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products/Sources/formale Sprachen/C/Firefox/editor/libeditor/ (Browser von der Mozilla Stiftung Version 136.0.1^©) Datei vom 10.2.2025 mit Größe 120 kB

Quelle HTMLEditUtils.cpp 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/. */

#include "HTMLEditUtils.h"

#include "AutoClonedRangeArray.h" // for AutoClonedRangeArray
#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 "WSRunScanner.h" // for WSRunScanner

#include "mozilla/ArrayUtils.h" // for ArrayLength
#include "mozilla/Assertions.h" // for MOZ_ASSERT, etc.
#include "mozilla/Attributes.h"
#include "mozilla/StaticPrefs_editor.h" // for StaticPrefs::editor_
#include "mozilla/RangeUtils.h" // for RangeUtils
#include "mozilla/dom/DocumentInlines.h" // for GetBodyElement()
#include "mozilla/dom/Element.h" // for Element, nsINode
#include "mozilla/dom/ElementInlines.h" // for IsContentEditablePlainTextOnly()
#include "mozilla/dom/HTMLAnchorElement.h"
#include "mozilla/dom/HTMLBodyElement.h"
#include "mozilla/dom/HTMLInputElement.h"
#include "mozilla/ServoCSSParser.h" // for ServoCSSParser
#include "mozilla/dom/StaticRange.h"
#include "mozilla/dom/Text.h" // for Text

#include "nsAString.h" // for nsAString::IsEmpty
#include "nsAtom.h" // for nsAtom
#include "nsAttrValue.h" // nsAttrValue
#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 "nsIContentInlines.h" // for nsIContent::IsInDesignMode(), etc.
#include "nsIFrameInlines.h" // for nsIFrame::IsFlexOrGridItem()
#include "nsLiteralString.h" // for NS_LITERAL_STRING
#include "nsNameSpaceManager.h" // for kNameSpaceID_None
#include "nsPrintfCString.h" // nsPringfCString
#include "nsString.h" // for nsAutoString
#include "nsStyledElement.h"
#include "nsStyleStruct.h" // for StyleDisplay
#include "nsStyleUtil.h" // for nsStyleUtil
#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,
 BlockInlineCheck aBlockInlineCheck, const Element* aAncestorLimiter);
template nsIContent* HTMLEditUtils::GetPreviousContent(
 const EditorRawDOMPoint& aPoint, const WalkTreeOptions& aOptions,
 BlockInlineCheck aBlockInlineCheck, const Element* aAncestorLimiter);
template nsIContent* HTMLEditUtils::GetPreviousContent(
 const EditorDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
 BlockInlineCheck aBlockInlineCheck, const Element* aAncestorLimiter);
template nsIContent* HTMLEditUtils::GetPreviousContent(
 const EditorRawDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
 BlockInlineCheck aBlockInlineCheck, const Element* aAncestorLimiter);
template nsIContent* HTMLEditUtils::GetNextContent(
 const EditorDOMPoint& aPoint, const WalkTreeOptions& aOptions,
 BlockInlineCheck aBlockInlineCheck, const Element* aAncestorLimiter);
template nsIContent* HTMLEditUtils::GetNextContent(
 const EditorRawDOMPoint& aPoint, const WalkTreeOptions& aOptions,
 BlockInlineCheck aBlockInlineCheck, const Element* aAncestorLimiter);
template nsIContent* HTMLEditUtils::GetNextContent(
 const EditorDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
 BlockInlineCheck aBlockInlineCheck, const Element* aAncestorLimiter);
template nsIContent* HTMLEditUtils::GetNextContent(
 const EditorRawDOMPointInText& aPoint, const WalkTreeOptions& aOptions,
 BlockInlineCheck aBlockInlineCheck, 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 EditorDOMPoint HTMLEditUtils::LineRequiresPaddingLineBreakToBeVisible(
 const EditorDOMPoint& aPoint, const Element& aEditingHost);
template EditorDOMPoint HTMLEditUtils::LineRequiresPaddingLineBreakToBeVisible(
 const EditorRawDOMPoint& aPoint, const Element& aEditingHost);
template EditorDOMPoint HTMLEditUtils::LineRequiresPaddingLineBreakToBeVisible(
 const EditorDOMPointInText& aPoint, const Element& aEditingHost);
template EditorDOMPoint HTMLEditUtils::LineRequiresPaddingLineBreakToBeVisible(
 const EditorRawDOMPointInText& aPoint, const Element& aEditingHost);

