Bug 1926483 - part 4: Make WSRunScanner::Scan(InclusiveNext|Previous)VisibleNodeOrBlockBoundary take WSRunScanner::Scan and ancestor limiter r=m_kato

Note that this removes a lot of `aEditingHost` params.  This may cause odd
behavior if editing host is changed by a legacy mutation event listener.
However, it'll be completely deleted soon and even if we meet some regressions,
we can just restore the param to set `aAncestorLimiter`.

Differential Revision: https://phabricator.services.mozilla.com/D233794

editor/libeditor/EditorDOMPoint.h

@@ -284,6 +284,11 @@ class EditorDOMPointBase final {
    */
   bool IsContainerElement() const { return mParent && mParent->IsElement(); }
 
+  /**
+   * Returns true if the container node is an editing host.
+   */
+  [[nodiscard]] bool IsContainerEditableRoot() const;
+
   /**
    * IsContainerHTMLElement() returns true if the container node is an HTML
    * element node and its node name is aTag.

editor/libeditor/EditorUtils.cpp

@@ -352,6 +352,15 @@ bool EditorDOMPointBase<
          EditorUtils::IsOnlyNewLinePreformatted(*ContainerAs<Text>());
 }
 
+template <typename PT, typename CT>
+bool EditorDOMPointBase<PT, CT>::IsContainerEditableRoot() const {
+  if (MOZ_UNLIKELY(!mParent) || MOZ_UNLIKELY(!mParent->IsEditable()) ||
+      NS_WARN_IF(mParent->IsInNativeAnonymousSubtree())) {
+    return false;
+  }
+  return HTMLEditUtils::ElementIsEditableRoot(*mParent);
+}
+
 /******************************************************************************
  * mozilla::EditorDOMRangeBase
  *****************************************************************************/

editor/libeditor/HTMLEditSubActionHandler.cpp

@@ -486,29 +486,26 @@ nsresult HTMLEditor::OnEndHandlingTopLevelEditSubActionInternal() {
         NS_WARNING("There was no selection range");
         return NS_ERROR_EDITOR_UNEXPECTED_DOM_TREE;
       }
-      if (const RefPtr<Element> editingHost =
+      Result<CreateLineBreakResult, nsresult>
-              ComputeEditingHost(LimitInBodyElement::No)) {
+          insertPaddingBRElementResultOrError =
-        Result<CreateLineBreakResult, nsresult>
+              InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded(
-            insertPaddingBRElementResultOrError =
+                  newCaretPosition);
-                InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded(
+      if (MOZ_UNLIKELY(insertPaddingBRElementResultOrError.isErr())) {
-                    newCaretPosition, *editingHost);
+        NS_WARNING(
-        if (MOZ_UNLIKELY(insertPaddingBRElementResultOrError.isErr())) {
+            "HTMLEditor::"
-          NS_WARNING(
+            "InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded() failed");
-              "HTMLEditor::"
+        return insertPaddingBRElementResultOrError.unwrapErr();
-              "InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded() failed");
-          return insertPaddingBRElementResultOrError.unwrapErr();
-        }
-        nsresult rv =
-            insertPaddingBRElementResultOrError.unwrap().SuggestCaretPointTo(
-                *this, {SuggestCaret::OnlyIfHasSuggestion});
-        if (NS_FAILED(rv)) {
-          NS_WARNING("CaretPoint::SuggestCaretPointTo() failed");
-          return rv;
-        }
-        NS_WARNING_ASSERTION(
-            rv != NS_SUCCESS_EDITOR_BUT_IGNORED_TRIVIAL_ERROR,
-            "CaretPoint::SuggestCaretPointTo() failed, but ignored");
       }
+      nsresult rv =
+          insertPaddingBRElementResultOrError.unwrap().SuggestCaretPointTo(
+              *this, {SuggestCaret::OnlyIfHasSuggestion});
+      if (NS_FAILED(rv)) {
+        NS_WARNING("CaretPoint::SuggestCaretPointTo() failed");
+        return rv;
+      }
+      NS_WARNING_ASSERTION(
+          rv != NS_SUCCESS_EDITOR_BUT_IGNORED_TRIVIAL_ERROR,
+          "CaretPoint::SuggestCaretPointTo() failed, but ignored");
     }
 
     // add in any needed <br>s, and remove any unneeded ones.
@@ -1208,7 +1205,7 @@ Result<EditActionResult, nsresult> HTMLEditor::HandleInsertText(
       const InsertTextResult insertEmptyTextResult =
           insertEmptyTextResultOrError.unwrap();
       nsresult rv = EnsureNoFollowingUnnecessaryLineBreak(
-          insertEmptyTextResult.EndOfInsertedTextRef(), *editingHost);
+          insertEmptyTextResult.EndOfInsertedTextRef());
       if (NS_FAILED(rv)) {
         NS_WARNING(
             "HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
@@ -1257,7 +1254,7 @@ Result<EditActionResult, nsresult> HTMLEditor::HandleInsertText(
     }
     InsertTextResult unwrappedReplacedTextResult = replaceTextResult.unwrap();
     nsresult rv = EnsureNoFollowingUnnecessaryLineBreak(
-        unwrappedReplacedTextResult.EndOfInsertedTextRef(), *editingHost);
+        unwrappedReplacedTextResult.EndOfInsertedTextRef());
     if (NS_FAILED(rv)) {
       NS_WARNING("HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
       return Err(rv);
@@ -1532,8 +1529,7 @@ Result<EditActionResult, nsresult> HTMLEditor::HandleInsertText(
       mLastCollapsibleWhiteSpaceAppendedTextNode =
           currentPoint.ContainerAs<Text>();
     }
-    nsresult rv =
+    nsresult rv = EnsureNoFollowingUnnecessaryLineBreak(currentPoint);
-        EnsureNoFollowingUnnecessaryLineBreak(currentPoint, *editingHost);
     if (NS_FAILED(rv)) {
       NS_WARNING("HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
       return Err(rv);
@@ -1661,7 +1657,8 @@ nsresult HTMLEditor::InsertLineBreakAsSubAction() {
     }
     const WSScanResult backwardScanFromBeforeBRElementResult =
         WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-            editingHost, insertLineBreakResult.AtLineBreak<EditorDOMPoint>(),
+            WSRunScanner::Scan::EditableNodes,
+            insertLineBreakResult.AtLineBreak<EditorDOMPoint>(),
             BlockInlineCheck::UseComputedDisplayStyle);
     if (MOZ_UNLIKELY(backwardScanFromBeforeBRElementResult.Failed())) {
       NS_WARNING(
@@ -1671,7 +1668,7 @@ nsresult HTMLEditor::InsertLineBreakAsSubAction() {
 
     const WSScanResult forwardScanFromAfterBRElementResult =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            editingHost, pointToPutCaret,
+            WSRunScanner::Scan::EditableNodes, pointToPutCaret,
             BlockInlineCheck::UseComputedDisplayStyle);
     if (MOZ_UNLIKELY(forwardScanFromAfterBRElementResult.Failed())) {
       NS_WARNING("WSRunScanner::ScanNextVisibleNodeOrBlockBoundary() failed");
@@ -1901,7 +1898,7 @@ HTMLEditor::InsertParagraphSeparatorAsSubAction(const Element& aEditingHost) {
       // table cell boundaries?
       Result<CaretPoint, nsresult> caretPointOrError =
           HandleInsertParagraphInMailCiteElement(*mailCiteElement,
-                                                 pointToInsert, aEditingHost);
+                                                 pointToInsert);
       if (MOZ_UNLIKELY(caretPointOrError.isErr())) {
         NS_WARNING(
             "HTMLEditor::HandleInsertParagraphInMailCiteElement() failed");
@@ -2472,7 +2469,7 @@ Result<CreateElementResult, nsresult> HTMLEditor::HandleInsertBRElement(
 
   const WSScanResult forwardScanFromAfterBRElementResult =
       WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-          &aEditingHost, afterBRElement,
+          WSRunScanner::Scan::EditableNodes, afterBRElement,
           BlockInlineCheck::UseComputedDisplayStyle);
   if (MOZ_UNLIKELY(forwardScanFromAfterBRElementResult.Failed())) {
     NS_WARNING("WSRunScanner::ScanNextVisibleNodeOrBlockBoundary() failed");
@@ -2687,8 +2684,7 @@ Result<EditorDOMPoint, nsresult> HTMLEditor::HandleInsertLinefeed(
 }
 
