Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

1 files changed, 2109 insertions, 0 deletions

diff --git a/dom/serializers/nsDocumentEncoder.cpp b/dom/serializers/nsDocumentEncoder.cpp
new file mode 100644
index 0000000000..14120bae64
--- /dev/null
+++ b/dom/serializers/nsDocumentEncoder.cpp
@@ -0,0 +1,2109 @@
+/* -*- 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/. */
+
+/*
+ * Object that can be used to serialize selections, ranges, or nodes
+ * to strings in a gazillion different ways.
+ */
+
+#include <utility>
+
+#include "nscore.h"
+#include "nsISupports.h"
+#include "nsCOMPtr.h"
+#include "nsCRT.h"
+#include "nsIContentSerializer.h"
+#include "nsIDocumentEncoder.h"
+#include "nsINode.h"
+#include "nsIContentInlines.h"
+#include "nsComponentManagerUtils.h"
+#include "nsIOutputStream.h"
+#include "nsRange.h"
+#include "nsGkAtoms.h"
+#include "nsHTMLDocument.h"
+#include "nsIContent.h"
+#include "nsIScriptContext.h"
+#include "nsIScriptGlobalObject.h"
+#include "nsITransferable.h"
+#include "mozilla/dom/Selection.h"
+#include "nsContentUtils.h"
+#include "nsElementTable.h"
+#include "nsUnicharUtils.h"
+#include "nsReadableUtils.h"
+#include "nsTArray.h"
+#include "nsIFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsStringBuffer.h"
+#include "mozilla/dom/Comment.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/DocumentType.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLBRElement.h"
+#include "mozilla/dom/ProcessingInstruction.h"
+#include "mozilla/dom/ShadowRoot.h"
+#include "mozilla/dom/Text.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/IntegerRange.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/UniquePtr.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+enum nsRangeIterationDirection { kDirectionOut = -1, kDirectionIn = 1 };
+
+class TextStreamer {
+ public:
+  /**
+   * @param aStream Will be kept alive by the TextStreamer.
+   * @param aUnicodeEncoder Needs to be non-nullptr.
+   */
+  TextStreamer(nsIOutputStream& aStream, UniquePtr<Encoder> aUnicodeEncoder,
+               bool aIsPlainText, nsAString& aOutputBuffer);
+
+  /**
+   * String will be truncated if it is written to stream.
+   */
+  nsresult FlushIfStringLongEnough();
+
+  /**
+   * String will be truncated.
+   */
+  nsresult ForceFlush();
+
+ private:
+  const static uint32_t kMaxLengthBeforeFlush = 1024;
+
+  const static uint32_t kEncoderBufferSizeInBytes = 4096;
+
+  nsresult EncodeAndWrite();
+
+  nsresult EncodeAndWriteAndTruncate();
+
+  const nsCOMPtr<nsIOutputStream> mStream;
+  const UniquePtr<Encoder> mUnicodeEncoder;
+  const bool mIsPlainText;
+  nsAString& mOutputBuffer;
+};
+
+TextStreamer::TextStreamer(nsIOutputStream& aStream,
+                           UniquePtr<Encoder> aUnicodeEncoder,
+                           bool aIsPlainText, nsAString& aOutputBuffer)
+    : mStream{&aStream},
+      mUnicodeEncoder(std::move(aUnicodeEncoder)),
+      mIsPlainText(aIsPlainText),
+      mOutputBuffer(aOutputBuffer) {
+  MOZ_ASSERT(mUnicodeEncoder);
+}
+
+nsresult TextStreamer::FlushIfStringLongEnough() {
+  nsresult rv = NS_OK;
+
+  if (mOutputBuffer.Length() > kMaxLengthBeforeFlush) {
+    rv = EncodeAndWriteAndTruncate();
+  }
+
+  return rv;
+}
+
+nsresult TextStreamer::ForceFlush() { return EncodeAndWriteAndTruncate(); }
+
+nsresult TextStreamer::EncodeAndWrite() {
+  if (mOutputBuffer.IsEmpty()) {
+    return NS_OK;
+  }
+
+  uint8_t buffer[kEncoderBufferSizeInBytes];
+  auto src = Span(mOutputBuffer);
+  auto bufferSpan = Span(buffer);
+  // Reserve space for terminator
+  auto dst = bufferSpan.To(bufferSpan.Length() - 1);
+  for (;;) {
+    uint32_t result;
+    size_t read;
+    size_t written;
+    if (mIsPlainText) {
+      std::tie(result, read, written) =
+          mUnicodeEncoder->EncodeFromUTF16WithoutReplacement(src, dst, false);
+      if (result != kInputEmpty && result != kOutputFull) {
+        // There's always room for one byte in the case of
+        // an unmappable character, because otherwise
+        // we'd have gotten `kOutputFull`.
+        dst[written++] = '?';
+      }
+    } else {
+      std::tie(result, read, written, std::ignore) =
+          mUnicodeEncoder->EncodeFromUTF16(src, dst, false);
+    }
+    src = src.From(read);
+    // Sadly, we still have test cases that implement nsIOutputStream in JS, so
+    // the buffer needs to be zero-terminated for XPConnect to do its thing.
+    // See bug 170416.
+    bufferSpan[written] = 0;
+    uint32_t streamWritten;
+    nsresult rv = mStream->Write(reinterpret_cast<char*>(dst.Elements()),
+                                 written, &streamWritten);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+    if (result == kInputEmpty) {
+      return NS_OK;
+    }
+  }
+}
+
+nsresult TextStreamer::EncodeAndWriteAndTruncate() {
+  const nsresult rv = EncodeAndWrite();
+  mOutputBuffer.Truncate();
+  return rv;
+}
+
+/**
+ * The scope may be limited to either a selection, range, or node.
+ */
+class EncodingScope {
+ public:
+  /**
+   * @return true, iff the scope is limited to a selection, range or node.
+   */
+  bool IsLimited() const;
+
+  RefPtr<Selection> mSelection;
+  RefPtr<nsRange> mRange;
+  nsCOMPtr<nsINode> mNode;
+  bool mNodeIsContainer = false;
+};
+
+bool EncodingScope::IsLimited() const { return mSelection || mRange || mNode; }
+
+struct RangeBoundariesInclusiveAncestorsAndOffsets {
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor.
+   */
+  using InclusiveAncestors = AutoTArray<nsIContent*, 8>;
+
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor.
+   */
+  using InclusiveAncestorsOffsets = AutoTArray<Maybe<uint32_t>, 8>;
+
+  // The first node is the range's boundary node, the following ones the
+  // ancestors.
+  InclusiveAncestors mInclusiveAncestorsOfStart;
+  // The first offset represents where at the boundary node the range starts.
+  // Each other offset is the index of the child relative to its parent.
+  InclusiveAncestorsOffsets mInclusiveAncestorsOffsetsOfStart;
+
+  // The first node is the range's boundary node, the following one the
+  // ancestors.
+  InclusiveAncestors mInclusiveAncestorsOfEnd;
+  // The first offset represents where at the boundary node the range ends.