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);
template EditorRawDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
 const nsIContent& aContentToInsert,
 const EditorRawDOMPoint& aPointToInsert);
template EditorDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
 const nsIContent& aContentToInsert,
 const EditorRawDOMPoint& aPointToInsert);
template EditorRawDOMPoint HTMLEditUtils::GetBetterInsertionPointFor(
 const nsIContent& aContentToInsert, const EditorDOMPoint& aPointToInsert);

template EditorDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
 const EditorDOMPoint& aPoint);
template EditorDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
 const EditorRawDOMPoint& aPoint);
template EditorRawDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
 const EditorDOMPoint& aPoint);
template EditorRawDOMPoint HTMLEditUtils::GetBetterCaretPositionToInsertText(
 const EditorRawDOMPoint& aPoint);

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);

template bool HTMLEditUtils::IsSameCSSColorValue(const nsAString& aColorA,
 const nsAString& aColorB);
template bool HTMLEditUtils::IsSameCSSColorValue(const nsACString& aColorA,
 const nsACString& aColorB);

template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorDOMPoint& aPoint);
template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorRawDOMPoint& aPoint);
template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorDOMPointInText& aPoint);
template Maybe<EditorLineBreak> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorRawDOMPointInText& aPoint);
template Maybe<EditorRawLineBreak>
HTMLEditUtils::GetFollowingUnnecessaryLineBreak(const EditorDOMPoint& aPoint);
template Maybe<EditorRawLineBreak>
HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorRawDOMPoint& aPoint);
template Maybe<EditorRawLineBreak>
HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorDOMPointInText& aPoint);
template Maybe<EditorRawLineBreak>
HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorRawDOMPointInText& aPoint);

template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
 const EditorDOMPoint& aPoint,
 IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
 const EditorRawDOMPoint& aPoint,
 IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
 const EditorDOMPointInText& aPoint,
 IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);
template bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
 const EditorRawDOMPointInText& aPoint,
 IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak);

template Maybe<EditorLineBreak> HTMLEditUtils::GetUnnecessaryLineBreak(
 const Element& aBlockElement, ScanLineBreak aScanLineBreak);
template Maybe<EditorRawLineBreak> HTMLEditUtils::GetUnnecessaryLineBreak(
 const Element& aBlockElement, ScanLineBreak aScanLineBreak);

bool HTMLEditUtils::ElementIsEditableRoot(const Element& aElement) {
 MOZ_ASSERT(!aElement.IsInNativeAnonymousSubtree());
 if (NS_WARN_IF(!aElement.IsEditable()) ||
 NS_WARN_IF(!aElement.IsInComposedDoc())) {
 return false;
 }
 return !aElement.GetParent() || // root element
 !aElement.GetParent()->IsEditable() || // editing host
 aElement.OwnerDoc()->GetBody() == &aElement; // the <body>
}

bool HTMLEditUtils::CanContentsBeJoined(const nsIContent& aLeftContent,
 const nsIContent& aRightContent) {
 if (aLeftContent.NodeInfo()->NameAtom() !=
 aRightContent.NodeInfo()->NameAtom()) {
 return false;
 }

 if (!aLeftContent.IsElement()) {
 return true; // can join text nodes, etc
 }
 MOZ_ASSERT(aRightContent.IsElement());

 if (aLeftContent.NodeInfo()->NameAtom() == nsGkAtoms::font) {
 const nsAttrValue* const leftSize =
 aLeftContent.AsElement()->GetParsedAttr(nsGkAtoms::size);
 const nsAttrValue* const rightSize =
 aRightContent.AsElement()->GetParsedAttr(nsGkAtoms::size);
 if (!leftSize ^ !rightSize || (leftSize && !leftSize->Equals(*rightSize))) {
 return false;
 }

 const nsAttrValue* const leftColor =
 aLeftContent.AsElement()->GetParsedAttr(nsGkAtoms::color);
 const nsAttrValue* const rightColor =
 aRightContent.AsElement()->GetParsedAttr(nsGkAtoms::color);
 if (!leftColor ^ !rightColor ||
 (leftColor && !leftColor->Equals(*rightColor))) {
 return false;
 }

 const nsAttrValue* const leftFace =
 aLeftContent.AsElement()->GetParsedAttr(nsGkAtoms::face);
 const nsAttrValue* const rightFace =
 aRightContent.AsElement()->GetParsedAttr(nsGkAtoms::face);
 if (!leftFace ^ !rightFace || (leftFace && !leftFace->Equals(*rightFace))) {
 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);
}

static bool IsHTMLBlockElementByDefault(const nsIContent& aContent) {
 if (!aContent.IsHTMLElement()) {
 return false;
 }
 if (aContent.IsHTMLElement(nsGkAtoms::br)) { // shortcut for TextEditor
 MOZ_ASSERT(!nsHTMLElement::IsBlock(
 nsHTMLTags::CaseSensitiveAtomTagToId(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::CaseSensitiveAtomTagToId(aContent.NodeInfo()->NameAtom()));
}