 Result<CaretPoint, nsresult> HTMLEditor::HandleInsertParagraphInMailCiteElement(
-    Element& aMailCiteElement, const EditorDOMPoint& aPointToSplit,
+    Element& aMailCiteElement, const EditorDOMPoint& aPointToSplit) {
-    const Element& aEditingHost) {
   MOZ_ASSERT(IsEditActionDataAvailable());
   MOZ_ASSERT(aPointToSplit.IsSet());
   NS_ASSERTION(!HTMLEditUtils::IsEmptyNode(
@@ -2711,7 +2707,8 @@ Result<CaretPoint, nsresult> HTMLEditor::HandleInsertParagraphInMailCiteElement(
     // mailquote may affect wrapping behavior, or font color, etc.
     const WSScanResult forwardScanFromPointToSplitResult =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost, pointToSplit, BlockInlineCheck::UseHTMLDefaultStyle);
+            WSRunScanner::Scan::EditableNodes, pointToSplit,
+            BlockInlineCheck::UseHTMLDefaultStyle);
     if (forwardScanFromPointToSplitResult.Failed()) {
       return Err(NS_ERROR_FAILURE);
     }
@@ -2831,7 +2828,7 @@ Result<CaretPoint, nsresult> HTMLEditor::HandleInsertParagraphInMailCiteElement(
       //     resultOfInsertingBRElement.inspect()?
       const WSScanResult backwardScanFromPointToCreateNewBRElementResult =
           WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-              &aEditingHost, pointToCreateNewBRElement,
+              WSRunScanner::Scan::EditableNodes, pointToCreateNewBRElement,
               BlockInlineCheck::UseHTMLDefaultStyle);
       if (MOZ_UNLIKELY(
               backwardScanFromPointToCreateNewBRElementResult.Failed())) {
@@ -2848,7 +2845,7 @@ Result<CaretPoint, nsresult> HTMLEditor::HandleInsertParagraphInMailCiteElement(
       }
       const WSScanResult forwardScanFromPointAfterNewBRElementResult =
           WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-              &aEditingHost,
+              WSRunScanner::Scan::EditableNodes,
               EditorRawDOMPoint::After(pointToCreateNewBRElement),
               BlockInlineCheck::UseHTMLDefaultStyle);
       if (MOZ_UNLIKELY(forwardScanFromPointAfterNewBRElementResult.Failed())) {
@@ -3407,8 +3404,7 @@ HTMLEditor::DeleteTextAndNormalizeSurroundingWhiteSpaces(
   {
     AutoTrackDOMPoint trackPointToPutCaret(RangeUpdaterRef(),
                                            &newCaretPosition);
-    nsresult rv =
+    nsresult rv = EnsureNoFollowingUnnecessaryLineBreak(newCaretPosition);
-        EnsureNoFollowingUnnecessaryLineBreak(newCaretPosition, aEditingHost);
     if (NS_FAILED(rv)) {
       NS_WARNING("HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
       return Err(rv);
@@ -3464,7 +3460,7 @@ bool HTMLEditor::CanInsertLineBreak(LineBreakType aLineBreakType,
 
 Result<CreateLineBreakResult, nsresult>
 HTMLEditor::InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded(
-    const EditorDOMPoint& aPointToInsert, const Element& aEditingHost) {
+    const EditorDOMPoint& aPointToInsert) {
   MOZ_ASSERT(IsEditActionDataAvailable());
   MOZ_ASSERT(aPointToInsert.IsSet());
 
@@ -3487,7 +3483,7 @@ HTMLEditor::InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded(
   // here.
   const WSScanResult previousThing =
       WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-          &aEditingHost, aPointToInsert,
+          WSRunScanner::Scan::EditableNodes, aPointToInsert,
           BlockInlineCheck::UseComputedDisplayStyle);
   if (!previousThing.ReachedLineBoundary()) {
     return CreateLineBreakResult::NotHandled();
@@ -3497,7 +3493,7 @@ HTMLEditor::InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded(
   // line break here.
   const WSScanResult nextThing =
       WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-          &aEditingHost, aPointToInsert,
+          WSRunScanner::Scan::EditableNodes, aPointToInsert,
           BlockInlineCheck::UseComputedDisplayStyle);
   if (!nextThing.ReachedBlockBoundary()) {
     return CreateLineBreakResult::NotHandled();
@@ -7043,8 +7039,7 @@ Result<EditorDOMPoint, nsresult> HTMLEditor::CreateStyleForInsertText(
     NS_WARNING("AutoClonedRangeArray::AutoClonedRangeArray() failed");
     return Err(NS_ERROR_FAILURE);
   }
-  nsresult rv =
+  nsresult rv = SetInlinePropertiesAroundRanges(ranges, stylesToSet);
-      SetInlinePropertiesAroundRanges(ranges, stylesToSet, aEditingHost);
   if (NS_FAILED(rv)) {
     NS_WARNING("HTMLEditor::SetInlinePropertiesAroundRanges() failed");
     return Err(rv);
@@ -9177,7 +9172,8 @@ HTMLEditor::HandleInsertParagraphInListItemElement(
   // the element is proper position.
   const WSScanResult forwardScanFromStartOfListItemResult =
       WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-          &aEditingHost, EditorRawDOMPoint(&rightListItemElement, 0u),
+          WSRunScanner::Scan::EditableNodes,
+          EditorRawDOMPoint(&rightListItemElement, 0u),
           BlockInlineCheck::UseComputedDisplayStyle);
   if (MOZ_UNLIKELY(forwardScanFromStartOfListItemResult.Failed())) {
     NS_WARNING("WSRunScanner::ScanNextVisibleNodeOrBlockBoundary() failed");
@@ -11212,7 +11208,7 @@ HTMLEditor::InsertPaddingBRElementIfNeeded(
     if (IsPlaintextMailComposer()) {
       const WSScanResult nextVisibleThing =
           WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-              &aEditingHost, aPoint,
+              WSRunScanner::Scan::EditableNodes, aPoint,
               BlockInlineCheck::UseComputedDisplayOutsideStyle);
       if (nextVisibleThing.ReachedBlockBoundary() &&
           HTMLEditUtils::IsMailCite(*nextVisibleThing.ElementPtr()) &&