+  // Each other offset is the index of the child relative to its parent.
+  InclusiveAncestorsOffsets mInclusiveAncestorsOffsetsOfEnd;
+};
+
+struct ContextInfoDepth {
+  uint32_t mStart = 0;
+  uint32_t mEnd = 0;
+};
+
+class nsDocumentEncoder : public nsIDocumentEncoder {
+ protected:
+  class RangeNodeContext {
+   public:
+    virtual ~RangeNodeContext() = default;
+
+    virtual bool IncludeInContext(nsINode& aNode) const { return false; }
+
+    virtual int32_t GetImmediateContextCount(
+        const nsTArray<nsINode*>& aAncestorArray) const {
+      return -1;
+    }
+  };
+
+ public:
+  nsDocumentEncoder();
+
+ protected:
+  /**
+   * @param aRangeNodeContext has to be non-null.
+   */
+  explicit nsDocumentEncoder(UniquePtr<RangeNodeContext> aRangeNodeContext);
+
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS(nsDocumentEncoder)
+  NS_DECL_NSIDOCUMENTENCODER
+
+ protected:
+  virtual ~nsDocumentEncoder();
+
+  void Initialize(bool aClearCachedSerializer = true);
+
+  /**
+   * @param aMaxLength As described at
+   * `nsIDocumentEncodder.encodeToStringWithMaxLength`.
+   */
+  nsresult SerializeDependingOnScope(uint32_t aMaxLength);
+
+  nsresult SerializeSelection();
+
+  nsresult SerializeNode();
+
+  /**
+   * @param aMaxLength As described at
+   * `nsIDocumentEncodder.encodeToStringWithMaxLength`.
+   */
+  nsresult SerializeWholeDocument(uint32_t aMaxLength);
+
+  /**
+   * @param aFlags multiple of the flags defined in nsIDocumentEncoder.idl.o
+   */
+  static bool IsInvisibleNodeAndShouldBeSkipped(const nsINode& aNode,
+                                                const uint32_t aFlags) {
+    if (aFlags & SkipInvisibleContent) {
+      // Treat the visibility of the ShadowRoot as if it were
+      // the host content.
+      //
+      // FIXME(emilio): I suspect instead of this a bunch of the GetParent()
+      // calls here should be doing GetFlattenedTreeParent, then this condition
+      // should be unreachable...
+      const nsINode* node{&aNode};
+      if (const ShadowRoot* shadowRoot = ShadowRoot::FromNode(node)) {
+        node = shadowRoot->GetHost();
+      }
+
+      if (node->IsContent()) {
+        nsIFrame* frame = node->AsContent()->GetPrimaryFrame();
+        if (!frame) {
+          if (node->IsElement() && node->AsElement()->IsDisplayContents()) {
+            return false;
+          }
+          if (node->IsText()) {
+            // We have already checked that our parent is visible.
+            //
+            // FIXME(emilio): Text not assigned to a <slot> in Shadow DOM should
+            // probably return false...
+            return false;
+          }
+          if (node->IsHTMLElement(nsGkAtoms::rp)) {
+            // Ruby parentheses are part of ruby structure, hence
+            // shouldn't be stripped out even if it is not displayed.
+            return false;
+          }
+          return true;
+        }
+        bool isVisible = frame->StyleVisibility()->IsVisible();
+        if (!isVisible && node->IsText()) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  void ReleaseDocumentReferenceAndInitialize(bool aClearCachedSerializer);
+
+  class MOZ_STACK_CLASS AutoReleaseDocumentIfNeeded final {
+   public:
+    explicit AutoReleaseDocumentIfNeeded(nsDocumentEncoder* aEncoder)
+        : mEncoder(aEncoder) {}
+
+    ~AutoReleaseDocumentIfNeeded() {
+      if (mEncoder->mFlags & RequiresReinitAfterOutput) {
+        const bool clearCachedSerializer = false;
+        mEncoder->ReleaseDocumentReferenceAndInitialize(clearCachedSerializer);
+      }
+    }
+
+   private:
+    nsDocumentEncoder* mEncoder;
+  };
+
+  nsCOMPtr<Document> mDocument;
+  EncodingScope mEncodingScope;
+  nsCOMPtr<nsIContentSerializer> mSerializer;
+
+  Maybe<TextStreamer> mTextStreamer;
+  nsCOMPtr<nsIDocumentEncoderNodeFixup> mNodeFixup;
+
+  nsString mMimeType;
+  const Encoding* mEncoding;
+  // Multiple of the flags defined in nsIDocumentEncoder.idl.
+  uint32_t mFlags;
+  uint32_t mWrapColumn;
+  // Whether the serializer cares about being notified to scan elements to
+  // keep track of whether they are preformatted.  This stores the out
+  // argument of nsIContentSerializer::Init().
+  bool mNeedsPreformatScanning;
+  bool mIsCopying;  // Set to true only while copying
+  nsStringBuffer* mCachedBuffer;
+
+  class NodeSerializer {
+   public:
+    /**
+     * @param aFlags multiple of the flags defined in nsIDocumentEncoder.idl.
+     */
+    NodeSerializer(const bool& aNeedsPreformatScanning,
+                   const nsCOMPtr<nsIContentSerializer>& aSerializer,
+                   const uint32_t& aFlags,
+                   const nsCOMPtr<nsIDocumentEncoderNodeFixup>& aNodeFixup,
+                   Maybe<TextStreamer>& aTextStreamer)
+        : mNeedsPreformatScanning{aNeedsPreformatScanning},
+          mSerializer{aSerializer},
+          mFlags{aFlags},
+          mNodeFixup{aNodeFixup},
+          mTextStreamer{aTextStreamer} {}
+
+    nsresult SerializeNodeStart(nsINode& aOriginalNode, int32_t aStartOffset,
+                                int32_t aEndOffset,
+                                nsINode* aFixupNode = nullptr) const;
+
+    enum class SerializeRoot { eYes, eNo };
+
+    nsresult SerializeToStringRecursive(nsINode* aNode,
+                                        SerializeRoot aSerializeRoot,
+                                        uint32_t aMaxLength = 0) const;
+
+    nsresult SerializeNodeEnd(nsINode& aOriginalNode,
+                              nsINode* aFixupNode = nullptr) const;
+
+    [[nodiscard]] nsresult SerializeTextNode(nsINode& aNode,
+                                             int32_t aStartOffset,
+                                             int32_t aEndOffset) const;
+
+    nsresult SerializeToStringIterative(nsINode* aNode) const;
+
+   private:
+    const bool& mNeedsPreformatScanning;
+    const nsCOMPtr<nsIContentSerializer>& mSerializer;
+    // Multiple of the flags defined in nsIDocumentEncoder.idl.
