Adding upstream version 110.0.1.upstream/110.0.1upstream

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

1 files changed, 2275 insertions, 0 deletions

diff --git a/editor/libeditor/HTMLEditUtils.cpp b/editor/libeditor/HTMLEditUtils.cpp
new file mode 100644
index 0000000000..41d887dfd0
--- /dev/null
+++ b/editor/libeditor/HTMLEditUtils.cpp
@@ -0,0 +1,2275 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "HTMLEditUtils.h"
+
+#include "AutoRangeArray.h"   // for AutoRangeArray
+#include "CSSEditUtils.h"     // for CSSEditUtils
+#include "EditAction.h"       // for EditAction
+#include "EditorBase.h"       // for EditorBase, EditorType
+#include "EditorDOMPoint.h"   // for EditorDOMPoint, etc.
+#include "EditorForwards.h"   // for CollectChildrenOptions
+#include "EditorUtils.h"      // for EditorUtils
+#include "HTMLEditHelpers.h"  // for EditorInlineStyle
+#include "WSRunObject.h"      // for WSRunScanner
+
+#include "mozilla/ArrayUtils.h"   // for ArrayLength
+#include "mozilla/Assertions.h"   // for MOZ_ASSERT, etc.
+#include "mozilla/RangeUtils.h"   // for RangeUtils
+#include "mozilla/dom/Element.h"  // for Element, nsINode
+#include "mozilla/dom/HTMLAnchorElement.h"
+#include "mozilla/dom/HTMLInputElement.h"
+#include "mozilla/dom/StaticRange.h"
+#include "mozilla/dom/Text.h"  // for Text
+
+#include "nsAString.h"  // for nsAString::IsEmpty
+#include "nsAtom.h"     // for nsAtom
+#include "nsCaseTreatment.h"
+#include "nsCOMPtr.h"            // for nsCOMPtr, operator==, etc.
+#include "nsComputedDOMStyle.h"  // for nsComputedDOMStyle
+#include "nsDebug.h"             // for NS_ASSERTION, etc.
+#include "nsElementTable.h"      // for nsHTMLElement
+#include "nsError.h"             // for NS_SUCCEEDED
+#include "nsGkAtoms.h"           // for nsGkAtoms, nsGkAtoms::a, etc.
+#include "nsHTMLTags.h"
+#include "nsLiteralString.h"     // for NS_LITERAL_STRING
+#include "nsNameSpaceManager.h"  // for kNameSpaceID_None
+#include "nsString.h"            // for nsAutoString
+#include "nsStyledElement.h"
+#include "nsTextFragment.h"  // for nsTextFragment
+#include "nsTextFrame.h"     // for nsTextFrame
+
+namespace mozilla {
+
+using namespace dom;
+using EditorType = EditorBase::EditorType;
+
+template nsIContent* HTMLEditUtils::GetPreviousContent(
+    const EditorDOMPoint& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+template nsIContent* HTMLEditUtils::GetPreviousContent(
+    const EditorRawDOMPoint& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+template nsIContent* HTMLEditUtils::GetPreviousContent(
+    const EditorDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+template nsIContent* HTMLEditUtils::GetPreviousContent(
+    const EditorRawDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+template nsIContent* HTMLEditUtils::GetNextContent(
+    const EditorDOMPoint& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+template nsIContent* HTMLEditUtils::GetNextContent(
+    const EditorRawDOMPoint& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+template nsIContent* HTMLEditUtils::GetNextContent(
+    const EditorDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+template nsIContent* HTMLEditUtils::GetNextContent(
+    const EditorRawDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter);
+
+template EditorDOMPoint HTMLEditUtils::GetPreviousEditablePoint(
+    nsIContent& aContent, const Element* aAncestorLimiter,
+    InvisibleWhiteSpaces aInvisibleWhiteSpaces,
+    TableBoundary aHowToTreatTableBoundary);
+template EditorRawDOMPoint HTMLEditUtils::GetPreviousEditablePoint(
+    nsIContent& aContent, const Element* aAncestorLimiter,
+    InvisibleWhiteSpaces aInvisibleWhiteSpaces,
+    TableBoundary aHowToTreatTableBoundary);
+template EditorDOMPoint HTMLEditUtils::GetNextEditablePoint(
+    nsIContent& aContent, const Element* aAncestorLimiter,
+    InvisibleWhiteSpaces aInvisibleWhiteSpaces,
+    TableBoundary aHowToTreatTableBoundary);
+template EditorRawDOMPoint HTMLEditUtils::GetNextEditablePoint(
+    nsIContent& aContent, const Element* aAncestorLimiter,
+    InvisibleWhiteSpaces aInvisibleWhiteSpaces,
+    TableBoundary aHowToTreatTableBoundary);
+
+template nsIContent* HTMLEditUtils::GetContentToPreserveInlineStyles(
+    const EditorDOMPoint& aPoint, const Element& aEditingHost);
+template nsIContent* HTMLEditUtils::GetContentToPreserveInlineStyles(
+    const EditorRawDOMPoint& aPoint, const Element& aEditingHost);
+
+template EditorDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
+    const nsIContent& aContentToInsert, const EditorDOMPoint& aPointToInsert,
+    const Element& aEditingHost);
+template EditorRawDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
+    const nsIContent& aContentToInsert, const EditorRawDOMPoint& aPointToInsert,
+    const Element& aEditingHost);
+template EditorDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
+    const nsIContent& aContentToInsert, const EditorRawDOMPoint& aPointToInsert,
+    const Element& aEditingHost);
+template EditorRawDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
+    const nsIContent& aContentToInsert, const EditorDOMPoint& aPointToInsert,
+    const Element& aEditingHost);
+
+template Result<EditorDOMPoint, nsresult>
+HTMLEditUtils::ComputePointToPutCaretInElementIfOutside(
+    const Element& aElement, const EditorDOMPoint& aCurrentPoint);
+template Result<EditorRawDOMPoint, nsresult>
+HTMLEditUtils::ComputePointToPutCaretInElementIfOutside(
+    const Element& aElement, const EditorDOMPoint& aCurrentPoint);
+template Result<EditorDOMPoint, nsresult>
+HTMLEditUtils::ComputePointToPutCaretInElementIfOutside(
+    const Element& aElement, const EditorRawDOMPoint& aCurrentPoint);
+template Result<EditorRawDOMPoint, nsresult>
+HTMLEditUtils::ComputePointToPutCaretInElementIfOutside(
+    const Element& aElement, const EditorRawDOMPoint& aCurrentPoint);
+
+bool HTMLEditUtils::CanContentsBeJoined(const nsIContent& aLeftContent,
+                                        const nsIContent& aRightContent,
+                                        StyleDifference aStyleDifference) {
+  if (aLeftContent.NodeInfo()->NameAtom() !=
+      aRightContent.NodeInfo()->NameAtom()) {
+    return false;
+  }
+  if (aStyleDifference == StyleDifference::Ignore ||
+      !aLeftContent.IsElement()) {
+    return true;
+  }
+  if (aStyleDifference == StyleDifference::CompareIfSpanElements &&
+      !aLeftContent.IsHTMLElement(nsGkAtoms::span)) {
+    return true;
+  }
+  if (!aLeftContent.IsElement() || !aRightContent.IsElement()) {
+    return false;
+  }
+  nsStyledElement* leftStyledElement =
+      nsStyledElement::FromNode(const_cast<nsIContent*>(&aLeftContent));
+  if (!leftStyledElement) {
+    return false;
+  }
+  nsStyledElement* rightStyledElement =
+      nsStyledElement::FromNode(const_cast<nsIContent*>(&aRightContent));
+  if (!rightStyledElement) {
+    return false;
+  }
+  return CSSEditUtils::DoStyledElementsHaveSameStyle(*leftStyledElement,
+                                                     *rightStyledElement);
+}
+
+bool HTMLEditUtils::IsBlockElement(const nsIContent& aContent) {
+  if (!aContent.IsElement()) {
+    return false;
+  }
+  if (aContent.IsHTMLElement(nsGkAtoms::br)) {  // shortcut for TextEditor
+    MOZ_ASSERT(!nsHTMLElement::IsBlock(nsHTMLTags::AtomTagToId(nsGkAtoms::br)));
+    return false;
+  }
+  // We want to treat these as block nodes even though nsHTMLElement says
+  // they're not.
+  if (aContent.IsAnyOfHTMLElements(
+          nsGkAtoms::body, nsGkAtoms::head, nsGkAtoms::tbody, nsGkAtoms::thead,
+          nsGkAtoms::tfoot, nsGkAtoms::tr, nsGkAtoms::th, nsGkAtoms::td,
+          nsGkAtoms::dt, nsGkAtoms::dd)) {
+    return true;
+  }
+
+  return nsHTMLElement::IsBlock(
+      nsHTMLTags::AtomTagToId(aContent.NodeInfo()->NameAtom()));
+}
+
+bool HTMLEditUtils::IsVisibleElementEvenIfLeafNode(const nsIContent& aContent) {
+  if (!aContent.IsElement()) {
+    return false;
+  }
+  // Assume non-HTML element is visible.
+  if (!aContent.IsHTMLElement()) {
+    return true;
+  }
+  if (HTMLEditUtils::IsBlockElement(aContent)) {
+    return true;
+  }
+  if (aContent.IsAnyOfHTMLElements(nsGkAtoms::applet, nsGkAtoms::iframe,
+                                   nsGkAtoms::img, nsGkAtoms::meter,
+                                   nsGkAtoms::progress, nsGkAtoms::select,
+                                   nsGkAtoms::textarea)) {
+    return true;
+  }
+  if (const HTMLInputElement* inputElement =
+          HTMLInputElement::FromNode(&aContent)) {
+    return inputElement->ControlType() != FormControlType::InputHidden;
+  }
+  // Maybe, empty inline element such as <span>.
+  return false;
+}
+
+/**
+ * IsInlineStyle() returns true if aNode is an inline style.
+ */
+bool HTMLEditUtils::IsInlineStyle(nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(
+      nsGkAtoms::b, nsGkAtoms::i, nsGkAtoms::u, nsGkAtoms::tt, nsGkAtoms::s,
+      nsGkAtoms::strike, nsGkAtoms::big, nsGkAtoms::small, nsGkAtoms::sub,
+      nsGkAtoms::sup, nsGkAtoms::font);
+}
+
+bool HTMLEditUtils::IsDisplayOutsideInline(const Element& aElement) {
+  RefPtr<const ComputedStyle> elementStyle =
+      nsComputedDOMStyle::GetComputedStyleNoFlush(&aElement);
+  if (!elementStyle) {
+    return false;
+  }
+  return elementStyle->StyleDisplay()->DisplayOutside() ==
+         StyleDisplayOutside::Inline;
+}
+
+bool HTMLEditUtils::IsDisplayInsideFlowRoot(const Element& aElement) {
+  RefPtr<const ComputedStyle> elementStyle =
+      nsComputedDOMStyle::GetComputedStyleNoFlush(&aElement);
+  if (!elementStyle) {
+    return false;
+  }
+  return elementStyle->StyleDisplay()->DisplayInside() ==
+         StyleDisplayInside::FlowRoot;
+}
+
+bool HTMLEditUtils::IsRemovableInlineStyleElement(Element& aElement) {
+  if (!aElement.IsHTMLElement()) {
+    return false;
+  }
+  // https://w3c.github.io/editing/execCommand.html#removeformat-candidate
+  if (aElement.IsAnyOfHTMLElements(
+          nsGkAtoms::abbr,  // Chrome ignores, but does not make sense.
+          nsGkAtoms::acronym, nsGkAtoms::b,
+          nsGkAtoms::bdi,  // Chrome ignores, but does not make sense.
+          nsGkAtoms::bdo, nsGkAtoms::big, nsGkAtoms::cite, nsGkAtoms::code,
+          // nsGkAtoms::del, Chrome ignores, but does not make sense but
+          // execCommand unofficial draft excludes this.  Spec issue:
+          // https://github.com/w3c/editing/issues/192
+          nsGkAtoms::dfn, nsGkAtoms::em, nsGkAtoms::font, nsGkAtoms::i,
+          nsGkAtoms::ins, nsGkAtoms::kbd,
+          nsGkAtoms::mark,  // Chrome ignores, but does not make sense.
+          nsGkAtoms::nobr, nsGkAtoms::q, nsGkAtoms::s, nsGkAtoms::samp,
+          nsGkAtoms::small, nsGkAtoms::span, nsGkAtoms::strike,
+          nsGkAtoms::strong, nsGkAtoms::sub, nsGkAtoms::sup, nsGkAtoms::tt,
+          nsGkAtoms::u, nsGkAtoms::var)) {
+    return true;
+  }
+  // If it's a <blink> element, we can remove it.