editor/libeditor/HTMLEditUtils.cpp

@@ -41,6 +41,7 @@
 #include "nsError.h"             // for NS_SUCCEEDED
 #include "nsGkAtoms.h"           // for nsGkAtoms, nsGkAtoms::a, etc.
 #include "nsHTMLTags.h"
+#include "nsIContentInlines.h"   // for nsIContent::IsInDesignMode(), etc.
 #include "nsIFrameInlines.h"     // for nsIFrame::IsFlexOrGridItem()
 #include "nsLiteralString.h"     // for NS_LITERAL_STRING
 #include "nsNameSpaceManager.h"  // for kNameSpaceID_None
@@ -125,13 +126,13 @@ template EditorRawDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
     const nsIContent& aContentToInsert, const EditorDOMPoint& aPointToInsert);
 
 template EditorDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
-    const EditorDOMPoint& aPoint, const Element& aEditingHost);
+    const EditorDOMPoint& aPoint);
 template EditorDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
-    const EditorRawDOMPoint& aPoint, const Element& aEditingHost);
+    const EditorRawDOMPoint& aPoint);
 template EditorRawDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
-    const EditorDOMPoint& aPoint, const Element& aEditingHost);
+    const EditorDOMPoint& aPoint);
 template EditorRawDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
-    const EditorRawDOMPoint& aPoint, const Element& aEditingHost);
+    const EditorRawDOMPoint& aPoint);
 
 template Result<EditorDOMPoint, nsresult>
 HTMLEditUtils::ComputePointToPutCaretInElementIfOutside(
@@ -152,48 +153,54 @@ template bool HTMLEditUtils::IsSameCSSColorValue(const nsACString& aColorA,
                                                  const nsACString& aColorB);
 
 template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
-    const EditorDOMPoint& aPoint, const Element& aEditingHost);
+    const EditorDOMPoint& aPoint);
 template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
-    const EditorRawDOMPoint& aPoint, const Element& aEditingHost);
+    const EditorRawDOMPoint& aPoint);
 template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
-    const EditorDOMPointInText& aPoint, const Element& aEditingHost);
+    const EditorDOMPointInText& aPoint);
 template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
-    const EditorRawDOMPointInText& aPoint, const Element& aEditingHost);
+    const EditorRawDOMPointInText& aPoint);
 template Maybe<EditorRawLineBreak>
-HTMLEditUtils::GetFollowingUnnecessaryLineBreak(const EditorDOMPoint& aPoint,
+HTMLEditUtils::GetFollowingUnnecessaryLineBreak(const EditorDOMPoint& aPoint);
-                                                const Element& aEditingHost);
-template Maybe<EditorRawLineBreak>
-HTMLEditUtils::GetFollowingUnnecessaryLineBreak(const EditorRawDOMPoint& aPoint,
-                                                const Element& aEditingHost);
 template Maybe<EditorRawLineBreak>
 HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
-    const EditorDOMPointInText& aPoint, const Element& aEditingHost);
+    const EditorRawDOMPoint& aPoint);
 template Maybe<EditorRawLineBreak>
 HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
-    const EditorRawDOMPointInText& aPoint, const Element& aEditingHost);
+    const EditorDOMPointInText& aPoint);
+template Maybe<EditorRawLineBreak>
+HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
+    const EditorRawDOMPointInText& aPoint);
 
 template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
     const EditorDOMPoint& aPoint,
-    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak,
+    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
-    const Element& aEditingHost);
 template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
     const EditorRawDOMPoint& aPoint,
-    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak,
+    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
-    const Element& aEditingHost);
 template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
     const EditorDOMPointInText& aPoint,
-    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak,
+    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
-    const Element& aEditingHost);
 template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
     const EditorRawDOMPointInText& aPoint,
-    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak,
+    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
-    const Element& aEditingHost);
 
 template Maybe<EditorLineBreak> HTMLEditUtils::GetUnnecessaryLineBreak(
     const Element& aBlockElement, ScanLineBreak aScanLineBreak);
 template Maybe<EditorRawLineBreak> HTMLEditUtils::GetUnnecessaryLineBreak(
     const Element& aBlockElement, ScanLineBreak aScanLineBreak);
 
+bool HTMLEditUtils::ElementIsEditableRoot(const Element& aElement) {
+  MOZ_ASSERT(!aElement.IsInNativeAnonymousSubtree());
+  if (NS_WARN_IF(!aElement.IsEditable()) ||
+      NS_WARN_IF(!aElement.IsInComposedDoc())) {
+    return false;
+  }
+  return !aElement.GetParent() ||                      // root element
+         !aElement.GetParent()->IsEditable() ||        // editing host
+         aElement.OwnerDoc()->GetBody() == &aElement;  // the <body>
+}
+
 bool HTMLEditUtils::CanContentsBeJoined(const nsIContent& aLeftContent,
                                         const nsIContent& aRightContent) {
   if (aLeftContent.NodeInfo()->NameAtom() !=
@@ -809,7 +816,7 @@ EditorDOMPoint HTMLEditUtils::LineRequiresPaddingLineBreakToBeVisible(
     }
     const WSScanResult nextThing =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost, point,
+            WSRunScanner::Scan::EditableNodes, point,
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     if (nextThing.ReachedBlockBoundary()) {
       if (nextThing.ReachedCurrentBlockBoundary()) {
@@ -831,7 +838,7 @@ EditorDOMPoint HTMLEditUtils::LineRequiresPaddingLineBreakToBeVisible(
     }
     const WSScanResult previousThing =
         WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-            &aEditingHost, preferredPaddingLineBreakPoint,
+            WSRunScanner::Scan::EditableNodes, preferredPaddingLineBreakPoint,
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     if (previousThing.ContentIsText()) {
       if (MOZ_UNLIKELY(!previousThing.TextPtr()->TextDataLength())) {
@@ -982,16 +989,15 @@ Element* HTMLEditUtils::GetElementOfImmediateBlockBoundary(
 template <typename PT, typename CT>
 bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
     const EditorDOMPointBase<PT, CT>& aPoint,
-    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak,
+    IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak) {
-    const Element& aEditingHost) {
   MOZ_ASSERT(aPoint.IsSetAndValidInComposedDoc());
 
   if (MOZ_UNLIKELY(!aPoint.IsInContentNode())) {
     return false;
   }
-  WSScanResult nextThing =
+  const WSScanResult nextThing =
       WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-          &aEditingHost, aPoint,
+          WSRunScanner::Scan::EditableNodes, aPoint,
           BlockInlineCheck::UseComputedDisplayOutsideStyle);
   if (nextThing.ReachedCurrentBlockBoundary()) {
     return true;
@@ -1000,9 +1006,9 @@ bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
     if (aIgnoreInvisibleLineBreak == IgnoreInvisibleLineBreak::No) {
       return false;
     }
-    WSScanResult afterInvisibleBRThing =
+    const WSScanResult afterInvisibleBRThing =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost,
+            WSRunScanner::Scan::EditableNodes,
             nextThing.PointAfterReachedContent<EditorRawDOMPoint>(),
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     return afterInvisibleBRThing.ReachedCurrentBlockBoundary();
@@ -1011,9 +1017,9 @@ bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
     if (aIgnoreInvisibleLineBreak == IgnoreInvisibleLineBreak::No) {
       return false;
     }
-    WSScanResult afterPreformattedLineBreakThing =
+    const WSScanResult afterPreformattedLineBreakThing =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost,
+            WSRunScanner::Scan::EditableNodes,
             nextThing.PointAfterReachedContent<EditorRawDOMPoint>(),
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     return afterPreformattedLineBreakThing.ReachedCurrentBlockBoundary();
@@ -1192,22 +1198,23 @@ Maybe<EditorLineBreakType> HTMLEditUtils::GetUnnecessaryLineBreak(
 
 template <typename EditorLineBreakType, typename EditorDOMPointType>
 Maybe<EditorLineBreakType> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
-    const EditorDOMPointType& aPoint, const Element& aEditingHost) {
+    const EditorDOMPointType& aPoint) {
   MOZ_ASSERT(aPoint.IsSetAndValid());
   MOZ_ASSERT(aPoint.IsInContentNode());
 