bool HTMLEditUtils::IsBlockElement(const nsIContent& aContent,
 BlockInlineCheck aBlockInlineCheck) {
 MOZ_ASSERT(aBlockInlineCheck != BlockInlineCheck::Unused);

 if (MOZ_UNLIKELY(!aContent.IsElement())) {
 return false;
 }
 // If it's a , we should always treat it as an inline element because
 // its preceding collapse white-spaces and another works same as usual
 // even if you set its style to `display:block`.
 if (aContent.IsHTMLElement(nsGkAtoms::br)) {
 return false;
 }
 if (aBlockInlineCheck == BlockInlineCheck::UseHTMLDefaultStyle) {
 return IsHTMLBlockElementByDefault(aContent);
 }
 // Let's treat the document element and the body element is a block to avoid
 // complicated things which may be detected by fuzzing.
 if (aContent.OwnerDoc()->GetDocumentElement() == &aContent ||
 (aContent.IsHTMLElement(nsGkAtoms::body) &&
 aContent.OwnerDoc()->GetBodyElement() == &aContent)) {
 return true;
 }
 RefPtr<const ComputedStyle> elementStyle =
 nsComputedDOMStyle::GetComputedStyleNoFlush(aContent.AsElement());
 if (MOZ_UNLIKELY(!elementStyle)) { // If aContent is not in the composed tree
 return IsHTMLBlockElementByDefault(aContent);
 }
 const nsStyleDisplay* styleDisplay = elementStyle->StyleDisplay();
 if (MOZ_UNLIKELY(styleDisplay->mDisplay == StyleDisplay::None)) {
 // Typically, we should not keep handling editing in invisible nodes, but if
 // we reach here, let's fallback to the default style for protecting the
 // structure as far as possible.
 return IsHTMLBlockElementByDefault(aContent);
 }
 // Both Blink and WebKit treat ruby style as a block, see IsEnclosingBlock()
 // in Chromium or isBlock() in WebKit.
 if (styleDisplay->IsRubyDisplayType()) {
 return true;
 }
 // If the outside is not inline, treat it as block.
 if (!styleDisplay->IsInlineOutsideStyle()) {
 return true;
 }
 // If we're checking display-inside, inline-block, etc should be a block too.
 return aBlockInlineCheck == BlockInlineCheck::UseComputedDisplayStyle &&
 styleDisplay->DisplayInside() == StyleDisplayInside::FlowRoot &&
 // Treat widgets as inline since they won't hide collapsible
 // white-spaces around them.
 styleDisplay->EffectiveAppearance() == StyleAppearance::None;
}

bool HTMLEditUtils::IsInlineContent(const nsIContent& aContent,
 BlockInlineCheck aBlockInlineCheck) {
 MOZ_ASSERT(aBlockInlineCheck != BlockInlineCheck::Unused);

 if (!aContent.IsElement()) {
 return true;
 }
 // If it's a , we should always treat it as an inline element because
 // its preceding collapse white-spaces and another works same as usual
 // even if you set its style to `display:block`.
 if (aContent.IsHTMLElement(nsGkAtoms::br)) {
 return true;
 }
 if (aBlockInlineCheck == BlockInlineCheck::UseHTMLDefaultStyle) {
 return !IsHTMLBlockElementByDefault(aContent);
 }
 // Let's treat the document element and the body element is a block to avoid
 // complicated things which may be detected by fuzzing.
 if (aContent.OwnerDoc()->GetDocumentElement() == &aContent ||
 (aContent.IsHTMLElement(nsGkAtoms::body) &&
 aContent.OwnerDoc()->GetBodyElement() == &aContent)) {
 return false;
 }
 RefPtr<const ComputedStyle> elementStyle =
 nsComputedDOMStyle::GetComputedStyleNoFlush(aContent.AsElement());
 if (MOZ_UNLIKELY(!elementStyle)) { // If aContent is not in the composed tree
 return !IsHTMLBlockElementByDefault(aContent);
 }
 const nsStyleDisplay* styleDisplay = elementStyle->StyleDisplay();
 if (MOZ_UNLIKELY(styleDisplay->mDisplay == StyleDisplay::None)) {
 // Similar to IsBlockElement, let's fallback to refer the default style.
 // Note that if you change here, you may need to check the parent element
 // style if aContent.
 return !IsHTMLBlockElementByDefault(aContent);
 }
 // Different block IsBlockElement, when the display-outside is inline, it's
 // simply an inline element.
 return styleDisplay->IsInlineOutsideStyle() ||
 styleDisplay->IsRubyDisplayType();
}