+  nsAutoString tagName;
+  aElement.GetTagName(tagName);
+  return tagName.LowerCaseEqualsASCII("blink");
+}
+
+/**
+ * IsFormatNode() returns true if aNode is a format node.
+ */
+bool HTMLEditUtils::IsFormatNode(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(
+      nsGkAtoms::p, nsGkAtoms::pre, nsGkAtoms::h1, nsGkAtoms::h2, nsGkAtoms::h3,
+      nsGkAtoms::h4, nsGkAtoms::h5, nsGkAtoms::h6, nsGkAtoms::address);
+}
+
+/**
+ * IsNodeThatCanOutdent() returns true if aNode is a list, list item or
+ * blockquote.
+ */
+bool HTMLEditUtils::IsNodeThatCanOutdent(nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(nsGkAtoms::ul, nsGkAtoms::ol, nsGkAtoms::dl,
+                                    nsGkAtoms::li, nsGkAtoms::dd, nsGkAtoms::dt,
+                                    nsGkAtoms::blockquote);
+}
+
+/**
+ * IsHeader() returns true if aNode is an html header.
+ */
+bool HTMLEditUtils::IsHeader(nsINode& aNode) {
+  return aNode.IsAnyOfHTMLElements(nsGkAtoms::h1, nsGkAtoms::h2, nsGkAtoms::h3,
+                                   nsGkAtoms::h4, nsGkAtoms::h5, nsGkAtoms::h6);
+}
+
+/**
+ * IsListItem() returns true if aNode is an html list item.
+ */
+bool HTMLEditUtils::IsListItem(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(nsGkAtoms::li, nsGkAtoms::dd,
+                                    nsGkAtoms::dt);
+}
+
+/**
+ * IsAnyTableElement() returns true if aNode is an html table, td, tr, ...
+ */
+bool HTMLEditUtils::IsAnyTableElement(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(
+      nsGkAtoms::table, nsGkAtoms::tr, nsGkAtoms::td, nsGkAtoms::th,
+      nsGkAtoms::thead, nsGkAtoms::tfoot, nsGkAtoms::tbody, nsGkAtoms::caption);
+}
+
+/**
+ * IsAnyTableElementButNotTable() returns true if aNode is an html td, tr, ...
+ * (doesn't include table)
+ */
+bool HTMLEditUtils::IsAnyTableElementButNotTable(nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(nsGkAtoms::tr, nsGkAtoms::td, nsGkAtoms::th,
+                                    nsGkAtoms::thead, nsGkAtoms::tfoot,
+                                    nsGkAtoms::tbody, nsGkAtoms::caption);
+}
+
+/**
+ * IsTable() returns true if aNode is an html table.
+ */
+bool HTMLEditUtils::IsTable(nsINode* aNode) {
+  return aNode && aNode->IsHTMLElement(nsGkAtoms::table);
+}
+
+/**
+ * IsTableRow() returns true if aNode is an html tr.
+ */
+bool HTMLEditUtils::IsTableRow(nsINode* aNode) {
+  return aNode && aNode->IsHTMLElement(nsGkAtoms::tr);
+}
+
+/**
+ * IsTableCell() returns true if aNode is an html td or th.
+ */
+bool HTMLEditUtils::IsTableCell(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(nsGkAtoms::td, nsGkAtoms::th);
+}
+
+/**
+ * IsTableCellOrCaption() returns true if aNode is an html td or th or caption.
+ */
+bool HTMLEditUtils::IsTableCellOrCaption(nsINode& aNode) {
+  return aNode.IsAnyOfHTMLElements(nsGkAtoms::td, nsGkAtoms::th,
+                                   nsGkAtoms::caption);
+}
+
+/**
+ * IsAnyListElement() returns true if aNode is an html list.
+ */
+bool HTMLEditUtils::IsAnyListElement(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(nsGkAtoms::ul, nsGkAtoms::ol,
+                                    nsGkAtoms::dl);
+}
+
+/**
+ * IsPre() returns true if aNode is an html pre node.
+ */
+bool HTMLEditUtils::IsPre(const nsINode* aNode) {
+  return aNode && aNode->IsHTMLElement(nsGkAtoms::pre);
+}
+
+/**
+ * IsImage() returns true if aNode is an html image node.
+ */
+bool HTMLEditUtils::IsImage(nsINode* aNode) {
+  return aNode && aNode->IsHTMLElement(nsGkAtoms::img);
+}
+
+bool HTMLEditUtils::IsLink(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+
+  if (!aNode->IsContent()) {
+    return false;
+  }
+
+  RefPtr<const dom::HTMLAnchorElement> anchor =
+      dom::HTMLAnchorElement::FromNodeOrNull(aNode->AsContent());
+  if (!anchor) {
+    return false;
+  }
+
+  nsAutoString tmpText;
+  anchor->GetHref(tmpText);
+  return !tmpText.IsEmpty();
+}
+
+bool HTMLEditUtils::IsNamedAnchor(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  if (!aNode->IsHTMLElement(nsGkAtoms::a)) {
+    return false;
+  }
+
+  nsAutoString text;
+  return aNode->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::name,
+                                     text) &&
+         !text.IsEmpty();
+}
+
+/**
+ * IsMozDiv() returns true if aNode is an html div node with |type = _moz|.
+ */
+bool HTMLEditUtils::IsMozDiv(nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsHTMLElement(nsGkAtoms::div) &&
+         aNode->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::type,
+                                         u"_moz"_ns, eIgnoreCase);
+}
+
+/**
+ * IsMailCite() returns true if aNode is an html blockquote with |type=cite|.
+ */
+bool HTMLEditUtils::IsMailCite(const Element& aElement) {
+  // don't ask me why, but our html mailcites are id'd by "type=cite"...
+  if (aElement.AttrValueIs(kNameSpaceID_None, nsGkAtoms::type, u"cite"_ns,
+                           eIgnoreCase)) {
+    return true;
+  }
+
+  // ... but our plaintext mailcites by "_moz_quote=true".  go figure.
+  if (aElement.AttrValueIs(kNameSpaceID_None, nsGkAtoms::mozquote, u"true"_ns,
+                           eIgnoreCase)) {
+    return true;
+  }
+
+  return false;
+}
+
+/**
+ * IsFormWidget() returns true if aNode is a form widget of some kind.
+ */
+bool HTMLEditUtils::IsFormWidget(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->IsAnyOfHTMLElements(nsGkAtoms::textarea, nsGkAtoms::select,
+                                    nsGkAtoms::button, nsGkAtoms::output,
+                                    nsGkAtoms::progress, nsGkAtoms::meter,
+                                    nsGkAtoms::input);
+}
+
+bool HTMLEditUtils::SupportsAlignAttr(nsINode& aNode) {
+  return aNode.IsAnyOfHTMLElements(
+      nsGkAtoms::hr, nsGkAtoms::table, nsGkAtoms::tbody, nsGkAtoms::tfoot,
+      nsGkAtoms::thead, nsGkAtoms::tr, nsGkAtoms::td, nsGkAtoms::th,
+      nsGkAtoms::div, nsGkAtoms::p, nsGkAtoms::h1, nsGkAtoms::h2, nsGkAtoms::h3,
+      nsGkAtoms::h4, nsGkAtoms::h5, nsGkAtoms::h6);
+}
+
+bool HTMLEditUtils::IsVisibleTextNode(const Text& aText) {
+  if (!aText.TextDataLength()) {
+    return false;
+  }
+
+  Maybe<uint32_t> visibleCharOffset =
+      HTMLEditUtils::GetInclusiveNextNonCollapsibleCharOffset(
+          EditorDOMPointInText(&aText, 0));
+  if (visibleCharOffset.isSome()) {
+    return true;
+  }
+
+  // Now, all characters in aText is collapsible white-spaces.  The node is
+  // invisible if next to block boundary.
+  return !HTMLEditUtils::GetElementOfImmediateBlockBoundary(
+             aText, WalkTreeDirection::Forward) &&
+         !HTMLEditUtils::GetElementOfImmediateBlockBoundary(
+             aText, WalkTreeDirection::Backward);
+}
+
+bool HTMLEditUtils::IsInVisibleTextFrames(nsPresContext* aPresContext,
+                                          const Text& aText) {
+  // TODO(dholbert): aPresContext is now unused; maybe we can remove it, here
+  // and in IsEmptyNode?  We do use it as a signal (implicitly here,
+  // more-explicitly in IsEmptyNode) that we are in a "SafeToAskLayout" case...
+  // If/when we remove it, we should be sure we're not losing that signal of
+  // strictness, since this function here does absolutely need to query layout.
+  MOZ_ASSERT(aPresContext);
+
+  if (!aText.TextDataLength()) {
+    return false;
+  }
+
+  nsTextFrame* textFrame = do_QueryFrame(aText.GetPrimaryFrame());
+  if (!textFrame) {
+    return false;
+  }
+
+  return textFrame->HasVisibleText();
+}
+
+Element* HTMLEditUtils::GetElementOfImmediateBlockBoundary(
+    const nsIContent& aContent, const WalkTreeDirection aDirection) {
+  MOZ_ASSERT(aContent.IsHTMLElement(nsGkAtoms::br) || aContent.IsText());
+
+  // First, we get a block container.  This is not designed for reaching
+  // no block boundaries in the tree.
+  Element* maybeNonEditableAncestorBlock = HTMLEditUtils::GetAncestorElement(
+      aContent, HTMLEditUtils::ClosestBlockElement);
+  if (NS_WARN_IF(!maybeNonEditableAncestorBlock)) {
+    return nullptr;
+  }
+
+  auto getNextContent = [&aDirection, &maybeNonEditableAncestorBlock](
+                            const nsIContent& aContent) -> nsIContent* {
+    return aDirection == WalkTreeDirection::Forward
+               ? HTMLEditUtils::GetNextContent(
+                     aContent,
+                     {WalkTreeOption::IgnoreDataNodeExceptText,
+                      WalkTreeOption::StopAtBlockBoundary},
+                     maybeNonEditableAncestorBlock)
+               : HTMLEditUtils::GetPreviousContent(
+                     aContent,
+                     {WalkTreeOption::IgnoreDataNodeExceptText,
+                      WalkTreeOption::StopAtBlockBoundary},
+                     maybeNonEditableAncestorBlock);
+  };
+
+  // Then, scan block element boundary while we don't see visible things.
+  const bool isBRElement = aContent.IsHTMLElement(nsGkAtoms::br);
+  for (nsIContent* nextContent = getNextContent(aContent); nextContent;
+       nextContent = getNextContent(*nextContent)) {
+    if (nextContent->IsElement()) {
+      // Break is right before a child block, it's not visible
+      if (HTMLEditUtils::IsBlockElement(*nextContent)) {
+        return nextContent->AsElement();
+      }
+
+      // XXX How about other non-HTML elements?  Assume they are styled as
+      //     blocks for now.
+      if (!nextContent->IsHTMLElement()) {
+        return nextContent->AsElement();
+      }
+
+      // If there is a visible content which generates something visible,
+      // stop scanning.
+      if (HTMLEditUtils::IsVisibleElementEvenIfLeafNode(*nextContent)) {
+        return nullptr;
+      }
+
+      if (nextContent->IsHTMLElement(nsGkAtoms::br)) {
+        // If aContent is a <br> element, another <br> element prevents the
+        // block boundary special handling.
+        if (isBRElement) {
+          return nullptr;
+        }
+
+        MOZ_ASSERT(aContent.IsText());
+        // Following <br> element always hides its following block boundary.
+        // I.e., white-spaces is at end of the text node is visible.
+        if (aDirection == WalkTreeDirection::Forward) {
+          return nullptr;
+        }
+        // Otherwise, if text node follows <br> element, its white-spaces at
+        // start of the text node are invisible.  In this case, we return
+        // the found <br> element.
+        return nextContent->AsElement();
+      }
+
+      continue;
+    }
+
+    Text* textNode = Text::FromNode(nextContent);
+    if (NS_WARN_IF(!textNode)) {
+      continue;  // XXX Is this possible?
+    }
+    if (!textNode->TextLength()) {
+      continue;  // empty invisible text node, keep scanning next one.
+    }
+    if (!textNode->TextIsOnlyWhitespace()) {
+      return nullptr;  // found a visible text node.
+    }
+    const nsTextFragment& textFragment = textNode->TextFragment();
+    const bool isWhiteSpacePreformatted =
+        EditorUtils::IsWhiteSpacePreformatted(*textNode);
+    const bool isNewLinePreformatted =
+        EditorUtils::IsNewLinePreformatted(*textNode);
+    if (!isWhiteSpacePreformatted && !isNewLinePreformatted) {
+      // if the white-space only text node is not preformatted, ignore it.
