SSL HTMLEditUtils.h Sprache: C

/* -*- 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/. */

#ifndef HTMLEditUtils_h
#define HTMLEditUtils_h

/**
* This header declares/defines static helper methods as members of
* HTMLEditUtils.  If you want to create or look for helper trivial classes for
* HTMLEditor, see HTMLEditHelpers.h.
*/

#include "EditorBase.h"
#include "EditorDOMPoint.h"
#include "EditorForwards.h"
#include "EditorLineBreak.h"
#include "EditorUtils.h"
#include "HTMLEditHelpers.h"

#include "mozilla/Attributes.h"
#include "mozilla/EnumSet.h"
#include "mozilla/IntegerRange.h"
#include "mozilla/Maybe.h"
#include "mozilla/Result.h"
#include "mozilla/dom/AbstractRange.h"
#include "mozilla/dom/AncestorIterator.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/HTMLBRElement.h"
#include "mozilla/dom/Selection.h"
#include "mozilla/dom/Text.h"

#include "nsContentUtils.h"
#include "nsCRT.h"
#include "nsGkAtoms.h"
#include "nsHTMLTags.h"
#include "nsTArray.h"

class nsAtom;
class nsPresContext;

namespace mozilla {

enum class CollectChildrenOption {
  // Ignore non-editable nodes
  IgnoreNonEditableChildren,
  // Ignore invisible text nodes
  IgnoreInvisibleTextNodes,
  // Collect list children too.
  CollectListChildren,
  // Collect table children too.
  CollectTableChildren,
};

class HTMLEditUtils final {
  using AbstractRange = dom::AbstractRange;
  using Element = dom::Element;
  using Selection = dom::Selection;
  using Text = dom::Text;

public:
  static constexpr char16_t kNewLine = '\n';
  static constexpr char16_t kCarriageReturn = '\r';
  static constexpr char16_t kTab = '\t';
  static constexpr char16_t kSpace = ' ';
  static constexpr char16_t kNBSP = 0x00A0;
  static constexpr char16_t kGreaterThan = '>';

  /**
   * IsSimplyEditableNode() returns true when aNode is simply editable.
   * This does NOT means that aNode can be removed from current parent nor
   * aNode's data is editable.
   */
  static bool IsSimplyEditableNode(const nsINode& aNode) {
    return aNode.IsEditable();
  }

  /**
   * Return true if aElement is an editing host which is either:
   * - the root element
   * - parent is not editable
   * - the <body> element of the document
   */
  [[nodiscard]] static bool ElementIsEditableRoot(const Element& aElement);

  /**
   * Return true if inclusive flat tree ancestor has `inert` state.
   */
  static bool ContentIsInert(const nsIContent& aContent);

  /**
   * IsNeverContentEditableElementByUser() returns true if the element's content
   * is never editable by user.  E.g., the content is always replaced by
   * native anonymous node or something.
   */
  static bool IsNeverElementContentsEditableByUser(const nsIContent& aContent) {
    return aContent.IsElement() &&
           (!HTMLEditUtils::IsContainerNode(aContent) ||
            aContent.IsAnyOfHTMLElements(
                nsGkAtoms::applet, nsGkAtoms::colgroup, nsGkAtoms::frameset,
                nsGkAtoms::head, nsGkAtoms::html, nsGkAtoms::iframe,
                nsGkAtoms::meter, nsGkAtoms::progress, nsGkAtoms::select,
                nsGkAtoms::textarea));
  }

  /**
   * IsNonEditableReplacedContent() returns true when aContent is an inclusive
   * descendant of a replaced element whose content shouldn't be editable by
   * user's operation.
   */
  static bool IsNonEditableReplacedContent(const nsIContent& aContent) {
    for (Element* element : aContent.InclusiveAncestorsOfType<Element>()) {
      if (element->IsAnyOfHTMLElements(nsGkAtoms::select, nsGkAtoms::option,
                                       nsGkAtoms::optgroup)) {
        return true;
      }
    }
    return false;
  }

  /*
   * IsRemovalNode() returns true when parent of aContent is editable even
   * if aContent isn't editable.
   * This is a valid method to check it if you find the content from point
   * of view of siblings or parents of aContent.
   * Note that padding `<br>` element for empty editor and manual native
   * anonymous content should be deletable even after `HTMLEditor` is destroyed
   * because they are owned/managed by `HTMLEditor`.
   */
  static bool IsRemovableNode(const nsIContent& aContent) {
    return EditorUtils::IsPaddingBRElementForEmptyEditor(aContent) ||
           aContent.IsRootOfNativeAnonymousSubtree() ||
           (aContent.GetParentNode() &&
            aContent.GetParentNode()->IsEditable() &&
            &aContent != aContent.OwnerDoc()->GetBody() &&
            &aContent != aContent.OwnerDoc()->GetDocumentElement());
  }

  /**
   * IsRemovableFromParentNode() returns true when aContent is editable, has a
   * parent node and the parent node is also editable.
   * This is a valid method to check it if you find the content from point
   * of view of descendants of aContent.
   * Note that padding `<br>` element for empty editor and manual native
   * anonymous content should be deletable even after `HTMLEditor` is destroyed
   * because they are owned/managed by `HTMLEditor`.
   */
  static bool IsRemovableFromParentNode(const nsIContent& aContent) {
    return EditorUtils::IsPaddingBRElementForEmptyEditor(aContent) ||
           aContent.IsRootOfNativeAnonymousSubtree() ||
           (aContent.IsEditable() && aContent.GetParentNode() &&
            aContent.GetParentNode()->IsEditable() &&
            &aContent != aContent.OwnerDoc()->GetBody() &&
            &aContent != aContent.OwnerDoc()->GetDocumentElement());
  }

  /**
   * CanContentsBeJoined() returns true if aLeftContent and aRightContent can be
   * joined.
   */
  static bool CanContentsBeJoined(const nsIContent& aLeftContent,
                                  const nsIContent& aRightContent);

  /**
   * Returns true if aContent is an element and it should be treated as a block.
   *
   * @param aBlockInlineCheck
   *  - If UseHTMLDefaultStyle, this returns true only for HTML elements which
   * are defined as a block by the default style.  I.e., non-HTML elements are
   * always treated as inline.
   *  - If UseComputedDisplayOutsideStyle, this returns true for element nodes
   * whose display-outside is not inline nor ruby.  This is useful to get
   * inclusive ancestor block element.
   *  - If UseComputedDisplayStyle, this returns true for element nodes whose
   * display-outside is not inline or whose display-inside is flow-root and they
   * do not appear as a form control.  This is useful to check whether
   * collapsible white-spaces at the element edges are visible or invisible or
   * whether <br> element at end of the element is visible or invisible.
   */
  [[nodiscard]] static bool IsBlockElement(const nsIContent& aContent,
                                           BlockInlineCheck aBlockInlineCheck);

  /**
   * This is designed to check elements or non-element nodes which are layed out
   * as inline.  Therefore, inline-block etc and ruby are treated as inline.
   * Note that invisible non-element nodes like comment nodes are also treated
   * as inline.
   *
   * @param aBlockInlineCheck   UseComputedDisplayOutsideStyle and
   *                            UseComputedDisplayStyle return same result for
   *                            any elements.
   */
  [[nodiscard]] static bool IsInlineContent(const nsIContent& aContent,
                                            BlockInlineCheck aBlockInlineCheck);

  /**
   * IsVisibleElementEvenIfLeafNode() returns true if aContent is an empty block
   * element, a visible replaced element such as a form control.  This does not
   * check the layout information.
   */
  static bool IsVisibleElementEvenIfLeafNode(const nsIContent& aContent);

  static bool IsInlineStyle(nsINode* aNode);

  /**
   * IsDisplayOutsideInline() returns true if display-outside value is
   * "inside".  This does NOT flush the layout.
   */
  [[nodiscard]] static bool IsDisplayOutsideInline(const Element& aElement);

  /**
   * IsDisplayInsideFlowRoot() returns true if display-inline value of aElement
   * is "flow-root".  This does NOT flush the layout.
   */
  [[nodiscard]] static bool IsDisplayInsideFlowRoot(const Element& aElement);