bool HTMLEditUtils::IsFlexOrGridItem(const Element& aElement) {
 nsIFrame* frame = aElement.GetPrimaryFrame();
 return frame && frame->IsFlexOrGridItem();
}

bool HTMLEditUtils::IsInclusiveAncestorCSSDisplayNone(
 const nsIContent& aContent) {
 if (NS_WARN_IF(!aContent.IsInComposedDoc())) {
 return true;
 }
 for (const Element* element :
 aContent.InclusiveFlatTreeAncestorsOfType<Element>()) {
 RefPtr<const ComputedStyle> elementStyle =
 nsComputedDOMStyle::GetComputedStyleNoFlush(element);
 if (NS_WARN_IF(!elementStyle)) {
 continue;
 }
 const nsStyleDisplay* styleDisplay = elementStyle->StyleDisplay();
 if (MOZ_UNLIKELY(styleDisplay->mDisplay == StyleDisplay::None)) {
 return true;
 }
 }
 return false;
}

bool HTMLEditUtils::IsVisibleElementEvenIfLeafNode(const nsIContent& aContent) {
 if (!aContent.IsElement()) {
 return false;
 }
 // Assume non-HTML element is visible.
 if (!aContent.IsHTMLElement()) {
 return true;
 }
 // XXX Should we return false if the element is display:none?
 if (HTMLEditUtils::IsBlockElement(
 aContent, BlockInlineCheck::UseComputedDisplayStyle)) {
 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;
 }
 // If the element has a primary frame and it's not empty, the element is
 // visible.
 // XXX This method does not guarantee that the layout has already been
 // updated. Therefore, this check might be wrong in the edge cases.
 // However, basically, editor apps should not depend on this path, this
 // is required if last before a block boundary becomes visible because
 // of followed by empty but styled frame like .
 if (aContent.GetPrimaryFrame() &&
 !aContent.GetPrimaryFrame()->GetSize().IsEmpty()) {
 return true;
 }
 // Maybe, empty inline element such as .
 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");
}

/**
* 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;
 }

 nsAutoCString 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(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();
}

template <typename PT, typename CT>
EditorDOMPoint HTMLEditUtils::LineRequiresPaddingLineBreakToBeVisible(
 const EditorDOMPointBase<PT, CT>& aPoint, const Element& aEditingHost) {
 if (MOZ_UNLIKELY(!aPoint.IsInContentNode())) {
 return EditorDOMPoint();
 }
 // First, if the container is an element node, get the next deepest point.
 EditorRawDOMPoint point = aPoint.template To<EditorRawDOMPoint>();
 if (point.IsContainerElement()) {
 for (nsIContent* child = point.GetChild(); child;
 child = child->GetFirstChild()) {
 if (child->IsHTMLElement(nsGkAtoms::br)) {
 return EditorDOMPoint();
 }
 if (!HTMLEditUtils::IsSimplyEditableNode(*child) ||
 HTMLEditUtils::IsBlockElement(
 *child, BlockInlineCheck::UseComputedDisplayOutsideStyle) ||
 (child->IsElement() && !HTMLEditUtils::IsContainerNode(*child))) {
 break;
 }
 point.Set(child, 0);
 }
 }
 // If the point is in a Text, check the next character in it to skip the
 // expensive check below.
 if (point.IsInTextNode()) {
 if (!point.IsStartOfContainer() &&
 !point.IsPreviousCharCollapsibleASCIISpace()) {
 return EditorDOMPoint(); // Not following collapsible white-space
 }
 if (!point.IsEndOfContainer()) {
 if (!point.IsCharCollapsibleASCIISpace()) {
 return EditorDOMPoint();
 }
 const bool linefeedPreformatted = EditorUtils::IsNewLinePreformatted(
 *point.template ContainerAs<Text>());
 const nsTextFragment& fragment =
 point.template ContainerAs<Text>()->TextFragment();
 for (uint32_t i : IntegerRange(point.Offset(), fragment.GetLength())) {
 const char16_t ch = fragment.CharAt(i);
 if (linefeedPreformatted && ch == HTMLEditUtils::kNewLine) {
 return EditorDOMPoint(); // Followed by a preformatted line break.
 }
 if (!nsCRT::IsAsciiSpace(ch)) {
 return EditorDOMPoint(); // Followed by a visible character.
 }
 }
 }
 }

