Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

1 files changed, 1826 insertions, 0 deletions

diff --git a/dom/serializers/nsPlainTextSerializer.cpp b/dom/serializers/nsPlainTextSerializer.cpp
new file mode 100644
index 0000000000..952ed39942
--- /dev/null
+++ b/dom/serializers/nsPlainTextSerializer.cpp
@@ -0,0 +1,1826 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/*
+ * nsIContentSerializer implementation that can be used with an
+ * nsIDocumentEncoder to convert a DOM into plaintext in a nice way
+ * (eg for copy/paste as plaintext).
+ */
+
+#include "nsPlainTextSerializer.h"
+
+#include <limits>
+
+#include "nsPrintfCString.h"
+#include "nsDebug.h"
+#include "nsGkAtoms.h"
+#include "nsNameSpaceManager.h"
+#include "nsTextFragment.h"
+#include "nsContentUtils.h"
+#include "nsReadableUtils.h"
+#include "nsUnicharUtils.h"
+#include "nsCRT.h"
+#include "mozilla/Casting.h"
+#include "mozilla/TextEditor.h"
+#include "mozilla/dom/CharacterData.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLBRElement.h"
+#include "mozilla/dom/Text.h"
+#include "mozilla/intl/Segmenter.h"
+#include "mozilla/intl/UnicodeProperties.h"
+#include "nsUnicodeProperties.h"
+#include "mozilla/Span.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_converter.h"
+#include "nsComputedDOMStyle.h"
+
+namespace mozilla {
+class Encoding;
+}
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+#define PREF_STRUCTS "converter.html2txt.structs"
+#define PREF_HEADER_STRATEGY "converter.html2txt.header_strategy"
+
+static const int32_t kTabSize = 4;
+static const int32_t kIndentSizeHeaders =
+    2; /* Indention of h1, if
+        mHeaderStrategy = kIndentIncreasedWithHeaderLevel
+        or = kNumberHeadingsAndIndentSlightly. Indention of
+        other headers is derived from that. */
+static const int32_t kIndentIncrementHeaders =
+    2; /* If mHeaderStrategy = kIndentIncreasedWithHeaderLevel,
+   indent h(x+1) this many
+   columns more than h(x) */
+static const int32_t kIndentSizeList = kTabSize;
+// Indention of non-first lines of ul and ol
+static const int32_t kIndentSizeDD = kTabSize;  // Indention of <dd>
+static const char16_t kNBSP = 160;
+static const char16_t kSPACE = ' ';
+
+static int32_t HeaderLevel(const nsAtom* aTag);
+static int32_t GetUnicharWidth(char32_t ucs);
+static int32_t GetUnicharStringWidth(Span<const char16_t> aString);
+
+// Someday may want to make this non-const:
+static const uint32_t TagStackSize = 500;
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsPlainTextSerializer)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(nsPlainTextSerializer)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsPlainTextSerializer)
+  NS_INTERFACE_MAP_ENTRY(nsIContentSerializer)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTION(nsPlainTextSerializer, mElement)
+
+nsresult NS_NewPlainTextSerializer(nsIContentSerializer** aSerializer) {
+  RefPtr<nsPlainTextSerializer> it = new nsPlainTextSerializer();
+  it.forget(aSerializer);
+  return NS_OK;
+}
+
+// @param aFlags As defined in nsIDocumentEncoder.idl.
+static void DetermineLineBreak(const int32_t aFlags, nsAString& aLineBreak) {
+  // Set the line break character:
+  if ((aFlags & nsIDocumentEncoder::OutputCRLineBreak) &&
+      (aFlags & nsIDocumentEncoder::OutputLFLineBreak)) {
+    // Windows
+    aLineBreak.AssignLiteral(u"\r\n");
+  } else if (aFlags & nsIDocumentEncoder::OutputCRLineBreak) {
+    // Mac
+    aLineBreak.AssignLiteral(u"\r");
+  } else if (aFlags & nsIDocumentEncoder::OutputLFLineBreak) {
+    // Unix/DOM
+    aLineBreak.AssignLiteral(u"\n");
+  } else {
+    // Platform/default
+    aLineBreak.AssignLiteral(NS_ULINEBREAK);
+  }
+}
+
+void nsPlainTextSerializer::CurrentLine::MaybeReplaceNbspsInContent(
+    const int32_t aFlags) {
+  if (!(aFlags & nsIDocumentEncoder::OutputPersistNBSP)) {
+    // First, replace all nbsp characters with spaces,
+    // which the unicode encoder won't do for us.
+    mContent.ReplaceChar(kNBSP, kSPACE);
+  }
+}
+
+void nsPlainTextSerializer::CurrentLine::ResetContentAndIndentationHeader() {
+  mContent.Truncate();
+  mIndentation.mHeader.Truncate();
+}
+
+int32_t nsPlainTextSerializer::CurrentLine::FindWrapIndexForContent(
+    const uint32_t aWrapColumn, bool aUseLineBreaker) const {
+  MOZ_ASSERT(!mContent.IsEmpty());
+
+  const uint32_t prefixwidth = DeterminePrefixWidth();
+  int32_t goodSpace = 0;
+
+  if (aUseLineBreaker) {
+    // We advance one line break point at a time from the beginning of the
+    // mContent until we find a width less than or equal to wrap column.
+    uint32_t width = 0;
+    intl::LineBreakIteratorUtf16 lineBreakIter(mContent);
+    while (const Maybe<uint32_t> nextGoodSpace = lineBreakIter.Next()) {
+      width += GetUnicharStringWidth(Span<const char16_t>(
+          mContent.get() + goodSpace, *nextGoodSpace - goodSpace));
+      if (prefixwidth + width > aWrapColumn) {
+        // The next break point makes the width exceeding the wrap column, so
+        // goodSpace is what we want.
+        break;
+      }
+      goodSpace = AssertedCast<int32_t>(*nextGoodSpace);
+    }
+
+    return goodSpace;
+  }
+
+  // In this case we don't want strings, especially CJK-ones, to be split. See
+  // bug 333064 for more information. We break only at ASCII spaces.
+  if (aWrapColumn >= prefixwidth) {
+    // Search backward from the adjusted wrap column or from the text end.
+    goodSpace =
+        std::min<int32_t>(aWrapColumn - prefixwidth, mContent.Length() - 1);
+    while (goodSpace >= 0) {
+      if (nsCRT::IsAsciiSpace(mContent.CharAt(goodSpace))) {
+        return goodSpace;
+      }
+      goodSpace--;
+    }
+  }
+
+  // Search forward from the adjusted wrap column.
+  goodSpace = (prefixwidth > aWrapColumn) ? 1 : aWrapColumn - prefixwidth;
+  const int32_t contentLength = mContent.Length();
+  while (goodSpace < contentLength &&
+         !nsCRT::IsAsciiSpace(mContent.CharAt(goodSpace))) {
+    goodSpace++;
+  }
+
+  return goodSpace;
+}
+
+nsPlainTextSerializer::OutputManager::OutputManager(const int32_t aFlags,
+                                                    nsAString& aOutput)
+    : mFlags{aFlags}, mOutput{aOutput}, mAtFirstColumn{true} {
+  MOZ_ASSERT(aOutput.IsEmpty());
+
+  DetermineLineBreak(mFlags, mLineBreak);
+}
+
+void nsPlainTextSerializer::OutputManager::Append(
+    const CurrentLine& aCurrentLine,
+    const StripTrailingWhitespaces aStripTrailingWhitespaces) {
+  if (IsAtFirstColumn()) {
+    nsAutoString quotesAndIndent;
+    aCurrentLine.CreateQuotesAndIndent(quotesAndIndent);
+
+    if ((aStripTrailingWhitespaces == StripTrailingWhitespaces::kMaybe)) {
+      const bool stripTrailingSpaces = aCurrentLine.mContent.IsEmpty();
+      if (stripTrailingSpaces) {
+        quotesAndIndent.Trim(" ", false, true, false);
+      }
+    }
+
+    Append(quotesAndIndent);
+  }
+
+  Append(aCurrentLine.mContent);
+}
+
+void nsPlainTextSerializer::OutputManager::Append(const nsAString& aString) {
+  if (!aString.IsEmpty()) {
+    mOutput.Append(aString);
+    mAtFirstColumn = false;
+  }
+}
+
+void nsPlainTextSerializer::OutputManager::AppendLineBreak() {
+  mOutput.Append(mLineBreak);
+  mAtFirstColumn = true;
+}
+
+uint32_t nsPlainTextSerializer::OutputManager::GetOutputLength() const {
+  return mOutput.Length();
+}
+
+nsPlainTextSerializer::nsPlainTextSerializer()
+    : mFloatingLines(-1),
+      mLineBreakDue(false),
+      kSpace(u" "_ns)  // Init of "constant"
+{
+  mHeadLevel = 0;
+  mHasWrittenCiteBlockquote = false;
+  mSpanLevel = 0;
+  for (int32_t i = 0; i <= 6; i++) {
+    mHeaderCounter[i] = 0;
+  }
+
+  // Flow
+  mEmptyLines = 1;  // The start of the document is an "empty line" in itself,
+  mInWhitespace = false;
+  mPreFormattedMail = false;
+
+  mPreformattedBlockBoundary = false;
+
+  // initialize the tag stack to zero:
+  // The stack only ever contains pointers to static atoms, so they don't
+  // need refcounting.