-  WSScanResult nextThing =
+  const WSScanResult nextThing =
       WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-          &aEditingHost, aPoint, BlockInlineCheck::UseComputedDisplayStyle);
+          WSRunScanner::Scan::EditableNodes, aPoint,
+          BlockInlineCheck::UseComputedDisplayStyle);
   if (!nextThing.ReachedBRElement() &&
       !(nextThing.ReachedPreformattedLineBreak() &&
         nextThing.PointAtReachedContent<EditorRawDOMPoint>()
             .IsAtLastContent())) {
     return Nothing();  // no line break next to aPoint
   }
-  WSScanResult nextThingOfLineBreak =
+  const WSScanResult nextThingOfLineBreak =
       WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-          &aEditingHost,
+          WSRunScanner::Scan::EditableNodes,
           nextThing.PointAfterReachedContent<EditorRawDOMPoint>(),
           BlockInlineCheck::UseComputedDisplayStyle);
   const Element* const blockElement =
@@ -2540,12 +2547,12 @@ nsIContent* HTMLEditUtils::GetContentToPreserveInlineStyles(
   for (auto point = aPoint.template To<EditorRawDOMPoint>(); point.IsSet();) {
     const WSScanResult nextVisibleThing =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost, point,
+            WSRunScanner::Scan::EditableNodes, point,
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     if (nextVisibleThing.InVisibleOrCollapsibleCharacters()) {
       return nextVisibleThing.TextPtr();
     }
-    if (nextVisibleThing.GetContent() == &aEditingHost) {
+    if (nextVisibleThing.IsContentEditableRoot()) {
       break;
     }
     // Ignore empty inline container elements because it's not visible for
@@ -2631,10 +2638,9 @@ EditorDOMPointType HTMLEditUtils::GetBetterInsertionPointFor(
 // static
 template <typename EditorDOMPointType, typename EditorDOMPointTypeInput>
 EditorDOMPointType HTMLEditUtils::GetBetterCaretPositionToInsertText(
-    const EditorDOMPointTypeInput& aPoint, const Element& aEditingHost) {
+    const EditorDOMPointTypeInput& aPoint) {
   MOZ_ASSERT(aPoint.IsSetAndValid());
-  MOZ_ASSERT(
+  MOZ_ASSERT(HTMLEditUtils::IsSimplyEditableNode(*aPoint.GetContainer()));
-      aPoint.GetContainer()->IsInclusiveFlatTreeDescendantOf(&aEditingHost));
 
   if (aPoint.IsInTextNode()) {
     return aPoint.template To<EditorDOMPointType>();
@@ -2646,7 +2652,8 @@ EditorDOMPointType HTMLEditUtils::GetBetterCaretPositionToInsertText(
   if (aPoint.IsEndOfContainer()) {
     const WSScanResult previousThing =
         WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-            &aEditingHost, aPoint, BlockInlineCheck::UseComputedDisplayStyle);
+            WSRunScanner::Scan::EditableNodes, aPoint,
+            BlockInlineCheck::UseComputedDisplayStyle);
     if (previousThing.InVisibleOrCollapsibleCharacters()) {
       return EditorDOMPointType::AtEndOf(*previousThing.TextPtr());
     }
@@ -2655,7 +2662,7 @@ EditorDOMPointType HTMLEditUtils::GetBetterCaretPositionToInsertText(
                                     *nsGkAtoms::textTagName)) {
     return aPoint.template To<EditorDOMPointType>();
   }
-  if (MOZ_UNLIKELY(aPoint.GetContainer() == &aEditingHost ||
+  if (MOZ_UNLIKELY(aPoint.GetContainer()->IsEditingHost() ||
                    !aPoint.template GetContainerParentAs<nsIContent>() ||
                    !HTMLEditUtils::CanNodeContain(
                        *aPoint.template ContainerParentAs<nsIContent>(),

editor/libeditor/HTMLEditUtils.h

@@ -76,6 +76,14 @@ class HTMLEditUtils final {
     return aNode.IsEditable();
   }
 
+  /**
+   * Return true if aElement is an editing host which is either:
+   * - the root element
+   * - parent is not editable
+   * - the <body> element of the document
+   */
+  [[nodiscard]] static bool ElementIsEditableRoot(const Element& aElement);
+
   /**
    * Return true if inclusive flat tree ancestor has `inert` state.
    */
@@ -540,8 +548,7 @@ class HTMLEditUtils final {
   template <typename PT, typename CT>
   [[nodiscard]] static bool PointIsImmediatelyBeforeCurrentBlockBoundary(
       const EditorDOMPointBase<PT, CT>& aPoint,
-      IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak,
+      IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
-      const Element& aEditingHost);
 
   /**
    * Return true if aRange crosses the inclusive ancestor block element at
@@ -2071,8 +2078,7 @@ class HTMLEditUtils final {
    */
   template <typename EditorLineBreakType, typename EditorDOMPointType>
   [[nodiscard]] static Maybe<EditorLineBreakType>
-  GetFollowingUnnecessaryLineBreak(const EditorDOMPointType& aPoint,
+  GetFollowingUnnecessaryLineBreak(const EditorDOMPointType& aPoint);
-                                   const Element& aEditingHost);
 
   /**
    * IsInTableCellSelectionMode() returns true when Gecko's editor thinks that
@@ -2382,7 +2388,7 @@ class HTMLEditUtils final {
    */
   template <typename EditorDOMPointType, typename EditorDOMPointTypeInput>
   static EditorDOMPointType GetBetterCaretPositionToInsertText(
-      const EditorDOMPointTypeInput& aPoint, const Element& aEditingHost);
+      const EditorDOMPointTypeInput& aPoint);
 
   /**
    * ComputePointToPutCaretInElementIfOutside() returns a good point in aElement

editor/libeditor/HTMLEditor.cpp

@@ -1194,7 +1194,7 @@ nsresult HTMLEditor::MaybeCollapseSelectionAtFirstEditableNode(
       // the visible character.
       const WSScanResult scanResultInTextNode =
           WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-              editingHost, EditorRawDOMPoint(text, 0),
+              WSRunScanner::Scan::EditableNodes, EditorRawDOMPoint(text, 0),
               BlockInlineCheck::UseComputedDisplayStyle);
       if ((scanResultInTextNode.InVisibleOrCollapsibleCharacters() ||
            scanResultInTextNode.ReachedPreformattedLineBreak()) &&
@@ -2295,8 +2295,7 @@ nsresult HTMLEditor::InsertElementAtSelectionAsAction(
     if (MOZ_LIKELY(aElement->IsInComposedDoc())) {
       const auto afterElement = EditorDOMPoint::After(*aElement);
       if (MOZ_LIKELY(afterElement.IsInContentNode())) {
-        nsresult rv =
+        nsresult rv = EnsureNoFollowingUnnecessaryLineBreak(afterElement);
-            EnsureNoFollowingUnnecessaryLineBreak(afterElement, *editingHost);
         if (NS_FAILED(rv)) {
           NS_WARNING(
               "HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
@@ -4519,8 +4518,7 @@ Result<CreateLineBreakResult, nsresult> HTMLEditor::InsertLineBreak(
 }
 
 nsresult HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak(
-    const EditorDOMPoint& aNextOrAfterModifiedPoint,
+    const EditorDOMPoint& aNextOrAfterModifiedPoint) {
-    const Element& aEditingHost) {
   MOZ_ASSERT(aNextOrAfterModifiedPoint.IsInContentNode());
 