 const auto AdjustPointToInsertPaddingLineBreak =
 [](EditorDOMPoint& aPointToInsertLineBreak,
 const Element* aParentBlockElement, const Element& aEditingHost) {
 if (MOZ_UNLIKELY(!aPointToInsertLineBreak.IsInContentNode())) {
 aPointToInsertLineBreak.Clear();
 return;
 }
 while (MOZ_UNLIKELY(!HTMLEditUtils::CanNodeContain(
 *aPointToInsertLineBreak.GetContainer(), *nsGkAtoms::br))) {
 if (MOZ_UNLIKELY(aPointToInsertLineBreak.GetContainer() ==
 aParentBlockElement ||
 aPointToInsertLineBreak.GetContainer() ==
 &aEditingHost)) {
 aPointToInsertLineBreak.Clear();
 return;
 }
 aPointToInsertLineBreak.SetAfterContainer();
 if (MOZ_UNLIKELY(!aPointToInsertLineBreak.IsInContentNode())) {
 aPointToInsertLineBreak.Clear();
 return;
 }
 }
 };

 // If the point is in an empty block, we can skip the expensive check below
 // too.
 const Element* maybeNonEditableBlock =
 HTMLEditUtils::GetInclusiveAncestorElement(
 *point.ContainerAs<nsIContent>(), ClosestBlockElement,
 BlockInlineCheck::UseComputedDisplayStyle);
 if (maybeNonEditableBlock &&
 HTMLEditUtils::IsEmptyNode(
 *maybeNonEditableBlock,
 {EmptyCheckOption::TreatSingleBRElementAsVisible})) {
 EditorDOMPoint pointToInsertLineBreak =
 HTMLEditUtils::GetDeepestEditableEndPointOf<EditorDOMPoint>(
 *maybeNonEditableBlock);
 if (pointToInsertLineBreak.IsInTextNode()) {
 pointToInsertLineBreak.SetAfterContainer();
 }
 AdjustPointToInsertPaddingLineBreak(pointToInsertLineBreak,
 maybeNonEditableBlock, aEditingHost);
 return pointToInsertLineBreak;
 }

 EditorDOMPoint preferredPaddingLineBreakPoint;
 const bool followedByBlockBoundary = [&]() {
 if (point.GetContainer() == maybeNonEditableBlock &&
 point.IsEndOfContainer()) {
 preferredPaddingLineBreakPoint = point.To<EditorDOMPoint>();
 return true;
 }
 if (point.GetContainer() == &aEditingHost && point.IsEndOfContainer()) {
 return false;
 }
 const WSScanResult nextThing =
 WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
 WSRunScanner::Scan::EditableNodes, point,
 BlockInlineCheck::UseComputedDisplayOutsideStyle);
 if (nextThing.ReachedBlockBoundary()) {
 if (nextThing.ReachedCurrentBlockBoundary()) {
 preferredPaddingLineBreakPoint = point.AfterContainer<EditorDOMPoint>();
 } else {
 preferredPaddingLineBreakPoint = point.To<EditorDOMPoint>();
 }
 return true;
 }
 return false;
 }();
 if (!followedByBlockBoundary) {
 return EditorDOMPoint();
 }
 const bool followingBlockBoundaryOrCollapsibleWhiteSpace = [&]() {
 if (point.GetContainer() == maybeNonEditableBlock &&
 point.IsStartOfContainer()) {
 return true;
 }
 const WSScanResult previousThing =
 WSRunScanner::ScanPreviousVisibleNodeOrBlockBoundary(
 WSRunScanner::Scan::EditableNodes, preferredPaddingLineBreakPoint,
 BlockInlineCheck::UseComputedDisplayOutsideStyle);
 if (previousThing.ContentIsText()) {
 if (MOZ_UNLIKELY(!previousThing.TextPtr()->TextDataLength())) {
 return false;
 }
 auto atLastChar = EditorRawDOMPointInText(
 previousThing.TextPtr(),
 previousThing.TextPtr()->TextDataLength() - 1);
 if (atLastChar.IsCharCollapsibleASCIISpace()) {
 preferredPaddingLineBreakPoint.SetAfter(previousThing.TextPtr());
 return true;
 }
 return false;
 }
 return previousThing.ReachedBlockBoundary();
 }();
 if (!followingBlockBoundaryOrCollapsibleWhiteSpace) {
 return EditorDOMPoint();
 }
 AdjustPointToInsertPaddingLineBreak(preferredPaddingLineBreakPoint,
 maybeNonEditableBlock, aEditingHost);
 return preferredPaddingLineBreakPoint;
}

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,
 BlockInlineCheck::UseComputedDisplayStyle);
 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},
 BlockInlineCheck::UseComputedDisplayStyle,
 maybeNonEditableAncestorBlock)
 : HTMLEditUtils::GetPreviousContent(
 aContent,
 {WalkTreeOption::IgnoreDataNodeExceptText,
 WalkTreeOption::StopAtBlockBoundary},
 BlockInlineCheck::UseComputedDisplayStyle,
 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, BlockInlineCheck::UseComputedDisplayStyle)) {
 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 element, another element prevents the
 // block boundary special handling.
 if (isBRElement) {
 return nullptr;
 }