+  mTagStack = new const nsAtom*[TagStackSize];
+  mTagStackIndex = 0;
+  mIgnoreAboveIndex = (uint32_t)kNotFound;
+
+  mULCount = 0;
+
+  mIgnoredChildNodeLevel = 0;
+}
+
+nsPlainTextSerializer::~nsPlainTextSerializer() {
+  delete[] mTagStack;
+  NS_WARNING_ASSERTION(mHeadLevel == 0, "Wrong head level!");
+}
+
+nsPlainTextSerializer::Settings::HeaderStrategy
+nsPlainTextSerializer::Settings::Convert(const int32_t aPrefHeaderStrategy) {
+  HeaderStrategy result{HeaderStrategy::kIndentIncreasedWithHeaderLevel};
+
+  switch (aPrefHeaderStrategy) {
+    case 0: {
+      result = HeaderStrategy::kNoIndentation;
+      break;
+    }
+    case 1: {
+      result = HeaderStrategy::kIndentIncreasedWithHeaderLevel;
+      break;
+    }
+    case 2: {
+      result = HeaderStrategy::kNumberHeadingsAndIndentSlightly;
+      break;
+    }
+    default: {
+      NS_WARNING(
+          nsPrintfCString("Header strategy pref contains undefined value: %i",
+                          aPrefHeaderStrategy)
+              .get());
+    }
+  }
+
+  return result;
+}
+
+const int32_t kDefaultHeaderStrategy = 1;
+
+void nsPlainTextSerializer::Settings::Init(const int32_t aFlags,
+                                           const uint32_t aWrapColumn) {
+  mFlags = aFlags;
+
+  if (mFlags & nsIDocumentEncoder::OutputFormatted) {
+    // Get some prefs that controls how we do formatted output
+    mStructs = Preferences::GetBool(PREF_STRUCTS, mStructs);
+
+    int32_t headerStrategy =
+        Preferences::GetInt(PREF_HEADER_STRATEGY, kDefaultHeaderStrategy);
+    mHeaderStrategy = Convert(headerStrategy);
+  }
+
+  mWithRubyAnnotation = StaticPrefs::converter_html2txt_always_include_ruby() ||
+                        (mFlags & nsIDocumentEncoder::OutputRubyAnnotation);
+
+  // XXX We should let the caller decide whether to do this or not
+  mFlags &= ~nsIDocumentEncoder::OutputNoFramesContent;
+
+  mWrapColumn = aWrapColumn;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::Init(const uint32_t aFlags, uint32_t aWrapColumn,
+                            const Encoding* aEncoding, bool aIsCopying,
+                            bool aIsWholeDocument,
+                            bool* aNeedsPreformatScanning, nsAString& aOutput) {
+#ifdef DEBUG
+  // Check if the major control flags are set correctly.
+  if (aFlags & nsIDocumentEncoder::OutputFormatFlowed) {
+    NS_ASSERTION(aFlags & nsIDocumentEncoder::OutputFormatted,
+                 "If you want format=flowed, you must combine it with "
+                 "nsIDocumentEncoder::OutputFormatted");
+  }
+
+  if (aFlags & nsIDocumentEncoder::OutputFormatted) {
+    NS_ASSERTION(
+        !(aFlags & nsIDocumentEncoder::OutputPreformatted),
+        "Can't do formatted and preformatted output at the same time!");
+  }
+#endif
+  MOZ_ASSERT(!(aFlags & nsIDocumentEncoder::OutputFormatDelSp) ||
+             (aFlags & nsIDocumentEncoder::OutputFormatFlowed));
+
+  *aNeedsPreformatScanning = true;
+  mSettings.Init(aFlags, aWrapColumn);
+  mOutputManager.emplace(mSettings.GetFlags(), aOutput);
+
+  mUseLineBreaker = mSettings.MayWrap() && mSettings.MayBreakLines();
+
+  mLineBreakDue = false;
+  mFloatingLines = -1;
+
+  mPreformattedBlockBoundary = false;
+
+  MOZ_ASSERT(mOLStack.IsEmpty());
+
+  return NS_OK;
+}
+
+bool nsPlainTextSerializer::GetLastBool(const nsTArray<bool>& aStack) {
+  uint32_t size = aStack.Length();
+  if (size == 0) {
+    return false;
+  }
+  return aStack.ElementAt(size - 1);
+}
+
+void nsPlainTextSerializer::SetLastBool(nsTArray<bool>& aStack, bool aValue) {
+  uint32_t size = aStack.Length();
+  if (size > 0) {
+    aStack.ElementAt(size - 1) = aValue;
+  } else {
+    NS_ERROR("There is no \"Last\" value");
+  }
+}
+
+void nsPlainTextSerializer::PushBool(nsTArray<bool>& aStack, bool aValue) {
+  aStack.AppendElement(bool(aValue));
+}
+
+bool nsPlainTextSerializer::PopBool(nsTArray<bool>& aStack) {
+  return aStack.Length() ? aStack.PopLastElement() : false;
+}
+
+bool nsPlainTextSerializer::IsIgnorableRubyAnnotation(
+    const nsAtom* aTag) const {
+  if (mSettings.GetWithRubyAnnotation()) {
+    return false;
+  }
+
+  return aTag == nsGkAtoms::rp || aTag == nsGkAtoms::rt ||
+         aTag == nsGkAtoms::rtc;
+}
+
+// Return true if aElement has 'display:none' or if we just don't know.
+static bool IsDisplayNone(Element* aElement) {
+  RefPtr<const ComputedStyle> computedStyle =
+      nsComputedDOMStyle::GetComputedStyleNoFlush(aElement);
+  return !computedStyle ||
+         computedStyle->StyleDisplay()->mDisplay == StyleDisplay::None;
+}
+
+static bool IsIgnorableScriptOrStyle(Element* aElement) {
+  return aElement->IsAnyOfHTMLElements(nsGkAtoms::script, nsGkAtoms::style) &&
+         IsDisplayNone(aElement);
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::AppendText(nsIContent* aText, int32_t aStartOffset,
+                                  int32_t aEndOffset) {
+  if (mIgnoreAboveIndex != (uint32_t)kNotFound) {
+    return NS_OK;
+  }
+
+  NS_ASSERTION(aStartOffset >= 0, "Negative start offset for text fragment!");
+  if (aStartOffset < 0) return NS_ERROR_INVALID_ARG;
+
+  NS_ENSURE_ARG(aText);
+
+  nsresult rv = NS_OK;
+
+  nsIContent* content = aText;
+  const nsTextFragment* frag;
+  if (!content || !(frag = content->GetText())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  int32_t fragLength = frag->GetLength();
+  int32_t endoffset =
+      (aEndOffset == -1) ? fragLength : std::min(aEndOffset, fragLength);
+  NS_ASSERTION(aStartOffset <= endoffset,
+               "A start offset is beyond the end of the text fragment!");
+
+  int32_t length = endoffset - aStartOffset;
+  if (length <= 0) {
+    return NS_OK;
+  }
+
+  nsAutoString textstr;
+  if (frag->Is2b()) {
+    textstr.Assign(frag->Get2b() + aStartOffset, length);
+  } else {
+    // AssignASCII is for 7-bit character only, so don't use it
+    const char* data = frag->Get1b();
+    CopyASCIItoUTF16(Substring(data + aStartOffset, data + endoffset), textstr);
+  }
+
+  // Mask the text if the text node is in a password field.