+    const uint32_t& mFlags;
+    const nsCOMPtr<nsIDocumentEncoderNodeFixup>& mNodeFixup;
+    Maybe<TextStreamer>& mTextStreamer;
+  };
+
+  NodeSerializer mNodeSerializer;
+
+  const UniquePtr<RangeNodeContext> mRangeNodeContext;
+
+  struct RangeContextSerializer final {
+    RangeContextSerializer(const RangeNodeContext& aRangeNodeContext,
+                           const NodeSerializer& aNodeSerializer)
+        : mDisableContextSerialize{false},
+          mRangeNodeContext{aRangeNodeContext},
+          mNodeSerializer{aNodeSerializer} {}
+
+    nsresult SerializeRangeContextStart(
+        const nsTArray<nsINode*>& aAncestorArray);
+    nsresult SerializeRangeContextEnd();
+
+    // Used when context has already been serialized for
+    // table cell selections (where parent is <tr>)
+    bool mDisableContextSerialize;
+    AutoTArray<AutoTArray<nsINode*, 8>, 8> mRangeContexts;
+
+    const RangeNodeContext& mRangeNodeContext;
+
+   private:
+    const NodeSerializer& mNodeSerializer;
+  };
+
+  RangeContextSerializer mRangeContextSerializer;
+
+  struct RangeSerializer {
+    // @param aFlags multiple of the flags defined in nsIDocumentEncoder.idl.
+    RangeSerializer(const uint32_t& aFlags,
+                    const NodeSerializer& aNodeSerializer,
+                    RangeContextSerializer& aRangeContextSerializer)
+        : mStartRootIndex{0},
+          mEndRootIndex{0},
+          mHaltRangeHint{false},
+          mFlags{aFlags},
+          mNodeSerializer{aNodeSerializer},
+          mRangeContextSerializer{aRangeContextSerializer} {}
+
+    void Initialize();
+
+    /**
+     * @param aDepth the distance (number of `GetParent` calls) from aNode to
+     *               aRange's closest common inclusive ancestor.
+     */
+    nsresult SerializeRangeNodes(const nsRange* aRange, nsINode* aNode,
+                                 int32_t aDepth);
+
+    /**
+     * Serialize aContent's children from aStartOffset to aEndOffset.
+     *
+     * @param aDepth the distance (number of `GetParent` calls) from aContent to
+     *               aRange's closest common inclusive ancestor.
+     */
+    [[nodiscard]] nsresult SerializeChildrenOfContent(nsIContent& aContent,
+                                                      uint32_t aStartOffset,
+                                                      uint32_t aEndOffset,
+                                                      const nsRange* aRange,
+                                                      int32_t aDepth);
+
+    nsresult SerializeRangeToString(const nsRange* aRange);
+
+    /**
+     * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor.
+     */
+    nsCOMPtr<nsINode> mClosestCommonInclusiveAncestorOfRange;
+
+    /**
+     * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor.
+     */
+    AutoTArray<nsINode*, 8> mCommonInclusiveAncestors;
+
+    ContextInfoDepth mContextInfoDepth;
+
+   private:
+    struct StartAndEndContent {
+      nsCOMPtr<nsIContent> mStart;
+      nsCOMPtr<nsIContent> mEnd;
+    };
+
+    StartAndEndContent GetStartAndEndContentForRecursionLevel(
+        int32_t aDepth) const;
+
+    bool HasInvisibleParentAndShouldBeSkipped(nsINode& aNode) const;
+
+    nsresult SerializeNodePartiallyContainedInRange(
+        nsINode& aNode, nsIContent& aContent,
+        const StartAndEndContent& aStartAndEndContent, const nsRange& aRange,
+        int32_t aDepth);
+
+    nsresult SerializeTextNode(nsINode& aNode, const nsIContent& aContent,
+                               const StartAndEndContent& aStartAndEndContent,
+                               const nsRange& aRange) const;
+
+    RangeBoundariesInclusiveAncestorsAndOffsets
+        mRangeBoundariesInclusiveAncestorsAndOffsets;
+    int32_t mStartRootIndex;
+    int32_t mEndRootIndex;
+    bool mHaltRangeHint;
+
+    // Multiple of the flags defined in nsIDocumentEncoder.idl.
+    const uint32_t& mFlags;
+
+    const NodeSerializer& mNodeSerializer;
+    RangeContextSerializer& mRangeContextSerializer;
+  };
+
+  RangeSerializer mRangeSerializer;
+};
+
+void nsDocumentEncoder::RangeSerializer::Initialize() {
+  mContextInfoDepth = {};
+  mStartRootIndex = 0;
+  mEndRootIndex = 0;
+  mHaltRangeHint = false;
+  mClosestCommonInclusiveAncestorOfRange = nullptr;
+  mRangeBoundariesInclusiveAncestorsAndOffsets = {};
+}
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsDocumentEncoder)
+NS_IMPL_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE(
+    nsDocumentEncoder, ReleaseDocumentReferenceAndInitialize(true))
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsDocumentEncoder)
+  NS_INTERFACE_MAP_ENTRY(nsIDocumentEncoder)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTION(
+    nsDocumentEncoder, mDocument, mEncodingScope.mSelection,
+    mEncodingScope.mRange, mEncodingScope.mNode, mSerializer,
+    mRangeSerializer.mClosestCommonInclusiveAncestorOfRange)
+
+nsDocumentEncoder::nsDocumentEncoder(
+    UniquePtr<RangeNodeContext> aRangeNodeContext)
+    : mEncoding(nullptr),
+      mIsCopying(false),
+      mCachedBuffer(nullptr),
+      mNodeSerializer(mNeedsPreformatScanning, mSerializer, mFlags, mNodeFixup,
+                      mTextStreamer),
+      mRangeNodeContext(std::move(aRangeNodeContext)),
+      mRangeContextSerializer(*mRangeNodeContext, mNodeSerializer),
+      mRangeSerializer(mFlags, mNodeSerializer, mRangeContextSerializer) {
+  MOZ_ASSERT(mRangeNodeContext);
+
+  Initialize();
+  mMimeType.AssignLiteral("text/plain");
+}
+
+nsDocumentEncoder::nsDocumentEncoder()
+    : nsDocumentEncoder(MakeUnique<RangeNodeContext>()) {}
+
+void nsDocumentEncoder::Initialize(bool aClearCachedSerializer) {
+  mFlags = 0;
+  mWrapColumn = 72;
+  mRangeSerializer.Initialize();
+  mNeedsPreformatScanning = false;
+  mRangeContextSerializer.mDisableContextSerialize = false;
+  mEncodingScope = {};
+  mNodeFixup = nullptr;
+  if (aClearCachedSerializer) {
+    mSerializer = nullptr;
+  }
+}
+
+static bool ParentIsTR(nsIContent* aContent) {
+  mozilla::dom::Element* parent = aContent->GetParentElement();
+  if (!parent) {
+    return false;
+  }
+  return parent->IsHTMLElement(nsGkAtoms::tr);
+}
+
+nsresult nsDocumentEncoder::SerializeDependingOnScope(uint32_t aMaxLength) {
+  nsresult rv = NS_OK;
+  if (mEncodingScope.mSelection) {
+    rv = SerializeSelection();
+  } else if (nsRange* range = mEncodingScope.mRange) {
+    rv = mRangeSerializer.SerializeRangeToString(range);
+  } else if (mEncodingScope.mNode) {
+    rv = SerializeNode();
+  } else {
+    rv = SerializeWholeDocument(aMaxLength);
+  }
+
+  mEncodingScope = {};
+
+  return rv;
+}
+
+nsresult nsDocumentEncoder::SerializeSelection() {
+  NS_ENSURE_TRUE(mEncodingScope.mSelection, NS_ERROR_FAILURE);
+
+  nsresult rv = NS_OK;
+  const Selection* selection = mEncodingScope.mSelection;
+  nsCOMPtr<nsINode> node;
+  nsCOMPtr<nsINode> prevNode;
+  uint32_t firstRangeStartDepth = 0;
+  const uint32_t rangeCount = selection->RangeCount();
+  for (const uint32_t i : IntegerRange(rangeCount)) {
+    MOZ_ASSERT(selection->RangeCount() == rangeCount);
+    RefPtr<const nsRange> range = selection->GetRangeAt(i);
+
+    // Bug 236546: newlines not added when copying table cells into clipboard
+    // Each selected cell shows up as a range containing a row with a single
+    // cell get the row, compare it to previous row and emit </tr><tr> as
+    // needed Bug 137450: Problem copying/pasting a table from a web page to
+    // Excel. Each separate block of <tr></tr> produced above will be wrapped
+    // by the immediate context. This assumes that you can't select cells that
+    // are multiple selections from two tables simultaneously.