+      continue;
+    }
+    for (uint32_t i = 0; i < textFragment.GetLength(); i++) {
+      if (textFragment.CharAt(i) == HTMLEditUtils::kNewLine) {
+        if (isNewLinePreformatted) {
+          return nullptr;  // found a visible text node.
+        }
+        continue;
+      }
+      if (isWhiteSpacePreformatted) {
+        return nullptr;  // found a visible text node.
+      }
+    }
+    // All white-spaces in the text node is invisible, keep scanning next one.
+  }
+
+  // There is no visible content and reached current block boundary.  Then,
+  // the <br> element is the last content in the block and invisible.
+  // XXX Should we treat it visible if it's the only child of a block?
+  return maybeNonEditableAncestorBlock;
+}
+
+nsIContent* HTMLEditUtils::GetUnnecessaryLineBreakContent(
+    const Element& aBlockElement, ScanLineBreak aScanLineBreak) {
+  auto* lastLineBreakContent = [&]() -> nsIContent* {
+    const LeafNodeTypes leafNodeOrNonEditableNode{
+        LeafNodeType::LeafNodeOrNonEditableNode};
+    const WalkTreeOptions onlyPrecedingLine{
+        WalkTreeOption::StopAtBlockBoundary};
+    for (nsIContent* content =
+             aScanLineBreak == ScanLineBreak::AtEndOfBlock
+                 ? HTMLEditUtils::GetLastLeafContent(aBlockElement,
+                                                     leafNodeOrNonEditableNode)
+                 : HTMLEditUtils::GetPreviousContent(
+                       aBlockElement, onlyPrecedingLine,
+                       aBlockElement.GetParentElement());
+         content;
+         content =
+             aScanLineBreak == ScanLineBreak::AtEndOfBlock
+                 ? HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
+                       *content, aBlockElement, leafNodeOrNonEditableNode)
+                 : HTMLEditUtils::GetPreviousContent(
+                       *content, onlyPrecedingLine,
+                       aBlockElement.GetParentElement())) {
+      // If we're scanning preceding <br> element of aBlockElement, we don't
+      // need to look for a line break in another block because the caller
+      // needs to handle only preceding <br> element of aBlockElement.
+      if (aScanLineBreak == ScanLineBreak::BeforeBlock &&
+          HTMLEditUtils::IsBlockElement(*content)) {
+        return nullptr;
+      }
+      if (Text* textNode = Text::FromNode(content)) {
+        if (!textNode->TextLength()) {
+          continue;  // ignore empty text node
+        }
+        const nsTextFragment& textFragment = textNode->TextFragment();
+        if (EditorUtils::IsNewLinePreformatted(*textNode) &&
+            textFragment.CharAt(textFragment.GetLength() - 1u) ==
+                HTMLEditUtils::kNewLine) {
+          // If the text node ends with a preserved line break, it's unnecessary
+          // unless it follows another preformatted line break.
+          if (textFragment.GetLength() == 1u) {
+            return textNode;  // Need to scan previous leaf.
+          }
+          return textFragment.CharAt(textFragment.GetLength() - 2u) ==
+                         HTMLEditUtils::kNewLine
+                     ? nullptr
+                     : textNode;
+        }
+        if (HTMLEditUtils::IsVisibleTextNode(*textNode)) {
+          return nullptr;
+        }
+        continue;
+      }
+      if (content->IsCharacterData()) {
+        continue;  // ignore hidden character data nodes like comment
+      }
+      if (content->IsHTMLElement(nsGkAtoms::br)) {
+        return content;
+      }
+      // If found element is empty block or visible element, there is no
+      // unnecessary line break.
+      if (HTMLEditUtils::IsVisibleElementEvenIfLeafNode(*content)) {
+        return nullptr;
+      }
+      // Otherwise, e.g., empty <b>, we should keep scanning.
+    }
+    return nullptr;
+  }();
+  if (!lastLineBreakContent) {
+    return nullptr;
+  }
+
+  // If the found node is a text node and contains only one preformatted new
+  // line break, we need to keep scanning previous one, but if it has 2 or more
+  // characters, we know it has redundant line break.
+  Text* lastLineBreakText = Text::FromNode(lastLineBreakContent);
+  if (lastLineBreakText && lastLineBreakText->TextDataLength() != 1u) {
+    return lastLineBreakText;
+  }
+
+  // Scan previous leaf content, but now, we can stop at child block boundary.
+  const LeafNodeTypes leafNodeOrNonEditableNodeOrChildBlock{
+      LeafNodeType::LeafNodeOrNonEditableNode,
+      LeafNodeType::LeafNodeOrChildBlock};
+  const Element* blockElement = HTMLEditUtils::GetAncestorElement(
+      *lastLineBreakContent, HTMLEditUtils::ClosestBlockElement);
+  for (nsIContent* content =
+           HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
+               *lastLineBreakContent, *blockElement,
+               leafNodeOrNonEditableNodeOrChildBlock);
+       content;
+       content = HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
+           *content, *blockElement, leafNodeOrNonEditableNodeOrChildBlock)) {
+    if (HTMLEditUtils::IsBlockElement(*content) ||
+        (content->IsElement() && !content->IsHTMLElement())) {
+      // Now, must found <div>...<div>...</div><br></div>
+      //                                       ^^^^
+      // In this case, the <br> element is necessary to make a following empty
+      // line of the inner <div> visible.
+      return nullptr;
+    }
+    if (Text* textNode = Text::FromNode(content)) {
+      if (!textNode->TextLength()) {
+        continue;  // ignore empty text node
+      }
+      const nsTextFragment& textFragment = textNode->TextFragment();
+      if (EditorUtils::IsNewLinePreformatted(*textNode) &&
+          textFragment.CharAt(textFragment.GetLength() - 1u) ==
+              HTMLEditUtils::kNewLine) {
+        // So, we are here because the preformatted line break is followed by
+        // lastLineBreakContent which is <br> or a text node containing only
+        // one.  In this case, even if their parents are different,
+        // lastLineBreakContent is necessary to make the last line visible.
+        return nullptr;
+      }
+      if (!HTMLEditUtils::IsVisibleTextNode(*textNode)) {
+        continue;
+      }
+      if (EditorUtils::IsWhiteSpacePreformatted(*textNode)) {
+        // If the white-space is preserved, neither following <br> nor a
+        // preformatted line break is not necessary.
+        return lastLineBreakContent;
+      }
+      // Otherwise, only if the last character is a collapsible white-space,
+      // we need lastLineBreakContent to make the trailing white-space visible.
+      switch (textFragment.CharAt(textFragment.GetLength() - 1u)) {
+        case HTMLEditUtils::kSpace:
+        case HTMLEditUtils::kCarriageReturn:
+        case HTMLEditUtils::kTab:
+        case HTMLEditUtils::kNBSP:
+          return nullptr;
+        default:
+          return lastLineBreakContent;
+      }
+    }
+    if (content->IsCharacterData()) {
+      continue;  // ignore hidden character data nodes like comment
+    }
+    // If lastLineBreakContent follows a <br> element in same block, it's
+    // necessary to make the empty last line visible.
+    if (content->IsHTMLElement(nsGkAtoms::br)) {
+      return nullptr;
+    }
+    // If it follows a visible element, it's unnecessary line break.
+    if (HTMLEditUtils::IsVisibleElementEvenIfLeafNode(*content)) {
+      return lastLineBreakContent;
+    }
+    // Otherwise, ignore empty inline elements such as <b>.
+  }
+  // If the block is empty except invisible data nodes and lastLineBreakContent,
+  // lastLineBreakContent is necessary to make the block visible.
+  return nullptr;
+}
+
+bool HTMLEditUtils::IsEmptyNode(nsPresContext* aPresContext,
+                                const nsINode& aNode,
+                                const EmptyCheckOptions& aOptions /* = {} */,
+                                bool* aSeenBR /* = nullptr */) {
+  MOZ_ASSERT_IF(aOptions.contains(EmptyCheckOption::SafeToAskLayout),
+                aPresContext);
+
+  if (aSeenBR) {
+    *aSeenBR = false;
+  }
+
+  if (const Text* text = Text::FromNode(&aNode)) {
+    return aOptions.contains(EmptyCheckOption::SafeToAskLayout)
+               ? !IsInVisibleTextFrames(aPresContext, *text)
+               : !IsVisibleTextNode(*text);
+  }
+
+  // XXX Why do we treat non-content node is not empty?
+  // XXX Why do we treat non-text data node may be not empty?
+  if (!aNode.IsContent() ||
+      // If it's not a container such as an <hr> or <br>, etc, it should be
+      // treated as not empty.
+      !IsContainerNode(*aNode.AsContent()) ||
+      // If it's a named anchor, we shouldn't treat it as empty because it
+      // has special meaning even if invisible.
+      IsNamedAnchor(&aNode) ||
+      // Form widgets should be treated as not empty because they have special
+      // meaning even if invisible.
+      IsFormWidget(&aNode) ||
+      // If the caller treats a list item element as visible, respect it.
+      (aOptions.contains(EmptyCheckOption::TreatListItemAsVisible) &&
+       IsListItem(&aNode)) ||
+      // If the caller treats a table cell element as visible, respect it.
+      (aOptions.contains(EmptyCheckOption::TreatTableCellAsVisible) &&
+       IsTableCell(&aNode))) {
+    return false;
+  }
+
+  const bool isListItem = IsListItem(&aNode);
+  const bool isTableCell = IsTableCell(&aNode);
+
+  bool seenBR = aSeenBR && *aSeenBR;
+  for (nsIContent* childContent = aNode.GetFirstChild(); childContent;
+       childContent = childContent->GetNextSibling()) {
+    // Is the child editable and non-empty?  if so, return false
+    if (!aOptions.contains(EmptyCheckOption::IgnoreEditableState) &&
+        !EditorUtils::IsEditableContent(*childContent, EditorType::HTML)) {
+      continue;
+    }
+
+    if (Text* text = Text::FromNode(childContent)) {
+      // break out if we find we aren't empty
+      if (aOptions.contains(EmptyCheckOption::SafeToAskLayout)
+              ? IsInVisibleTextFrames(aPresContext, *text)
+              : IsVisibleTextNode(*text)) {
+        return false;
+      }
+      continue;
+    }
+
+    // An editable, non-text node. We need to check its content.
+    // Is it the node we are iterating over?
+    if (childContent == &aNode) {
+      break;
+    }
+
+    if (!aOptions.contains(EmptyCheckOption::TreatSingleBRElementAsVisible) &&
+        !seenBR && childContent->IsHTMLElement(nsGkAtoms::br)) {
+      // Ignore first <br> element in it if caller wants so because it's
+      // typically a padding <br> element of for a parent block.
+      seenBR = true;
+      if (aSeenBR) {
+        *aSeenBR = true;
+      }
+      continue;
+    }
+
+    // is it an empty node of some sort?
+    // note: list items or table cells are not considered empty
+    // if they contain other lists or tables
+    if (childContent->IsElement()) {
+      if (isListItem || isTableCell) {
+        if (IsAnyListElement(childContent) ||
+            childContent->IsHTMLElement(nsGkAtoms::table)) {
+          // break out if we find we aren't empty
+          return false;
+        }
+      } else if (IsFormWidget(childContent)) {
+        // is it a form widget?
+        // break out if we find we aren't empty
+        return false;
+      }
+    }
+
+    if (!IsEmptyNode(aPresContext, *childContent, aOptions, &seenBR)) {
+      if (aSeenBR) {
+        *aSeenBR = seenBR;
+      }
+      return false;
+    }
+  }
+
+  if (aSeenBR) {
+    *aSeenBR = seenBR;
+  }
+  return true;
+}
+
+bool HTMLEditUtils::ShouldInsertLinefeedCharacter(
+    const EditorDOMPoint& aPointToInsert, const Element& aEditingHost) {
+  MOZ_ASSERT(aPointToInsert.IsSetAndValid());
+
+  if (!aPointToInsert.IsInContentNode()) {
+    return false;
+  }
+
+  // closestEditableBlockElement can be nullptr if aEditingHost is an inline
+  // element.
+  Element* closestEditableBlockElement =
+      HTMLEditUtils::GetInclusiveAncestorElement(
+          *aPointToInsert.ContainerAs<nsIContent>(),
+          HTMLEditUtils::ClosestEditableBlockElement);
+
+  // If and only if the nearest block is the editing host or its parent,
+  // and the outer display value of the editing host is inline, and new
+  // line character is preformatted, we should insert a linefeed.