+  if (content->HasFlag(NS_MAYBE_MASKED)) {
+    TextEditor::MaskString(textstr, *content->AsText(), 0, aStartOffset);
+  }
+
+  // We have to split the string across newlines
+  // to match parser behavior
+  int32_t start = 0;
+  int32_t offset = textstr.FindCharInSet(u"\n\r");
+  while (offset != kNotFound) {
+    if (offset > start) {
+      // Pass in the line
+      DoAddText(false, Substring(textstr, start, offset - start));
+    }
+
+    // Pass in a newline
+    DoAddText();
+
+    start = offset + 1;
+    offset = textstr.FindCharInSet(u"\n\r", start);
+  }
+
+  // Consume the last bit of the string if there's any left
+  if (start < length) {
+    if (start) {
+      DoAddText(false, Substring(textstr, start, length - start));
+    } else {
+      DoAddText(false, textstr);
+    }
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::AppendCDATASection(nsIContent* aCDATASection,
+                                          int32_t aStartOffset,
+                                          int32_t aEndOffset) {
+  return AppendText(aCDATASection, aStartOffset, aEndOffset);
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::ScanElementForPreformat(Element* aElement) {
+  mPreformatStack.push(IsElementPreformatted(aElement));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::ForgetElementForPreformat(Element* aElement) {
+  MOZ_RELEASE_ASSERT(!mPreformatStack.empty(),
+                     "Tried to pop without previous push.");
+  mPreformatStack.pop();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::AppendElementStart(Element* aElement,
+                                          Element* aOriginalElement) {
+  NS_ENSURE_ARG(aElement);
+
+  mElement = aElement;
+
+  nsresult rv;
+  nsAtom* id = GetIdForContent(mElement);
+
+  bool isContainer = !FragmentOrElement::IsHTMLVoid(id);
+
+  if (isContainer) {
+    rv = DoOpenContainer(id);
+  } else {
+    rv = DoAddLeaf(id);
+  }
+
+  mElement = nullptr;
+
+  if (id == nsGkAtoms::head) {
+    ++mHeadLevel;
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::AppendElementEnd(Element* aElement,
+                                        Element* aOriginalElement) {
+  NS_ENSURE_ARG(aElement);
+
+  mElement = aElement;
+
+  nsresult rv;
+  nsAtom* id = GetIdForContent(mElement);
+
+  bool isContainer = !FragmentOrElement::IsHTMLVoid(id);
+
+  rv = NS_OK;
+  if (isContainer) {
+    rv = DoCloseContainer(id);
+  }
+
+  mElement = nullptr;
+
+  if (id == nsGkAtoms::head) {
+    NS_ASSERTION(mHeadLevel != 0, "mHeadLevel being decremented below 0");
+    --mHeadLevel;
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::FlushAndFinish() {
+  MOZ_ASSERT(mOutputManager);
+
+  mOutputManager->Flush(mCurrentLine);
+  return Finish();
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::Finish() {
+  mOutputManager.reset();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::GetOutputLength(uint32_t& aLength) const {
+  MOZ_ASSERT(mOutputManager);
+
+  aLength = mOutputManager->GetOutputLength();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPlainTextSerializer::AppendDocumentStart(Document* aDocument) {
+  return NS_OK;
+}
+
+constexpr int32_t kOlStackDummyValue = 0;
+
+nsresult nsPlainTextSerializer::DoOpenContainer(const nsAtom* aTag) {
+  if (IsIgnorableRubyAnnotation(aTag)) {
+    // Ignorable ruby annotation shouldn't be replaced by a placeholder
+    // character, neither any of its descendants.
+    mIgnoredChildNodeLevel++;
+    return NS_OK;
+  }
+  if (IsIgnorableScriptOrStyle(mElement)) {
+    mIgnoredChildNodeLevel++;
+    return NS_OK;
+  }
+
+  if (mSettings.HasFlag(nsIDocumentEncoder::OutputForPlainTextClipboardCopy)) {
+    if (mPreformattedBlockBoundary && DoOutput()) {
+      // Should always end a line, but get no more whitespace
+      if (mFloatingLines < 0) mFloatingLines = 0;
+      mLineBreakDue = true;
+    }
+    mPreformattedBlockBoundary = false;
+  }
+
+  if (mSettings.HasFlag(nsIDocumentEncoder::OutputRaw)) {
+    // Raw means raw.  Don't even think about doing anything fancy
+    // here like indenting, adding line breaks or any other
+    // characters such as list item bullets, quote characters
+    // around <q>, etc.
+
+    return NS_OK;
+  }
+
+  if (mTagStackIndex < TagStackSize) {
+    mTagStack[mTagStackIndex++] = aTag;
+  }
+
+  if (mIgnoreAboveIndex != (uint32_t)kNotFound) {
+    return NS_OK;
+  }
+
+  // Reset this so that <blockquote type=cite> doesn't affect the whitespace
+  // above random <pre>s below it.
+  mHasWrittenCiteBlockquote =
+      mHasWrittenCiteBlockquote && aTag == nsGkAtoms::pre;
+
+  bool isInCiteBlockquote = false;
+
+  // XXX special-case <blockquote type=cite> so that we don't add additional
+  // newlines before the text.
+  if (aTag == nsGkAtoms::blockquote) {
+    nsAutoString value;
+    nsresult rv = GetAttributeValue(nsGkAtoms::type, value);
+    isInCiteBlockquote = NS_SUCCEEDED(rv) && value.EqualsIgnoreCase("cite");
+  }
+
+  if (mLineBreakDue && !isInCiteBlockquote) EnsureVerticalSpace(mFloatingLines);
+
+  // Check if this tag's content that should not be output
+  if ((aTag == nsGkAtoms::noscript &&
+       !mSettings.HasFlag(nsIDocumentEncoder::OutputNoScriptContent)) ||
+      ((aTag == nsGkAtoms::iframe || aTag == nsGkAtoms::noframes) &&
+       !mSettings.HasFlag(nsIDocumentEncoder::OutputNoFramesContent))) {
+    // Ignore everything that follows the current tag in
+    // question until a matching end tag is encountered.
+    mIgnoreAboveIndex = mTagStackIndex - 1;
+    return NS_OK;
+  }
+
+  if (aTag == nsGkAtoms::body) {
+    // Try to figure out here whether we have a
+    // preformatted style attribute set by Thunderbird.
+    //
+    // Trigger on the presence of a "pre-wrap" in the
+    // style attribute. That's a very simplistic way to do
+    // it, but better than nothing.
+    nsAutoString style;
+    int32_t whitespace;
+    if (NS_SUCCEEDED(GetAttributeValue(nsGkAtoms::style, style)) &&
+        (kNotFound != (whitespace = style.Find(u"white-space:")))) {
+      if (kNotFound != style.LowerCaseFindASCII("pre-wrap", whitespace)) {
+#ifdef DEBUG_preformatted
+        printf("Set mPreFormattedMail based on style pre-wrap\n");
+#endif
+        mPreFormattedMail = true;
+      } else if (kNotFound != style.LowerCaseFindASCII("pre", whitespace)) {
+#ifdef DEBUG_preformatted
+        printf("Set mPreFormattedMail based on style pre\n");
+#endif
+        mPreFormattedMail = true;
+      }
+    } else {
+      /* See comment at end of function. */
+      mInWhitespace = true;
+      mPreFormattedMail = false;
+    }
+
+    return NS_OK;
+  }
+
+  // Keep this in sync with DoCloseContainer!
+  if (!DoOutput()) {
+    return NS_OK;
+  }
+
+  if (aTag == nsGkAtoms::p)
+    EnsureVerticalSpace(1);
+  else if (aTag == nsGkAtoms::pre) {
+    if (GetLastBool(mIsInCiteBlockquote))
+      EnsureVerticalSpace(0);
+    else if (mHasWrittenCiteBlockquote) {
+      EnsureVerticalSpace(0);
+      mHasWrittenCiteBlockquote = false;
+    } else
+      EnsureVerticalSpace(1);
+  } else if (aTag == nsGkAtoms::tr) {
+    PushBool(mHasWrittenCellsForRow, false);
+  } else if (aTag == nsGkAtoms::td || aTag == nsGkAtoms::th) {
+    // We must make sure that the content of two table cells get a
+    // space between them.
+
+    // To make the separation between cells most obvious and
+    // importable, we use a TAB.
+    if (mHasWrittenCellsForRow.IsEmpty()) {
+      // We don't always see a <tr> (nor a <table>) before the <td> if we're
+      // copying part of a table
+      PushBool(mHasWrittenCellsForRow, true);  // will never be popped
+    } else if (GetLastBool(mHasWrittenCellsForRow)) {
+      // Bypass |Write| so that the TAB isn't compressed away.