 MOZ_ASSERT(aContent.IsText());
 // Following 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 element, its white-spaces at
 // start of the text node are invisible. In this case, we return
 // the found element.
 return nextContent->AsElement();
 }

 continue;
 }

 switch (nextContent->NodeType()) {
 case nsINode::TEXT_NODE:
 case nsINode::CDATA_SECTION_NODE:
 break;
 default:
 continue;
 }

 Text* textNode = Text::FromNode(nextContent);
 MOZ_ASSERT(textNode);
 if (!textNode->TextLength()) {
 continue; // empty invisible text node, keep scanning next one.
 }
 if (HTMLEditUtils::IsInclusiveAncestorCSSDisplayNone(*textNode)) {
 continue; // Styled as invisible.
 }
 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 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;
}

template <typename PT, typename CT>
bool HTMLEditUtils::PointIsImmediatelyBeforeCurrentBlockBoundary(
 const EditorDOMPointBase<PT, CT>& aPoint,
 IgnoreInvisibleLineBreak aIgnoreInvisibleLineBreak) {
 MOZ_ASSERT(aPoint.IsSetAndValidInComposedDoc());

 if (MOZ_UNLIKELY(!aPoint.IsInContentNode())) {
 return false;
 }
 const WSScanResult nextThing =
 WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
 WSRunScanner::Scan::EditableNodes, aPoint,
 BlockInlineCheck::UseComputedDisplayOutsideStyle);
 if (nextThing.ReachedCurrentBlockBoundary()) {
 return true;
 }
 if (nextThing.ReachedInvisibleBRElement()) {
 if (aIgnoreInvisibleLineBreak == IgnoreInvisibleLineBreak::No) {
 return false;
 }
 const WSScanResult afterInvisibleBRThing =
 WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
 WSRunScanner::Scan::EditableNodes,
 nextThing.PointAfterReachedContent<EditorRawDOMPoint>(),
 BlockInlineCheck::UseComputedDisplayOutsideStyle);
 return afterInvisibleBRThing.ReachedCurrentBlockBoundary();
 }
 if (nextThing.ReachedPreformattedLineBreak()) {
 if (aIgnoreInvisibleLineBreak == IgnoreInvisibleLineBreak::No) {
 return false;
 }
 const WSScanResult afterPreformattedLineBreakThing =
 WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
 WSRunScanner::Scan::EditableNodes,
 nextThing.PointAfterReachedContent<EditorRawDOMPoint>(),
 BlockInlineCheck::UseComputedDisplayOutsideStyle);
 return afterPreformattedLineBreakThing.ReachedCurrentBlockBoundary();
 }
 return false;
}

template <typename EditorLineBreakType>
Maybe<EditorLineBreakType> HTMLEditUtils::GetUnnecessaryLineBreak(
 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,
 BlockInlineCheck::UseComputedDisplayStyle,
 aBlockElement.GetParentElement());
 content;
 content =
 aScanLineBreak == ScanLineBreak::AtEndOfBlock
 ? HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
 *content, leafNodeOrNonEditableNode,
 BlockInlineCheck::UseComputedDisplayStyle,
 &aBlockElement)
 : HTMLEditUtils::GetPreviousContent(
 *content, onlyPrecedingLine,
 BlockInlineCheck::UseComputedDisplayStyle,
 aBlockElement.GetParentElement())) {
 // If we're scanning preceding element of aBlockElement, we don't
 // need to look for a line break in another block because the caller
 // needs to handle only preceding element of aBlockElement.
 if (aScanLineBreak == ScanLineBreak::BeforeBlock &&
 HTMLEditUtils::IsBlockElement(
 *content, BlockInlineCheck::UseComputedDisplayStyle)) {
 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 (HTMLEditUtils::IsVisibleElementEvenIfLeafNode(*content)) {
 return nullptr;
 }
 // Otherwise, e.g., empty , we should keep scanning.
 }
 return nullptr;
 }();
 if (!lastLineBreakContent) {
 return Nothing();
 }

 // 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* const lastLineBreakText = Text::FromNode(lastLineBreakContent);
 if (lastLineBreakText && lastLineBreakText->TextDataLength() != 1u) {
 return Some(EditorLineBreakType::AtLastChar(*lastLineBreakText));
 }
 HTMLBRElement* const lastBRElement =
 lastLineBreakText ? nullptr
 : HTMLBRElement::FromNode(lastLineBreakContent);
 MOZ_ASSERT_IF(!lastLineBreakText, lastBRElement);