  /**
   * Return true if aElement is a flex item or a grid item.  This works only
   * when aElement has a primary frame.
   */
  [[nodiscard]] static bool IsFlexOrGridItem(const Element& aElement);

  /**
   * IsRemovableInlineStyleElement() returns true if aElement is an inline
   * element and can be removed or split to in order to modifying inline
   * styles.
   */
  static bool IsRemovableInlineStyleElement(Element& aElement);

  /**
   * Return true if aTagName is one of the format element name of
   * Document.execCommand("formatBlock").
   */
  [[nodiscard]] static bool IsFormatTagForFormatBlockCommand(
      const nsStaticAtom& aTagName) {
    return
        // clang-format off
        &aTagName == nsGkAtoms::address ||
        &aTagName == nsGkAtoms::article ||
        &aTagName == nsGkAtoms::aside ||
        &aTagName == nsGkAtoms::blockquote ||
        &aTagName == nsGkAtoms::dd ||
        &aTagName == nsGkAtoms::div ||
        &aTagName == nsGkAtoms::dl ||
        &aTagName == nsGkAtoms::dt ||
        &aTagName == nsGkAtoms::footer ||
        &aTagName == nsGkAtoms::h1 ||
        &aTagName == nsGkAtoms::h2 ||
        &aTagName == nsGkAtoms::h3 ||
        &aTagName == nsGkAtoms::h4 ||
        &aTagName == nsGkAtoms::h5 ||
        &aTagName == nsGkAtoms::h6 ||
        &aTagName == nsGkAtoms::header ||
        &aTagName == nsGkAtoms::hgroup ||
        &aTagName == nsGkAtoms::main ||
        &aTagName == nsGkAtoms::nav ||
        &aTagName == nsGkAtoms::p ||
        &aTagName == nsGkAtoms::pre ||
        &aTagName == nsGkAtoms::section;
    // clang-format on
  }

  /**
   * Return true if aContent is a format element of
   * Document.execCommand("formatBlock").
   */
  [[nodiscard]] static bool IsFormatElementForFormatBlockCommand(
      const nsIContent& aContent) {
    if (!aContent.IsHTMLElement() ||
        !aContent.NodeInfo()->NameAtom()->IsStatic()) {
      return false;
    }
    const nsStaticAtom* tagName = aContent.NodeInfo()->NameAtom()->AsStatic();
    return IsFormatTagForFormatBlockCommand(*tagName);
  }

  /**
   * Return true if aTagName is one of the format element name of
   * cmd_paragraphState.
   */
  [[nodiscard]] static bool IsFormatTagForParagraphStateCommand(
      const nsStaticAtom& aTagName) {
    return
        // clang-format off
        &aTagName == nsGkAtoms::address ||
        &aTagName == nsGkAtoms::dd ||
        &aTagName == nsGkAtoms::dl ||
        &aTagName == nsGkAtoms::dt ||
        &aTagName == nsGkAtoms::h1 ||
        &aTagName == nsGkAtoms::h2 ||
        &aTagName == nsGkAtoms::h3 ||
        &aTagName == nsGkAtoms::h4 ||
        &aTagName == nsGkAtoms::h5 ||
        &aTagName == nsGkAtoms::h6 ||
        &aTagName == nsGkAtoms::p ||
        &aTagName == nsGkAtoms::pre;
    // clang-format on
  }

  /**
   * Return true if aContent is a format element of cmd_paragraphState.
   */
  [[nodiscard]] static bool IsFormatElementForParagraphStateCommand(
      const nsIContent& aContent) {
    if (!aContent.IsHTMLElement() ||
        !aContent.NodeInfo()->NameAtom()->IsStatic()) {
      return false;
    }
    const nsStaticAtom* tagName = aContent.NodeInfo()->NameAtom()->AsStatic();
    return IsFormatTagForParagraphStateCommand(*tagName);
  }

  static bool IsNodeThatCanOutdent(nsINode* aNode);
  static bool IsHeader(nsINode& aNode);
  static bool IsListItem(const nsINode* aNode);
  static bool IsTable(nsINode* aNode);
  static bool IsTableRow(nsINode* aNode);
  static bool IsAnyTableElement(const nsINode* aNode);
  static bool IsAnyTableElementButNotTable(nsINode* aNode);
  static bool IsTableCell(const nsINode* aNode);
  static bool IsTableCellOrCaption(nsINode& aNode);
  static bool IsAnyListElement(const nsINode* aNode);
  static bool IsPre(const nsINode* aNode);
  static bool IsImage(nsINode* aNode);
  static bool IsLink(const nsINode* aNode);
  static bool IsNamedAnchor(const nsINode* aNode);
  static bool IsMozDiv(nsINode* aNode);
  static bool IsMailCite(const Element& aElement);
  static bool IsFormWidget(const nsINode* aNode);
  static bool SupportsAlignAttr(nsINode& aNode);

  static bool CanNodeContain(const nsINode& aParent, const nsIContent& aChild) {
    switch (aParent.NodeType()) {
      case nsINode::ELEMENT_NODE:
      case nsINode::DOCUMENT_FRAGMENT_NODE:
        return HTMLEditUtils::CanNodeContain(*aParent.NodeInfo()->NameAtom(),
                                             aChild);
    }
    return false;
  }

  static bool CanNodeContain(const nsINode& aParent,
                             const nsAtom& aChildNodeName) {
    switch (aParent.NodeType()) {
      case nsINode::ELEMENT_NODE:
      case nsINode::DOCUMENT_FRAGMENT_NODE:
        return HTMLEditUtils::CanNodeContain(*aParent.NodeInfo()->NameAtom(),
                                             aChildNodeName);
    }
    return false;
  }

  static bool CanNodeContain(const nsAtom& aParentNodeName,
                             const nsIContent& aChild) {
    switch (aChild.NodeType()) {
      case nsINode::TEXT_NODE:
      case nsINode::COMMENT_NODE:
      case nsINode::CDATA_SECTION_NODE:
      case nsINode::ELEMENT_NODE:
      case nsINode::DOCUMENT_FRAGMENT_NODE:
        return HTMLEditUtils::CanNodeContain(aParentNodeName,
                                             *aChild.NodeInfo()->NameAtom());
    }
    return false;
  }

  // XXX Only this overload does not check the node type.  Therefore, only this
  //     handle Document and ProcessingInstructionTagName.
  static bool CanNodeContain(const nsAtom& aParentNodeName,
                             const nsAtom& aChildNodeName) {
    nsHTMLTag childTagEnum;
    if (&aChildNodeName == nsGkAtoms::textTagName) {
      childTagEnum = eHTMLTag_text;
    } else if (&aChildNodeName == nsGkAtoms::commentTagName ||
               &aChildNodeName == nsGkAtoms::cdataTagName) {
      childTagEnum = eHTMLTag_comment;
    } else {
      childTagEnum =
          nsHTMLTags::AtomTagToId(const_cast<nsAtom*>(&aChildNodeName));
    }

    nsHTMLTag parentTagEnum =
        nsHTMLTags::AtomTagToId(const_cast<nsAtom*>(&aParentNodeName));
    return HTMLEditUtils::CanNodeContain(parentTagEnum, childTagEnum);
  }

  /**
   * CanElementContainParagraph() returns true if aElement can have a <p>
   * element as its child or its descendant.
   */
  static bool CanElementContainParagraph(const Element& aElement) {
    if (HTMLEditUtils::CanNodeContain(aElement, *nsGkAtoms::p)) {
      return true;
    }

    // Even if the element cannot have a <p> element as a child, it can contain
    // <p> element as a descendant if it's one of the following elements.
    if (aElement.IsAnyOfHTMLElements(nsGkAtoms::ol, nsGkAtoms::ul,
                                     nsGkAtoms::dl, nsGkAtoms::table,
                                     nsGkAtoms::thead, nsGkAtoms::tbody,
                                     nsGkAtoms::tfoot, nsGkAtoms::tr)) {
      return true;
    }

    // XXX Otherwise, Chromium checks the CSS box is a block, but we don't do it
    //     for now.
    return false;
  }