   // If the point is in a mailcite in plaintext mail composer (it is a <span>
@@ -4548,7 +4546,7 @@ nsresult HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak(
 
   const Maybe<EditorLineBreak> unnecessaryLineBreak =
       HTMLEditUtils::GetFollowingUnnecessaryLineBreak<EditorLineBreak>(
-          aNextOrAfterModifiedPoint, aEditingHost);
+          aNextOrAfterModifiedPoint);
   if (MOZ_LIKELY(unnecessaryLineBreak.isNothing())) {
     return NS_OK;
   }
@@ -7847,7 +7845,7 @@ nsresult HTMLEditor::OnModifyDocument(const DocumentModifiedEvent& aRunner) {
         }
         const WSScanResult nextThing =
             WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-                editingHost,
+                WSRunScanner::Scan::EditableNodes,
                 atCollapsibleWhiteSpace.AfterContainer<EditorRawDOMPoint>(),
                 BlockInlineCheck::UseComputedDisplayStyle);
         if (!nextThing.ReachedBlockBoundary()) {
@@ -7909,21 +7907,18 @@ void HTMLEditor::DocumentModifiedEvent::MaybeAppendNewInvisibleWhiteSpace(
       !aContentWillBeRemoved->IsHTMLElement(nsGkAtoms::br)) {
     return;
   }
-  const Element* const editingHost =
-      const_cast<nsIContent*>(aContentWillBeRemoved)->GetEditingHost();
-  if (MOZ_UNLIKELY(!editingHost)) {
-    return;
-  }
   const WSScanResult nextThing =
       WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-          editingHost, EditorRawDOMPoint::After(*aContentWillBeRemoved),
+          WSRunScanner::Scan::EditableNodes,
+          EditorRawDOMPoint::After(*aContentWillBeRemoved),
           BlockInlineCheck::UseComputedDisplayStyle);
   if (!nextThing.ReachedBlockBoundary()) {
     return;
   }
   const WSScanResult previousThing =
       WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-          editingHost, EditorRawDOMPoint(aContentWillBeRemoved),
+          WSRunScanner::Scan::EditableNodes,
+          EditorRawDOMPoint(aContentWillBeRemoved),
           BlockInlineCheck::UseComputedDisplayOutsideStyle);
   if (!previousThing.ContentIsText() || !previousThing.IsContentEditable()) {
     return;

editor/libeditor/HTMLEditor.h

@@ -1213,14 +1213,12 @@ class HTMLEditor final : public EditorBase,
    *
    * @param aMailCiteElement    The mail-cite element which should be split.
    * @param aPointToSplit       The point to split.
-   * @param aEditingHost        The editing host.
    * @return                    Candidate caret position where is at inserted
    *                            <br> element into the split point.
    */
   [[nodiscard]] MOZ_CAN_RUN_SCRIPT Result<CaretPoint, nsresult>
   HandleInsertParagraphInMailCiteElement(Element& aMailCiteElement,
-                                         const EditorDOMPoint& aPointToSplit,
+                                         const EditorDOMPoint& aPointToSplit);
-                                         const Element& aEditingHost);
 
   /**
    * HandleInsertBRElement() inserts a <br> element into aPointToBreak.
@@ -1657,7 +1655,7 @@ class HTMLEditor final : public EditorBase,
    */
   [[nodiscard]] MOZ_CAN_RUN_SCRIPT Result<CreateLineBreakResult, nsresult>
   InsertPaddingBRElementToMakeEmptyLineVisibleIfNeeded(
-      const EditorDOMPoint& aPointToInsert, const Element& aEditingHost);
+      const EditorDOMPoint& aPointToInsert);
 
   /**
    * Insert a padding <br> if aPoint is in an empty block.
@@ -3400,12 +3398,10 @@ class HTMLEditor final : public EditorBase,
    *                                    content.
    *                                    If you deleted something, this should be
    *                                    end of the deleted range.
-   * @param aEditingHost                The editing host.
    */
   [[nodiscard]] MOZ_CAN_RUN_SCRIPT nsresult
   EnsureNoFollowingUnnecessaryLineBreak(
-      const EditorDOMPoint& aNextOrAfterModifiedPoint,
+      const EditorDOMPoint& aNextOrAfterModifiedPoint);
-      const Element& aEditingHost);
 
   /**
    * IndentAsSubAction() indents the content around Selection.
@@ -3455,8 +3451,7 @@ class HTMLEditor final : public EditorBase,
   template <size_t N>
   [[nodiscard]] MOZ_CAN_RUN_SCRIPT nsresult SetInlinePropertiesAroundRanges(
       AutoClonedRangeArray& aRanges,
-      const AutoTArray<EditorInlineStyleAndValue, N>& aStylesToSet,
+      const AutoTArray<EditorInlineStyleAndValue, N>& aStylesToSet);
-      const Element& aEditingHost);
 
   /**
    * RemoveInlinePropertiesAsSubAction() removes specified styles from

editor/libeditor/HTMLEditorDataTransfer.cpp

@@ -903,7 +903,7 @@ Result<EditActionResult, nsresult> HTMLEditor::HTMLWithContextInserter::Run(
         lastInsertedPoint.inspect().NextPointOrAfterContainer();
     if (MOZ_LIKELY(afterLastInsertedContent.IsInContentNode())) {
       nsresult rv = mHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(
-          afterLastInsertedContent, mEditingHost);
+          afterLastInsertedContent);
       if (NS_FAILED(rv)) {
         NS_WARNING(
             "HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");