+      AddToLine(u"\t", 1);
+      mInWhitespace = true;
+    } else {
+      SetLastBool(mHasWrittenCellsForRow, true);
+    }
+  } else if (aTag == nsGkAtoms::ul) {
+    // Indent here to support nested lists, which aren't included in li :-(
+    EnsureVerticalSpace(IsInOlOrUl() ? 0 : 1);
+    // Must end the current line before we change indention
+    mCurrentLine.mIndentation.mLength += kIndentSizeList;
+    mULCount++;
+  } else if (aTag == nsGkAtoms::ol) {
+    EnsureVerticalSpace(IsInOlOrUl() ? 0 : 1);
+    if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+      // Must end the current line before we change indention
+      nsAutoString startAttr;
+      int32_t startVal = 1;
+      if (NS_SUCCEEDED(GetAttributeValue(nsGkAtoms::start, startAttr))) {
+        nsresult rv = NS_OK;
+        startVal = startAttr.ToInteger(&rv);
+        if (NS_FAILED(rv)) {
+          startVal = 1;
+        }
+      }
+      mOLStack.AppendElement(startVal);
+    } else {
+      mOLStack.AppendElement(kOlStackDummyValue);
+    }
+    mCurrentLine.mIndentation.mLength += kIndentSizeList;  // see ul
+  } else if (aTag == nsGkAtoms::li &&
+             mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+    if (mTagStackIndex > 1 && IsInOL()) {
+      if (!mOLStack.IsEmpty()) {
+        nsAutoString valueAttr;
+        if (NS_SUCCEEDED(GetAttributeValue(nsGkAtoms::value, valueAttr))) {
+          nsresult rv = NS_OK;
+          int32_t valueAttrVal = valueAttr.ToInteger(&rv);
+          if (NS_SUCCEEDED(rv)) {
+            mOLStack.LastElement() = valueAttrVal;
+          }
+        }
+        // This is what nsBulletFrame does for OLs:
+        mCurrentLine.mIndentation.mHeader.AppendInt(mOLStack.LastElement(), 10);
+        mOLStack.LastElement()++;
+      } else {
+        mCurrentLine.mIndentation.mHeader.Append(char16_t('#'));
+      }
+
+      mCurrentLine.mIndentation.mHeader.Append(char16_t('.'));
+
+    } else {
+      static const char bulletCharArray[] = "*o+#";
+      uint32_t index = mULCount > 0 ? (mULCount - 1) : 3;
+      char bulletChar = bulletCharArray[index % 4];
+      mCurrentLine.mIndentation.mHeader.Append(char16_t(bulletChar));
+    }
+
+    mCurrentLine.mIndentation.mHeader.Append(char16_t(' '));
+  } else if (aTag == nsGkAtoms::dl) {
+    EnsureVerticalSpace(1);
+  } else if (aTag == nsGkAtoms::dt) {
+    EnsureVerticalSpace(0);
+  } else if (aTag == nsGkAtoms::dd) {
+    EnsureVerticalSpace(0);
+    mCurrentLine.mIndentation.mLength += kIndentSizeDD;
+  } else if (aTag == nsGkAtoms::span) {
+    ++mSpanLevel;
+  } else if (aTag == nsGkAtoms::blockquote) {
+    // Push
+    PushBool(mIsInCiteBlockquote, isInCiteBlockquote);
+    if (isInCiteBlockquote) {
+      EnsureVerticalSpace(0);
+      mCurrentLine.mCiteQuoteLevel++;
+    } else {
+      EnsureVerticalSpace(1);
+      mCurrentLine.mIndentation.mLength +=
+          kTabSize;  // Check for some maximum value?
+    }
+  } else if (aTag == nsGkAtoms::q) {
+    Write(u"\""_ns);
+  }
+
+  // Else make sure we'll separate block level tags,
+  // even if we're about to leave, before doing any other formatting.
+  else if (IsCssBlockLevelElement(mElement)) {
+    EnsureVerticalSpace(0);
+  }
+
+  if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+    OpenContainerForOutputFormatted(aTag);
+  }
+  return NS_OK;
+}
+
+void nsPlainTextSerializer::OpenContainerForOutputFormatted(
+    const nsAtom* aTag) {
+  const bool currentNodeIsConverted = IsCurrentNodeConverted();
+
+  if (aTag == nsGkAtoms::h1 || aTag == nsGkAtoms::h2 || aTag == nsGkAtoms::h3 ||
+      aTag == nsGkAtoms::h4 || aTag == nsGkAtoms::h5 || aTag == nsGkAtoms::h6) {
+    EnsureVerticalSpace(2);
+    if (mSettings.GetHeaderStrategy() ==
+        Settings::HeaderStrategy::kNumberHeadingsAndIndentSlightly) {
+      mCurrentLine.mIndentation.mLength += kIndentSizeHeaders;
+      // Caching
+      int32_t level = HeaderLevel(aTag);
+      // Increase counter for current level
+      mHeaderCounter[level]++;
+      // Reset all lower levels
+      int32_t i;
+
+      for (i = level + 1; i <= 6; i++) {
+        mHeaderCounter[i] = 0;
+      }
+
+      // Construct numbers
+      nsAutoString leadup;
+      for (i = 1; i <= level; i++) {
+        leadup.AppendInt(mHeaderCounter[i]);
+        leadup.Append(char16_t('.'));
+      }
+      leadup.Append(char16_t(' '));
+      Write(leadup);
+    } else if (mSettings.GetHeaderStrategy() ==
+               Settings::HeaderStrategy::kIndentIncreasedWithHeaderLevel) {
+      mCurrentLine.mIndentation.mLength += kIndentSizeHeaders;
+      for (int32_t i = HeaderLevel(aTag); i > 1; i--) {
+        // for h(x), run x-1 times
+        mCurrentLine.mIndentation.mLength += kIndentIncrementHeaders;
+      }
+    }
+  } else if (aTag == nsGkAtoms::sup && mSettings.GetStructs() &&
+             !currentNodeIsConverted) {
+    Write(u"^"_ns);
+  } else if (aTag == nsGkAtoms::sub && mSettings.GetStructs() &&
+             !currentNodeIsConverted) {
+    Write(u"_"_ns);
+  } else if (aTag == nsGkAtoms::code && mSettings.GetStructs() &&
+             !currentNodeIsConverted) {
+    Write(u"|"_ns);
+  } else if ((aTag == nsGkAtoms::strong || aTag == nsGkAtoms::b) &&
+             mSettings.GetStructs() && !currentNodeIsConverted) {
+    Write(u"*"_ns);
+  } else if ((aTag == nsGkAtoms::em || aTag == nsGkAtoms::i) &&
+             mSettings.GetStructs() && !currentNodeIsConverted) {
+    Write(u"/"_ns);
+  } else if (aTag == nsGkAtoms::u && mSettings.GetStructs() &&
+             !currentNodeIsConverted) {
+    Write(u"_"_ns);
+  }
+
+  /* Container elements are always block elements, so we shouldn't
+     output any whitespace immediately after the container tag even if
+     there's extra whitespace there because the HTML is pretty-printed
+     or something. To ensure that happens, tell the serializer we're
+     already in whitespace so it won't output more. */
+  mInWhitespace = true;
+}
+
+nsresult nsPlainTextSerializer::DoCloseContainer(const nsAtom* aTag) {
+  if (IsIgnorableRubyAnnotation(aTag)) {
+    mIgnoredChildNodeLevel--;
+    return NS_OK;
+  }
+  if (IsIgnorableScriptOrStyle(mElement)) {
+    mIgnoredChildNodeLevel--;
+    return NS_OK;
+  }
+
+  if (mSettings.HasFlag(nsIDocumentEncoder::OutputForPlainTextClipboardCopy)) {
+    if (DoOutput() && IsElementPreformatted() &&
+        IsCssBlockLevelElement(mElement)) {
+      // If we're closing a preformatted block element, output a line break
+      // when we find a new container.
+      mPreformattedBlockBoundary = true;
+    }
+  }
+
+  if (mSettings.HasFlag(nsIDocumentEncoder::OutputRaw)) {
+    // Raw means raw.  Don't even think about doing anything fancy
+    // here like indenting, adding line breaks or any other
+    // characters such as list item bullets, quote characters
+    // around <q>, etc.
+
+    return NS_OK;
+  }
+
+  if (mTagStackIndex > 0) {
+    --mTagStackIndex;
+  }
+
+  if (mTagStackIndex >= mIgnoreAboveIndex) {
+    if (mTagStackIndex == mIgnoreAboveIndex) {
+      // We're dealing with the close tag whose matching
+      // open tag had set the mIgnoreAboveIndex value.
+      // Reset mIgnoreAboveIndex before discarding this tag.
+      mIgnoreAboveIndex = (uint32_t)kNotFound;
+    }
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(mOutputManager);
+
+  // End current line if we're ending a block level tag
+  if ((aTag == nsGkAtoms::body) || (aTag == nsGkAtoms::html)) {
+    // We want the output to end with a new line,
+    // but in preformatted areas like text fields,
+    // we can't emit newlines that weren't there.
+    // So add the newline only in the case of formatted output.
+    if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+      EnsureVerticalSpace(0);
+    } else {
+      mOutputManager->Flush(mCurrentLine);
+    }
+    // We won't want to do anything with these in formatted mode either,
+    // so just return now:
+    return NS_OK;
+  }
+
+  // Keep this in sync with DoOpenContainer!
+  if (!DoOutput()) {
+    return NS_OK;
+  }
+
+  if (aTag == nsGkAtoms::tr) {
+    PopBool(mHasWrittenCellsForRow);
+    // Should always end a line, but get no more whitespace
+    if (mFloatingLines < 0) mFloatingLines = 0;
+    mLineBreakDue = true;
+  } else if (((aTag == nsGkAtoms::li) || (aTag == nsGkAtoms::dt)) &&
+             mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+    // Items that should always end a line, but get no more whitespace
+    if (mFloatingLines < 0) mFloatingLines = 0;
+    mLineBreakDue = true;
+  } else if (aTag == nsGkAtoms::pre) {
+    mFloatingLines = GetLastBool(mIsInCiteBlockquote) ? 0 : 1;
+    mLineBreakDue = true;
+  } else if (aTag == nsGkAtoms::ul) {
+    mOutputManager->Flush(mCurrentLine);
+    mCurrentLine.mIndentation.mLength -= kIndentSizeList;
+    --mULCount;
+    if (!IsInOlOrUl()) {
+      mFloatingLines = 1;
+      mLineBreakDue = true;
+    }
+  } else if (aTag == nsGkAtoms::ol) {
+    mOutputManager->Flush(mCurrentLine);  // Doing this after decreasing
+                                          // OLStackIndex would be wrong.