  /**
   * Return a point which can insert a node whose name is aTagName scanning
   * from aPoint to its ancestor points.
   */
  template <typename EditorDOMPointType>
  static EditorDOMPoint GetInsertionPointInInclusiveAncestor(
      const nsAtom& aTagName, const EditorDOMPointType& aPoint,
      const Element* aAncestorLimit = nullptr) {
    if (MOZ_UNLIKELY(!aPoint.IsInContentNode())) {
      return EditorDOMPoint();
    }
    Element* lastChild = nullptr;
    for (Element* containerElement :
         aPoint.template ContainerAs<nsIContent>()
             ->template InclusiveAncestorsOfType<Element>()) {
      if (!HTMLEditUtils::IsSimplyEditableNode(*containerElement)) {
        return EditorDOMPoint();
      }
      if (HTMLEditUtils::CanNodeContain(*containerElement, aTagName)) {
        return lastChild ? EditorDOMPoint(lastChild)
                         : aPoint.template To<EditorDOMPoint>();
      }
      if (containerElement == aAncestorLimit) {
        return EditorDOMPoint();
      }
      lastChild = containerElement;
    }
    return EditorDOMPoint();
  }

  /**
   * IsContainerNode() returns true if aContent is a container node.
   */
  static bool IsContainerNode(const nsIContent& aContent) {
    nsHTMLTag tagEnum;
    // XXX Should this handle #cdata-section too?
    if (aContent.IsText()) {
      tagEnum = eHTMLTag_text;
    } else {
      // XXX Why don't we use nsHTMLTags::AtomTagToId?  Are there some
      //     difference?
      tagEnum = nsHTMLTags::StringTagToId(aContent.NodeName());
    }
    return HTMLEditUtils::IsContainerNode(tagEnum);
  }

  /**
   * IsSplittableNode() returns true if aContent can split.
   */
  static bool IsSplittableNode(const nsIContent& aContent) {
    if (!EditorUtils::IsEditableContent(aContent,
                                        EditorUtils::EditorType::HTML) ||
        !HTMLEditUtils::IsRemovableFromParentNode(aContent)) {
      return false;
    }
    if (aContent.IsElement()) {
      // XXX Perhaps, instead of using container, we should have "splittable"
      //     information in the DB.  E.g., `<template>`, `<script>` elements
      //     can have children, but shouldn't be split.
      return HTMLEditUtils::IsContainerNode(aContent) &&
             !aContent.IsAnyOfHTMLElements(nsGkAtoms::body, nsGkAtoms::button,
                                           nsGkAtoms::caption, nsGkAtoms::table,
                                           nsGkAtoms::tbody, nsGkAtoms::tfoot,
                                           nsGkAtoms::thead, nsGkAtoms::tr) &&
             !HTMLEditUtils::IsNeverElementContentsEditableByUser(aContent) &&
             !HTMLEditUtils::IsNonEditableReplacedContent(aContent);
    }
    return aContent.IsText() && aContent.Length() > 0;
  }

  /**
   * See execCommand spec:
   * https://w3c.github.io/editing/execCommand.html#non-list-single-line-container
   * https://w3c.github.io/editing/execCommand.html#single-line-container
   */
  static bool IsNonListSingleLineContainer(const nsINode& aNode);
  static bool IsSingleLineContainer(const nsINode& aNode);

  /**
   * Return true if aText has only a linefeed and it's preformatted.
   */
  [[nodiscard]] static bool TextHasOnlyOnePreformattedLinefeed(
      const Text& aText) {
    return aText.TextDataLength() == 1u &&
           aText.TextFragment().CharAt(0u) == kNewLine &&
           EditorUtils::IsNewLinePreformatted(aText);
  }

  /**
   * IsVisibleTextNode() returns true if aText has visible text.  If it has
   * only white-spaces and they are collapsed, returns false.
   */
  [[nodiscard]] static bool IsVisibleTextNode(const Text& aText);

  /**
   * IsInVisibleTextFrames() returns true if any text in aText is in visible
   * text frames.  Callers have to guarantee that there is no pending reflow.
   */
  static bool IsInVisibleTextFrames(nsPresContext* aPresContext,
                                    const Text& aText);

  /**
   * IsVisibleBRElement() and IsInvisibleBRElement() return true if aContent is
   * a visible HTML <br> element, i.e., not a padding <br> element for making
   * last line in a block element visible, or an invisible <br> element.
   */
  static bool IsVisibleBRElement(const nsIContent& aContent) {
    if (const dom::HTMLBRElement* brElement =
            dom::HTMLBRElement::FromNode(&aContent)) {
      return IsVisibleBRElement(*brElement);
    }
    return false;
  }
  static bool IsVisibleBRElement(const dom::HTMLBRElement& aBRElement) {
    // If followed by a block boundary without visible content, it's invisible
    // <br> element.
    return !HTMLEditUtils::GetElementOfImmediateBlockBoundary(
        aBRElement, WalkTreeDirection::Forward);
  }
  static bool IsInvisibleBRElement(const nsIContent& aContent) {
    if (const dom::HTMLBRElement* brElement =
            dom::HTMLBRElement::FromNode(&aContent)) {
      return IsInvisibleBRElement(*brElement);
    }
    return false;
  }
  static bool IsInvisibleBRElement(const dom::HTMLBRElement& aBRElement) {
    return !HTMLEditUtils::IsVisibleBRElement(aBRElement);
  }

  enum class IgnoreInvisibleLineBreak { No, Yes };

  /**
   * Return true if aPoint is immediately before current block boundary.  If
   * aIgnoreInvisibleLineBreak is "Yes", this returns true if aPoint is before
   * invisible line break before a block boundary.
   */
  template <typename PT, typename CT>
  [[nodiscard]] static bool PointIsImmediatelyBeforeCurrentBlockBoundary(
      const EditorDOMPointBase<PT, CT>& aPoint,
      IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);

  /**
   * Return true if aRange crosses the inclusive ancestor block element at
   * start boundary, in other words, if aRange ends outside of the inclusive
   * ancestor block of the start boundary.
   */
  template <typename EditorDOMPointType>
  [[nodiscard]] static bool RangeIsAcrossStartBlockBoundary(
      const EditorDOMRangeBase<EditorDOMPointType>& aRange) {
    MOZ_ASSERT(aRange.IsPositionedAndValid());
    if (MOZ_UNLIKELY(!aRange.StartRef().IsInContentNode())) {
      return false;
    }
    const Element* const startBlockElement =
        HTMLEditUtils::GetInclusiveAncestorElement(
            *aRange.StartRef().template ContainerAs<nsIContent>(),
            ClosestBlockElement,
            BlockInlineCheck::UseComputedDisplayOutsideStyle);
    if (MOZ_UNLIKELY(!startBlockElement)) {
      return false;
    }
    return EditorRawDOMPoint::After(*startBlockElement)
        .EqualsOrIsBefore(aRange.EndRef());
  }

  /**
   * Return true if `display` of inclusive ancestor of aContent is `none`.
   */
  static bool IsInclusiveAncestorCSSDisplayNone(const nsIContent& aContent);