+  return (!closestEditableBlockElement ||
+          closestEditableBlockElement == &aEditingHost) &&
+         HTMLEditUtils::IsDisplayOutsideInline(aEditingHost) &&
+         EditorUtils::IsNewLinePreformatted(
+             *aPointToInsert.ContainerAs<nsIContent>());
+}
+
+// We use bitmasks to test containment of elements. Elements are marked to be
+// in certain groups by setting the mGroup member of the `ElementInfo` struct
+// to the corresponding GROUP_ values (OR'ed together). Similarly, elements are
+// marked to allow containment of certain groups by setting the
+// mCanContainGroups member of the `ElementInfo` struct to the corresponding
+// GROUP_ values (OR'ed together).
+// Testing containment then simply consists of checking whether the
+// mCanContainGroups bitmask of an element and the mGroup bitmask of a
+// potential child overlap.
+
+#define GROUP_NONE 0
+
+// body, head, html
+#define GROUP_TOPLEVEL (1 << 1)
+
+// base, link, meta, script, style, title
+#define GROUP_HEAD_CONTENT (1 << 2)
+
+// b, big, i, s, small, strike, tt, u
+#define GROUP_FONTSTYLE (1 << 3)
+
+// abbr, acronym, cite, code, datalist, del, dfn, em, ins, kbd, mark, rb, rp
+// rt, rtc, ruby, samp, strong, var
+#define GROUP_PHRASE (1 << 4)
+
+// a, applet, basefont, bdi, bdo, br, font, iframe, img, map, meter, object,
+// output, picture, progress, q, script, span, sub, sup
+#define GROUP_SPECIAL (1 << 5)
+
+// button, form, input, label, select, textarea
+#define GROUP_FORMCONTROL (1 << 6)
+
+// address, applet, article, aside, blockquote, button, center, del, details,
+// dialog, dir, div, dl, fieldset, figure, footer, form, h1, h2, h3, h4, h5,
+// h6, header, hgroup, hr, iframe, ins, main, map, menu, nav, noframes,
+// noscript, object, ol, p, pre, table, section, summary, ul
+#define GROUP_BLOCK (1 << 7)
+
+// frame, frameset
+#define GROUP_FRAME (1 << 8)
+
+// col, tbody
+#define GROUP_TABLE_CONTENT (1 << 9)
+
+// tr
+#define GROUP_TBODY_CONTENT (1 << 10)
+
+// td, th
+#define GROUP_TR_CONTENT (1 << 11)
+
+// col
+#define GROUP_COLGROUP_CONTENT (1 << 12)
+
+// param
+#define GROUP_OBJECT_CONTENT (1 << 13)
+
+// li
+#define GROUP_LI (1 << 14)
+
+// area
+#define GROUP_MAP_CONTENT (1 << 15)
+
+// optgroup, option
+#define GROUP_SELECT_CONTENT (1 << 16)
+
+// option
+#define GROUP_OPTIONS (1 << 17)
+
+// dd, dt
+#define GROUP_DL_CONTENT (1 << 18)
+
+// p
+#define GROUP_P (1 << 19)
+
+// text, white-space, newline, comment
+#define GROUP_LEAF (1 << 20)
+
+// XXX This is because the editor does sublists illegally.
+// ol, ul
+#define GROUP_OL_UL (1 << 21)
+
+// h1, h2, h3, h4, h5, h6
+#define GROUP_HEADING (1 << 22)
+
+// figcaption
+#define GROUP_FIGCAPTION (1 << 23)
+
+// picture members (img, source)
+#define GROUP_PICTURE_CONTENT (1 << 24)
+
+#define GROUP_INLINE_ELEMENT                                            \
+  (GROUP_FONTSTYLE | GROUP_PHRASE | GROUP_SPECIAL | GROUP_FORMCONTROL | \
+   GROUP_LEAF)
+
+#define GROUP_FLOW_ELEMENT (GROUP_INLINE_ELEMENT | GROUP_BLOCK)
+
+struct ElementInfo final {
+#ifdef DEBUG
+  nsHTMLTag mTag;
+#endif
+  // See `GROUP_NONE`'s comment.
+  uint32_t mGroup;
+  // See `GROUP_NONE`'s comment.
+  uint32_t mCanContainGroups;
+  bool mIsContainer;
+  bool mCanContainSelf;
+};
+
+#ifdef DEBUG
+#  define ELEM(_tag, _isContainer, _canContainSelf, _group, _canContainGroups) \
+    {                                                                          \
+      eHTMLTag_##_tag, _group, _canContainGroups, _isContainer,                \
+          _canContainSelf                                                      \
+    }
+#else
+#  define ELEM(_tag, _isContainer, _canContainSelf, _group, _canContainGroups) \
+    { _group, _canContainGroups, _isContainer, _canContainSelf }
+#endif
+
+static const ElementInfo kElements[eHTMLTag_userdefined] = {
+    ELEM(a, true, false, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(abbr, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(acronym, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(address, true, true, GROUP_BLOCK, GROUP_INLINE_ELEMENT | GROUP_P),
+    // While applet is no longer a valid tag, removing it here breaks the editor
+    // (compiles, but causes many tests to fail in odd ways). This list is
+    // tracked against the main HTML Tag list, so any changes will require more
+    // than just removing entries.
+    ELEM(applet, true, true, GROUP_SPECIAL | GROUP_BLOCK,
+         GROUP_FLOW_ELEMENT | GROUP_OBJECT_CONTENT),
+    ELEM(area, false, false, GROUP_MAP_CONTENT, GROUP_NONE),
+    ELEM(article, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(aside, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(audio, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(b, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    ELEM(base, false, false, GROUP_HEAD_CONTENT, GROUP_NONE),
+    ELEM(basefont, false, false, GROUP_SPECIAL, GROUP_NONE),
+    ELEM(bdi, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(bdo, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(bgsound, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(big, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    ELEM(blockquote, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(body, true, true, GROUP_TOPLEVEL, GROUP_FLOW_ELEMENT),
+    ELEM(br, false, false, GROUP_SPECIAL, GROUP_NONE),
+    ELEM(button, true, true, GROUP_FORMCONTROL | GROUP_BLOCK,
+         GROUP_FLOW_ELEMENT),
+    ELEM(canvas, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(caption, true, true, GROUP_NONE, GROUP_INLINE_ELEMENT),
+    ELEM(center, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(cite, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(code, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(col, false, false, GROUP_TABLE_CONTENT | GROUP_COLGROUP_CONTENT,
+         GROUP_NONE),
+    ELEM(colgroup, true, false, GROUP_NONE, GROUP_COLGROUP_CONTENT),
+    ELEM(data, true, false, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(datalist, true, false, GROUP_PHRASE,
+         GROUP_OPTIONS | GROUP_INLINE_ELEMENT),
+    ELEM(dd, true, false, GROUP_DL_CONTENT, GROUP_FLOW_ELEMENT),
+    ELEM(del, true, true, GROUP_PHRASE | GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(details, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(dfn, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(dialog, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(dir, true, false, GROUP_BLOCK, GROUP_LI),
+    ELEM(div, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(dl, true, false, GROUP_BLOCK, GROUP_DL_CONTENT),
+    ELEM(dt, true, true, GROUP_DL_CONTENT, GROUP_INLINE_ELEMENT),
+    ELEM(em, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(embed, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(fieldset, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(figcaption, true, false, GROUP_FIGCAPTION, GROUP_FLOW_ELEMENT),
+    ELEM(figure, true, true, GROUP_BLOCK,
+         GROUP_FLOW_ELEMENT | GROUP_FIGCAPTION),
+    ELEM(font, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(footer, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(form, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(frame, false, false, GROUP_FRAME, GROUP_NONE),
+    ELEM(frameset, true, true, GROUP_FRAME, GROUP_FRAME),
+    ELEM(h1, true, false, GROUP_BLOCK | GROUP_HEADING, GROUP_INLINE_ELEMENT),
+    ELEM(h2, true, false, GROUP_BLOCK | GROUP_HEADING, GROUP_INLINE_ELEMENT),
+    ELEM(h3, true, false, GROUP_BLOCK | GROUP_HEADING, GROUP_INLINE_ELEMENT),
+    ELEM(h4, true, false, GROUP_BLOCK | GROUP_HEADING, GROUP_INLINE_ELEMENT),
+    ELEM(h5, true, false, GROUP_BLOCK | GROUP_HEADING, GROUP_INLINE_ELEMENT),
+    ELEM(h6, true, false, GROUP_BLOCK | GROUP_HEADING, GROUP_INLINE_ELEMENT),
+    ELEM(head, true, false, GROUP_TOPLEVEL, GROUP_HEAD_CONTENT),
+    ELEM(header, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(hgroup, true, false, GROUP_BLOCK, GROUP_HEADING),
+    ELEM(hr, false, false, GROUP_BLOCK, GROUP_NONE),
+    ELEM(html, true, false, GROUP_TOPLEVEL, GROUP_TOPLEVEL),
+    ELEM(i, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    ELEM(iframe, true, true, GROUP_SPECIAL | GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(image, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(img, false, false, GROUP_SPECIAL | GROUP_PICTURE_CONTENT, GROUP_NONE),
+    ELEM(input, false, false, GROUP_FORMCONTROL, GROUP_NONE),
+    ELEM(ins, true, true, GROUP_PHRASE | GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(kbd, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(keygen, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(label, true, false, GROUP_FORMCONTROL, GROUP_INLINE_ELEMENT),
+    ELEM(legend, true, true, GROUP_NONE, GROUP_INLINE_ELEMENT),
+    ELEM(li, true, false, GROUP_LI, GROUP_FLOW_ELEMENT),
+    ELEM(link, false, false, GROUP_HEAD_CONTENT, GROUP_NONE),
+    ELEM(listing, true, true, GROUP_BLOCK, GROUP_INLINE_ELEMENT),
+    ELEM(main, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(map, true, true, GROUP_SPECIAL, GROUP_BLOCK | GROUP_MAP_CONTENT),
+    ELEM(mark, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(marquee, true, false, GROUP_NONE, GROUP_NONE),
+    ELEM(menu, true, true, GROUP_BLOCK, GROUP_LI | GROUP_FLOW_ELEMENT),
+    ELEM(meta, false, false, GROUP_HEAD_CONTENT, GROUP_NONE),
+    ELEM(meter, true, false, GROUP_SPECIAL, GROUP_FLOW_ELEMENT),
+    ELEM(multicol, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(nav, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(nobr, true, false, GROUP_NONE, GROUP_NONE),
+    ELEM(noembed, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(noframes, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(noscript, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(object, true, true, GROUP_SPECIAL | GROUP_BLOCK,
+         GROUP_FLOW_ELEMENT | GROUP_OBJECT_CONTENT),
+    // XXX Can contain self and ul because editor does sublists illegally.
+    ELEM(ol, true, true, GROUP_BLOCK | GROUP_OL_UL, GROUP_LI | GROUP_OL_UL),
+    ELEM(optgroup, true, false, GROUP_SELECT_CONTENT, GROUP_OPTIONS),
+    ELEM(option, true, false, GROUP_SELECT_CONTENT | GROUP_OPTIONS, GROUP_LEAF),
+    ELEM(output, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(p, true, false, GROUP_BLOCK | GROUP_P, GROUP_INLINE_ELEMENT),
+    ELEM(param, false, false, GROUP_OBJECT_CONTENT, GROUP_NONE),
+    ELEM(picture, true, false, GROUP_SPECIAL, GROUP_PICTURE_CONTENT),
+    ELEM(plaintext, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(pre, true, true, GROUP_BLOCK, GROUP_INLINE_ELEMENT),
+    ELEM(progress, true, false, GROUP_SPECIAL, GROUP_FLOW_ELEMENT),
+    ELEM(q, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(rb, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(rp, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(rt, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(rtc, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(ruby, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(s, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    ELEM(samp, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(script, true, false, GROUP_HEAD_CONTENT | GROUP_SPECIAL, GROUP_LEAF),
+    ELEM(section, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(select, true, false, GROUP_FORMCONTROL, GROUP_SELECT_CONTENT),
+    ELEM(small, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    ELEM(slot, true, false, GROUP_NONE, GROUP_FLOW_ELEMENT),
+    ELEM(source, false, false, GROUP_PICTURE_CONTENT, GROUP_NONE),
+    ELEM(span, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(strike, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    ELEM(strong, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(style, true, false, GROUP_HEAD_CONTENT, GROUP_LEAF),
+    ELEM(sub, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(summary, true, true, GROUP_BLOCK, GROUP_FLOW_ELEMENT),
+    ELEM(sup, true, true, GROUP_SPECIAL, GROUP_INLINE_ELEMENT),
+    ELEM(table, true, false, GROUP_BLOCK, GROUP_TABLE_CONTENT),
+    ELEM(tbody, true, false, GROUP_TABLE_CONTENT, GROUP_TBODY_CONTENT),
+    ELEM(td, true, false, GROUP_TR_CONTENT, GROUP_FLOW_ELEMENT),
+    ELEM(textarea, true, false, GROUP_FORMCONTROL, GROUP_LEAF),
+    ELEM(tfoot, true, false, GROUP_NONE, GROUP_TBODY_CONTENT),
+    ELEM(th, true, false, GROUP_TR_CONTENT, GROUP_FLOW_ELEMENT),
+    ELEM(thead, true, false, GROUP_NONE, GROUP_TBODY_CONTENT),
+    ELEM(template, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(time, true, false, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(title, true, false, GROUP_HEAD_CONTENT, GROUP_LEAF),
+    ELEM(tr, true, false, GROUP_TBODY_CONTENT, GROUP_TR_CONTENT),
+    ELEM(track, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(tt, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    ELEM(u, true, true, GROUP_FONTSTYLE, GROUP_INLINE_ELEMENT),
+    // XXX Can contain self and ol because editor does sublists illegally.