+    mCurrentLine.mIndentation.mLength -= kIndentSizeList;
+    MOZ_ASSERT(!mOLStack.IsEmpty(), "Wrong OLStack level!");
+    mOLStack.RemoveLastElement();
+    if (!IsInOlOrUl()) {
+      mFloatingLines = 1;
+      mLineBreakDue = true;
+    }
+  } else if (aTag == nsGkAtoms::dl) {
+    mFloatingLines = 1;
+    mLineBreakDue = true;
+  } else if (aTag == nsGkAtoms::dd) {
+    mOutputManager->Flush(mCurrentLine);
+    mCurrentLine.mIndentation.mLength -= kIndentSizeDD;
+  } else if (aTag == nsGkAtoms::span) {
+    NS_ASSERTION(mSpanLevel, "Span level will be negative!");
+    --mSpanLevel;
+  } else if (aTag == nsGkAtoms::div) {
+    if (mFloatingLines < 0) mFloatingLines = 0;
+    mLineBreakDue = true;
+  } else if (aTag == nsGkAtoms::blockquote) {
+    mOutputManager->Flush(mCurrentLine);  // Is this needed?
+
+    // Pop
+    bool isInCiteBlockquote = PopBool(mIsInCiteBlockquote);
+
+    if (isInCiteBlockquote) {
+      NS_ASSERTION(mCurrentLine.mCiteQuoteLevel,
+                   "CiteQuote level will be negative!");
+      mCurrentLine.mCiteQuoteLevel--;
+      mFloatingLines = 0;
+      mHasWrittenCiteBlockquote = true;
+    } else {
+      mCurrentLine.mIndentation.mLength -= kTabSize;
+      mFloatingLines = 1;
+    }
+    mLineBreakDue = true;
+  } else if (aTag == nsGkAtoms::q) {
+    Write(u"\""_ns);
+  } else if (IsCssBlockLevelElement(mElement)) {
+    // All other blocks get 1 vertical space after them
+    // in formatted mode, otherwise 0.
+    // This is hard. Sometimes 0 is a better number, but
+    // how to know?
+    if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+      EnsureVerticalSpace(1);
+    } else {
+      if (mFloatingLines < 0) mFloatingLines = 0;
+      mLineBreakDue = true;
+    }
+  }
+
+  if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+    CloseContainerForOutputFormatted(aTag);
+  }
+
+  return NS_OK;
+}
+
+void nsPlainTextSerializer::CloseContainerForOutputFormatted(
+    const nsAtom* aTag) {
+  const bool currentNodeIsConverted = IsCurrentNodeConverted();
+
+  if (aTag == nsGkAtoms::h1 || aTag == nsGkAtoms::h2 || aTag == nsGkAtoms::h3 ||
+      aTag == nsGkAtoms::h4 || aTag == nsGkAtoms::h5 || aTag == nsGkAtoms::h6) {
+    using HeaderStrategy = Settings::HeaderStrategy;
+    if ((mSettings.GetHeaderStrategy() ==
+         HeaderStrategy::kIndentIncreasedWithHeaderLevel) ||
+        (mSettings.GetHeaderStrategy() ==
+         HeaderStrategy::kNumberHeadingsAndIndentSlightly)) {
+      mCurrentLine.mIndentation.mLength -= kIndentSizeHeaders;
+    }
+    if (mSettings.GetHeaderStrategy() ==
+        HeaderStrategy::kIndentIncreasedWithHeaderLevel) {
+      for (int32_t i = HeaderLevel(aTag); i > 1; i--) {
+        // for h(x), run x-1 times
+        mCurrentLine.mIndentation.mLength -= kIndentIncrementHeaders;
+      }
+    }
+    EnsureVerticalSpace(1);
+  } else if (aTag == nsGkAtoms::a && !currentNodeIsConverted) {
+    nsAutoString url;
+    if (NS_SUCCEEDED(GetAttributeValue(nsGkAtoms::href, url)) &&
+        !url.IsEmpty()) {
+      nsAutoString temp;
+      temp.AssignLiteral(" <");
+      temp += url;
+      temp.Append(char16_t('>'));
+      Write(temp);
+    }
+  } else if ((aTag == nsGkAtoms::sup || aTag == nsGkAtoms::sub) &&
+             mSettings.GetStructs() && !currentNodeIsConverted) {
+    Write(kSpace);
+  } else if (aTag == nsGkAtoms::code && mSettings.GetStructs() &&
+             !currentNodeIsConverted) {
+    Write(u"|"_ns);
+  } else if ((aTag == nsGkAtoms::strong || aTag == nsGkAtoms::b) &&
+             mSettings.GetStructs() && !currentNodeIsConverted) {
+    Write(u"*"_ns);
+  } else if ((aTag == nsGkAtoms::em || aTag == nsGkAtoms::i) &&
+             mSettings.GetStructs() && !currentNodeIsConverted) {
+    Write(u"/"_ns);
+  } else if (aTag == nsGkAtoms::u && mSettings.GetStructs() &&
+             !currentNodeIsConverted) {
+    Write(u"_"_ns);
+  }
+}
+
+bool nsPlainTextSerializer::MustSuppressLeaf() const {
+  if (mIgnoredChildNodeLevel > 0) {
+    return true;
+  }
+
+  if ((mTagStackIndex > 1 &&
+       mTagStack[mTagStackIndex - 2] == nsGkAtoms::select) ||
+      (mTagStackIndex > 0 &&
+       mTagStack[mTagStackIndex - 1] == nsGkAtoms::select)) {
+    // Don't output the contents of SELECT elements;
+    // Might be nice, eventually, to output just the selected element.
+    // Read more in bug 31994.
+    return true;
+  }
+
+  return false;
+}
+
+void nsPlainTextSerializer::DoAddText() { DoAddText(true, u""_ns); }
+
+void nsPlainTextSerializer::DoAddText(bool aIsLineBreak,
+                                      const nsAString& aText) {
+  // If we don't want any output, just return
+  if (!DoOutput()) {
+    return;
+  }
+
+  if (!aIsLineBreak) {
+    // Make sure to reset this, since it's no longer true.
+    mHasWrittenCiteBlockquote = false;
+  }
+
+  if (mLineBreakDue) EnsureVerticalSpace(mFloatingLines);
+
+  if (MustSuppressLeaf()) {
+    return;
+  }
+
+  if (aIsLineBreak) {
+    // The only times we want to pass along whitespace from the original
+    // html source are if we're forced into preformatted mode via flags,
+    // or if we're prettyprinting and we're inside a <pre>.
+    // Otherwise, either we're collapsing to minimal text, or we're
+    // prettyprinting to mimic the html format, and in neither case
+    // does the formatting of the html source help us.
+    if (mSettings.HasFlag(nsIDocumentEncoder::OutputPreformatted) ||
+        (mPreFormattedMail && !mSettings.GetWrapColumn()) ||
+        IsElementPreformatted()) {
+      EnsureVerticalSpace(mEmptyLines + 1);
+    } else if (!mInWhitespace) {
+      Write(kSpace);
+      mInWhitespace = true;
+    }
+    return;
+  }
+
+  Write(aText);
+}
+
+void CreateLineOfDashes(nsAString& aResult, const uint32_t aWrapColumn) {
+  MOZ_ASSERT(aResult.IsEmpty());
+
+  const uint32_t width = (aWrapColumn > 0 ? aWrapColumn : 25);
+  while (aResult.Length() < width) {
+    aResult.Append(char16_t('-'));
+  }
+}
+
+nsresult nsPlainTextSerializer::DoAddLeaf(const nsAtom* aTag) {
+  mPreformattedBlockBoundary = false;
+
+  if (!DoOutput()) {
+    return NS_OK;
+  }
+
+  if (mLineBreakDue) EnsureVerticalSpace(mFloatingLines);
+
+  if (MustSuppressLeaf()) {
+    return NS_OK;
+  }
+
+  if (aTag == nsGkAtoms::br) {
+    // Another egregious editor workaround, see bug 38194:
+    // ignore the bogus br tags that the editor sticks here and there.
+    // FYI: `brElement` may be `nullptr` if the element is <br> element
+    //      of non-HTML element.
+    // XXX Do we need to call `EnsureVerticalSpace()` when the <br> element
+    //     is not an HTML element?