  /**
   * IsVisiblePreformattedNewLine() and IsInvisiblePreformattedNewLine() return
   * true if the point is preformatted linefeed and it's visible or invisible.
   * If linefeed is immediately before a block boundary, it's invisible.
   *
   * @param aFollowingBlockElement  [out] If the node is followed by a block
   *                                boundary, this is set to the element
   *                                creating the block boundary.
   */
  template <typename EditorDOMPointType>
  static bool IsVisiblePreformattedNewLine(
      const EditorDOMPointType& aPoint,
      Element** aFollowingBlockElement = nullptr) {
    if (aFollowingBlockElement) {
      *aFollowingBlockElement = nullptr;
    }
    if (!aPoint.IsInTextNode() || aPoint.IsEndOfContainer() ||
        !aPoint.IsCharPreformattedNewLine()) {
      return false;
    }
    // If there are some other characters in the text node, it's a visible
    // linefeed.
    if (!aPoint.IsAtLastContent()) {
      if (EditorUtils::IsWhiteSpacePreformatted(
              *aPoint.template ContainerAs<Text>())) {
        return true;
      }
      const nsTextFragment& textFragment =
          aPoint.template ContainerAs<Text>()->TextFragment();
      for (uint32_t offset = aPoint.Offset() + 1;
           offset < textFragment.GetLength(); ++offset) {
        char16_t ch = textFragment.CharAt(AssertedCast<int32_t>(offset));
        if (nsCRT::IsAsciiSpace(ch) && ch != HTMLEditUtils::kNewLine) {
          continue;  // ASCII white-space which is collapsed into the linefeed.
        }
        return true;  // There is a visible character after it.
      }
    }
    // If followed by a block boundary without visible content, it's invisible
    // linefeed.
    Element* followingBlockElement =
        HTMLEditUtils::GetElementOfImmediateBlockBoundary(
            *aPoint.template ContainerAs<Text>(), WalkTreeDirection::Forward);
    if (aFollowingBlockElement) {
      *aFollowingBlockElement = followingBlockElement;
    }
    return !followingBlockElement;
  }
  template <typename EditorDOMPointType>
  static bool IsInvisiblePreformattedNewLine(
      const EditorDOMPointType& aPoint,
      Element** aFollowingBlockElement = nullptr) {
    if (!aPoint.IsInTextNode() || aPoint.IsEndOfContainer() ||
        !aPoint.IsCharPreformattedNewLine()) {
      if (aFollowingBlockElement) {
        *aFollowingBlockElement = nullptr;
      }
      return false;
    }
    return !IsVisiblePreformattedNewLine(aPoint, aFollowingBlockElement);
  }

  /**
   * Return a point to insert a padding line break if aPoint is following a
   * collapsible ASCII white-space or a block boundary and the line containing
   * aPoint requires a following padding line break which there is not.
   */
  template <typename PT, typename CT>
  static EditorDOMPoint LineRequiresPaddingLineBreakToBeVisible(
      const EditorDOMPointBase<PT, CT>& aPoint, const Element& aEditingHost);

  /**
   * ShouldInsertLinefeedCharacter() returns true if the caller should insert
   * a linefeed character instead of <br> element.
   */
  static bool ShouldInsertLinefeedCharacter(
      const EditorDOMPoint& aPointToInsert, const Element& aEditingHost);

  /**
   * IsEmptyNode() returns false if aNode has some visible content nodes,
   * list elements or table elements.
   *
   * @param aPresContext    Must not be nullptr if
   *                        EmptyCheckOption::SafeToAskLayout is set.
   * @param aNode           The node to check whether it's empty.
   * @param aOptions        You can specify which type of elements are visible
   *                        and/or whether this can access layout information.
   * @param aSeenBR         [Out] Set to true if this meets an <br> element
   *                        before meeting visible things.
   */
  enum class EmptyCheckOption {
    TreatSingleBRElementAsVisible,
    TreatBlockAsVisible,
    TreatListItemAsVisible,
    TreatTableCellAsVisible,
    TreatNonEditableContentAsInvisible,
    SafeToAskLayout,
  };
  using EmptyCheckOptions = EnumSet<EmptyCheckOption, uint32_t>;
  static bool IsEmptyNode(nsPresContext* aPresContext, const nsINode& aNode,
                          const EmptyCheckOptions& aOptions = {},
                          bool* aSeenBR = nullptr);
  static bool IsEmptyNode(const nsINode& aNode,
                          const EmptyCheckOptions& aOptions = {},
                          bool* aSeenBR = nullptr) {
    MOZ_ASSERT(!aOptions.contains(EmptyCheckOption::SafeToAskLayout));
    return IsEmptyNode(nullptr, aNode, aOptions, aSeenBR);
  }

  /**
   * IsEmptyInlineContainer() returns true if aContent is an inline element
   * which can have children and does not have meaningful content.
   */
  static bool IsEmptyInlineContainer(const nsIContent& aContent,
                                     const EmptyCheckOptions& aOptions,
                                     BlockInlineCheck aBlockInlineCheck) {
    return HTMLEditUtils::IsInlineContent(aContent, aBlockInlineCheck) &&
           HTMLEditUtils::IsContainerNode(aContent) &&
           HTMLEditUtils::IsEmptyNode(aContent, aOptions);
  }

  /**
   * IsEmptyBlockElement() returns true if aElement is a block level element
   * and it doesn't have any visible content.
   */
  static bool IsEmptyBlockElement(const Element& aElement,
                                  const EmptyCheckOptions& aOptions,
                                  BlockInlineCheck aBlockInlineCheck) {
    return HTMLEditUtils::IsBlockElement(aElement, aBlockInlineCheck) &&
           HTMLEditUtils::IsEmptyNode(aElement, aOptions);
  }

  /**
   * Return true if aListElement is completely empty or it has only one list
   * item element which is empty.
   */
  [[nodiscard]] static bool IsEmptyAnyListElement(const Element& aListElement) {
    MOZ_ASSERT(HTMLEditUtils::IsAnyListElement(&aListElement));
    bool foundListItem = false;
    for (nsIContent* child = aListElement.GetFirstChild(); child;
         child = child->GetNextSibling()) {
      if (HTMLEditUtils::IsListItem(child)) {
        if (foundListItem) {
          return false;  // 2 list items found.
        }
        if (!IsEmptyNode(*child, {})) {
          return false;  // found non-empty list item.
        }
        foundListItem = true;
        continue;
      }
      if (child->IsElement()) {
        return false;  // found sublist or illegal child.
      }
      if (child->IsText() &&
          HTMLEditUtils::IsVisibleTextNode(*child->AsText())) {
        return false;  // found illegal visible text node.
      }
    }
    return true;
  }

  /**
   * Return true if aListElement does not have invalid child.
   */
  enum class TreatSubListElementAs { Invalid, Valid };
  [[nodiscard]] static bool IsValidListElement(
      const Element& aListElement,
      TreatSubListElementAs aTreatSubListElementAs) {
    MOZ_ASSERT(HTMLEditUtils::IsAnyListElement(&aListElement));
    for (nsIContent* child = aListElement.GetFirstChild(); child;
         child = child->GetNextSibling()) {
      if (HTMLEditUtils::IsAnyListElement(child)) {
        if (aTreatSubListElementAs == TreatSubListElementAs::Invalid) {
          return false;
        }
        continue;
      }
      if (child->IsHTMLElement(nsGkAtoms::li)) {
        if (MOZ_UNLIKELY(!aListElement.IsAnyOfHTMLElements(nsGkAtoms::ol,
                                                           nsGkAtoms::ul))) {
          return false;
        }
        continue;
      }
      if (child->IsAnyOfHTMLElements(nsGkAtoms::dt, nsGkAtoms::dd)) {
        if (MOZ_UNLIKELY(!aListElement.IsAnyOfHTMLElements(nsGkAtoms::dl))) {
          return false;
        }
        continue;
      }
      if (MOZ_UNLIKELY(child->IsElement())) {
        return false;
      }
      if (MOZ_LIKELY(child->IsText())) {
        if (MOZ_UNLIKELY(HTMLEditUtils::IsVisibleTextNode(*child->AsText()))) {
          return false;
        }
      }
    }
    return true;
  }

  /**
   * IsEmptyOneHardLine() returns true if aArrayOfContents does not represent
   * 2 or more lines and have meaningful content.
   */
  static bool IsEmptyOneHardLine(
      nsTArray<OwningNonNull<nsIContent>>& aArrayOfContents,
      BlockInlineCheck aBlockInlineCheck) {
    if (NS_WARN_IF(aArrayOfContents.IsEmpty())) {
      return true;
    }

    bool brElementHasFound = false;
    for (OwningNonNull<nsIContent>& content : aArrayOfContents) {
      if (!EditorUtils::IsEditableContent(content,
                                          EditorUtils::EditorType::HTML)) {
        continue;
      }
      if (content->IsHTMLElement(nsGkAtoms::br)) {
        // If there are 2 or more `<br>` elements, it's not empty line since
        // there may be only one `<br>` element in a hard line.
        if (brElementHasFound) {
          return false;
        }
        brElementHasFound = true;
        continue;
      }
      if (!HTMLEditUtils::IsEmptyInlineContainer(
              content,
              {EmptyCheckOption::TreatSingleBRElementAsVisible,
               EmptyCheckOption::TreatNonEditableContentAsInvisible},
              aBlockInlineCheck)) {
        return false;
      }
    }
    return true;
  }