+    node = range->GetStartContainer();
+    NS_ENSURE_TRUE(node, NS_ERROR_FAILURE);
+    if (node != prevNode) {
+      if (prevNode) {
+        rv = mNodeSerializer.SerializeNodeEnd(*prevNode);
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+      nsCOMPtr<nsIContent> content = nsIContent::FromNodeOrNull(node);
+      if (content && content->IsHTMLElement(nsGkAtoms::tr) &&
+          !ParentIsTR(content)) {
+        if (!prevNode) {
+          // Went from a non-<tr> to a <tr>
+          mRangeSerializer.mCommonInclusiveAncestors.Clear();
+          nsContentUtils::GetInclusiveAncestors(
+              node->GetParentNode(),
+              mRangeSerializer.mCommonInclusiveAncestors);
+          rv = mRangeContextSerializer.SerializeRangeContextStart(
+              mRangeSerializer.mCommonInclusiveAncestors);
+          NS_ENSURE_SUCCESS(rv, rv);
+          // Don't let SerializeRangeToString serialize the context again
+          mRangeContextSerializer.mDisableContextSerialize = true;
+        }
+
+        rv = mNodeSerializer.SerializeNodeStart(*node, 0, -1);
+        NS_ENSURE_SUCCESS(rv, rv);
+        prevNode = node;
+      } else if (prevNode) {
+        // Went from a <tr> to a non-<tr>
+        mRangeContextSerializer.mDisableContextSerialize = false;
+
+        // `mCommonInclusiveAncestors` is used in `EncodeToStringWithContext`
+        // too. Update it here to mimic the old behavior.
+        mRangeSerializer.mCommonInclusiveAncestors.Clear();
+        nsContentUtils::GetInclusiveAncestors(
+            prevNode->GetParentNode(),
+            mRangeSerializer.mCommonInclusiveAncestors);
+
+        rv = mRangeContextSerializer.SerializeRangeContextEnd();
+        NS_ENSURE_SUCCESS(rv, rv);
+        prevNode = nullptr;
+      }
+    }
+
+    rv = mRangeSerializer.SerializeRangeToString(range);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (i == 0) {
+      firstRangeStartDepth = mRangeSerializer.mContextInfoDepth.mStart;
+    }
+  }
+  mRangeSerializer.mContextInfoDepth.mStart = firstRangeStartDepth;
+
+  if (prevNode) {
+    rv = mNodeSerializer.SerializeNodeEnd(*prevNode);
+    NS_ENSURE_SUCCESS(rv, rv);
+    mRangeContextSerializer.mDisableContextSerialize = false;
+
+    // `mCommonInclusiveAncestors` is used in `EncodeToStringWithContext`
+    // too. Update it here to mimic the old behavior.
+    mRangeSerializer.mCommonInclusiveAncestors.Clear();
+    nsContentUtils::GetInclusiveAncestors(
+        prevNode->GetParentNode(), mRangeSerializer.mCommonInclusiveAncestors);
+
+    rv = mRangeContextSerializer.SerializeRangeContextEnd();
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // Just to be safe
+  mRangeContextSerializer.mDisableContextSerialize = false;
+
+  return rv;
+}
+
+nsresult nsDocumentEncoder::SerializeNode() {
+  NS_ENSURE_TRUE(mEncodingScope.mNode, NS_ERROR_FAILURE);
+
+  nsresult rv = NS_OK;
+  nsINode* node = mEncodingScope.mNode;
+  const bool nodeIsContainer = mEncodingScope.mNodeIsContainer;
+  if (!mNodeFixup && !(mFlags & SkipInvisibleContent) && !mTextStreamer &&
+      nodeIsContainer) {
+    rv = mNodeSerializer.SerializeToStringIterative(node);
+  } else {
+    rv = mNodeSerializer.SerializeToStringRecursive(
+        node, nodeIsContainer ? NodeSerializer::SerializeRoot::eNo
+                              : NodeSerializer::SerializeRoot::eYes);
+  }
+
+  return rv;
+}
+
+nsresult nsDocumentEncoder::SerializeWholeDocument(uint32_t aMaxLength) {
+  NS_ENSURE_FALSE(mEncodingScope.mSelection, NS_ERROR_FAILURE);
+  NS_ENSURE_FALSE(mEncodingScope.mRange, NS_ERROR_FAILURE);
+  NS_ENSURE_FALSE(mEncodingScope.mNode, NS_ERROR_FAILURE);
+
+  nsresult rv = mSerializer->AppendDocumentStart(mDocument);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = mNodeSerializer.SerializeToStringRecursive(
+      mDocument, NodeSerializer::SerializeRoot::eYes, aMaxLength);
+  return rv;
+}
+
+nsDocumentEncoder::~nsDocumentEncoder() {
+  if (mCachedBuffer) {
+    mCachedBuffer->Release();
+  }
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::Init(Document* aDocument, const nsAString& aMimeType,
+                        uint32_t aFlags) {
+  return NativeInit(aDocument, aMimeType, aFlags);
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::NativeInit(Document* aDocument, const nsAString& aMimeType,
+                              uint32_t aFlags) {
+  if (!aDocument) return NS_ERROR_INVALID_ARG;
+
+  Initialize(!mMimeType.Equals(aMimeType));
+
+  mDocument = aDocument;
+
+  mMimeType = aMimeType;
+
+  mFlags = aFlags;
+  mIsCopying = false;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::SetWrapColumn(uint32_t aWC) {
+  mWrapColumn = aWC;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::SetSelection(Selection* aSelection) {
+  mEncodingScope.mSelection = aSelection;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::SetRange(nsRange* aRange) {
+  mEncodingScope.mRange = aRange;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::SetNode(nsINode* aNode) {
+  mEncodingScope.mNodeIsContainer = false;
+  mEncodingScope.mNode = aNode;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::SetContainerNode(nsINode* aContainer) {
+  mEncodingScope.mNodeIsContainer = true;
+  mEncodingScope.mNode = aContainer;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::SetCharset(const nsACString& aCharset) {
+  const Encoding* encoding = Encoding::ForLabel(aCharset);
+  if (!encoding) {
+    return NS_ERROR_UCONV_NOCONV;
+  }
+  mEncoding = encoding->OutputEncoding();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::GetMimeType(nsAString& aMimeType) {
+  aMimeType = mMimeType;
+  return NS_OK;
+}
+
+class FixupNodeDeterminer {
+ public:
+  FixupNodeDeterminer(nsIDocumentEncoderNodeFixup* aNodeFixup,
+                      nsINode* aFixupNode, nsINode& aOriginalNode)
+      : mIsSerializationOfFixupChildrenNeeded{false},
+        mNodeFixup(aNodeFixup),
+        mOriginalNode(aOriginalNode) {
+    if (mNodeFixup) {
+      if (aFixupNode) {
+        mFixupNode = aFixupNode;
+      } else {
+        mNodeFixup->FixupNode(&mOriginalNode,
+                              &mIsSerializationOfFixupChildrenNeeded,
+                              getter_AddRefs(mFixupNode));
+      }
+    }
+  }
+
+  bool IsSerializationOfFixupChildrenNeeded() const {
+    return mIsSerializationOfFixupChildrenNeeded;
+  }
+
+  /**
+   * @return The fixup node, if available, otherwise the original node. The
+   * former is kept alive by this object.