 // 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,
 BlockInlineCheck::UseComputedDisplayStyle);
 for (nsIContent* content =
 HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
 *lastLineBreakContent, leafNodeOrNonEditableNodeOrChildBlock,
 BlockInlineCheck::UseComputedDisplayStyle, blockElement);
 content;
 content = HTMLEditUtils::GetPreviousLeafContentOrPreviousBlockElement(
 *content, leafNodeOrNonEditableNodeOrChildBlock,
 BlockInlineCheck::UseComputedDisplayStyle, blockElement)) {
 if (HTMLEditUtils::IsBlockElement(
 *content, BlockInlineCheck::UseComputedDisplayStyle) ||
 (content->IsElement() && !content->IsHTMLElement())) {
 // Now, must found <div>...<div>...</div> </div>
 // ^^^^
 // In this case, the element is necessary to make a following empty
 // line of the inner <div> visible.
 return Nothing();
 }
 if (Text* textNode = Text::FromNode(content)) {
 if (!textNode->TextDataLength()) {
 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 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 Nothing();
 }
 if (!HTMLEditUtils::IsVisibleTextNode(*textNode)) {
 continue;
 }
 if (EditorUtils::IsWhiteSpacePreformatted(*textNode)) {
 // If the white-space is preserved, neither following nor a
 // preformatted line break is not necessary.
 return Some(lastLineBreakText
 ? EditorLineBreakType::AtLastChar(*lastLineBreakText)
 : EditorLineBreakType(*lastBRElement));
 }
 // 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::kNewLine:
 case HTMLEditUtils::kCarriageReturn:
 case HTMLEditUtils::kTab:
 return Nothing();
 default:
 return Some(lastLineBreakText
 ? EditorLineBreakType::AtLastChar(*lastLineBreakText)
 : EditorLineBreakType(*lastBRElement));
 }
 }
 if (content->IsCharacterData()) {
 continue; // ignore hidden character data nodes like comment
 }
 // If lastLineBreakContent follows a element in same block, it's
 // necessary to make the empty last line visible.
 if (content->IsHTMLElement(nsGkAtoms::br)) {
 return Nothing();
 }
 if (HTMLEditUtils::IsVisibleElementEvenIfLeafNode(*content)) {
 return Some(lastLineBreakText
 ? EditorLineBreakType::AtLastChar(*lastLineBreakText)
 : EditorLineBreakType(*lastBRElement));
 }
 // Otherwise, ignore empty inline elements such as .
 }
 // If the block is empty except invisible data nodes and lastLineBreakContent,
 // lastLineBreakContent is necessary to make the block visible.
 return Nothing();
}

template <typename EditorLineBreakType, typename EditorDOMPointType>
Maybe<EditorLineBreakType> HTMLEditUtils::GetFollowingUnnecessaryLineBreak(
 const EditorDOMPointType& aPoint) {
 MOZ_ASSERT(aPoint.IsSetAndValid());
 MOZ_ASSERT(aPoint.IsInContentNode());

 const WSScanResult nextThing =
 WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
 WSRunScanner::Scan::EditableNodes, aPoint,
 BlockInlineCheck::UseComputedDisplayStyle);
 if (!nextThing.ReachedBRElement() &&
 !(nextThing.ReachedPreformattedLineBreak() &&
 nextThing.PointAtReachedContent<EditorRawDOMPoint>()
 .IsAtLastContent())) {
 return Nothing(); // no line break next to aPoint
 }
 const WSScanResult nextThingOfLineBreak =
 WSRunScanner::ScanInclusiveNextVisibleNodeOrBlockBoundary(
 WSRunScanner::Scan::EditableNodes,
 nextThing.PointAfterReachedContent<EditorRawDOMPoint>(),
 BlockInlineCheck::UseComputedDisplayStyle);
 const Element* const blockElement =
 nextThingOfLineBreak.ReachedBlockBoundary()
 ? nextThingOfLineBreak.ElementPtr()
 : HTMLEditUtils::GetAncestorElement(
 *nextThing.GetContent(), {AncestorType::ClosestBlockElement},
 BlockInlineCheck::UseComputedDisplayStyle);
 if (MOZ_UNLIKELY(!blockElement)) {
 return Nothing();
 }
 Maybe<EditorLineBreakType> unnecessaryLineBreak =
 GetUnnecessaryLineBreak<EditorLineBreakType>(
 *blockElement, nextThingOfLineBreak.ReachedOtherBlockElement()
 ? ScanLineBreak::BeforeBlock
 : ScanLineBreak::AtEndOfBlock);
 // If the line break content is different from the found line break
 // immediately after aPoint, it's too far. So, the caller should not touch it.
 if (unnecessaryLineBreak.isSome() &&
 &unnecessaryLineBreak->ContentRef() != nextThing.GetContent()) {
 unnecessaryLineBreak.reset();
 }
 return unnecessaryLineBreak;
}