+    ELEM(ul, true, true, GROUP_BLOCK | GROUP_OL_UL, GROUP_LI | GROUP_OL_UL),
+    ELEM(var, true, true, GROUP_PHRASE, GROUP_INLINE_ELEMENT),
+    ELEM(video, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(wbr, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(xmp, true, false, GROUP_BLOCK, GROUP_NONE),
+
+    // These aren't elements.
+    ELEM(text, false, false, GROUP_LEAF, GROUP_NONE),
+    ELEM(whitespace, false, false, GROUP_LEAF, GROUP_NONE),
+    ELEM(newline, false, false, GROUP_LEAF, GROUP_NONE),
+    ELEM(comment, false, false, GROUP_LEAF, GROUP_NONE),
+    ELEM(entity, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(doctypeDecl, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(markupDecl, false, false, GROUP_NONE, GROUP_NONE),
+    ELEM(instruction, false, false, GROUP_NONE, GROUP_NONE),
+
+    ELEM(userdefined, true, false, GROUP_NONE, GROUP_FLOW_ELEMENT)};
+
+bool HTMLEditUtils::CanNodeContain(nsHTMLTag aParentTagId,
+                                   nsHTMLTag aChildTagId) {
+  NS_ASSERTION(
+      aParentTagId > eHTMLTag_unknown && aParentTagId <= eHTMLTag_userdefined,
+      "aParentTagId out of range!");
+  NS_ASSERTION(
+      aChildTagId > eHTMLTag_unknown && aChildTagId <= eHTMLTag_userdefined,
+      "aChildTagId out of range!");
+
+#ifdef DEBUG
+  static bool checked = false;
+  if (!checked) {
+    checked = true;
+    int32_t i;
+    for (i = 1; i <= eHTMLTag_userdefined; ++i) {
+      NS_ASSERTION(kElements[i - 1].mTag == i,
+                   "You need to update kElements (missing tags).");
+    }
+  }
+#endif
+
+  // Special-case button.
+  if (aParentTagId == eHTMLTag_button) {
+    static const nsHTMLTag kButtonExcludeKids[] = {
+        eHTMLTag_a,     eHTMLTag_fieldset, eHTMLTag_form,    eHTMLTag_iframe,
+        eHTMLTag_input, eHTMLTag_select,   eHTMLTag_textarea};
+
+    uint32_t j;
+    for (j = 0; j < ArrayLength(kButtonExcludeKids); ++j) {
+      if (kButtonExcludeKids[j] == aChildTagId) {
+        return false;
+      }
+    }
+  }
+
+  // Deprecated elements.
+  if (aChildTagId == eHTMLTag_bgsound) {
+    return false;
+  }
+
+  // Bug #67007, dont strip userdefined tags.
+  if (aChildTagId == eHTMLTag_userdefined) {
+    return true;
+  }
+
+  const ElementInfo& parent = kElements[aParentTagId - 1];
+  if (aParentTagId == aChildTagId) {
+    return parent.mCanContainSelf;
+  }
+
+  const ElementInfo& child = kElements[aChildTagId - 1];
+  return !!(parent.mCanContainGroups & child.mGroup);
+}
+
+bool HTMLEditUtils::IsContainerNode(nsHTMLTag aTagId) {
+  NS_ASSERTION(aTagId > eHTMLTag_unknown && aTagId <= eHTMLTag_userdefined,
+               "aTagId out of range!");
+
+  return kElements[aTagId - 1].mIsContainer;
+}
+
+bool HTMLEditUtils::IsNonListSingleLineContainer(const nsINode& aNode) {
+  return aNode.IsAnyOfHTMLElements(
+      nsGkAtoms::address, nsGkAtoms::div, nsGkAtoms::h1, nsGkAtoms::h2,
+      nsGkAtoms::h3, nsGkAtoms::h4, nsGkAtoms::h5, nsGkAtoms::h6,
+      nsGkAtoms::listing, nsGkAtoms::p, nsGkAtoms::pre, nsGkAtoms::xmp);
+}
+
+bool HTMLEditUtils::IsSingleLineContainer(const nsINode& aNode) {
+  return IsNonListSingleLineContainer(aNode) ||
+         aNode.IsAnyOfHTMLElements(nsGkAtoms::li, nsGkAtoms::dt, nsGkAtoms::dd);
+}
+
+// static
+template <typename PT, typename CT>
+nsIContent* HTMLEditUtils::GetPreviousContent(
+    const EditorDOMPointBase<PT, CT>& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter /* = nullptr */) {
+  MOZ_ASSERT(aPoint.IsSetAndValid());
+  NS_WARNING_ASSERTION(
+      !aPoint.IsInDataNode() || aPoint.IsInTextNode(),
+      "GetPreviousContent() doesn't assume that the start point is a "
+      "data node except text node");
+
+  // If we are at the beginning of the node, or it is a text node, then just
+  // look before it.
+  if (aPoint.IsStartOfContainer() || aPoint.IsInTextNode()) {
+    if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
+        aPoint.IsInContentNode() &&
+        HTMLEditUtils::IsBlockElement(
+            *aPoint.template ContainerAs<nsIContent>())) {
+      // If we aren't allowed to cross blocks, don't look before this block.
+      return nullptr;
+    }
+    return HTMLEditUtils::GetPreviousContent(*aPoint.GetContainer(), aOptions,
+                                             aAncestorLimiter);
+  }
+
+  // else look before the child at 'aOffset'
+  if (aPoint.GetChild()) {
+    return HTMLEditUtils::GetPreviousContent(*aPoint.GetChild(), aOptions,
+                                             aAncestorLimiter);
+  }
+
+  // unless there isn't one, in which case we are at the end of the node
+  // and want the deep-right child.
+  nsIContent* lastLeafContent = HTMLEditUtils::GetLastLeafContent(
+      *aPoint.GetContainer(),
+      {aOptions.contains(WalkTreeOption::StopAtBlockBoundary)
+           ? LeafNodeType::LeafNodeOrChildBlock
+           : LeafNodeType::OnlyLeafNode});
+  if (!lastLeafContent) {
+    return nullptr;
+  }
+
+  if (!HTMLEditUtils::IsContentIgnored(*lastLeafContent, aOptions)) {
+    return lastLeafContent;
+  }
+
+  // restart the search from the non-editable node we just found
+  return HTMLEditUtils::GetPreviousContent(*lastLeafContent, aOptions,
+                                           aAncestorLimiter);
+}
+
+// static
+template <typename PT, typename CT>
+nsIContent* HTMLEditUtils::GetNextContent(
+    const EditorDOMPointBase<PT, CT>& aPoint, const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter /* = nullptr */) {
+  MOZ_ASSERT(aPoint.IsSetAndValid());
+  NS_WARNING_ASSERTION(
+      !aPoint.IsInDataNode() || aPoint.IsInTextNode(),
+      "GetNextContent() doesn't assume that the start point is a "
+      "data node except text node");
+
+  auto point = aPoint.template To<EditorRawDOMPoint>();
+
+  // if the container is a text node, use its location instead
+  if (point.IsInTextNode()) {
+    point.SetAfter(point.GetContainer());
+    if (NS_WARN_IF(!point.IsSet())) {
+      return nullptr;
+    }
+  }
+
+  if (point.GetChild()) {
+    if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
+        HTMLEditUtils::IsBlockElement(*point.GetChild())) {
+      return point.GetChild();
+    }
+
+    nsIContent* firstLeafContent = HTMLEditUtils::GetFirstLeafContent(
+        *point.GetChild(),
+        {aOptions.contains(WalkTreeOption::StopAtBlockBoundary)
+             ? LeafNodeType::LeafNodeOrChildBlock
+             : LeafNodeType::OnlyLeafNode});
+    if (!firstLeafContent) {
+      return point.GetChild();
+    }
+
+    // XXX Why do we need to do this check?  The leaf node must be a descendant
+    //     of `point.GetChild()`.
+    if (aAncestorLimiter &&
+        (firstLeafContent == aAncestorLimiter ||
+         !firstLeafContent->IsInclusiveDescendantOf(aAncestorLimiter))) {
+      return nullptr;
+    }
+
+    if (!HTMLEditUtils::IsContentIgnored(*firstLeafContent, aOptions)) {
+      return firstLeafContent;
+    }
+
+    // restart the search from the non-editable node we just found
+    return HTMLEditUtils::GetNextContent(*firstLeafContent, aOptions,
+                                         aAncestorLimiter);
+  }
+
+  // unless there isn't one, in which case we are at the end of the node
+  // and want the next one.
+  if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
+      point.IsInContentNode() &&
+      HTMLEditUtils::IsBlockElement(
+          *point.template ContainerAs<nsIContent>())) {
+    // don't cross out of parent block
+    return nullptr;
+  }
+
+  return HTMLEditUtils::GetNextContent(*point.GetContainer(), aOptions,
+                                       aAncestorLimiter);
+}
+
+// static
+nsIContent* HTMLEditUtils::GetAdjacentLeafContent(
+    const nsINode& aNode, WalkTreeDirection aWalkTreeDirection,
+    const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter /* = nullptr */) {
+  // called only by GetPriorNode so we don't need to check params.
+  MOZ_ASSERT(&aNode != aAncestorLimiter);
+  MOZ_ASSERT_IF(aAncestorLimiter,
+                aAncestorLimiter->IsInclusiveDescendantOf(aAncestorLimiter));
+
+  const nsINode* node = &aNode;
+  for (;;) {
+    // if aNode has a sibling in the right direction, return
+    // that sibling's closest child (or itself if it has no children)
+    nsIContent* sibling = aWalkTreeDirection == WalkTreeDirection::Forward
+                              ? node->GetNextSibling()
+                              : node->GetPreviousSibling();
+    if (sibling) {
+      if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
+          HTMLEditUtils::IsBlockElement(*sibling)) {
+        // don't look inside prevsib, since it is a block
+        return sibling;
+      }
+      const LeafNodeTypes leafNodeTypes = {
+          aOptions.contains(WalkTreeOption::StopAtBlockBoundary)
+              ? LeafNodeType::LeafNodeOrChildBlock
+              : LeafNodeType::OnlyLeafNode};
+      nsIContent* leafContent =
+          aWalkTreeDirection == WalkTreeDirection::Forward
+              ? HTMLEditUtils::GetFirstLeafContent(*sibling, leafNodeTypes)
+              : HTMLEditUtils::GetLastLeafContent(*sibling, leafNodeTypes);
+      return leafContent ? leafContent : sibling;
+    }
+
+    nsIContent* parent = node->GetParent();
+    if (!parent) {
+      return nullptr;
+    }
+
+    if (parent == aAncestorLimiter ||
+        (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
+         HTMLEditUtils::IsBlockElement(*parent))) {
+      return nullptr;
+    }
+
+    node = parent;
+  }
+
+  MOZ_ASSERT_UNREACHABLE("What part of for(;;) do you not understand?");
+  return nullptr;
+}
+
+// static
+nsIContent* HTMLEditUtils::GetAdjacentContent(
+    const nsINode& aNode, WalkTreeDirection aWalkTreeDirection,
+    const WalkTreeOptions& aOptions,
+    const Element* aAncestorLimiter /* = nullptr */) {
+  if (&aNode == aAncestorLimiter) {
+    // Don't allow traversal above the root node! This helps
+    // prevent us from accidentally editing browser content
+    // when the editor is in a text widget.