+   */
+  nsINode& GetFixupNodeFallBackToOriginalNode() const {
+    return mFixupNode ? *mFixupNode : mOriginalNode;
+  }
+
+ private:
+  bool mIsSerializationOfFixupChildrenNeeded;
+  nsIDocumentEncoderNodeFixup* mNodeFixup;
+  nsCOMPtr<nsINode> mFixupNode;
+  nsINode& mOriginalNode;
+};
+
+nsresult nsDocumentEncoder::NodeSerializer::SerializeNodeStart(
+    nsINode& aOriginalNode, int32_t aStartOffset, int32_t aEndOffset,
+    nsINode* aFixupNode) const {
+  if (mNeedsPreformatScanning) {
+    if (aOriginalNode.IsElement()) {
+      mSerializer->ScanElementForPreformat(aOriginalNode.AsElement());
+    } else if (aOriginalNode.IsText()) {
+      const nsCOMPtr<nsINode> parent = aOriginalNode.GetParent();
+      if (parent && parent->IsElement()) {
+        mSerializer->ScanElementForPreformat(parent->AsElement());
+      }
+    }
+  }
+
+  if (IsInvisibleNodeAndShouldBeSkipped(aOriginalNode, mFlags)) {
+    return NS_OK;
+  }
+
+  FixupNodeDeterminer fixupNodeDeterminer{mNodeFixup, aFixupNode,
+                                          aOriginalNode};
+  nsINode* node = &fixupNodeDeterminer.GetFixupNodeFallBackToOriginalNode();
+
+  nsresult rv = NS_OK;
+
+  if (node->IsElement()) {
+    if ((mFlags & (nsIDocumentEncoder::OutputPreformatted |
+                   nsIDocumentEncoder::OutputDropInvisibleBreak)) &&
+        nsLayoutUtils::IsInvisibleBreak(node)) {
+      return rv;
+    }
+    rv = mSerializer->AppendElementStart(node->AsElement(),
+                                         aOriginalNode.AsElement());
+    return rv;
+  }
+
+  switch (node->NodeType()) {
+    case nsINode::TEXT_NODE: {
+      rv = mSerializer->AppendText(static_cast<nsIContent*>(node), aStartOffset,
+                                   aEndOffset);
+      break;
+    }
+    case nsINode::CDATA_SECTION_NODE: {
+      rv = mSerializer->AppendCDATASection(static_cast<nsIContent*>(node),
+                                           aStartOffset, aEndOffset);
+      break;
+    }
+    case nsINode::PROCESSING_INSTRUCTION_NODE: {
+      rv = mSerializer->AppendProcessingInstruction(
+          static_cast<ProcessingInstruction*>(node), aStartOffset, aEndOffset);
+      break;
+    }
+    case nsINode::COMMENT_NODE: {
+      rv = mSerializer->AppendComment(static_cast<Comment*>(node), aStartOffset,
+                                      aEndOffset);
+      break;
+    }
+    case nsINode::DOCUMENT_TYPE_NODE: {
+      rv = mSerializer->AppendDoctype(static_cast<DocumentType*>(node));
+      break;
+    }
+  }
+
+  return rv;
+}
+
+nsresult nsDocumentEncoder::NodeSerializer::SerializeNodeEnd(
+    nsINode& aOriginalNode, nsINode* aFixupNode) const {
+  if (mNeedsPreformatScanning) {
+    if (aOriginalNode.IsElement()) {
+      mSerializer->ForgetElementForPreformat(aOriginalNode.AsElement());
+    } else if (aOriginalNode.IsText()) {
+      const nsCOMPtr<nsINode> parent = aOriginalNode.GetParent();
+      if (parent && parent->IsElement()) {
+        mSerializer->ForgetElementForPreformat(parent->AsElement());
+      }
+    }
+  }
+
+  if (IsInvisibleNodeAndShouldBeSkipped(aOriginalNode, mFlags)) {
+    return NS_OK;
+  }
+
+  nsresult rv = NS_OK;
+
+  FixupNodeDeterminer fixupNodeDeterminer{mNodeFixup, aFixupNode,
+                                          aOriginalNode};
+  nsINode* node = &fixupNodeDeterminer.GetFixupNodeFallBackToOriginalNode();
+
+  if (node->IsElement()) {
+    rv = mSerializer->AppendElementEnd(node->AsElement(),
+                                       aOriginalNode.AsElement());
+  }
+
+  return rv;
+}
+
+nsresult nsDocumentEncoder::NodeSerializer::SerializeToStringRecursive(
+    nsINode* aNode, SerializeRoot aSerializeRoot, uint32_t aMaxLength) const {
+  uint32_t outputLength{0};
+  nsresult rv = mSerializer->GetOutputLength(outputLength);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (aMaxLength > 0 && outputLength >= aMaxLength) {
+    return NS_OK;
+  }
+
+  NS_ENSURE_TRUE(aNode, NS_ERROR_NULL_POINTER);
+
+  if (IsInvisibleNodeAndShouldBeSkipped(*aNode, mFlags)) {
+    return NS_OK;
+  }
+
+  FixupNodeDeterminer fixupNodeDeterminer{mNodeFixup, nullptr, *aNode};
+  nsINode* maybeFixedNode =
+      &fixupNodeDeterminer.GetFixupNodeFallBackToOriginalNode();
+
+  if (mFlags & SkipInvisibleContent) {
+    if (aNode->IsContent()) {
+      if (nsIFrame* frame = aNode->AsContent()->GetPrimaryFrame()) {
+        if (!frame->IsSelectable(nullptr)) {
+          aSerializeRoot = SerializeRoot::eNo;
+        }
+      }
+    }
+  }
+
+  if (aSerializeRoot == SerializeRoot::eYes) {
+    int32_t endOffset = -1;
+    if (aMaxLength > 0) {
+      MOZ_ASSERT(aMaxLength >= outputLength);
+      endOffset = aMaxLength - outputLength;
+    }
+    rv = SerializeNodeStart(*aNode, 0, endOffset, maybeFixedNode);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  nsINode* node = fixupNodeDeterminer.IsSerializationOfFixupChildrenNeeded()
+                      ? maybeFixedNode
+                      : aNode;
+
+  for (nsINode* child = node->GetFirstChildOfTemplateOrNode(); child;
+       child = child->GetNextSibling()) {
+    rv = SerializeToStringRecursive(child, SerializeRoot::eYes, aMaxLength);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (aSerializeRoot == SerializeRoot::eYes) {
+    rv = SerializeNodeEnd(*aNode, maybeFixedNode);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (mTextStreamer) {
+    rv = mTextStreamer->FlushIfStringLongEnough();
+  }
+
+  return rv;
+}
+
+nsresult nsDocumentEncoder::NodeSerializer::SerializeToStringIterative(
+    nsINode* aNode) const {
+  nsresult rv;
+
+  nsINode* node = aNode->GetFirstChildOfTemplateOrNode();
+  while (node) {
+    nsINode* current = node;
+    rv = SerializeNodeStart(*current, 0, -1, current);
+    NS_ENSURE_SUCCESS(rv, rv);
+    node = current->GetFirstChildOfTemplateOrNode();
+    while (!node && current && current != aNode) {
+      rv = SerializeNodeEnd(*current);
+      NS_ENSURE_SUCCESS(rv, rv);
+      // Check if we have siblings.