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);
 }

 if (!aNode.IsElement()) {
 return false;
 }

 if (
 // If it's not a container such as an <hr> or , 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)) {
 return false;
 }

 const auto [isListItem, isTableCell, hasAppearance] =
 [&]() MOZ_NEVER_INLINE_DEBUG -> std::tuple<bool, bool, bool> {
 // Let's stop treating the document element and the <body> as a list item
 // nor a table cell to avoid tricky cases.
 if (aNode.OwnerDoc()->GetDocumentElement() == &aNode ||
 (aNode.IsHTMLElement(nsGkAtoms::body) &&
 aNode.OwnerDoc()->GetBodyElement() == &aNode)) {
 return {false, false, false};
 }

 RefPtr<const ComputedStyle> elementStyle =
 nsComputedDOMStyle::GetComputedStyleNoFlush(aNode.AsElement());
 // If there is no style information like in a document fragment, let's refer
 // the default style.
 if (MOZ_UNLIKELY(!elementStyle)) {
 return {IsListItem(&aNode), IsTableCell(&aNode), false};
 }
 const nsStyleDisplay* styleDisplay = elementStyle->StyleDisplay();
 if (NS_WARN_IF(!styleDisplay)) {
 return {IsListItem(&aNode), IsTableCell(&aNode), false};
 }
 if (styleDisplay->mDisplay != StyleDisplay::None &&
 styleDisplay->HasAppearance()) {
 return {false, false, true};
 }
 if (styleDisplay->IsListItem()) {
 return {true, false, false};
 }
 if (styleDisplay->mDisplay == StyleDisplay::TableCell) {
 return {false, true, false};
 }
 // The default display of <dt> and <dd> is block. Therefore, we need
 // special handling for them.
 return {styleDisplay->mDisplay == StyleDisplay::Block &&
 aNode.IsAnyOfHTMLElements(nsGkAtoms::dd, nsGkAtoms::dt),
 false, false};
 }();

 // The web author created native widget without form control elements. Let's
 // treat it as visible.
 if (hasAppearance) {
 return false;
 }

 if (isListItem &&
 aOptions.contains(EmptyCheckOption::TreatListItemAsVisible)) {
 return false;
 }
 if (isTableCell &&
 aOptions.contains(EmptyCheckOption::TreatTableCellAsVisible)) {
 return false;
 }

 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::TreatNonEditableContentAsInvisible) &&
 !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;
 }

 MOZ_ASSERT(childContent != &aNode);

 if (!aOptions.contains(EmptyCheckOption::TreatSingleBRElementAsVisible) &&
 !seenBR && childContent->IsHTMLElement(nsGkAtoms::br)) {
 // Ignore first element in it if caller wants so because it's
 // typically a padding element of for a parent block.
 seenBR = true;
 if (aSeenBR) {
 *aSeenBR = true;
 }
 continue;
 }

 if (aOptions.contains(EmptyCheckOption::TreatBlockAsVisible) &&
 HTMLEditUtils::IsBlockElement(
 *childContent, BlockInlineCheck::UseComputedDisplayOutsideStyle)) {
 return false;
 }

 // Note: list items or table cells are not considered empty
 // if they contain other lists or tables
 EmptyCheckOptions options(aOptions);
 if (childContent->IsElement() && (isListItem || isTableCell)) {
 options += {EmptyCheckOption::TreatListItemAsVisible,
 EmptyCheckOption::TreatTableCellAsVisible};
 }
 if (!IsEmptyNode(aPresContext, *childContent, options, &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;
 }

 // If in contenteditable=plaintext-only, we should use linefeed when it's
 // preformatted.
 if (aEditingHost.IsContentEditablePlainTextOnly()) {
 return EditorUtils::IsNewLinePreformatted(
 *aPointToInsert.ContainerAs<nsIContent>());
 }

 // closestEditableBlockElement can be nullptr if aEditingHost is an inline
 // element.
 Element* closestEditableBlockElement =
 HTMLEditUtils::GetInclusiveAncestorElement(
 *aPointToInsert.ContainerAs<nsIContent>(),
 HTMLEditUtils::ClosestEditableBlockElement,
 BlockInlineCheck::UseComputedDisplayOutsideStyle);

 // If and only if the nearest block is the editing host or its parent,
 // and new line character is preformatted, we should insert a linefeed.
 return (!closestEditableBlockElement ||
 closestEditableBlockElement == &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, search, 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),
--> --------------------

--> maximum size reached

--> --------------------

quality98%

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