+    HTMLBRElement* brElement = HTMLBRElement::FromNodeOrNull(mElement);
+    if (!brElement || !brElement->IsPaddingForEmptyLastLine()) {
+      EnsureVerticalSpace(mEmptyLines + 1);
+    }
+  } else if (aTag == nsGkAtoms::hr &&
+             mSettings.HasFlag(nsIDocumentEncoder::OutputFormatted)) {
+    EnsureVerticalSpace(0);
+
+    // Make a line of dashes as wide as the wrap width
+    // XXX honoring percentage would be nice
+    nsAutoString line;
+    CreateLineOfDashes(line, mSettings.GetWrapColumn());
+    Write(line);
+
+    EnsureVerticalSpace(0);
+  } else if (aTag == nsGkAtoms::img) {
+    /* Output (in decreasing order of preference)
+       alt, title or nothing */
+    // See <http://www.w3.org/TR/REC-html40/struct/objects.html#edef-IMG>
+    nsAutoString imageDescription;
+    if (NS_SUCCEEDED(GetAttributeValue(nsGkAtoms::alt, imageDescription))) {
+      // If the alt attribute has an empty value (|alt=""|), output nothing
+    } else if (NS_SUCCEEDED(
+                   GetAttributeValue(nsGkAtoms::title, imageDescription)) &&
+               !imageDescription.IsEmpty()) {
+      imageDescription = u" ["_ns + imageDescription + u"] "_ns;
+    }
+
+    Write(imageDescription);
+  }
+
+  return NS_OK;
+}
+
+/**
+ * Adds as many newline as necessary to get |aNumberOfRows| empty lines
+ *
+ * aNumberOfRows = -1    :   Being in the middle of some line of text
+ * aNumberOfRows =  0    :   Being at the start of a line
+ * aNumberOfRows =  n>0  :   Having n empty lines before the current line.
+ */
+void nsPlainTextSerializer::EnsureVerticalSpace(const int32_t aNumberOfRows) {
+  // If we have something in the indent we probably want to output
+  // it and it's not included in the count for empty lines so we don't
+  // realize that we should start a new line.
+  if (aNumberOfRows >= 0 && !mCurrentLine.mIndentation.mHeader.IsEmpty()) {
+    EndLine(false);
+    mInWhitespace = true;
+  }
+
+  while (mEmptyLines < aNumberOfRows) {
+    EndLine(false);
+    mInWhitespace = true;
+  }
+  mLineBreakDue = false;
+  mFloatingLines = -1;
+}
+
+void nsPlainTextSerializer::OutputManager::Flush(CurrentLine& aCurrentLine) {
+  if (!aCurrentLine.mContent.IsEmpty()) {
+    aCurrentLine.MaybeReplaceNbspsInContent(mFlags);
+
+    Append(aCurrentLine, StripTrailingWhitespaces::kNo);
+
+    aCurrentLine.ResetContentAndIndentationHeader();
+  }
+}
+
+static bool IsSpaceStuffable(const char16_t* s) {
+  return (s[0] == '>' || s[0] == ' ' || s[0] == kNBSP ||
+          NS_strncmp(s, u"From ", 5) == 0);
+}
+
+void nsPlainTextSerializer::MaybeWrapAndOutputCompleteLines() {
+  if (!mSettings.MayWrap()) {
+    return;
+  }
+
+  const uint32_t prefixwidth = mCurrentLine.DeterminePrefixWidth();
+
+  // Yes, wrap!
+  // The "+4" is to avoid wrap lines that only would be a couple
+  // of letters too long. We give this bonus only if the
+  // wrapcolumn is more than 20.
+  const uint32_t wrapColumn = mSettings.GetWrapColumn();
+  uint32_t bonuswidth = (wrapColumn > 20) ? 4 : 0;
+
+  while (!mCurrentLine.mContent.IsEmpty()) {
+    // The width of the line as it will appear on the screen (approx.).
+    const uint32_t currentLineContentWidth =
+        GetUnicharStringWidth(mCurrentLine.mContent);
+    if (currentLineContentWidth + prefixwidth <= wrapColumn + bonuswidth) {
+      break;
+    }
+
+    const int32_t goodSpace =
+        mCurrentLine.FindWrapIndexForContent(wrapColumn, mUseLineBreaker);
+
+    const int32_t contentLength = mCurrentLine.mContent.Length();
+    if ((goodSpace < contentLength) && (goodSpace > 0)) {
+      // Found a place to break
+
+      // -1 (trim a char at the break position)
+      // only if the line break was a space.
+      nsAutoString restOfContent;
+      if (nsCRT::IsAsciiSpace(mCurrentLine.mContent.CharAt(goodSpace))) {
+        mCurrentLine.mContent.Right(restOfContent,
+                                    contentLength - goodSpace - 1);
+      } else {
+        mCurrentLine.mContent.Right(restOfContent, contentLength - goodSpace);
+      }
+      // if breaker was U+0020, it has to consider for delsp=yes support
+      const bool breakBySpace = mCurrentLine.mContent.CharAt(goodSpace) == ' ';
+      mCurrentLine.mContent.Truncate(goodSpace);
+      EndLine(true, breakBySpace);
+      mCurrentLine.mContent.Truncate();
+      // Space stuff new line?
+      if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatFlowed)) {
+        if (!restOfContent.IsEmpty() && IsSpaceStuffable(restOfContent.get()) &&
+            mCurrentLine.mCiteQuoteLevel ==
+                0  // We space-stuff quoted lines anyway
+        ) {
+          // Space stuffing a la RFC 2646 (format=flowed).
+          mCurrentLine.mContent.Append(char16_t(' '));
+          // XXX doesn't seem to work correctly for ' '
+        }
+      }
+      mCurrentLine.mContent.Append(restOfContent);
+      mEmptyLines = -1;
+    } else {
+      // Nothing to do. Hopefully we get more data later
+      // to use for a place to break line
+      break;
+    }
+  }
+}
+
+/**
+ * This function adds a piece of text to the current stored line. If we are
+ * wrapping text and the stored line will become too long, a suitable
+ * location to wrap will be found and the line that's complete will be
+ * output.
+ */
+void nsPlainTextSerializer::AddToLine(const char16_t* aLineFragment,
+                                      int32_t aLineFragmentLength) {
+  if (mLineBreakDue) EnsureVerticalSpace(mFloatingLines);
+
+  if (mCurrentLine.mContent.IsEmpty()) {
+    if (0 == aLineFragmentLength) {
+      return;
+    }
+
+    if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatFlowed)) {
+      if (IsSpaceStuffable(aLineFragment) &&
+          mCurrentLine.mCiteQuoteLevel ==
+              0  // We space-stuff quoted lines anyway
+      ) {
+        // Space stuffing a la RFC 2646 (format=flowed).
+        mCurrentLine.mContent.Append(char16_t(' '));
+      }
+    }
+    mEmptyLines = -1;
+  }
+
+  mCurrentLine.mContent.Append(aLineFragment, aLineFragmentLength);
+
+  MaybeWrapAndOutputCompleteLines();
+}
+
+// The signature separator (RFC 2646).
+const char kSignatureSeparator[] = "-- ";
+
+// The OpenPGP dash-escaped signature separator in inline
+// signed messages according to the OpenPGP standard (RFC 2440).
+const char kDashEscapedSignatureSeparator[] = "- -- ";
+
+static bool IsSignatureSeparator(const nsAString& aString) {
+  return aString.EqualsLiteral(kSignatureSeparator) ||
+         aString.EqualsLiteral(kDashEscapedSignatureSeparator);
+}
+
+/**
+ * Outputs the contents of mCurrentLine.mContent, and resets line
+ * specific variables. Also adds an indentation and prefix if there is one
+ * specified. Strips ending spaces from the line if it isn't preformatted.
+ */
+void nsPlainTextSerializer::EndLine(bool aSoftLineBreak, bool aBreakBySpace) {
+  if (aSoftLineBreak && mCurrentLine.mContent.IsEmpty()) {
+    // No meaning
+    return;
+  }
+
+  /* In non-preformatted mode, remove spaces from the end of the line for
+   * format=flowed compatibility. Don't do this for these special cases:
+   * "-- ", the signature separator (RFC 2646) shouldn't be touched and
+   * "- -- ", the OpenPGP dash-escaped signature separator in inline
+   * signed messages according to the OpenPGP standard (RFC 2440).
+   */
+  if (!mSettings.HasFlag(nsIDocumentEncoder::OutputPreformatted) &&
+      (aSoftLineBreak || !IsSignatureSeparator(mCurrentLine.mContent))) {
+    mCurrentLine.mContent.Trim(" ", false, true, false);
+  }
+
+  if (aSoftLineBreak &&
+      mSettings.HasFlag(nsIDocumentEncoder::OutputFormatFlowed) &&
+      (mCurrentLine.mIndentation.mLength == 0)) {
+    // Add the soft part of the soft linebreak (RFC 2646 4.1)
+    // We only do this when there is no indentation since format=flowed
+    // lines and indentation doesn't work well together.
+
+    // If breaker character is ASCII space with RFC 3676 support (delsp=yes),
+    // add twice space.