editor/libeditor/HTMLEditorDeleteHandler.cpp

@@ -2373,8 +2373,8 @@ Result<CaretPoint, nsresult> HTMLEditor::AutoDeleteRangesHandler::
   if (MOZ_LIKELY(pointToPutCaret.IsInContentNode())) {
     AutoTrackDOMPoint trackPointToPutCaret(aHTMLEditor.RangeUpdaterRef(),
                                            &pointToPutCaret);
-    nsresult rv = aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(
+    nsresult rv =
-        pointToPutCaret, aEditingHost);
+        aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(pointToPutCaret);
     if (NS_FAILED(rv)) {
       NS_WARNING("HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
       return Err(rv);
@@ -2581,8 +2581,8 @@ Result<CaretPoint, nsresult> HTMLEditor::AutoDeleteRangesHandler::
   if (MOZ_LIKELY(pointToPutCaret.IsInContentNode())) {
     AutoTrackDOMPoint trackPointToPutCaret(aHTMLEditor.RangeUpdaterRef(),
                                            &pointToPutCaret);
-    nsresult rv = aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(
+    nsresult rv =
-        pointToPutCaret, aEditingHost);
+        aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(pointToPutCaret);
     if (NS_FAILED(rv)) {
       NS_WARNING("HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
       return Err(rv);
@@ -2756,8 +2756,8 @@ HTMLEditor::AutoDeleteRangesHandler::HandleDeleteAtomicContent(
   if (MOZ_LIKELY(pointToPutCaret.IsInContentNode())) {
     AutoTrackDOMPoint trackPointToPutCaret(aHTMLEditor.RangeUpdaterRef(),
                                            &pointToPutCaret);
-    nsresult rv = aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(
+    nsresult rv =
-        pointToPutCaret, aEditingHost);
+        aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(pointToPutCaret);
     if (NS_FAILED(rv)) {
       NS_WARNING("HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
       return Err(rv);
@@ -3586,7 +3586,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
       }
       const WSScanResult prevVisibleThingBeforeCurrentBlock =
           WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-              &aEditingHost,
+              WSRunScanner::Scan::EditableNodes,
               EditorRawDOMPoint(
                   inclusiveAncestorOfRightChildBlockOrError.inspect()),
               BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -3605,7 +3605,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
       MOZ_ASSERT(atPrecedingLineBreak.IsSet());
       const WSScanResult prevVisibleThingBeforeLineBreak =
           WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-              &aEditingHost, atPrecedingLineBreak,
+              WSRunScanner::Scan::EditableNodes, atPrecedingLineBreak,
               BlockInlineCheck::UseComputedDisplayOutsideStyle);
       if (prevVisibleThingBeforeLineBreak.ReachedBRElement() ||
           prevVisibleThingBeforeLineBreak.ReachedPreformattedLineBreak() ||
@@ -4214,7 +4214,8 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
     // rough check.
     const WSScanResult nextVisibleThingOfEndBoundary =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost, EditorRawDOMPoint(aRangeToDelete.EndRef()),
+            WSRunScanner::Scan::EditableNodes,
+            EditorRawDOMPoint(aRangeToDelete.EndRef()),
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     if (!nextVisibleThingOfEndBoundary.ReachedCurrentBlockBoundary()) {
       MOZ_ASSERT(mLeftContent->IsElement());
@@ -4227,7 +4228,8 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
       if (MOZ_LIKELY(mostDistantBlockOrError.inspect())) {
         const WSScanResult prevVisibleThingOfStartBoundary =
             WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-                &aEditingHost, EditorRawDOMPoint(aRangeToDelete.StartRef()),
+                WSRunScanner::Scan::EditableNodes,
+                EditorRawDOMPoint(aRangeToDelete.StartRef()),
                 BlockInlineCheck::UseComputedDisplayOutsideStyle);
         if (prevVisibleThingOfStartBoundary.ReachedBRElement()) {
           // If the range start after a <br> followed by the block boundary,
@@ -4235,7 +4237,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
           // not a part of empty line like `<div>abc<br>{<div>]def`.
           const WSScanResult nextVisibleThingOfBR =
               WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-                  &aEditingHost,
+                  WSRunScanner::Scan::EditableNodes,
                   EditorRawDOMPoint::After(
                       *prevVisibleThingOfStartBoundary.GetContent()),
                   BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -4249,7 +4251,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
           }
           const WSScanResult prevVisibleThingOfBR =
               WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-                  &aEditingHost,
+                  WSRunScanner::Scan::EditableNodes,
                   EditorRawDOMPoint(
                       prevVisibleThingOfStartBoundary.GetContent()),
                   BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -4264,7 +4266,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
                        .ReachedPreformattedLineBreak()) {
           const WSScanResult nextVisibleThingOfLineBreak =
               WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-                  &aEditingHost,
+                  WSRunScanner::Scan::EditableNodes,
                   prevVisibleThingOfStartBoundary
                       .PointAfterReachedContent<EditorRawDOMPoint>(),
                   BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -4279,7 +4281,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
           }
           const WSScanResult prevVisibleThingOfLineBreak =
               WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-                  &aEditingHost,
+                  WSRunScanner::Scan::EditableNodes,
                   prevVisibleThingOfStartBoundary
                       .PointAtReachedContent<EditorRawDOMPoint>(),
                   BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -4296,7 +4298,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
                      mLeftContent);
           const WSScanResult firstVisibleThingInBlock =
               WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-                  &aEditingHost,
+                  WSRunScanner::Scan::EditableNodes,
                   EditorRawDOMPoint(
                       prevVisibleThingOfStartBoundary.ElementPtr(), 0),
                   BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -4309,7 +4311,7 @@ bool HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
         } else if (prevVisibleThingOfStartBoundary.ReachedOtherBlockElement()) {
           const WSScanResult firstVisibleThingAfterBlock =
               WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-                  &aEditingHost,
+                  WSRunScanner::Scan::EditableNodes,
                   EditorRawDOMPoint::After(
                       *prevVisibleThingOfStartBoundary.ElementPtr()),
                   BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -4903,8 +4905,8 @@ Result<Element*, nsresult> HTMLEditor::AutoDeleteRangesHandler::
 
   const WSScanResult prevVisibleThing =
       WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-          aAncestorLimiter, aPoint,
+          WSRunScanner::Scan::EditableNodes, aPoint,
-          BlockInlineCheck::UseComputedDisplayOutsideStyle);
+          BlockInlineCheck::UseComputedDisplayOutsideStyle, aAncestorLimiter);
   if (!ReachedCurrentBlockBoundaryWhichWeCanCross(prevVisibleThing)) {
     return nullptr;
   }
@@ -4914,8 +4916,8 @@ Result<Element*, nsresult> HTMLEditor::AutoDeleteRangesHandler::
   for (Element* ancestorBlock = prevVisibleThing.ElementPtr(); ancestorBlock;) {
     const WSScanResult prevVisibleThing =
         WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-            aAncestorLimiter, EditorRawDOMPoint(ancestorBlock),
+            WSRunScanner::Scan::EditableNodes, EditorRawDOMPoint(ancestorBlock),
-            BlockInlineCheck::UseComputedDisplayOutsideStyle);
+            BlockInlineCheck::UseComputedDisplayOutsideStyle, aAncestorLimiter);
     if (!ReachedCurrentBlockBoundaryWhichWeCanCross(prevVisibleThing)) {
       return ancestorBlock;
     }
@@ -4981,7 +4983,8 @@ void HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
 