+    return nullptr;
+  }
+
+  nsIContent* leafContent = HTMLEditUtils::GetAdjacentLeafContent(
+      aNode, aWalkTreeDirection, aOptions, aAncestorLimiter);
+  if (!leafContent) {
+    return nullptr;
+  }
+
+  if (!HTMLEditUtils::IsContentIgnored(*leafContent, aOptions)) {
+    return leafContent;
+  }
+
+  return HTMLEditUtils::GetAdjacentContent(*leafContent, aWalkTreeDirection,
+                                           aOptions, aAncestorLimiter);
+}
+
+// static
+template <typename EditorDOMPointType>
+EditorDOMPointType HTMLEditUtils::GetPreviousEditablePoint(
+    nsIContent& aContent, const Element* aAncestorLimiter,
+    InvisibleWhiteSpaces aInvisibleWhiteSpaces,
+    TableBoundary aHowToTreatTableBoundary) {
+  MOZ_ASSERT(HTMLEditUtils::IsSimplyEditableNode(aContent));
+  NS_ASSERTION(!HTMLEditUtils::IsAnyTableElement(&aContent) ||
+                   HTMLEditUtils::IsTableCellOrCaption(aContent),
+               "HTMLEditUtils::GetPreviousEditablePoint() may return a point "
+               "between table structure elements");
+
+  // First, look for previous content.
+  nsIContent* previousContent = aContent.GetPreviousSibling();
+  if (!previousContent) {
+    if (!aContent.GetParentElement()) {
+      return EditorDOMPointType();
+    }
+    nsIContent* inclusiveAncestor = &aContent;
+    for (Element* parentElement : aContent.AncestorsOfType<Element>()) {
+      previousContent = parentElement->GetPreviousSibling();
+      if (!previousContent &&
+          (parentElement == aAncestorLimiter ||
+           !HTMLEditUtils::IsSimplyEditableNode(*parentElement) ||
+           !HTMLEditUtils::CanCrossContentBoundary(*parentElement,
+                                                   aHowToTreatTableBoundary))) {
+        // If cannot cross the parent element boundary, return the point of
+        // last inclusive ancestor point.
+        return EditorDOMPointType(inclusiveAncestor);
+      }
+
+      // Start of the parent element is a next editable point if it's an
+      // element which is not a table structure element.
+      if (!HTMLEditUtils::IsAnyTableElement(parentElement) ||
+          HTMLEditUtils::IsTableCellOrCaption(*parentElement)) {
+        inclusiveAncestor = parentElement;
+      }
+
+      if (!previousContent) {
+        continue;  // Keep looking for previous sibling of an ancestor.
+      }
+
+      // XXX Should we ignore data node like CDATA, Comment, etc?
+
+      // If previous content is not editable, let's return the point after it.
+      if (!HTMLEditUtils::IsSimplyEditableNode(*previousContent)) {
+        return EditorDOMPointType::After(*previousContent);
+      }
+
+      // If cannot cross previous content boundary, return start of last
+      // inclusive ancestor.
+      if (!HTMLEditUtils::CanCrossContentBoundary(*previousContent,
+                                                  aHowToTreatTableBoundary)) {
+        return inclusiveAncestor == &aContent
+                   ? EditorDOMPointType(inclusiveAncestor)
+                   : EditorDOMPointType(inclusiveAncestor, 0);
+      }
+      break;
+    }
+    if (!previousContent) {
+      return EditorDOMPointType(inclusiveAncestor);
+    }
+  } else if (!HTMLEditUtils::IsSimplyEditableNode(*previousContent)) {
+    return EditorDOMPointType::After(*previousContent);
+  } else if (!HTMLEditUtils::CanCrossContentBoundary(
+                 *previousContent, aHowToTreatTableBoundary)) {
+    return EditorDOMPointType(&aContent);
+  }
+
+  // Next, look for end of the previous content.
+  nsIContent* leafContent = previousContent;
+  if (previousContent->GetChildCount() &&
+      HTMLEditUtils::IsContainerNode(*previousContent)) {
+    for (nsIContent* maybeLeafContent = previousContent->GetLastChild();
+         maybeLeafContent;
+         maybeLeafContent = maybeLeafContent->GetLastChild()) {
+      // If it's not an editable content or cannot cross the boundary,
+      // return the point after the content.  Note that in this case,
+      // the content must not be any table elements except `<table>`
+      // because we've climbed down the tree.
+      if (!HTMLEditUtils::IsSimplyEditableNode(*maybeLeafContent) ||
+          !HTMLEditUtils::CanCrossContentBoundary(*maybeLeafContent,
+                                                  aHowToTreatTableBoundary)) {
+        return EditorDOMPointType::After(*maybeLeafContent);
+      }
+      leafContent = maybeLeafContent;
+      if (!HTMLEditUtils::IsContainerNode(*leafContent)) {
+        break;
+      }
+    }
+  }
+
+  if (leafContent->IsText()) {
+    Text* textNode = leafContent->AsText();
+    if (aInvisibleWhiteSpaces == InvisibleWhiteSpaces::Preserve) {
+      return EditorDOMPointType::AtEndOf(*textNode);
+    }
+    // There may be invisible trailing white-spaces which should be
+    // ignored.  Let's scan its start.
+    return WSRunScanner::GetAfterLastVisiblePoint<EditorDOMPointType>(
+        *textNode, aAncestorLimiter);
+  }
+
+  // If it's a container element, return end of it.  Otherwise, return
+  // the point after the non-container element.
+  return HTMLEditUtils::IsContainerNode(*leafContent)
+             ? EditorDOMPointType::AtEndOf(*leafContent)
+             : EditorDOMPointType::After(*leafContent);
+}
+
+// static
+template <typename EditorDOMPointType>
+EditorDOMPointType HTMLEditUtils::GetNextEditablePoint(
+    nsIContent& aContent, const Element* aAncestorLimiter,
+    InvisibleWhiteSpaces aInvisibleWhiteSpaces,
+    TableBoundary aHowToTreatTableBoundary) {
+  MOZ_ASSERT(HTMLEditUtils::IsSimplyEditableNode(aContent));
+  NS_ASSERTION(!HTMLEditUtils::IsAnyTableElement(&aContent) ||
+                   HTMLEditUtils::IsTableCellOrCaption(aContent),
+               "HTMLEditUtils::GetPreviousEditablePoint() may return a point "
+               "between table structure elements");
+
+  // First, look for next content.
+  nsIContent* nextContent = aContent.GetNextSibling();
+  if (!nextContent) {
+    if (!aContent.GetParentElement()) {
+      return EditorDOMPointType();
+    }
+    nsIContent* inclusiveAncestor = &aContent;
+    for (Element* parentElement : aContent.AncestorsOfType<Element>()) {
+      // End of the parent element is a next editable point if it's an
+      // element which is not a table structure element.
+      if (!HTMLEditUtils::IsAnyTableElement(parentElement) ||
+          HTMLEditUtils::IsTableCellOrCaption(*parentElement)) {
+        inclusiveAncestor = parentElement;
+      }
+
+      nextContent = parentElement->GetNextSibling();
+      if (!nextContent &&
+          (parentElement == aAncestorLimiter ||
+           !HTMLEditUtils::IsSimplyEditableNode(*parentElement) ||
+           !HTMLEditUtils::CanCrossContentBoundary(*parentElement,
+                                                   aHowToTreatTableBoundary))) {
+        // If cannot cross the parent element boundary, return the point of
+        // last inclusive ancestor point.
+        return EditorDOMPointType(inclusiveAncestor);
+      }
+
+      // End of the parent element is a next editable point if it's an
+      // element which is not a table structure element.
+      if (!HTMLEditUtils::IsAnyTableElement(parentElement) ||
+          HTMLEditUtils::IsTableCellOrCaption(*parentElement)) {
+        inclusiveAncestor = parentElement;
+      }
+
+      if (!nextContent) {
+        continue;  // Keep looking for next sibling of an ancestor.
+      }
+
+      // XXX Should we ignore data node like CDATA, Comment, etc?
+
+      // If next content is not editable, let's return the point after
+      // the last inclusive ancestor.
+      if (!HTMLEditUtils::IsSimplyEditableNode(*nextContent)) {
+        return EditorDOMPointType::After(*parentElement);
+      }
+
+      // If cannot cross next content boundary, return after the last
+      // inclusive ancestor.
+      if (!HTMLEditUtils::CanCrossContentBoundary(*nextContent,
+                                                  aHowToTreatTableBoundary)) {
+        return EditorDOMPointType::After(*inclusiveAncestor);
+      }
+      break;
+    }
+    if (!nextContent) {
+      return EditorDOMPointType::After(*inclusiveAncestor);
+    }
+  } else if (!HTMLEditUtils::IsSimplyEditableNode(*nextContent)) {
+    return EditorDOMPointType::After(aContent);
+  } else if (!HTMLEditUtils::CanCrossContentBoundary(
+                 *nextContent, aHowToTreatTableBoundary)) {
+    return EditorDOMPointType::After(aContent);
+  }
+
+  // Next, look for start of the next content.
+  nsIContent* leafContent = nextContent;
+  if (nextContent->GetChildCount() &&
+      HTMLEditUtils::IsContainerNode(*nextContent)) {
+    for (nsIContent* maybeLeafContent = nextContent->GetFirstChild();
+         maybeLeafContent;
+         maybeLeafContent = maybeLeafContent->GetFirstChild()) {
+      // If it's not an editable content or cannot cross the boundary,
+      // return the point at the content (i.e., start of its parent).  Note
+      // that in this case, the content must not be any table elements except
+      // `<table>` because we've climbed down the tree.
+      if (!HTMLEditUtils::IsSimplyEditableNode(*maybeLeafContent) ||
+          !HTMLEditUtils::CanCrossContentBoundary(*maybeLeafContent,
+                                                  aHowToTreatTableBoundary)) {
+        return EditorDOMPointType(maybeLeafContent);
+      }
+      leafContent = maybeLeafContent;
+      if (!HTMLEditUtils::IsContainerNode(*leafContent)) {
+        break;
+      }
+    }
+  }
+
+  if (leafContent->IsText()) {
+    Text* textNode = leafContent->AsText();
+    if (aInvisibleWhiteSpaces == InvisibleWhiteSpaces::Preserve) {
+      return EditorDOMPointType(textNode, 0);
+    }
+    // There may be invisible leading white-spaces which should be
+    // ignored.  Let's scan its start.
+    return WSRunScanner::GetFirstVisiblePoint<EditorDOMPointType>(
+        *textNode, aAncestorLimiter);
+  }
+
+  // If it's a container element, return start of it.  Otherwise, return
+  // the point at the non-container element (i.e., start of its parent).