+      node = current->GetNextSibling();
+      if (!node) {
+        // Perhaps parent node has siblings.
+        current = current->GetParentNode();
+
+        // Handle template element. If the parent is a template's content,
+        // then adjust the parent to be the template element.
+        if (current && current != aNode && current->IsDocumentFragment()) {
+          nsIContent* host = current->AsDocumentFragment()->GetHost();
+          if (host && host->IsHTMLElement(nsGkAtoms::_template)) {
+            current = host;
+          }
+        }
+      }
+    }
+  }
+
+  return NS_OK;
+}
+
+static bool IsTextNode(nsINode* aNode) { return aNode && aNode->IsText(); }
+
+nsresult nsDocumentEncoder::NodeSerializer::SerializeTextNode(
+    nsINode& aNode, int32_t aStartOffset, int32_t aEndOffset) const {
+  MOZ_ASSERT(IsTextNode(&aNode));
+
+  nsresult rv = SerializeNodeStart(aNode, aStartOffset, aEndOffset);
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = SerializeNodeEnd(aNode);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return rv;
+}
+
+nsDocumentEncoder::RangeSerializer::StartAndEndContent
+nsDocumentEncoder::RangeSerializer::GetStartAndEndContentForRecursionLevel(
+    const int32_t aDepth) const {
+  StartAndEndContent result;
+
+  const auto& inclusiveAncestorsOfStart =
+      mRangeBoundariesInclusiveAncestorsAndOffsets.mInclusiveAncestorsOfStart;
+  const auto& inclusiveAncestorsOfEnd =
+      mRangeBoundariesInclusiveAncestorsAndOffsets.mInclusiveAncestorsOfEnd;
+  int32_t start = mStartRootIndex - aDepth;
+  if (start >= 0 && (uint32_t)start <= inclusiveAncestorsOfStart.Length()) {
+    result.mStart = inclusiveAncestorsOfStart[start];
+  }
+
+  int32_t end = mEndRootIndex - aDepth;
+  if (end >= 0 && (uint32_t)end <= inclusiveAncestorsOfEnd.Length()) {
+    result.mEnd = inclusiveAncestorsOfEnd[end];
+  }
+
+  return result;
+}
+
+nsresult nsDocumentEncoder::RangeSerializer::SerializeTextNode(
+    nsINode& aNode, const nsIContent& aContent,
+    const StartAndEndContent& aStartAndEndContent,
+    const nsRange& aRange) const {
+  const int32_t startOffset =
+      (aStartAndEndContent.mStart == &aContent) ? aRange.StartOffset() : 0;
+  const int32_t endOffset =
+      (aStartAndEndContent.mEnd == &aContent) ? aRange.EndOffset() : -1;
+  return mNodeSerializer.SerializeTextNode(aNode, startOffset, endOffset);
+}
+
+nsresult nsDocumentEncoder::RangeSerializer::SerializeRangeNodes(
+    const nsRange* const aRange, nsINode* const aNode, const int32_t aDepth) {
+  MOZ_ASSERT(aDepth >= 0);
+  MOZ_ASSERT(aRange);
+
+  nsCOMPtr<nsIContent> content = nsIContent::FromNodeOrNull(aNode);
+  NS_ENSURE_TRUE(content, NS_ERROR_FAILURE);
+
+  if (nsDocumentEncoder::IsInvisibleNodeAndShouldBeSkipped(*aNode, mFlags)) {
+    return NS_OK;
+  }
+
+  nsresult rv = NS_OK;
+
+  StartAndEndContent startAndEndContent =
+      GetStartAndEndContentForRecursionLevel(aDepth);
+
+  if (startAndEndContent.mStart != content &&
+      startAndEndContent.mEnd != content) {
+    // node is completely contained in range.  Serialize the whole subtree
+    // rooted by this node.
+    rv = mNodeSerializer.SerializeToStringRecursive(
+        aNode, NodeSerializer::SerializeRoot::eYes);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else {
+    rv = SerializeNodePartiallyContainedInRange(
+        *aNode, *content, startAndEndContent, *aRange, aDepth);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsDocumentEncoder::RangeSerializer::SerializeNodePartiallyContainedInRange(
+    nsINode& aNode, nsIContent& aContent,
+    const StartAndEndContent& aStartAndEndContent, const nsRange& aRange,
+    const int32_t aDepth) {
+  // due to implementation it is impossible for text node to be both start and
+  // end of range.  We would have handled that case without getting here.
+  // XXXsmaug What does this all mean?
+  if (IsTextNode(&aNode)) {
+    nsresult rv =
+        SerializeTextNode(aNode, aContent, aStartAndEndContent, aRange);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else {
+    if (&aNode != mClosestCommonInclusiveAncestorOfRange) {
+      if (mRangeContextSerializer.mRangeNodeContext.IncludeInContext(aNode)) {
+        // halt the incrementing of mContextInfoDepth.  This
+        // is so paste client will include this node in paste.