   const WSScanResult prevVisibleThingOfStartBoundary =
       WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-          &aEditingHost, EditorRawDOMPoint(aRangeToDelete.StartRef()),
+          WSRunScanner::Scan::EditableNodes,
+          EditorRawDOMPoint(aRangeToDelete.StartRef()),
           BlockInlineCheck::UseComputedDisplayOutsideStyle);
   // If the range starts after an invisible <br> of empty line immediately
   // before the most distant inclusive ancestor of the right block like
@@ -4991,13 +4994,13 @@ void HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
       prevVisibleThingOfStartBoundary.ReachedPreformattedLineBreak()) {
     const WSScanResult prevVisibleThingOfPreviousLineBreak =
         WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-            &aEditingHost,
+            WSRunScanner::Scan::EditableNodes,
             prevVisibleThingOfStartBoundary
                 .PointAtReachedContent<EditorRawDOMPoint>(),
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     const WSScanResult nextVisibleThingOfPreviousBR =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost,
+            WSRunScanner::Scan::EditableNodes,
             prevVisibleThingOfStartBoundary
                 .PointAfterReachedContent<EditorRawDOMPoint>(),
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -5028,8 +5031,9 @@ void HTMLEditor::AutoDeleteRangesHandler::AutoBlockElementsJoiner::
       while (true) {
         WSScanResult scanResult =
             WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-                mLeftContent->AsElement(), scanStartPoint,
+                WSRunScanner::Scan::EditableNodes, scanStartPoint,
-                BlockInlineCheck::UseComputedDisplayOutsideStyle);
+                BlockInlineCheck::UseComputedDisplayOutsideStyle,
+                mLeftContent->AsElement());
         if (scanResult.ReachedBlockBoundary() ||
             scanResult.ReachedInlineEditingHostBoundary()) {
           return lastScanResult;
@@ -5181,7 +5185,7 @@ Result<EditActionResult, nsresult> HTMLEditor::AutoDeleteRangesHandler::
       mMode != Mode::DeletePrecedingLinesAndContentInRange &&
       HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
           EditorRawDOMPoint(aRangeToDelete.StartRef()),
-          HTMLEditUtils::IgnoreInvisibleLineBreak::Yes, aEditingHost);
+          HTMLEditUtils::IgnoreInvisibleLineBreak::Yes);
   const PutCaretTo putCaretTo = [&]() {
     // When we delete only preceding lines of the right child block, we should
     // put caret into start of the right block.
@@ -5405,8 +5409,8 @@ Result<EditActionResult, nsresult> HTMLEditor::AutoDeleteRangesHandler::
                 aHTMLEditor.RangeUpdaterRef(), &moveFirstLineResult);
             AutoTrackDOMPoint trackPointToPutCaret(
                 aHTMLEditor.RangeUpdaterRef(), &pointToPutCaret);
-            nsresult rv = aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(
+            nsresult rv =
-                aPoint, aEditingHost);
+                aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(aPoint);
             NS_WARNING_ASSERTION(
                 NS_SUCCEEDED(rv),
                 "HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
@@ -5496,7 +5500,7 @@ Result<EditActionResult, nsresult> HTMLEditor::AutoDeleteRangesHandler::
             }
             WSScanResult nextThing =
                 WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-                    &aEditingHost,
+                    WSRunScanner::Scan::EditableNodes,
                     deleteContentResult.DeleteRangeRef().EndRef(),
                     BlockInlineCheck::UseComputedDisplayOutsideStyle);
             return nextThing.ReachedBRElement() ||
@@ -5645,8 +5649,8 @@ nsresult HTMLEditor::AutoDeleteRangesHandler::DeleteUnnecessaryNodes(
 
   if (MOZ_LIKELY(range.EndRef().IsInContentNode())) {
     AutoTrackDOMRange trackRange(aHTMLEditor.RangeUpdaterRef(), &range);
-    nsresult rv = aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(
+    nsresult rv =
-        range.EndRef(), aEditingHost);
+        aHTMLEditor.EnsureNoFollowingUnnecessaryLineBreak(range.EndRef());
     if (NS_FAILED(rv)) {
       NS_WARNING("HTMLEditor::EnsureNoFollowingUnnecessaryLineBreak() failed");
       return Err(rv);
@@ -5737,7 +5741,7 @@ HTMLEditor::AutoDeleteRangesHandler::DeleteParentBlocksWithTransactionIfEmpty(
     if (wsScannerForPoint.GetEndReasonContent()->GetNextSibling()) {
       const WSScanResult scanResult =
           WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-              editingHost,
+              WSRunScanner::Scan::EditableNodes,
               EditorRawDOMPoint::After(
                   *wsScannerForPoint.GetEndReasonContent()),
               BlockInlineCheck::UseComputedDisplayOutsideStyle);
@@ -8349,7 +8353,7 @@ HTMLEditor::AutoDeleteRangesHandler::ExtendOrShrinkRangeToDelete(
     for (;;) {
       const WSScanResult backwardScanFromStartResult =
           WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
-              closestEditingHost, rangeToDelete.StartRef(),
+              WSRunScanner::Scan::EditableNodes, rangeToDelete.StartRef(),
               BlockInlineCheck::UseComputedDisplayOutsideStyle);
       if (!backwardScanFromStartResult.ReachedCurrentBlockBoundary() &&
           !backwardScanFromStartResult.ReachedInlineEditingHostBoundary()) {

editor/libeditor/HTMLEditorNestedClasses.h

@@ -78,8 +78,7 @@ class MOZ_STACK_CLASS HTMLEditor::AutoInlineStyleSetter final
    * See comments in the definition what this does.
    */
   Result<EditorRawDOMRange, nsresult> ExtendOrShrinkRangeToApplyTheStyle(
-      const HTMLEditor& aHTMLEditor, const EditorDOMRange& aRange,
+      const HTMLEditor& aHTMLEditor, const EditorDOMRange& aRange) const;
-      const Element& aEditingHost) const;
 
   /**
    * Returns next/previous sibling of aContent or an ancestor of it if it's
@@ -104,7 +103,6 @@ class MOZ_STACK_CLASS HTMLEditor::AutoInlineStyleSetter final
    * @param aHTMLEditor                 The editor.
    * @param aCandidatePointToInsert     The point where the caller wants to
    *                                    insert new text.
-   * @param aEditingHost                The editing host.
    * @return            If this creates new empty text node returns it.
    *                    If this couldn't create new empty text node due to
    *                    the point or aEditingHost cannot have text node,
@@ -112,9 +110,8 @@ class MOZ_STACK_CLASS HTMLEditor::AutoInlineStyleSetter final
    *                    Otherwise, returns error.
    */
   [[nodiscard]] MOZ_CAN_RUN_SCRIPT static Result<RefPtr<Text>, nsresult>
-  GetEmptyTextNodeToApplyNewStyle(HTMLEditor& aHTMLEditor,
+  GetEmptyTextNodeToApplyNewStyle(
-                                  const EditorDOMPoint& aCandidatePointToInsert,
+      HTMLEditor& aHTMLEditor, const EditorDOMPoint& aCandidatePointToInsert);
-                                  const Element& aEditingHost);
 
  private:
   [[nodiscard]] MOZ_CAN_RUN_SCRIPT Result<CaretPoint, nsresult> ApplyStyle(

editor/libeditor/HTMLStyleEditor.cpp

@@ -75,12 +75,10 @@ template nsresult HTMLEditor::SetInlinePropertiesAsSubAction(
 
 template nsresult HTMLEditor::SetInlinePropertiesAroundRanges(
     AutoClonedRangeArray& aRanges,
-    const AutoTArray<EditorInlineStyleAndValue, 1>& aStylesToSet,
+    const AutoTArray<EditorInlineStyleAndValue, 1>& aStylesToSet);
-    const Element& aEditingHost);
 template nsresult HTMLEditor::SetInlinePropertiesAroundRanges(
     AutoClonedRangeArray& aRanges,
-    const AutoTArray<EditorInlineStyleAndValue, 32>& aStylesToSet,
+    const AutoTArray<EditorInlineStyleAndValue, 32>& aStylesToSet);
-    const Element& aEditingHost);
 
 nsresult HTMLEditor::SetInlinePropertyAsAction(nsStaticAtom& aProperty,
                                                nsStaticAtom* aAttribute,
@@ -310,8 +308,7 @@ nsresult HTMLEditor::SetInlinePropertiesAsSubAction(
   AutoTransactionsConserveSelection dontChangeMySelection(*this);
 