+    if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatDelSp) &&
+        aBreakBySpace) {
+      mCurrentLine.mContent.AppendLiteral("  ");
+    } else {
+      mCurrentLine.mContent.Append(char16_t(' '));
+    }
+  }
+
+  if (aSoftLineBreak) {
+    mEmptyLines = 0;
+  } else {
+    // Hard break
+    if (mCurrentLine.HasContentOrIndentationHeader()) {
+      mEmptyLines = 0;
+    } else {
+      mEmptyLines++;
+    }
+  }
+
+  MOZ_ASSERT(mOutputManager);
+
+  mCurrentLine.MaybeReplaceNbspsInContent(mSettings.GetFlags());
+
+  // If we don't have anything "real" to output we have to
+  // make sure the indent doesn't end in a space since that
+  // would trick a format=flowed-aware receiver.
+  mOutputManager->Append(mCurrentLine,
+                         OutputManager::StripTrailingWhitespaces::kMaybe);
+  mOutputManager->AppendLineBreak();
+  mCurrentLine.ResetContentAndIndentationHeader();
+  mInWhitespace = true;
+  mLineBreakDue = false;
+  mFloatingLines = -1;
+}
+
+/**
+ * Creates the calculated and stored indent and text in the indentation. That is
+ * quote chars and numbers for numbered lists and such.
+ */
+void nsPlainTextSerializer::CurrentLine::CreateQuotesAndIndent(
+    nsAString& aResult) const {
+  // Put the mail quote "> " chars in, if appropriate:
+  if (mCiteQuoteLevel > 0) {
+    nsAutoString quotes;
+    for (int i = 0; i < mCiteQuoteLevel; i++) {
+      quotes.Append(char16_t('>'));
+    }
+    if (!mContent.IsEmpty()) {
+      /* Better don't output a space here, if the line is empty,
+         in case a receiving format=flowed-aware UA thinks, this were a flowed
+         line, which it isn't - it's just empty. (Flowed lines may be joined
+         with the following one, so the empty line may be lost completely.) */
+      quotes.Append(char16_t(' '));
+    }
+    aResult = quotes;
+  }
+
+  // Indent if necessary
+  int32_t indentwidth = mIndentation.mLength - mIndentation.mHeader.Length();
+  if (indentwidth > 0 && HasContentOrIndentationHeader()
+      // Don't make empty lines look flowed
+  ) {
+    nsAutoString spaces;
+    for (int i = 0; i < indentwidth; ++i) spaces.Append(char16_t(' '));
+    aResult += spaces;
+  }
+
+  if (!mIndentation.mHeader.IsEmpty()) {
+    aResult += mIndentation.mHeader;
+  }
+}
+
+static bool IsLineFeedCarriageReturnBlankOrTab(char16_t c) {
+  return ('\n' == c || '\r' == c || ' ' == c || '\t' == c);
+}
+
+static void ReplaceVisiblyTrailingNbsps(nsAString& aString) {
+  const int32_t totLen = aString.Length();
+  for (int32_t i = totLen - 1; i >= 0; i--) {
+    char16_t c = aString[i];
+    if (IsLineFeedCarriageReturnBlankOrTab(c)) {
+      continue;
+    }
+    if (kNBSP == c) {
+      aString.Replace(i, 1, ' ');
+    } else {
+      break;
+    }
+  }
+}
+
+void nsPlainTextSerializer::ConvertToLinesAndOutput(const nsAString& aString) {
+  const int32_t totLen = aString.Length();
+  int32_t newline{0};
+
+  // Put the mail quote "> " chars in, if appropriate.
+  // Have to put it in before every line.
+  int32_t bol = 0;
+  while (bol < totLen) {
+    bool outputLineBreak = false;
+    bool spacesOnly = true;
+
+    // Find one of '\n' or '\r' using iterators since nsAString
+    // doesn't have the old FindCharInSet function.
+    nsAString::const_iterator iter;
+    aString.BeginReading(iter);
+    nsAString::const_iterator done_searching;
+    aString.EndReading(done_searching);
+    iter.advance(bol);
+    int32_t new_newline = bol;
+    newline = kNotFound;
+    while (iter != done_searching) {
+      if ('\n' == *iter || '\r' == *iter) {
+        newline = new_newline;
+        break;
+      }
+      if (' ' != *iter) {
+        spacesOnly = false;
+      }
+      ++new_newline;
+      ++iter;
+    }
+
+    // Done searching
+    nsAutoString stringpart;
+    if (newline == kNotFound) {
+      // No new lines.
+      stringpart.Assign(Substring(aString, bol, totLen - bol));
+      if (!stringpart.IsEmpty()) {
+        char16_t lastchar = stringpart.Last();
+        mInWhitespace = IsLineFeedCarriageReturnBlankOrTab(lastchar);
+      }
+      mEmptyLines = -1;
+      bol = totLen;
+    } else {
+      // There is a newline
+      stringpart.Assign(Substring(aString, bol, newline - bol));
+      mInWhitespace = true;
+      outputLineBreak = true;
+      mEmptyLines = 0;
+      bol = newline + 1;
+      if ('\r' == *iter && bol < totLen && '\n' == *++iter) {
+        // There was a CRLF in the input. This used to be illegal and
+        // stripped by the parser. Apparently not anymore. Let's skip
+        // over the LF.
+        bol++;
+      }
+    }
+
+    if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatFlowed)) {
+      if ((outputLineBreak || !spacesOnly) &&  // bugs 261467,125928
+          !IsQuotedLine(stringpart) && !IsSignatureSeparator(stringpart)) {
+        stringpart.Trim(" ", false, true, true);
+      }
+      if (IsSpaceStuffable(stringpart.get()) && !IsQuotedLine(stringpart)) {
+        mCurrentLine.mContent.Append(char16_t(' '));
+      }
+    }
+    mCurrentLine.mContent.Append(stringpart);
+
+    mCurrentLine.MaybeReplaceNbspsInContent(mSettings.GetFlags());
+
+    mOutputManager->Append(mCurrentLine,
+                           OutputManager::StripTrailingWhitespaces::kNo);
+    if (outputLineBreak) {
+      mOutputManager->AppendLineBreak();
+    }
+
+    mCurrentLine.ResetContentAndIndentationHeader();
+  }
+
+#ifdef DEBUG_wrapping
+  printf("No wrapping: newline is %d, totLen is %d\n", newline, totLen);
+#endif
+}
+
+/**
+ * Write a string. This is the highlevel function to use to get text output.
+ * By using AddToLine, Output, EndLine and other functions it handles quotation,
+ * line wrapping, indentation, whitespace compression and other things.
+ */
+void nsPlainTextSerializer::Write(const nsAString& aStr) {
+  // XXX Copy necessary to use nsString methods and gain
+  // access to underlying buffer
+  nsAutoString str(aStr);
+
+#ifdef DEBUG_wrapping
+  printf("Write(%s): wrap col = %d\n", NS_ConvertUTF16toUTF8(str).get(),
+         mSettings.GetWrapColumn());
+#endif
+
+  const int32_t totLen = str.Length();
+
+  // If the string is empty, do nothing:
+  if (totLen <= 0) return;
+
+  // For Flowed text change nbsp-ses to spaces at end of lines to allow them
+  // to be cut off along with usual spaces if required. (bug #125928)
+  if (mSettings.HasFlag(nsIDocumentEncoder::OutputFormatFlowed)) {
+    ReplaceVisiblyTrailingNbsps(str);
+  }
+
+  // We have two major codepaths here. One that does preformatted text and one
+  // that does normal formatted text. The one for preformatted text calls
+  // Output directly while the other code path goes through AddToLine.
+  if ((mPreFormattedMail && !mSettings.GetWrapColumn()) ||
+      (IsElementPreformatted() && !mPreFormattedMail) ||
+      (mSpanLevel > 0 && mEmptyLines >= 0 && IsQuotedLine(str))) {
+    // No intelligent wrapping.
+
+    // This mustn't be mixed with intelligent wrapping without clearing
+    // the mCurrentLine.mContent buffer before!!!