+  return HTMLEditUtils::IsContainerNode(*leafContent)
+             ? EditorDOMPointType(leafContent, 0)
+             : EditorDOMPointType(leafContent);
+}
+
+// static
+Element* HTMLEditUtils::GetAncestorElement(
+    const nsIContent& aContent, const AncestorTypes& aAncestorTypes,
+    const Element* aAncestorLimiter /* = nullptr */) {
+  MOZ_ASSERT(
+      aAncestorTypes.contains(AncestorType::ClosestBlockElement) ||
+      aAncestorTypes.contains(AncestorType::MostDistantInlineElementInBlock) ||
+      aAncestorTypes.contains(AncestorType::ButtonElement));
+
+  if (&aContent == aAncestorLimiter) {
+    return nullptr;
+  }
+
+  const Element* theBodyElement = aContent.OwnerDoc()->GetBody();
+  const Element* theDocumentElement = aContent.OwnerDoc()->GetDocumentElement();
+  Element* lastAncestorElement = nullptr;
+  const bool editableElementOnly =
+      aAncestorTypes.contains(AncestorType::EditableElement);
+  const bool lookingForClosestBlockElement =
+      aAncestorTypes.contains(AncestorType::ClosestBlockElement);
+  const bool lookingForMostDistantInlineElementInBlock =
+      aAncestorTypes.contains(AncestorType::MostDistantInlineElementInBlock);
+  const bool ignoreHRElement =
+      aAncestorTypes.contains(AncestorType::IgnoreHRElement);
+  const bool lookingForButtonElement =
+      aAncestorTypes.contains(AncestorType::ButtonElement);
+  auto IsSearchingElementType = [&](const nsIContent& aContent) -> bool {
+    if (!aContent.IsElement() ||
+        (ignoreHRElement && aContent.IsHTMLElement(nsGkAtoms::hr))) {
+      return false;
+    }
+    if (editableElementOnly &&
+        !EditorUtils::IsEditableContent(aContent, EditorType::HTML)) {
+      return false;
+    }
+    return (lookingForClosestBlockElement &&
+            HTMLEditUtils::IsBlockElement(aContent)) ||
+           (lookingForMostDistantInlineElementInBlock &&
+            HTMLEditUtils::IsInlineElement(aContent)) ||
+           (lookingForButtonElement &&
+            aContent.IsHTMLElement(nsGkAtoms::button));
+  };
+  for (Element* element : aContent.AncestorsOfType<Element>()) {
+    if (editableElementOnly &&
+        !EditorUtils::IsEditableContent(*element, EditorType::HTML)) {
+      return lastAncestorElement && IsSearchingElementType(*lastAncestorElement)
+                 ? lastAncestorElement  // editing host (can be inline element)
+                 : nullptr;
+    }
+    if (ignoreHRElement && element->IsHTMLElement(nsGkAtoms::hr)) {
+      if (element == aAncestorLimiter) {
+        break;
+      }
+      continue;
+    }
+    if (lookingForButtonElement && element->IsHTMLElement(nsGkAtoms::button)) {
+      return element;  // closest button element
+    }
+    if (HTMLEditUtils::IsBlockElement(*element)) {
+      if (lookingForClosestBlockElement) {
+        return element;  // closest block element
+      }
+      MOZ_ASSERT_IF(lastAncestorElement,
+                    HTMLEditUtils::IsInlineElement(*lastAncestorElement));
+      return lastAncestorElement;  // the last inline element which we found
+    }
+    if (element == aAncestorLimiter || element == theBodyElement ||
+        element == theDocumentElement) {
+      break;
+    }
+    lastAncestorElement = element;
+  }
+  return lastAncestorElement && IsSearchingElementType(*lastAncestorElement)
+             ? lastAncestorElement
+             : nullptr;
+}
+
+// static
+Element* HTMLEditUtils::GetInclusiveAncestorElement(
+    const nsIContent& aContent, const AncestorTypes& aAncestorTypes,
+    const Element* aAncestorLimiter /* = nullptr */) {
+  MOZ_ASSERT(
+      aAncestorTypes.contains(AncestorType::ClosestBlockElement) ||
+      aAncestorTypes.contains(AncestorType::MostDistantInlineElementInBlock) ||
+      aAncestorTypes.contains(AncestorType::ButtonElement));
+
+  const Element* theBodyElement = aContent.OwnerDoc()->GetBody();
+  const Element* theDocumentElement = aContent.OwnerDoc()->GetDocumentElement();
+  const bool editableElementOnly =
+      aAncestorTypes.contains(AncestorType::EditableElement);
+  const bool lookingForClosestBlockElement =
+      aAncestorTypes.contains(AncestorType::ClosestBlockElement);
+  const bool lookingForMostDistantInlineElementInBlock =
+      aAncestorTypes.contains(AncestorType::MostDistantInlineElementInBlock);
+  const bool lookingForButtonElement =
+      aAncestorTypes.contains(AncestorType::ButtonElement);
+  const bool ignoreHRElement =
+      aAncestorTypes.contains(AncestorType::IgnoreHRElement);
+  auto IsSearchingElementType = [&](const nsIContent& aContent) -> bool {
+    if (!aContent.IsElement() ||
+        (ignoreHRElement && aContent.IsHTMLElement(nsGkAtoms::hr))) {
+      return false;
+    }
+    if (editableElementOnly &&
+        !EditorUtils::IsEditableContent(aContent, EditorType::HTML)) {
+      return false;
+    }
+    return (lookingForClosestBlockElement &&
+            HTMLEditUtils::IsBlockElement(aContent)) ||
+           (lookingForMostDistantInlineElementInBlock &&
+            HTMLEditUtils::IsInlineElement(aContent)) ||
+           (lookingForButtonElement &&
+            aContent.IsHTMLElement(nsGkAtoms::button));
+  };
+
+  // If aContent is the body element or the document element, we shouldn't climb
+  // up to its parent.
+  if (editableElementOnly &&
+      (&aContent == theBodyElement || &aContent == theDocumentElement)) {
+    return IsSearchingElementType(aContent)
+               ? const_cast<Element*>(aContent.AsElement())
+               : nullptr;
+  }
+
+  if (lookingForButtonElement && aContent.IsHTMLElement(nsGkAtoms::button)) {
+    return const_cast<Element*>(aContent.AsElement());
+  }
+
+  // If aContent is a block element, we don't need to climb up the tree.
+  // Consider the result right now.
+  if ((lookingForClosestBlockElement ||
+       lookingForMostDistantInlineElementInBlock) &&
+      HTMLEditUtils::IsBlockElement(aContent) &&
+      !(ignoreHRElement && aContent.IsHTMLElement(nsGkAtoms::hr))) {
+    return IsSearchingElementType(aContent)
+               ? const_cast<Element*>(aContent.AsElement())
+               : nullptr;
+  }
+
+  // If aContent is the last element to search range because of the parent
+  // element type, consider the result before calling GetAncestorElement()
+  // because it won't return aContent.
+  if (!aContent.GetParent() ||
+      (editableElementOnly && !EditorUtils::IsEditableContent(
+                                  *aContent.GetParent(), EditorType::HTML)) ||
+      (!lookingForClosestBlockElement &&
+       HTMLEditUtils::IsBlockElement(*aContent.GetParent()) &&
+       !(ignoreHRElement &&
+         aContent.GetParent()->IsHTMLElement(nsGkAtoms::hr)))) {
+    return IsSearchingElementType(aContent)
+               ? const_cast<Element*>(aContent.AsElement())
+               : nullptr;
+  }
+
+  if (&aContent == aAncestorLimiter) {
+    return nullptr;
+  }
+
+  return HTMLEditUtils::GetAncestorElement(aContent, aAncestorTypes,
+                                           aAncestorLimiter);
+}
+
+// static
+Element* HTMLEditUtils::GetClosestAncestorAnyListElement(
+    const nsIContent& aContent) {
+  for (Element* element : aContent.AncestorsOfType<Element>()) {
+    if (HTMLEditUtils::IsAnyListElement(element)) {
+      return element;
+    }
+  }
+
+  return nullptr;
+}
+
+EditAction HTMLEditUtils::GetEditActionForInsert(const nsAtom& aTagName) {
+  // This method may be in a hot path.  So, return only necessary
+  // EditAction::eInsert*Element.
+  if (&aTagName == nsGkAtoms::ul) {
+    // For InputEvent.inputType, "insertUnorderedList".
+    return EditAction::eInsertUnorderedListElement;
+  }
+  if (&aTagName == nsGkAtoms::ol) {
+    // For InputEvent.inputType, "insertOrderedList".
+    return EditAction::eInsertOrderedListElement;
+  }
+  if (&aTagName == nsGkAtoms::hr) {
+    // For InputEvent.inputType, "insertHorizontalRule".
+    return EditAction::eInsertHorizontalRuleElement;
+  }
+  return EditAction::eInsertNode;
+}
+
+EditAction HTMLEditUtils::GetEditActionForRemoveList(const nsAtom& aTagName) {
+  // This method may be in a hot path.  So, return only necessary
+  // EditAction::eRemove*Element.
+  if (&aTagName == nsGkAtoms::ul) {
+    // For InputEvent.inputType, "insertUnorderedList".
+    return EditAction::eRemoveUnorderedListElement;
+  }
+  if (&aTagName == nsGkAtoms::ol) {
+    // For InputEvent.inputType, "insertOrderedList".
+    return EditAction::eRemoveOrderedListElement;
+  }
+  return EditAction::eRemoveListElement;
+}
+
+EditAction HTMLEditUtils::GetEditActionForInsert(const Element& aElement) {
+  return GetEditActionForInsert(*aElement.NodeInfo()->NameAtom());
+}
+
+EditAction HTMLEditUtils::GetEditActionForFormatText(const nsAtom& aProperty,
+                                                     const nsAtom* aAttribute,
+                                                     bool aToSetStyle) {
+  // This method may be in a hot path.  So, return only necessary
+  // EditAction::eSet*Property or EditAction::eRemove*Property.
+  if (&aProperty == nsGkAtoms::b) {
+    return aToSetStyle ? EditAction::eSetFontWeightProperty
+                       : EditAction::eRemoveFontWeightProperty;
+  }
+  if (&aProperty == nsGkAtoms::i) {
+    return aToSetStyle ? EditAction::eSetTextStyleProperty
+                       : EditAction::eRemoveTextStyleProperty;
+  }
+  if (&aProperty == nsGkAtoms::u) {
+    return aToSetStyle ? EditAction::eSetTextDecorationPropertyUnderline
+                       : EditAction::eRemoveTextDecorationPropertyUnderline;
+  }
+  if (&aProperty == nsGkAtoms::strike) {
+    return aToSetStyle ? EditAction::eSetTextDecorationPropertyLineThrough
+                       : EditAction::eRemoveTextDecorationPropertyLineThrough;
+  }
+  if (&aProperty == nsGkAtoms::sup) {
+    return aToSetStyle ? EditAction::eSetVerticalAlignPropertySuper
+                       : EditAction::eRemoveVerticalAlignPropertySuper;
+  }
+  if (&aProperty == nsGkAtoms::sub) {
+    return aToSetStyle ? EditAction::eSetVerticalAlignPropertySub
+                       : EditAction::eRemoveVerticalAlignPropertySub;
+  }
+  if (&aProperty == nsGkAtoms::font) {
+    if (aAttribute == nsGkAtoms::face) {
+      return aToSetStyle ? EditAction::eSetFontFamilyProperty
+                         : EditAction::eRemoveFontFamilyProperty;
+    }
+    if (aAttribute == nsGkAtoms::color) {
+      return aToSetStyle ? EditAction::eSetColorProperty
+                         : EditAction::eRemoveColorProperty;
+    }
+    if (aAttribute == nsGkAtoms::bgcolor) {
+      return aToSetStyle ? EditAction::eSetBackgroundColorPropertyInline
+                         : EditAction::eRemoveBackgroundColorPropertyInline;
+    }
+  }
+  return aToSetStyle ? EditAction::eSetInlineStyleProperty
+                     : EditAction::eRemoveInlineStyleProperty;
+}
+
+EditAction HTMLEditUtils::GetEditActionForAlignment(
+    const nsAString& aAlignType) {
+  // This method may be in a hot path.  So, return only necessary
+  // EditAction::eAlign*.
+  if (aAlignType.EqualsLiteral("left")) {
+    return EditAction::eAlignLeft;
+  }
+  if (aAlignType.EqualsLiteral("right")) {
+    return EditAction::eAlignRight;
+  }
+  if (aAlignType.EqualsLiteral("center")) {
+    return EditAction::eAlignCenter;
+  }
+  if (aAlignType.EqualsLiteral("justify")) {
+    return EditAction::eJustify;
+  }
+  return EditAction::eSetAlignment;
+}
+
+// static
+template <typename EditorDOMPointType>
+nsIContent* HTMLEditUtils::GetContentToPreserveInlineStyles(
+    const EditorDOMPointType& aPoint, const Element& aEditingHost) {
+  MOZ_ASSERT(aPoint.IsSetAndValid());
+  if (MOZ_UNLIKELY(!aPoint.IsInContentNode())) {
+    return nullptr;
+  }
+  // If it points middle of a text node, use it.  Otherwise, scan next visible
+  // thing and use the style of following text node if there is.
+  if (aPoint.IsInTextNode() && !aPoint.IsEndOfContainer()) {
+    return aPoint.template ContainerAs<nsIContent>();
+  }
+  for (auto point = aPoint.template To<EditorRawDOMPoint>(); point.IsSet();) {
+    WSScanResult nextVisibleThing =
+        WSRunScanner::ScanNextVisibleNodeOrBlockBoundary(&aEditingHost, point);
+    if (nextVisibleThing.InVisibleOrCollapsibleCharacters()) {
+      return nextVisibleThing.TextPtr();
+    }
+    // Ignore empty inline container elements because it's not visible for
+    // users so that using the style will appear suddenly from point of
+    // view of users.
+    if (nextVisibleThing.ReachedSpecialContent() &&
+        nextVisibleThing.IsContentEditable() &&
+        nextVisibleThing.GetContent()->IsElement() &&
+        !nextVisibleThing.GetContent()->HasChildNodes() &&
+        HTMLEditUtils::IsContainerNode(*nextVisibleThing.ElementPtr())) {
+      point.SetAfter(nextVisibleThing.ElementPtr());
+      continue;
+    }
+    // Otherwise, we should use style of the container of the start point.
+    break;
+  }
+  return aPoint.template ContainerAs<nsIContent>();
+}
+
+template <typename EditorDOMPointType, typename EditorDOMPointTypeInput>
+EditorDOMPointType HTMLEditUtils::GetBetterInsertionPointFor(
+    const nsIContent& aContentToInsert,
+    const EditorDOMPointTypeInput& aPointToInsert,
+    const Element& aEditingHost) {
+  if (NS_WARN_IF(!aPointToInsert.IsSet())) {
+    return EditorDOMPointType();
+  }
+
+  auto pointToInsert =
+      aPointToInsert.template GetNonAnonymousSubtreePoint<EditorDOMPointType>();
+  if (MOZ_UNLIKELY(
+          NS_WARN_IF(!pointToInsert.IsSet()) ||
+          NS_WARN_IF(!pointToInsert.GetContainer()->IsInclusiveDescendantOf(
+              &aEditingHost)))) {
+    // Cannot insert aContentToInsert into this DOM tree.
