && aTextNode->HasTextNodeDirectionalityMap()) {

     if (aNullParent) {

       nsTextNodeDirectionalityMap::ClearTextNodeDirection(aTextNode);

     } else {

       nsTextNodeDirectionalityMap::ResetTextNodeDirection(aTextNode);

     }

   }

 }

 void

 SetDirectionalityFromValue(Element* aElement, const nsAString& value,

                            bool aNotify)

 {

   Directionality dir = GetDirectionFromText(PromiseFlatString(value).get(),

                                             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->IsHTML(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()) {

       nsINode* setByNode =

         static_cast<nsINode*>(aElement->GetProperty(nsGkAtoms::dirAutoSetBy));

       nsTextNodeDirectionalityMap::RemoveElementFromMap(setByNode, aElement);

     }

     SetDirectionalityOnDescendants(aElement,

                                    RecomputeDirectionality(aElement, aNotify),

                                    aNotify);

   }

 }

 void

 SetDirOnBind(mozilla::dom::Element* aElement, nsIContent* aParent)

 {

   // Set the AncestorHasDirAuto flag, unless this element shouldn't affect

   // ancestors that have dir=auto

   if (!DoesNotParticipateInAutoDirection(aElement) &&

       !aElement->IsHTML(nsGkAtoms::bdi) &&

       aParent && aParent->NodeOrAncestorHasDirAuto()) {

     aElement->SetAncestorHasDirAuto();

     nsIContent* child = aElement->GetFirstChild();

     if (child) {

       // If we are binding an element to the tree that already has descendants,

       // and the parent has NodeHasDirAuto or NodeAncestorHasDirAuto, we need

       // to set NodeAncestorHasDirAuto on all the element's descendants, except

       // for nodes that don't affect the direction of their ancestors.

       do {

         if (child->IsElement() &&

             DoesNotAffectDirectionOfAncestors(child->AsElement())) {

           child = child->GetNextNonChildNode(aElement);

           continue;

         }

         child->SetAncestorHasDirAuto();

         child = child->GetNextNode(aElement);

       } while (child);

       // 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(mozilla::dom::Element* aElement)

 {

   if (aElement->HasDirAutoSet()) {

     nsINode* setByNode =

       static_cast<nsINode*>(aElement->GetProperty(nsGkAtoms::dirAutoSetBy));

     nsTextNodeDirectionalityMap::RemoveElementFromMap(setByNode, aElement);

   }

   if (!aElement->HasDirAuto()) {

     RecomputeDirectionality(aElement, false);

   }

 }

 } // end namespace mozilla