+    NS_ASSERTION(mCurrentLine.mContent.IsEmpty() ||
+                     (IsElementPreformatted() && !mPreFormattedMail),
+                 "Mixed wrapping data and nonwrapping data on the same line");
+    MOZ_ASSERT(mOutputManager);
+
+    if (!mCurrentLine.mContent.IsEmpty()) {
+      mOutputManager->Flush(mCurrentLine);
+    }
+
+    ConvertToLinesAndOutput(str);
+    return;
+  }
+
+  // Intelligent handling of text
+  // If needed, strip out all "end of lines"
+  // and multiple whitespace between words
+  int32_t nextpos;
+  const char16_t* offsetIntoBuffer = nullptr;
+
+  int32_t bol = 0;
+  while (bol < totLen) {  // Loop over lines
+    // Find a place where we may have to do whitespace compression
+    nextpos = str.FindCharInSet(u" \t\n\r", bol);
+#ifdef DEBUG_wrapping
+    nsAutoString remaining;
+    str.Right(remaining, totLen - bol);
+    foo = ToNewCString(remaining);
+    // printf("Next line: bol = %d, newlinepos = %d, totLen = %d, "
+    //        "string = '%s'\n", bol, nextpos, totLen, foo);
+    free(foo);
+#endif
+
+    if (nextpos == kNotFound) {
+      // The rest of the string
+      offsetIntoBuffer = str.get() + bol;
+      AddToLine(offsetIntoBuffer, totLen - bol);
+      bol = totLen;
+      mInWhitespace = false;
+    } else {
+      // There's still whitespace left in the string
+      if (nextpos != 0 && (nextpos + 1) < totLen) {
+        offsetIntoBuffer = str.get() + nextpos;
+        // skip '\n' if it is between CJ chars
+        if (offsetIntoBuffer[0] == '\n' && IS_CJ_CHAR(offsetIntoBuffer[-1]) &&
+            IS_CJ_CHAR(offsetIntoBuffer[1])) {
+          offsetIntoBuffer = str.get() + bol;
+          AddToLine(offsetIntoBuffer, nextpos - bol);
+          bol = nextpos + 1;
+          continue;
+        }
+      }
+      // If we're already in whitespace and not preformatted, just skip it:
+      if (mInWhitespace && (nextpos == bol) && !mPreFormattedMail &&
+          !mSettings.HasFlag(nsIDocumentEncoder::OutputPreformatted)) {
+        // Skip whitespace
+        bol++;
+        continue;
+      }
+
+      if (nextpos == bol) {
+        // Note that we are in whitespace.
+        mInWhitespace = true;
+        offsetIntoBuffer = str.get() + nextpos;
+        AddToLine(offsetIntoBuffer, 1);
+        bol++;
+        continue;
+      }
+
+      mInWhitespace = true;
+
+      offsetIntoBuffer = str.get() + bol;
+      if (mPreFormattedMail ||
+          mSettings.HasFlag(nsIDocumentEncoder::OutputPreformatted)) {
+        // Preserve the real whitespace character
+        nextpos++;
+        AddToLine(offsetIntoBuffer, nextpos - bol);
+        bol = nextpos;
+      } else {
+        // Replace the whitespace with a space
+        AddToLine(offsetIntoBuffer, nextpos - bol);
+        AddToLine(kSpace.get(), 1);
+        bol = nextpos + 1;  // Let's eat the whitespace
+      }
+    }
+  }  // Continue looping over the string
+}
+
+/**
+ * Gets the value of an attribute in a string. If the function returns
+ * NS_ERROR_NOT_AVAILABLE, there was none such attribute specified.
+ */
+nsresult nsPlainTextSerializer::GetAttributeValue(const nsAtom* aName,
+                                                  nsString& aValueRet) const {
+  if (mElement) {
+    if (mElement->GetAttr(kNameSpaceID_None, aName, aValueRet)) {
+      return NS_OK;
+    }
+  }
+
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+/**
+ * Returns true, if the element was inserted by Moz' TXT->HTML converter.
+ * In this case, we should ignore it.
+ */
+bool nsPlainTextSerializer::IsCurrentNodeConverted() const {
+  nsAutoString value;
+  nsresult rv = GetAttributeValue(nsGkAtoms::_class, value);
+  return (NS_SUCCEEDED(rv) &&
+          (StringBeginsWith(value, u"moz-txt"_ns,
+                            nsASCIICaseInsensitiveStringComparator) ||
+           StringBeginsWith(value, u"\"moz-txt"_ns,
+                            nsASCIICaseInsensitiveStringComparator)));
+}
+
+// static
+nsAtom* nsPlainTextSerializer::GetIdForContent(nsIContent* aContent) {
+  if (!aContent->IsHTMLElement()) {
+    return nullptr;
+  }
+
+  nsAtom* localName = aContent->NodeInfo()->NameAtom();
+  return localName->IsStatic() ? localName : nullptr;
+}
+
+bool nsPlainTextSerializer::IsElementPreformatted() const {
+  return !mPreformatStack.empty() && mPreformatStack.top();
+}
+
+bool nsPlainTextSerializer::IsElementPreformatted(Element* aElement) {
+  RefPtr<const ComputedStyle> computedStyle =
+      nsComputedDOMStyle::GetComputedStyleNoFlush(aElement);
+  if (computedStyle) {
+    const nsStyleText* textStyle = computedStyle->StyleText();
+    return textStyle->WhiteSpaceOrNewlineIsSignificant();
+  }
+  // Fall back to looking at the tag, in case there is no style information.
+  return GetIdForContent(aElement) == nsGkAtoms::pre;
+}
+
+bool nsPlainTextSerializer::IsCssBlockLevelElement(Element* aElement) {
+  RefPtr<const ComputedStyle> computedStyle =
+      nsComputedDOMStyle::GetComputedStyleNoFlush(aElement);
+  if (computedStyle) {
+    const nsStyleDisplay* displayStyle = computedStyle->StyleDisplay();
+    return displayStyle->IsBlockOutsideStyle();
+  }
+  // Fall back to looking at the tag, in case there is no style information.
+  return nsContentUtils::IsHTMLBlockLevelElement(aElement);
+}
+
+/**
+ * This method is required only to identify LI's inside OL.
+ * Returns TRUE if we are inside an OL tag and FALSE otherwise.
+ */
+bool nsPlainTextSerializer::IsInOL() const {
+  int32_t i = mTagStackIndex;
+  while (--i >= 0) {
+    if (mTagStack[i] == nsGkAtoms::ol) return true;
+    if (mTagStack[i] == nsGkAtoms::ul) {
+      // If a UL is reached first, LI belongs the UL nested in OL.
+      return false;
+    }
+  }
+  // We may reach here for orphan LI's.
+  return false;
+}
+
+bool nsPlainTextSerializer::IsInOlOrUl() const {
+  return (mULCount > 0) || !mOLStack.IsEmpty();
+}
+
+/*
+  @return 0 = no header, 1 = h1, ..., 6 = h6
+*/
+int32_t HeaderLevel(const nsAtom* aTag) {
+  if (aTag == nsGkAtoms::h1) {
+    return 1;
+  }
+  if (aTag == nsGkAtoms::h2) {
+    return 2;
+  }
+  if (aTag == nsGkAtoms::h3) {
+    return 3;
+  }
+  if (aTag == nsGkAtoms::h4) {
+    return 4;
+  }
+  if (aTag == nsGkAtoms::h5) {
+    return 5;
+  }
+  if (aTag == nsGkAtoms::h6) {
+    return 6;
+  }
+  return 0;
+}
+
+/* These functions define the column width of an ISO 10646 character
+ * as follows:
+ *
+ *    - The null character (U+0000) has a column width of 0.
+ *
+ *    - Other C0/C1 control characters and DEL will lead to a return
+ *      value of -1.
+ *
+ *    - Non-spacing and enclosing combining characters (general
+ *      category code Mn or Me in the Unicode database) have a
+ *      column width of 0.
+ *
+ *    - Spacing characters in the East Asian Wide (W) or East Asian
+ *      FullWidth (F) category as defined in Unicode Technical
+ *      Report #11 have a column width of 2.
+ *
+ *    - All remaining characters (including all printable
+ *      ISO 8859-1 and WGL4 characters, Unicode control characters,
+ *      etc.) have a column width of 1.
+ */
+
+int32_t GetUnicharWidth(char32_t aCh) {
+  /* test for 8-bit control characters */
+  if (aCh == 0) {
+    return 0;
+  }
+  if (aCh < 32 || (aCh >= 0x7f && aCh < 0xa0)) {
+    return -1;
+  }
+
+  /* The first combining char in Unicode is U+0300 */
+  if (aCh < 0x0300) {
+    return 1;
+  }
+
+  auto gc = unicode::GetGeneralCategory(aCh);
+  if (gc == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK ||
+      gc == HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) {
+    return 0;
+  }
+
+  /* if we arrive here, ucs is not a combining or C0/C1 control character */
+
+  /* fast test for majority of non-wide scripts */
+  if (aCh < 0x1100) {
+    return 1;
+  }
+
+  return intl::UnicodeProperties::IsEastAsianWidthFW(aCh) ? 2 : 1;
+}
+
+int32_t GetUnicharStringWidth(Span<const char16_t> aString) {
+  int32_t width = 0;
+  for (auto iter = aString.begin(); iter != aString.end(); ++iter) {
+    char32_t c = *iter;
+    if (NS_IS_HIGH_SURROGATE(c) && (iter + 1) != aString.end() &&
+        NS_IS_LOW_SURROGATE(*(iter + 1))) {
+      c = SURROGATE_TO_UCS4(c, *++iter);
+    }
+    const int32_t w = GetUnicharWidth(c);
+    // Taking 1 as the width of non-printable character, for bug 94475.
+    width += (w < 0 ? 1 : w);
+  }
+  return width;
+}