+    return EditorDOMPointType();
+  }
+
+  // If the node to insert is not a block level element, we can insert it
+  // at any point.
+  if (!HTMLEditUtils::IsBlockElement(aContentToInsert)) {
+    return pointToInsert;
+  }
+
+  WSRunScanner wsScannerForPointToInsert(const_cast<Element*>(&aEditingHost),
+                                         pointToInsert);
+
+  // If the insertion position is after the last visible item in a line,
+  // i.e., the insertion position is just before a visible line break <br>,
+  // we want to skip to the position just after the line break (see bug 68767).
+  WSScanResult forwardScanFromPointToInsertResult =
+      wsScannerForPointToInsert.ScanNextVisibleNodeOrBlockBoundaryFrom(
+          pointToInsert);
+  // So, if the next visible node isn't a <br> element, we can insert the block
+  // level element to the point.
+  if (!forwardScanFromPointToInsertResult.GetContent() ||
+      !forwardScanFromPointToInsertResult.ReachedBRElement()) {
+    return pointToInsert;
+  }
+
+  // However, we must not skip next <br> element when the caret appears to be
+  // positioned at the beginning of a block, in that case skipping the <br>
+  // would not insert the <br> at the caret position, but after the current
+  // empty line.
+  WSScanResult backwardScanFromPointToInsertResult =
+      wsScannerForPointToInsert.ScanPreviousVisibleNodeOrBlockBoundaryFrom(
+          pointToInsert);
+  // So, if there is no previous visible node,
+  // or, if both nodes of the insertion point is <br> elements,
+  // or, if the previous visible node is different block,
+  // we need to skip the following <br>.  So, otherwise, we can insert the
+  // block at the insertion point.
+  if (!backwardScanFromPointToInsertResult.GetContent() ||
+      backwardScanFromPointToInsertResult.ReachedBRElement() ||
+      backwardScanFromPointToInsertResult.ReachedCurrentBlockBoundary()) {
+    return pointToInsert;
+  }
+
+  return forwardScanFromPointToInsertResult
+      .template PointAfterContent<EditorDOMPointType>();
+}
+
+//  static
+template <typename EditorDOMPointType, typename EditorDOMPointTypeInput>
+Result<EditorDOMPointType, nsresult>
+HTMLEditUtils::ComputePointToPutCaretInElementIfOutside(
+    const Element& aElement, const EditorDOMPointTypeInput& aCurrentPoint) {
+  MOZ_ASSERT(aCurrentPoint.IsSet());
+
+  // FYI: This was moved from
+  // https://searchfox.org/mozilla-central/rev/d3c2f51d89c3ca008ff0cb5a057e77ccd973443e/editor/libeditor/HTMLEditSubActionHandler.cpp#9193
+
+  // Use ranges and RangeUtils::CompareNodeToRange() to compare selection
+  // start to new block.
+  RefPtr<StaticRange> staticRange =
+      StaticRange::Create(aCurrentPoint.ToRawRangeBoundary(),
+                          aCurrentPoint.ToRawRangeBoundary(), IgnoreErrors());
+  if (MOZ_UNLIKELY(!staticRange)) {
+    NS_WARNING("StaticRange::Create() failed");
+    return Err(NS_ERROR_FAILURE);
+  }
+
+  bool nodeBefore, nodeAfter;
+  nsresult rv = RangeUtils::CompareNodeToRange(
+      const_cast<Element*>(&aElement), staticRange, &nodeBefore, &nodeAfter);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("RangeUtils::CompareNodeToRange() failed");
+    return Err(rv);
+  }
+
+  if (nodeBefore && nodeAfter) {
+    return EditorDOMPointType();  // aCurrentPoint is in aElement
+  }
+
+  if (nodeBefore) {
+    // selection is after block.  put at end of block.
+    const nsIContent* lastEditableContent = HTMLEditUtils::GetLastChild(
+        aElement, {WalkTreeOption::IgnoreNonEditableNode});
+    if (!lastEditableContent) {
+      lastEditableContent = &aElement;
+    }
+    if (lastEditableContent->IsText() ||
+        HTMLEditUtils::IsContainerNode(*lastEditableContent)) {
+      return EditorDOMPointType::AtEndOf(*lastEditableContent);
+    }
+    MOZ_ASSERT(lastEditableContent->GetParentNode());
+    return EditorDOMPointType::After(*lastEditableContent);
+  }
+
+  // selection is before block.  put at start of block.
+  const nsIContent* firstEditableContent = HTMLEditUtils::GetFirstChild(
+      aElement, {WalkTreeOption::IgnoreNonEditableNode});
+  if (!firstEditableContent) {
+    firstEditableContent = &aElement;
+  }
+  if (firstEditableContent->IsText() ||
+      HTMLEditUtils::IsContainerNode(*firstEditableContent)) {
+    MOZ_ASSERT(firstEditableContent->GetParentNode());
+    // XXX Shouldn't this be EditorDOMPointType(firstEditableContent, 0u)?
+    return EditorDOMPointType(firstEditableContent);
+  }
+  // XXX And shouldn't this be EditorDOMPointType(firstEditableContent)?
+  return EditorDOMPointType(firstEditableContent, 0u);
+}
+
+// static
+bool HTMLEditUtils::IsInlineStyleSetByElement(
+    const nsIContent& aContent, const EditorInlineStyle& aStyle,
+    const nsAString* aValue, nsAString* aOutValue /* = nullptr */) {
+  for (Element* element : aContent.InclusiveAncestorsOfType<Element>()) {
+    if (aStyle.mHTMLProperty != element->NodeInfo()->NameAtom()) {
+      continue;
+    }
+    if (!aStyle.mAttribute) {
+      return true;
+    }
+    nsAutoString value;
+    element->GetAttr(kNameSpaceID_None, aStyle.mAttribute, value);
+    if (aOutValue) {
+      *aOutValue = value;
+    }
+    if (!value.IsEmpty()) {
+      if (!aValue) {
+        return true;
+      }
+      if (aValue->Equals(value, nsCaseInsensitiveStringComparator)) {
+        return true;
+      }
+      // We found the prop with the attribute, but the value doesn't match.
+      return false;
+    }
+  }
+  return false;
+}
+
+// static
+size_t HTMLEditUtils::CollectChildren(
+    const nsINode& aNode,
+    nsTArray<OwningNonNull<nsIContent>>& aOutArrayOfContents,
+    size_t aIndexToInsertChildren, const CollectChildrenOptions& aOptions) {
+  // FYI: This was moved from
+  // https://searchfox.org/mozilla-central/rev/4bce7d85ba4796dd03c5dcc7cfe8eee0e4c07b3b/editor/libeditor/HTMLEditSubActionHandler.cpp#6261
+
+  size_t numberOfFoundChildren = 0;
+  for (nsIContent* content =
+           GetFirstChild(aNode, {WalkTreeOption::IgnoreNonEditableNode});
+       content; content = content->GetNextSibling()) {
+    if ((aOptions.contains(CollectChildrenOption::CollectListChildren) &&
+         (HTMLEditUtils::IsAnyListElement(content) ||
+          HTMLEditUtils::IsListItem(content))) ||
+        (aOptions.contains(CollectChildrenOption::CollectTableChildren) &&
+         HTMLEditUtils::IsAnyTableElement(content))) {
+      numberOfFoundChildren += HTMLEditUtils::CollectChildren(
+          *content, aOutArrayOfContents,
+          aIndexToInsertChildren + numberOfFoundChildren, aOptions);
+      continue;
+    }
+
+    if (aOptions.contains(CollectChildrenOption::IgnoreNonEditableChildren) &&
+        !EditorUtils::IsEditableContent(*content, EditorType::HTML)) {
+      continue;
+    }
+    if (aOptions.contains(CollectChildrenOption::IgnoreInvisibleTextNodes) &&
+        content->IsText() &&
+        !HTMLEditUtils::IsVisibleTextNode(*content->AsText())) {
+      continue;
+    }
+    aOutArrayOfContents.InsertElementAt(
+        aIndexToInsertChildren + numberOfFoundChildren++, *content);
+  }
+  return numberOfFoundChildren;
+}
+
+// static
+size_t HTMLEditUtils::CollectEmptyInlineContainerDescendants(
+    const nsINode& aNode,
+    nsTArray<OwningNonNull<nsIContent>>& aOutArrayOfContents,
+    const EmptyCheckOptions& aOptions) {
+  size_t numberOfFoundElements = 0;
+  for (Element* element = aNode.GetFirstElementChild(); element;) {
+    if (HTMLEditUtils::IsEmptyInlineContainer(*element, aOptions)) {
+      aOutArrayOfContents.AppendElement(*element);
+      numberOfFoundElements++;
+      nsIContent* nextContent = element->GetNextNonChildNode(&aNode);
+      element = nullptr;
+      for (; nextContent; nextContent = nextContent->GetNextNode(&aNode)) {
+        if (nextContent->IsElement()) {
+          element = nextContent->AsElement();
+          break;
+        }
+      }
+      continue;
+    }
+
+    nsIContent* nextContent = element->GetNextNode(&aNode);
+    element = nullptr;
+    for (; nextContent; nextContent = nextContent->GetNextNode(&aNode)) {
+      if (nextContent->IsElement()) {
+        element = nextContent->AsElement();
+        break;
+      }
+    }
+  }
+  return numberOfFoundElements;
+}
+
+// static
+bool HTMLEditUtils::ElementHasAttributeExcept(const Element& aElement,
+                                              const nsAtom& aAttribute1,
+                                              const nsAtom& aAttribute2,
+                                              const nsAtom& aAttribute3) {
+  // FYI: This was moved from
+  // https://searchfox.org/mozilla-central/rev/0b1543e85d13c30a13c57e959ce9815a3f0fa1d3/editor/libeditor/HTMLStyleEditor.cpp#1626
+  for (auto i : IntegerRange<uint32_t>(aElement.GetAttrCount())) {
+    const nsAttrName* name = aElement.GetAttrNameAt(i);
+    if (!name->NamespaceEquals(kNameSpaceID_None)) {
+      return true;
+    }
+
+    if (name->LocalName() == &aAttribute1 ||
+        name->LocalName() == &aAttribute2 ||
+        name->LocalName() == &aAttribute3) {
+      continue;  // Ignore the given attribute
+    }
+
+    // Ignore empty style, class and id attributes because those attributes are
+    // not meaningful with empty value.
+    if (name->LocalName() == nsGkAtoms::style ||
+        name->LocalName() == nsGkAtoms::_class ||
+        name->LocalName() == nsGkAtoms::id) {
+      if (aElement.HasNonEmptyAttr(name->LocalName())) {
+        return true;
+      }
+      continue;
+    }
+
+    // Ignore special _moz attributes
+    nsAutoString attrString;
+    name->LocalName()->ToString(attrString);
+    if (!StringBeginsWith(attrString, u"_moz"_ns)) {
+      return true;
+    }
+  }
+  // if we made it through all of them without finding a real attribute
+  // other than aAttribute, then return true
+  return false;
+}
+
+/******************************************************************************
+ * SelectedTableCellScanner
+ ******************************************************************************/
+
+SelectedTableCellScanner::SelectedTableCellScanner(
+    const AutoRangeArray& aRanges) {
+  if (aRanges.Ranges().IsEmpty()) {
+    return;
+  }
+  Element* firstSelectedCellElement =
+      HTMLEditUtils::GetTableCellElementIfOnlyOneSelected(
+          aRanges.FirstRangeRef());
+  if (!firstSelectedCellElement) {
+    return;  // We're not in table cell selection mode.
+  }
+  mSelectedCellElements.SetCapacity(aRanges.Ranges().Length());
+  mSelectedCellElements.AppendElement(*firstSelectedCellElement);
+  for (uint32_t i = 1; i < aRanges.Ranges().Length(); i++) {
+    nsRange* range = aRanges.Ranges()[i];
+    if (NS_WARN_IF(!range) || NS_WARN_IF(!range->IsPositioned())) {
+      continue;  // Shouldn't occur in normal conditions.
+    }
+    // Just ignore selection ranges which do not select only one table
+    // cell element.  This is possible case if web apps sets multiple
+    // selections and first range selects a table cell element.
+    if (Element* selectedCellElement =
+            HTMLEditUtils::GetTableCellElementIfOnlyOneSelected(*range)) {
+      mSelectedCellElements.AppendElement(*selectedCellElement);
+    }
+  }
+}
+
+}  // namespace mozilla