  /**
   * IsPointAtEdgeOfLink() returns true if aPoint is at start or end of a
   * link.
   */
  template <typename PT, typename CT>
  static bool IsPointAtEdgeOfLink(const EditorDOMPointBase<PT, CT>& aPoint,
                                  Element** aFoundLinkElement = nullptr) {
    if (aFoundLinkElement) {
      *aFoundLinkElement = nullptr;
    }
    if (!aPoint.IsInContentNode()) {
      return false;
    }
    if (!aPoint.IsStartOfContainer() && !aPoint.IsEndOfContainer()) {
      return false;
    }
    // XXX Assuming it's not in an empty text node because it's unrealistic edge
    //     case.
    bool maybeStartOfAnchor = aPoint.IsStartOfContainer();
    for (EditorRawDOMPoint point(aPoint.template ContainerAs<nsIContent>());
         point.IsSet() && (maybeStartOfAnchor ? point.IsStartOfContainer()
                                              : point.IsAtLastContent());
         point = point.ParentPoint()) {
      if (HTMLEditUtils::IsLink(point.GetContainer())) {
        // Now, we're at start or end of <a href>.
        if (aFoundLinkElement) {
          *aFoundLinkElement =
              do_AddRef(point.template ContainerAs<Element>()).take();
        }
        return true;
      }
    }
    return false;
  }

  /**
   * IsContentInclusiveDescendantOfLink() returns true if aContent is a
   * descendant of a link element.
   * Note that this returns true even if editing host of aContent is in a link
   * element.
   */
  static bool IsContentInclusiveDescendantOfLink(
      nsIContent& aContent, Element** aFoundLinkElement = nullptr) {
    if (aFoundLinkElement) {
      *aFoundLinkElement = nullptr;
    }
    for (Element* element : aContent.InclusiveAncestorsOfType<Element>()) {
      if (HTMLEditUtils::IsLink(element)) {
        if (aFoundLinkElement) {
          *aFoundLinkElement = do_AddRef(element).take();
        }
        return true;
      }
    }
    return false;
  }

  /**
   * IsRangeEntirelyInLink() returns true if aRange is entirely in a link
   * element.
   * Note that this returns true even if editing host of the range is in a link
   * element.
   */
  template <typename EditorDOMRangeType>
  static bool IsRangeEntirelyInLink(const EditorDOMRangeType& aRange,
                                    Element** aFoundLinkElement = nullptr) {
    MOZ_ASSERT(aRange.IsPositionedAndValid());
    if (aFoundLinkElement) {
      *aFoundLinkElement = nullptr;
    }
    nsINode* commonAncestorNode =
        nsContentUtils::GetClosestCommonInclusiveAncestor(
            aRange.StartRef().GetContainer(), aRange.EndRef().GetContainer());
    if (NS_WARN_IF(!commonAncestorNode) || !commonAncestorNode->IsContent()) {
      return false;
    }
    return IsContentInclusiveDescendantOfLink(*commonAncestorNode->AsContent(),
                                              aFoundLinkElement);
  }

  /**
   * Get adjacent content node of aNode if there is (even if one is in different
   * parent element).
   *
   * @param aNode               The node from which we start to walk the DOM
   *                            tree.
   * @param aOptions            See WalkTreeOption for the detail.
   * @param aBlockInlineCheck   Whether considering block vs. inline with the
   *                            computed style or the HTML default style.
   * @param aAncestorLimiter    Ancestor limiter element which these methods
   *                            never cross its boundary.  This is typically
   *                            the editing host.
   */
  enum class WalkTreeOption {
    IgnoreNonEditableNode,     // Ignore non-editable nodes and their children.
    IgnoreDataNodeExceptText,  // Ignore data nodes which are not text node.
    IgnoreWhiteSpaceOnlyText,  // Ignore text nodes having only white-spaces.
    StopAtBlockBoundary,       // Stop waking the tree at a block boundary.
  };
  using WalkTreeOptions = EnumSet<WalkTreeOption>;
  static nsIContent* GetPreviousContent(
      const nsINode& aNode, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck,
      const Element* aAncestorLimiter = nullptr) {
    if (&aNode == aAncestorLimiter ||
        (aAncestorLimiter &&
         !aNode.IsInclusiveDescendantOf(aAncestorLimiter))) {
      return nullptr;
    }
    return HTMLEditUtils::GetAdjacentContent(aNode, WalkTreeDirection::Backward,
                                             aOptions, aBlockInlineCheck,
                                             aAncestorLimiter);
  }
  static nsIContent* GetNextContent(const nsINode& aNode,
                                    const WalkTreeOptions& aOptions,
                                    BlockInlineCheck aBlockInlineCheck,
                                    const Element* aAncestorLimiter = nullptr) {
    if (&aNode == aAncestorLimiter ||
        (aAncestorLimiter &&
         !aNode.IsInclusiveDescendantOf(aAncestorLimiter))) {
      return nullptr;
    }
    return HTMLEditUtils::GetAdjacentContent(aNode, WalkTreeDirection::Forward,
                                             aOptions, aBlockInlineCheck,
                                             aAncestorLimiter);
  }

  /**
   * And another version that takes a point in DOM tree rather than a node.
   */
  template <typename PT, typename CT>
  static nsIContent* GetPreviousContent(
      const EditorDOMPointBase<PT, CT>& aPoint, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck,
      const Element* aAncestorLimiter = nullptr);

  /**
   * And another version that takes a point in DOM tree rather than a node.
   *
   * Note that this may return the child at the offset.  E.g., following code
   * causes infinite loop.
   *
   * EditorRawDOMPoint point(aEditableNode);
   * while (nsIContent* content =
   *          GetNextContent(point, {WalkTreeOption::IgnoreNonEditableNode})) {
   *   // Do something...
   *   point.Set(content);
   * }
   *
   * Following code must be you expected:
   *
   * while (nsIContent* content =
   *          GetNextContent(point, {WalkTreeOption::IgnoreNonEditableNode}) {
   *   // Do something...
   *   DebugOnly<bool> advanced = point.Advanced();
   *   MOZ_ASSERT(advanced);
   *   point.Set(point.GetChild());
   * }
   */
  template <typename PT, typename CT>
  static nsIContent* GetNextContent(const EditorDOMPointBase<PT, CT>& aPoint,
                                    const WalkTreeOptions& aOptions,
                                    BlockInlineCheck aBlockInlineCheck,
                                    const Element* aAncestorLimiter = nullptr);

  /**
   * GetPreviousSibling() return the preceding sibling of aContent which matches
   * with aOption.
   *
   * @param aBlockInlineCheck   Can be Unused if aOptions does not contain
   *                            StopAtBlockBoundary.
   */
  static nsIContent* GetPreviousSibling(
      const nsIContent& aContent, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused) {
    for (nsIContent* sibling = aContent.GetPreviousSibling(); sibling;
         sibling = sibling->GetPreviousSibling()) {
      if (HTMLEditUtils::IsContentIgnored(*sibling, aOptions)) {
        continue;
      }
      if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
          HTMLEditUtils::IsBlockElement(*sibling, aBlockInlineCheck)) {
        return nullptr;
      }
      return sibling;
    }
    return nullptr;
  }

  /**
   * GetNextSibling() return the following sibling of aContent which matches
   * with aOption.
   *
   * @param aBlockInlineCheck   Can be Unused if aOptions does not contain
   *                            StopAtBlockBoundary.
   */
  static nsIContent* GetNextSibling(
      const nsIContent& aContent, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused) {
    for (nsIContent* sibling = aContent.GetNextSibling(); sibling;
         sibling = sibling->GetNextSibling()) {
      if (HTMLEditUtils::IsContentIgnored(*sibling, aOptions)) {
        continue;
      }
      if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
          HTMLEditUtils::IsBlockElement(*sibling, aBlockInlineCheck)) {
        return nullptr;
      }
      return sibling;
    }
    return nullptr;
  }