+        mHaltRangeHint = true;
+      }
+      if ((aStartAndEndContent.mStart == &aContent) && !mHaltRangeHint) {
+        ++mContextInfoDepth.mStart;
+      }
+      if ((aStartAndEndContent.mEnd == &aContent) && !mHaltRangeHint) {
+        ++mContextInfoDepth.mEnd;
+      }
+
+      // serialize the start of this node
+      nsresult rv = mNodeSerializer.SerializeNodeStart(aNode, 0, -1);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+
+    const auto& inclusiveAncestorsOffsetsOfStart =
+        mRangeBoundariesInclusiveAncestorsAndOffsets
+            .mInclusiveAncestorsOffsetsOfStart;
+    const auto& inclusiveAncestorsOffsetsOfEnd =
+        mRangeBoundariesInclusiveAncestorsAndOffsets
+            .mInclusiveAncestorsOffsetsOfEnd;
+    // do some calculations that will tell us which children of this
+    // node are in the range.
+    Maybe<uint32_t> startOffset = Some(0);
+    Maybe<uint32_t> endOffset;
+    if (aStartAndEndContent.mStart == &aContent && mStartRootIndex >= aDepth) {
+      startOffset = inclusiveAncestorsOffsetsOfStart[mStartRootIndex - aDepth];
+    }
+    if (aStartAndEndContent.mEnd == &aContent && mEndRootIndex >= aDepth) {
+      endOffset = inclusiveAncestorsOffsetsOfEnd[mEndRootIndex - aDepth];
+    }
+    // generated aContent will cause offset values of Nothing to be returned.
+    if (startOffset.isNothing()) {
+      startOffset = Some(0);
+    }
+    if (endOffset.isNothing()) {
+      endOffset = Some(aContent.GetChildCount());
+    } else {
+      // if we are at the "tip" of the selection, endOffset is fine.
+      // otherwise, we need to add one.  This is because of the semantics
+      // of the offset list created by GetInclusiveAncestorsAndOffsets().  The
+      // intermediate points on the list use the endOffset of the
+      // location of the ancestor, rather than just past it.  So we need
+      // to add one here in order to include it in the children we serialize.
+      if (&aNode != aRange.GetEndContainer()) {
+        MOZ_ASSERT(*endOffset != UINT32_MAX);
+        endOffset.ref()++;
+      }
+    }
+
+    if (*endOffset) {
+      nsresult rv = SerializeChildrenOfContent(aContent, *startOffset,
+                                               *endOffset, &aRange, aDepth);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+    // serialize the end of this node
+    if (&aNode != mClosestCommonInclusiveAncestorOfRange) {
+      nsresult rv = mNodeSerializer.SerializeNodeEnd(aNode);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocumentEncoder::RangeSerializer::SerializeChildrenOfContent(
+    nsIContent& aContent, uint32_t aStartOffset, uint32_t aEndOffset,
+    const nsRange* aRange, int32_t aDepth) {
+  // serialize the children of this node that are in the range
+  nsIContent* childAsNode = aContent.GetFirstChild();
+  uint32_t j = 0;
+
+  for (; j < aStartOffset && childAsNode; ++j) {
+    childAsNode = childAsNode->GetNextSibling();
+  }
+
+  MOZ_ASSERT(j == aStartOffset);
+
+  for (; childAsNode && j < aEndOffset; ++j) {
+    nsresult rv{NS_OK};
+    if ((j == aStartOffset) || (j == aEndOffset - 1)) {
+      rv = SerializeRangeNodes(aRange, childAsNode, aDepth + 1);
+    } else {
+      rv = mNodeSerializer.SerializeToStringRecursive(
+          childAsNode, NodeSerializer::SerializeRoot::eYes);
+    }
+
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    childAsNode = childAsNode->GetNextSibling();
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocumentEncoder::RangeContextSerializer::SerializeRangeContextStart(
+    const nsTArray<nsINode*>& aAncestorArray) {
+  if (mDisableContextSerialize) {
+    return NS_OK;
+  }
+
+  AutoTArray<nsINode*, 8>* serializedContext = mRangeContexts.AppendElement();
+
+  int32_t i = aAncestorArray.Length(), j;
+  nsresult rv = NS_OK;
+
+  // currently only for table-related elements; see Bug 137450
+  j = mRangeNodeContext.GetImmediateContextCount(aAncestorArray);
+
+  while (i > 0) {
+    nsINode* node = aAncestorArray.ElementAt(--i);
+    if (!node) break;
+
+    // Either a general inclusion or as immediate context
+    if (mRangeNodeContext.IncludeInContext(*node) || i < j) {
+      rv = mNodeSerializer.SerializeNodeStart(*node, 0, -1);
+      serializedContext->AppendElement(node);
+      if (NS_FAILED(rv)) break;
+    }
+  }
+
+  return rv;
+}
+
+nsresult nsDocumentEncoder::RangeContextSerializer::SerializeRangeContextEnd() {
+  if (mDisableContextSerialize) {
+    return NS_OK;
+  }
+
+  MOZ_RELEASE_ASSERT(!mRangeContexts.IsEmpty(),
+                     "Tried to end context without starting one.");
+  AutoTArray<nsINode*, 8>& serializedContext = mRangeContexts.LastElement();
+
+  nsresult rv = NS_OK;
+  for (nsINode* node : Reversed(serializedContext)) {
+    rv = mNodeSerializer.SerializeNodeEnd(*node);
+
+    if (NS_FAILED(rv)) break;
+  }
+
+  mRangeContexts.RemoveLastElement();
+  return rv;
+}
+
+bool nsDocumentEncoder::RangeSerializer::HasInvisibleParentAndShouldBeSkipped(
+    nsINode& aNode) const {
+  if (!(mFlags & SkipInvisibleContent)) {
+    return false;
+  }
+
+  // Check that the parent is visible if we don't a frame.
+  // IsInvisibleNodeAndShouldBeSkipped() will do it when there's a frame.