   AutoClonedSelectionRangeArray selectionRanges(SelectionRef());
-  nsresult rv = SetInlinePropertiesAroundRanges(selectionRanges, aStylesToSet,
+  nsresult rv = SetInlinePropertiesAroundRanges(selectionRanges, aStylesToSet);
-                                                aEditingHost);
   if (NS_FAILED(rv)) {
     NS_WARNING("HTMLEditor::SetInlinePropertiesAroundRanges() failed");
     return rv;
@@ -329,8 +326,7 @@ nsresult HTMLEditor::SetInlinePropertiesAsSubAction(
 template <size_t N>
 nsresult HTMLEditor::SetInlinePropertiesAroundRanges(
     AutoClonedRangeArray& aRanges,
-    const AutoTArray<EditorInlineStyleAndValue, N>& aStylesToSet,
+    const AutoTArray<EditorInlineStyleAndValue, N>& aStylesToSet) {
-    const Element& aEditingHost) {
   MOZ_ASSERT(!aRanges.HasSavedRanges());
   for (const EditorInlineStyleAndValue& styleToSet : aStylesToSet) {
     AutoInlineStyleSetter inlineStyleSetter(styleToSet);
@@ -371,8 +367,7 @@ nsresult HTMLEditor::SetInlinePropertiesAroundRanges(
           }
         }
         Result<EditorRawDOMRange, nsresult> rangeOrError =
-            inlineStyleSetter.ExtendOrShrinkRangeToApplyTheStyle(*this, range,
+            inlineStyleSetter.ExtendOrShrinkRangeToApplyTheStyle(*this, range);
-                                                                 aEditingHost);
         if (MOZ_UNLIKELY(rangeOrError.isErr())) {
           NS_WARNING(
               "HTMLEditor::ExtendOrShrinkRangeToApplyTheStyle() failed, but "
@@ -394,7 +389,7 @@ nsresult HTMLEditor::SetInlinePropertiesAroundRanges(
       if (range.Collapsed()) {
         Result<RefPtr<Text>, nsresult> emptyTextNodeOrError =
             AutoInlineStyleSetter::GetEmptyTextNodeToApplyNewStyle(
-                *this, range.StartRef(), aEditingHost);
+                *this, range.StartRef());
         if (MOZ_UNLIKELY(emptyTextNodeOrError.isErr())) {
           NS_WARNING(
               "AutoInlineStyleSetter::GetEmptyTextNodeToApplyNewStyle() "
@@ -579,11 +574,10 @@ nsresult HTMLEditor::SetInlinePropertiesAroundRanges(
 // static
 Result<RefPtr<Text>, nsresult>
 HTMLEditor::AutoInlineStyleSetter::GetEmptyTextNodeToApplyNewStyle(
-    HTMLEditor& aHTMLEditor, const EditorDOMPoint& aCandidatePointToInsert,
+    HTMLEditor& aHTMLEditor, const EditorDOMPoint& aCandidatePointToInsert) {
-    const Element& aEditingHost) {
   auto pointToInsertNewText =
       HTMLEditUtils::GetBetterCaretPositionToInsertText<EditorDOMPoint>(
-          aCandidatePointToInsert, aEditingHost);
+          aCandidatePointToInsert);
   if (MOZ_UNLIKELY(!pointToInsertNewText.IsSet())) {
     return RefPtr<Text>();  // cannot insert text there
   }
@@ -1925,8 +1919,7 @@ EditorRawDOMRange HTMLEditor::AutoInlineStyleSetter::
 
 Result<EditorRawDOMRange, nsresult>
 HTMLEditor::AutoInlineStyleSetter::ExtendOrShrinkRangeToApplyTheStyle(
-    const HTMLEditor& aHTMLEditor, const EditorDOMRange& aRange,
+    const HTMLEditor& aHTMLEditor, const EditorDOMRange& aRange) const {
-    const Element& aEditingHost) const {
   if (NS_WARN_IF(!aRange.IsPositioned())) {
     return Err(NS_ERROR_FAILURE);
   }
@@ -1945,7 +1938,7 @@ HTMLEditor::AutoInlineStyleSetter::ExtendOrShrinkRangeToApplyTheStyle(
   if (range.EndRef().IsInContentNode()) {
     const WSScanResult nextContentData =
         WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
-            &aEditingHost, range.EndRef(),
+            WSRunScanner::Scan::EditableNodes, range.EndRef(),
             BlockInlineCheck::UseComputedDisplayOutsideStyle);
     if (nextContentData.ReachedInvisibleBRElement() &&
         nextContentData.BRElementPtr()->GetParentElement() &&

editor/libeditor/WSRunScanner.h

@@ -238,6 +238,11 @@ class MOZ_STACK_CLASS WSScanResult final {
    */
   bool IsContentEditable() const { return mContent && mContent->IsEditable(); }
 
+  [[nodiscard]] bool IsContentEditableRoot() const {
+    return mContent && mContent->IsElement() &&
+           HTMLEditUtils::ElementIsEditableRoot(*mContent->AsElement());
+  }
+
   /**
    * Offset_Deprecated() returns meaningful value only when
    * InVisibleOrCollapsibleCharacters() returns true or the scanner reached to
@@ -455,10 +460,10 @@ class MOZ_STACK_CLASS WSRunScanner final {
       const EditorDOMPointBase<PT, CT>& aPoint) const;
   template <typename PT, typename CT>
   static WSScanResult ScanInclusiveNextVisibleNodeOrBlockBoundary(
-      const Element* aEditingHost, const EditorDOMPointBase<PT, CT>& aPoint,
+      Scan aScanMode, const EditorDOMPointBase<PT, CT>& aPoint,
-      BlockInlineCheck aBlockInlineCheck) {
+      BlockInlineCheck aBlockInlineCheck,
-    return WSRunScanner(Scan::EditableNodes, aPoint, aBlockInlineCheck,
+      const Element* aAncestorLimiter = nullptr) {
-                        aEditingHost)
+    return WSRunScanner(aScanMode, aPoint, aBlockInlineCheck, aAncestorLimiter)
         .ScanInclusiveNextVisibleNodeOrBlockBoundaryFrom(aPoint);
   }
 
@@ -473,10 +478,10 @@ class MOZ_STACK_CLASS WSRunScanner final {
       const EditorDOMPointBase<PT, CT>& aPoint) const;
   template <typename PT, typename CT>
   static WSScanResult ScanPreviousVisibleNodeOrBlockBoundary(
-      const Element* aEditingHost, const EditorDOMPointBase<PT, CT>& aPoint,
+      Scan aScanMode, const EditorDOMPointBase<PT, CT>& aPoint,
-      BlockInlineCheck aBlockInlineCheck) {
+      BlockInlineCheck aBlockInlineCheck,
-    return WSRunScanner(Scan::EditableNodes, aPoint, aBlockInlineCheck,
+      const Element* aAncestorLimiter = nullptr) {
-                        aEditingHost)
+    return WSRunScanner(aScanMode, aPoint, aBlockInlineCheck, aAncestorLimiter)
         .ScanPreviousVisibleNodeOrBlockBoundaryFrom(aPoint);
   }