  /**
   * Return the last child of aNode which matches with aOption.
   *
   * @param aBlockInlineCheck   Can be unused if aOptions does not contain
   *                            StopAtBlockBoundary.
   */
  static nsIContent* GetLastChild(
      const nsINode& aNode, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused) {
    for (nsIContent* child = aNode.GetLastChild(); child;
         child = child->GetPreviousSibling()) {
      if (HTMLEditUtils::IsContentIgnored(*child, aOptions)) {
        continue;
      }
      if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
          HTMLEditUtils::IsBlockElement(*child, aBlockInlineCheck)) {
        return nullptr;
      }
      return child;
    }
    return nullptr;
  }

  /**
   * Return the first child of aNode which matches with aOption.
   *
   * @param aBlockInlineCheck   Can be unused if aOptions does not contain
   *                            StopAtBlockBoundary.
   */
  static nsIContent* GetFirstChild(
      const nsINode& aNode, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused) {
    for (nsIContent* child = aNode.GetFirstChild(); child;
         child = child->GetNextSibling()) {
      if (HTMLEditUtils::IsContentIgnored(*child, aOptions)) {
        continue;
      }
      if (aOptions.contains(WalkTreeOption::StopAtBlockBoundary) &&
          HTMLEditUtils::IsBlockElement(*child, aBlockInlineCheck)) {
        return nullptr;
      }
      return child;
    }
    return nullptr;
  }

  /**
   * Return true if aContent is the last child of aNode with ignoring all
   * children which do not match with aOption.
   *
   * @param aBlockInlineCheck   Can be unused if aOptions does not contain
   *                            StopAtBlockBoundary.
   */
  static bool IsLastChild(
      const nsIContent& aContent, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused) {
    nsINode* parentNode = aContent.GetParentNode();
    if (!parentNode) {
      return false;
    }
    return HTMLEditUtils::GetLastChild(*parentNode, aOptions,
                                       aBlockInlineCheck) == &aContent;
  }

  /**
   * Return true if aContent is the first child of aNode with ignoring all
   * children which do not match with aOption.
   *
   * @param aBlockInlineCheck   Can be unused if aOptions does not contain
   *                            StopAtBlockBoundary.
   */
  static bool IsFirstChild(
      const nsIContent& aContent, const WalkTreeOptions& aOptions,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused) {
    nsINode* parentNode = aContent.GetParentNode();
    if (!parentNode) {
      return false;
    }
    return HTMLEditUtils::GetFirstChild(*parentNode, aOptions,
                                        aBlockInlineCheck) == &aContent;
  }

  /**
   * GetAdjacentContentToPutCaret() walks the DOM tree to find an editable node
   * near aPoint where may be a good point to put caret and keep typing or
   * deleting.
   *
   * @param aPoint      The DOM point where to start to search from.
   * @return            If found, returns non-nullptr.  Otherwise, nullptr.
   *                    Note that if found node is in different table structure
   *                    element, this returns nullptr.
   */
  enum class WalkTreeDirection { Forward, Backward };
  template <typename PT, typename CT>
  static nsIContent* GetAdjacentContentToPutCaret(
      const EditorDOMPointBase<PT, CT>& aPoint,
      WalkTreeDirection aWalkTreeDirection, const Element& aEditingHost) {
    MOZ_ASSERT(aPoint.IsSetAndValid());

    nsIContent* editableContent = nullptr;
    if (aWalkTreeDirection == WalkTreeDirection::Backward) {
      editableContent = HTMLEditUtils::GetPreviousContent(
          aPoint, {WalkTreeOption::IgnoreNonEditableNode},
          BlockInlineCheck::UseComputedDisplayStyle, &aEditingHost);
      if (!editableContent) {
        return nullptr;  // Not illegal.
      }
    } else {
      editableContent = HTMLEditUtils::GetNextContent(
          aPoint, {WalkTreeOption::IgnoreNonEditableNode},
          BlockInlineCheck::UseComputedDisplayStyle, &aEditingHost);
      if (NS_WARN_IF(!editableContent)) {
        // Perhaps, illegal because the node pointed by aPoint isn't editable
        // and nobody of previous nodes is editable.
        return nullptr;
      }
    }

    // scan in the right direction until we find an eligible text node,
    // but don't cross any breaks, images, or table elements.
    // XXX This comment sounds odd.  editableContent may have already crossed
    //     breaks and/or images if they are non-editable.
    while (editableContent && !editableContent->IsText() &&
           !editableContent->IsHTMLElement(nsGkAtoms::br) &&
           !HTMLEditUtils::IsImage(editableContent)) {
      if (aWalkTreeDirection == WalkTreeDirection::Backward) {
        editableContent = HTMLEditUtils::GetPreviousContent(
            *editableContent, {WalkTreeOption::IgnoreNonEditableNode},
            BlockInlineCheck::UseComputedDisplayStyle, &aEditingHost);
        if (NS_WARN_IF(!editableContent)) {
          return nullptr;
        }
      } else {
        editableContent = HTMLEditUtils::GetNextContent(
            *editableContent, {WalkTreeOption::IgnoreNonEditableNode},
            BlockInlineCheck::UseComputedDisplayStyle, &aEditingHost);
        if (NS_WARN_IF(!editableContent)) {
          return nullptr;
        }
      }
    }

    // don't cross any table elements
    if ((!aPoint.IsInContentNode() &&
         !!HTMLEditUtils::GetInclusiveAncestorAnyTableElement(
             *editableContent)) ||
        (HTMLEditUtils::GetInclusiveAncestorAnyTableElement(*editableContent) !=
         HTMLEditUtils::GetInclusiveAncestorAnyTableElement(
             *aPoint.template ContainerAs<nsIContent>()))) {
      return nullptr;
    }

    // otherwise, ok, we have found a good spot to put the selection
    return editableContent;
  }

  enum class LeafNodeType {
    // Even if there is a child block, keep scanning a leaf content in it.
    OnlyLeafNode,
    // If there is a child block, return it too.  Note that this does not
    // mean that block siblings are not treated as leaf nodes.
    LeafNodeOrChildBlock,
    // If there is a non-editable element if and only if scanning from editable
    // node, return it too.
    LeafNodeOrNonEditableNode,
    // Ignore non-editable content at walking the tree.
    OnlyEditableLeafNode,
  };
  using LeafNodeTypes = EnumSet<LeafNodeType>;

  /**
   * GetLastLeafContent() returns rightmost leaf content in aNode.  It depends
   * on aLeafNodeTypes whether this which types of nodes are treated as leaf
   * nodes.
   *
   * @param aBlockInlineCheck   Can be Unused if aLeafNodeTypes does not contain
   *                            LeafNodeOrCHildBlock.
   */
  static nsIContent* GetLastLeafContent(
      const nsINode& aNode, const LeafNodeTypes& aLeafNodeTypes,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused,
      const Element* aAncestorLimiter = nullptr) {
    MOZ_ASSERT_IF(
        aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
        !aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode));
    // editor shouldn't touch child nodes which are replaced with native
    // anonymous nodes.
    if (aNode.IsElement() &&
        HTMLEditUtils::IsNeverElementContentsEditableByUser(
            *aNode.AsElement())) {
      return nullptr;
    }
    for (nsIContent* content = aNode.GetLastChild(); content;) {
      if (aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode) &&
          !EditorUtils::IsEditableContent(*content,
                                          EditorUtils::EditorType::HTML)) {
        content = HTMLEditUtils::GetPreviousContent(
            *content, {WalkTreeOption::IgnoreNonEditableNode},
            aBlockInlineCheck, aAncestorLimiter);
        continue;
      }
      if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrChildBlock) &&
          HTMLEditUtils::IsBlockElement(*content, aBlockInlineCheck)) {
        return content;
      }
      if (!content->HasChildren() ||
          HTMLEditUtils::IsNeverElementContentsEditableByUser(*content)) {
        return content;
      }
      if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
          !HTMLEditUtils::IsSimplyEditableNode(*content)) {
        return content;
      }
      content = content->GetLastChild();
    }
    return nullptr;
  }

  /**
   * GetFirstLeafContent() returns leftmost leaf content in aNode.  It depends
   * on aLeafNodeTypes whether this scans into a block child or treat block as a
   * leaf.
   *
   * @param aBlockInlineCheck   Can be Unused if aLeafNodeTypes does not contain
   *                            LeafNodeOrCHildBlock.
   */
  static nsIContent* GetFirstLeafContent(
      const nsINode& aNode, const LeafNodeTypes& aLeafNodeTypes,
      BlockInlineCheck aBlockInlineCheck = BlockInlineCheck::Unused,
      const Element* aAncestorLimiter = nullptr) {
    MOZ_ASSERT_IF(
        aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
        !aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode));
    // editor shouldn't touch child nodes which are replaced with native
    // anonymous nodes.
    if (aNode.IsElement() &&
        HTMLEditUtils::IsNeverElementContentsEditableByUser(
            *aNode.AsElement())) {
      return nullptr;
    }
    for (nsIContent* content = aNode.GetFirstChild(); content;) {
      if (aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode) &&
          !EditorUtils::IsEditableContent(*content,
                                          EditorUtils::EditorType::HTML)) {
        content = HTMLEditUtils::GetNextContent(
            *content, {WalkTreeOption::IgnoreNonEditableNode},
            aBlockInlineCheck, aAncestorLimiter);
        continue;
      }
      if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrChildBlock) &&
          HTMLEditUtils::IsBlockElement(*content, aBlockInlineCheck)) {
        return content;
      }
      if (!content->HasChildren() ||
          HTMLEditUtils::IsNeverElementContentsEditableByUser(*content)) {
        return content;
      }
      if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
          !HTMLEditUtils::IsSimplyEditableNode(*content)) {
        return content;
      }
      content = content->GetFirstChild();
    }
    return nullptr;
  }

  /**
   * GetNextLeafContentOrNextBlockElement() returns next leaf content or
   * next block element of aStartContent inside aAncestorLimiter.
   *
   * @param aStartContent       The start content to scan next content.
   * @param aLeafNodeTypes      See LeafNodeType.
   * @param aAncestorLimiter    Optional, if you set this, it must be an
   *                            inclusive ancestor of aStartContent.
   */
  static nsIContent* GetNextLeafContentOrNextBlockElement(
      const nsIContent& aStartContent, const LeafNodeTypes& aLeafNodeTypes,
      BlockInlineCheck aBlockInlineCheck,
      const Element* aAncestorLimiter = nullptr) {
    MOZ_ASSERT_IF(
        aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
        !aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode));

    if (&aStartContent == aAncestorLimiter) {
      return nullptr;
    }

    nsIContent* nextContent = aStartContent.GetNextSibling();
    if (!nextContent) {
      if (!aStartContent.GetParentElement()) {
        NS_WARNING("Reached orphan node while climbing up the DOM tree");
        return nullptr;
      }
      for (Element* parentElement : aStartContent.AncestorsOfType<Element>()) {
        if (parentElement == aAncestorLimiter ||
            HTMLEditUtils::IsBlockElement(*parentElement, aBlockInlineCheck)) {
          return nullptr;
        }
        if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
            !parentElement->IsEditable()) {
          return nullptr;
        }
        nextContent = parentElement->GetNextSibling();
        if (nextContent) {
          break;
        }
        if (!parentElement->GetParentElement()) {
          NS_WARNING("Reached orphan node while climbing up the DOM tree");
          return nullptr;
        }
      }
      MOZ_ASSERT(nextContent);
      aBlockInlineCheck = IgnoreInsideBlockBoundary(aBlockInlineCheck);
    }

    // We have a next content.  If it's a block, return it.
    if (HTMLEditUtils::IsBlockElement(*nextContent, aBlockInlineCheck)) {
      return nextContent;
    }
    if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
        !nextContent->IsEditable()) {
      return nextContent;
    }
    if (HTMLEditUtils::IsContainerNode(*nextContent)) {
      // Else if it's a container, get deep leftmost child
      if (nsIContent* child = HTMLEditUtils::GetFirstLeafContent(
              *nextContent, aLeafNodeTypes, aBlockInlineCheck)) {
        return child;
      }
    }
    // Else return the next content itself.
    return nextContent;
  }

  /**
   * Similar to the above method, but take a DOM point to specify scan start
   * point.
   */
  template <typename PT, typename CT>
  static nsIContent* GetNextLeafContentOrNextBlockElement(
      const EditorDOMPointBase<PT, CT>& aStartPoint,
      const LeafNodeTypes& aLeafNodeTypes, BlockInlineCheck aBlockInlineCheck,
      const Element* aAncestorLimiter = nullptr) {
    MOZ_ASSERT(aStartPoint.IsSet());
    MOZ_ASSERT_IF(
        aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
        !aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode));
    NS_ASSERTION(!aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
                 "Not implemented yet");

    if (!aStartPoint.IsInContentNode()) {
      return nullptr;
    }
    if (aStartPoint.IsInTextNode()) {
      return HTMLEditUtils::GetNextLeafContentOrNextBlockElement(
          *aStartPoint.template ContainerAs<Text>(), aLeafNodeTypes,
          aBlockInlineCheck, aAncestorLimiter);
    }
    if (!HTMLEditUtils::IsContainerNode(
            *aStartPoint.template ContainerAs<nsIContent>())) {
      return HTMLEditUtils::GetNextLeafContentOrNextBlockElement(
          *aStartPoint.template ContainerAs<nsIContent>(), aLeafNodeTypes,
          aBlockInlineCheck, aAncestorLimiter);
    }

    nsCOMPtr<nsIContent> nextContent = aStartPoint.GetChild();
    if (!nextContent) {
      if (aStartPoint.GetContainer() == aAncestorLimiter ||
          HTMLEditUtils::IsBlockElement(
              *aStartPoint.template ContainerAs<nsIContent>(),
              aBlockInlineCheck)) {
        // We are at end of the block.
        return nullptr;
      }

      // We are at end of non-block container
      return HTMLEditUtils::GetNextLeafContentOrNextBlockElement(
          *aStartPoint.template ContainerAs<nsIContent>(), aLeafNodeTypes,
          IgnoreInsideBlockBoundary(aBlockInlineCheck), aAncestorLimiter);
    }

    // We have a next node.  If it's a block, return it.
    if (HTMLEditUtils::IsBlockElement(*nextContent, aBlockInlineCheck)) {
      return nextContent;
    }
    if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
        !HTMLEditUtils::IsSimplyEditableNode(*nextContent)) {
      return nextContent;
    }
    if (HTMLEditUtils::IsContainerNode(*nextContent)) {
      // else if it's a container, get deep leftmost child
      if (nsIContent* child = HTMLEditUtils::GetFirstLeafContent(
              *nextContent, aLeafNodeTypes,
              IgnoreInsideBlockBoundary(aBlockInlineCheck))) {
        return child;
      }
    }
    // Else return the node itself
    return nextContent;
  }

  /**
   * GetPreviousLeafContentOrPreviousBlockElement() returns previous leaf
   * content or previous block element of aStartContent inside
   * aAncestorLimiter.
   *
   * @param aStartContent       The start content to scan previous content.
   * @param aLeafNodeTypes      See LeafNodeType.
   * @param aAncestorLimiter    Optional, if you set this, it must be an
   *                            inclusive ancestor of aStartContent.
   */
  static nsIContent* GetPreviousLeafContentOrPreviousBlockElement(
      const nsIContent& aStartContent, const LeafNodeTypes& aLeafNodeTypes,
      BlockInlineCheck aBlockInlineCheck,
      const Element* aAncestorLimiter = nullptr) {
    MOZ_ASSERT_IF(
        aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
        !aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode));
    NS_ASSERTION(!aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
                 "Not implemented yet");

    if (&aStartContent == aAncestorLimiter) {
      return nullptr;
    }

    nsIContent* previousContent = aStartContent.GetPreviousSibling();
    if (!previousContent) {
      if (!aStartContent.GetParentElement()) {
        NS_WARNING("Reached orphan node while climbing up the DOM tree");
        return nullptr;
      }
      for (Element* parentElement : aStartContent.AncestorsOfType<Element>()) {
        if (parentElement == aAncestorLimiter ||
            HTMLEditUtils::IsBlockElement(*parentElement, aBlockInlineCheck)) {
          return nullptr;
        }
        if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
            !parentElement->IsEditable()) {
          return nullptr;
        }
        previousContent = parentElement->GetPreviousSibling();
        if (previousContent) {
          break;
        }
        if (!parentElement->GetParentElement()) {
          NS_WARNING("Reached orphan node while climbing up the DOM tree");
          return nullptr;
        }
      }
      MOZ_ASSERT(previousContent);
      aBlockInlineCheck = IgnoreInsideBlockBoundary(aBlockInlineCheck);
    }

    // We have a next content.  If it's a block, return it.
    if (HTMLEditUtils::IsBlockElement(*previousContent, aBlockInlineCheck)) {
      return previousContent;
    }
    if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
        !HTMLEditUtils::IsSimplyEditableNode(*previousContent)) {
      return previousContent;
    }
    if (HTMLEditUtils::IsContainerNode(*previousContent)) {
      // Else if it's a container, get deep rightmost child
      if (nsIContent* child = HTMLEditUtils::GetLastLeafContent(
              *previousContent, aLeafNodeTypes, aBlockInlineCheck)) {
        return child;
      }
    }
    // Else return the next content itself.
    return previousContent;
  }

  /**
   * Similar to the above method, but take a DOM point to specify scan start
   * point.
   */
  template <typename PT, typename CT>
  static nsIContent* GetPreviousLeafContentOrPreviousBlockElement(
      const EditorDOMPointBase<PT, CT>& aStartPoint,
      const LeafNodeTypes& aLeafNodeTypes, BlockInlineCheck aBlockInlineCheck,
      const Element* aAncestorLimiter = nullptr) {
    MOZ_ASSERT(aStartPoint.IsSet());
    MOZ_ASSERT_IF(
        aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
        !aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode));
    NS_ASSERTION(!aLeafNodeTypes.contains(LeafNodeType::OnlyEditableLeafNode),
                 "Not implemented yet");

    if (!aStartPoint.IsInContentNode()) {
      return nullptr;
    }
    if (aStartPoint.IsInTextNode()) {
      return HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
          *aStartPoint.template ContainerAs<Text>(), aLeafNodeTypes,
          aBlockInlineCheck, aAncestorLimiter);
    }
    if (!HTMLEditUtils::IsContainerNode(
            *aStartPoint.template ContainerAs<nsIContent>())) {
      return HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
          *aStartPoint.template ContainerAs<nsIContent>(), aLeafNodeTypes,
          aBlockInlineCheck, aAncestorLimiter);
    }

    if (aStartPoint.IsStartOfContainer()) {
      if (aStartPoint.GetContainer() == aAncestorLimiter ||
          HTMLEditUtils::IsBlockElement(
              *aStartPoint.template ContainerAs<nsIContent>(),
              aBlockInlineCheck)) {
        // We are at start of the block.
        return nullptr;
      }

      // We are at start of non-block container
      return HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
          *aStartPoint.template ContainerAs<nsIContent>(), aLeafNodeTypes,
          IgnoreInsideBlockBoundary(aBlockInlineCheck), aAncestorLimiter);
    }

    nsCOMPtr<nsIContent> previousContent =
        aStartPoint.GetPreviousSiblingOfChild();
    if (NS_WARN_IF(!previousContent)) {
      return nullptr;
    }

    // We have a prior node.  If it's a block, return it.
    if (HTMLEditUtils::IsBlockElement(*previousContent, aBlockInlineCheck)) {
      return previousContent;
    }
    if (aLeafNodeTypes.contains(LeafNodeType::LeafNodeOrNonEditableNode) &&
        !HTMLEditUtils::IsSimplyEditableNode(*previousContent)) {
      return previousContent;
    }
    if (HTMLEditUtils::IsContainerNode(*previousContent)) {
      // Else if it's a container, get deep rightmost child
      if (nsIContent* child = HTMLEditUtils::GetLastLeafContent(
              *previousContent, aLeafNodeTypes,
              IgnoreInsideBlockBoundary(aBlockInlineCheck))) {
        return child;
      }
    }
    // Else return the node itself
    return previousContent;
  }

  /**
   * Returns a content node whose inline styles should be preserved after
   * deleting content in a range.  Typically, you should set aPoint to start
   * boundary of the range to delete.
   */
  template <typename EditorDOMPointType>
  static nsIContent* GetContentToPreserveInlineStyles(
      const EditorDOMPointType& aPoint, const Element& aEditingHost);

  /**
   * Get previous/next editable point from start or end of aContent.
   */
  enum class InvisibleWhiteSpaces {
    Ignore,    // Ignore invisible white-spaces, i.e., don't return middle of
               // them.
    Preserve,  // Preserve invisible white-spaces, i.e., result may be start or
               // end of a text node even if it begins or ends with invisible
               // white-spaces.
  };
  enum class TableBoundary {
    Ignore,                  // May cross any table element boundary.
    NoCrossTableElement,     // Won't cross `<table>` element boundary.
    NoCrossAnyTableElement,  // Won't cross any table element boundary.
  };
  template <typename EditorDOMPointType>
  static EditorDOMPointType GetPreviousEditablePoint(
      nsIContent& aContent, const Element* aAncestorLimiter,
      InvisibleWhiteSpaces aInvisibleWhiteSpaces,
      TableBoundary aHowToTreatTableBoundary);
  template <typename EditorDOMPointType>
  static EditorDOMPointType GetNextEditablePoint(
      nsIContent& aContent, const Element* aAncestorLimiter,
      InvisibleWhiteSpaces aInvisibleWhiteSpaces,
      TableBoundary aHowToTreatTableBoundary);

  /**
   * GetAncestorElement() and GetInclusiveAncestorElement() return
   * (inclusive) block ancestor element of aContent whose time matches
   * aAncestorTypes.
   */
  enum class AncestorType {
    // If there is an ancestor block, it's a limiter of the scan.
    ClosestBlockElement,
    // If there is no ancestor block in the range, the topmost inline element is
    // a limiter of the scan.
    MostDistantInlineElementInBlock,
    // Ignore ancestor <hr> elements to check whether a block.
    IgnoreHRElement,
    // If there is an ancestor <button> element, it's also a limiter of the
    // scan.
    ButtonElement,
    // The root element of the scan start node or the ancestor limiter may be
    // return if there is no proper element.
    AllowRootOrAncestorLimiterElement,

    // Limit to editable elements.  If it reaches an non-editable element,
    // return its child element.
    EditableElement,
  };
  using AncestorTypes = EnumSet<AncestorType>;
  constexpr static AncestorTypes
      ClosestEditableBlockElementOrInlineEditingHost = {
          AncestorType::ClosestBlockElement,
          AncestorType::MostDistantInlineElementInBlock,
          AncestorType::EditableElement};
  constexpr static AncestorTypes ClosestBlockElement = {
      AncestorType::ClosestBlockElement};
  constexpr static AncestorTypes ClosestEditableBlockElement = {
      AncestorType::ClosestBlockElement, AncestorType::EditableElement};
  constexpr static AncestorTypes ClosestBlockElementExceptHRElement = {
      AncestorType::ClosestBlockElement, AncestorType::IgnoreHRElement};
  constexpr static AncestorTypes ClosestEditableBlockElementExceptHRElement = {
      AncestorType::ClosestBlockElement, AncestorType::IgnoreHRElement,
      AncestorType::EditableElement};
  constexpr static AncestorTypes ClosestEditableBlockElementOrButtonElement = {
      AncestorType::ClosestBlockElement, AncestorType::EditableElement,
      AncestorType::ButtonElement};
  static Element* GetAncestorElement(const nsIContent& aContent,
                                     const AncestorTypes& aAncestorTypes,
                                     BlockInlineCheck aBlockInlineCheck,
                                     const Element* aAncestorLimiter = nullptr);
  static Element* GetInclusiveAncestorElement(
      const nsIContent& aContent, const AncestorTypes& aAncestorTypes,
      BlockInlineCheck aBlockInlineCheck,
      const Element* aAncestorLimiter = nullptr);

  /**
   * GetClosestAncestorTableElement() returns the nearest inclusive ancestor
   * <table> element of aContent.
   */
  static Element* GetClosestAncestorTableElement(const nsIContent& aContent) {
    // TODO: the method name and its documentation clash with the
    // implementation. Split this method into
    // `GetClosestAncestorTableElement` and
    // `GetClosestInclusiveAncestorTableElement`.
    if (!aContent.GetParent()) {
      return nullptr;
    }
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