+  nsCOMPtr<nsIContent> content = nsIContent::FromNode(aNode);
+  if (content && !content->GetPrimaryFrame()) {
+    nsIContent* parent = content->GetParent();
+    return !parent || IsInvisibleNodeAndShouldBeSkipped(*parent, mFlags);
+  }
+
+  return false;
+}
+
+nsresult nsDocumentEncoder::RangeSerializer::SerializeRangeToString(
+    const nsRange* aRange) {
+  if (!aRange || aRange->Collapsed()) return NS_OK;
+
+  mClosestCommonInclusiveAncestorOfRange =
+      aRange->GetClosestCommonInclusiveAncestor();
+
+  if (!mClosestCommonInclusiveAncestorOfRange) {
+    return NS_OK;
+  }
+
+  nsINode* startContainer = aRange->GetStartContainer();
+  NS_ENSURE_TRUE(startContainer, NS_ERROR_FAILURE);
+  int32_t startOffset = aRange->StartOffset();
+
+  nsINode* endContainer = aRange->GetEndContainer();
+  NS_ENSURE_TRUE(endContainer, NS_ERROR_FAILURE);
+  int32_t endOffset = aRange->EndOffset();
+
+  mContextInfoDepth = {};
+  mCommonInclusiveAncestors.Clear();
+
+  mRangeBoundariesInclusiveAncestorsAndOffsets = {};
+  auto& inclusiveAncestorsOfStart =
+      mRangeBoundariesInclusiveAncestorsAndOffsets.mInclusiveAncestorsOfStart;
+  auto& inclusiveAncestorsOffsetsOfStart =
+      mRangeBoundariesInclusiveAncestorsAndOffsets
+          .mInclusiveAncestorsOffsetsOfStart;
+  auto& inclusiveAncestorsOfEnd =
+      mRangeBoundariesInclusiveAncestorsAndOffsets.mInclusiveAncestorsOfEnd;
+  auto& inclusiveAncestorsOffsetsOfEnd =
+      mRangeBoundariesInclusiveAncestorsAndOffsets
+          .mInclusiveAncestorsOffsetsOfEnd;
+
+  nsContentUtils::GetInclusiveAncestors(mClosestCommonInclusiveAncestorOfRange,
+                                        mCommonInclusiveAncestors);
+  nsContentUtils::GetInclusiveAncestorsAndOffsets(
+      startContainer, startOffset, &inclusiveAncestorsOfStart,
+      &inclusiveAncestorsOffsetsOfStart);
+  nsContentUtils::GetInclusiveAncestorsAndOffsets(
+      endContainer, endOffset, &inclusiveAncestorsOfEnd,
+      &inclusiveAncestorsOffsetsOfEnd);
+
+  nsCOMPtr<nsIContent> commonContent =
+      nsIContent::FromNodeOrNull(mClosestCommonInclusiveAncestorOfRange);
+  mStartRootIndex = inclusiveAncestorsOfStart.IndexOf(commonContent);
+  mEndRootIndex = inclusiveAncestorsOfEnd.IndexOf(commonContent);
+
+  nsresult rv = NS_OK;
+
+  rv = mRangeContextSerializer.SerializeRangeContextStart(
+      mCommonInclusiveAncestors);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (startContainer == endContainer && IsTextNode(startContainer)) {
+    if (HasInvisibleParentAndShouldBeSkipped(*startContainer)) {
+      return NS_OK;
+    }
+    rv = mNodeSerializer.SerializeTextNode(*startContainer, startOffset,
+                                           endOffset);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else {
+    rv = SerializeRangeNodes(aRange, mClosestCommonInclusiveAncestorOfRange, 0);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+  rv = mRangeContextSerializer.SerializeRangeContextEnd();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return rv;
+}
+
+void nsDocumentEncoder::ReleaseDocumentReferenceAndInitialize(
+    bool aClearCachedSerializer) {
+  mDocument = nullptr;
+
+  Initialize(aClearCachedSerializer);
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::EncodeToString(nsAString& aOutputString) {
+  return EncodeToStringWithMaxLength(0, aOutputString);
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::EncodeToStringWithMaxLength(uint32_t aMaxLength,
+                                               nsAString& aOutputString) {
+  MOZ_ASSERT(mRangeContextSerializer.mRangeContexts.IsEmpty(),
+             "Re-entrant call to nsDocumentEncoder.");
+  auto rangeContextGuard =
+      MakeScopeExit([&] { mRangeContextSerializer.mRangeContexts.Clear(); });
+
+  if (!mDocument) return NS_ERROR_NOT_INITIALIZED;
+
+  AutoReleaseDocumentIfNeeded autoReleaseDocument(this);
+
+  aOutputString.Truncate();
+
+  nsString output;
+  static const size_t kStringBufferSizeInBytes = 2048;
+  if (!mCachedBuffer) {
+    mCachedBuffer = nsStringBuffer::Alloc(kStringBufferSizeInBytes).take();
+    if (NS_WARN_IF(!mCachedBuffer)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+  }
+  NS_ASSERTION(
+      !mCachedBuffer->IsReadonly(),
+      "nsIDocumentEncoder shouldn't keep reference to non-readonly buffer!");
+  static_cast<char16_t*>(mCachedBuffer->Data())[0] = char16_t(0);
+  mCachedBuffer->ToString(0, output, true);
+  // output owns the buffer now!
+  mCachedBuffer = nullptr;
+
+  if (!mSerializer) {
+    nsAutoCString progId(NS_CONTENTSERIALIZER_CONTRACTID_PREFIX);
+    AppendUTF16toUTF8(mMimeType, progId);
+
+    mSerializer = do_CreateInstance(progId.get());
+    NS_ENSURE_TRUE(mSerializer, NS_ERROR_NOT_IMPLEMENTED);
+  }
+
+  nsresult rv = NS_OK;
+
+  bool rewriteEncodingDeclaration =
+      !mEncodingScope.IsLimited() &&
+      !(mFlags & OutputDontRewriteEncodingDeclaration);
+  mSerializer->Init(mFlags, mWrapColumn, mEncoding, mIsCopying,
+                    rewriteEncodingDeclaration, &mNeedsPreformatScanning,
+                    output);
+
+  rv = SerializeDependingOnScope(aMaxLength);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = mSerializer->FlushAndFinish();
+
+  mCachedBuffer = nsStringBuffer::FromString(output);
+  // We have to be careful how we set aOutputString, because we don't
+  // want it to end up sharing mCachedBuffer if we plan to reuse it.
+  bool setOutput = false;
+  // Try to cache the buffer.
+  if (mCachedBuffer) {
+    if ((mCachedBuffer->StorageSize() == kStringBufferSizeInBytes) &&
+        !mCachedBuffer->IsReadonly()) {
+      mCachedBuffer->AddRef();
+    } else {
+      if (NS_SUCCEEDED(rv)) {
+        mCachedBuffer->ToString(output.Length(), aOutputString);
+        setOutput = true;
+      }
+      mCachedBuffer = nullptr;
+    }
+  }
+
+  if (!setOutput && NS_SUCCEEDED(rv)) {
+    aOutputString.Append(output.get(), output.Length());
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::EncodeToStream(nsIOutputStream* aStream) {
+  MOZ_ASSERT(mRangeContextSerializer.mRangeContexts.IsEmpty(),
+             "Re-entrant call to nsDocumentEncoder.");
+  auto rangeContextGuard =
+      MakeScopeExit([&] { mRangeContextSerializer.mRangeContexts.Clear(); });
+  NS_ENSURE_ARG_POINTER(aStream);
+
+  nsresult rv = NS_OK;
+
+  if (!mDocument) return NS_ERROR_NOT_INITIALIZED;
+
+  if (!mEncoding) {
+    return NS_ERROR_UCONV_NOCONV;
+  }
+
+  nsAutoString buf;
+  const bool isPlainText = mMimeType.LowerCaseEqualsLiteral(kTextMime);
+  mTextStreamer.emplace(*aStream, mEncoding->NewEncoder(), isPlainText, buf);
+
+  rv = EncodeToString(buf);
+
+  // Force a flush of the last chunk of data.
+  rv = mTextStreamer->ForceFlush();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mTextStreamer.reset();
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::EncodeToStringWithContext(nsAString& aContextString,
+                                             nsAString& aInfoString,
+                                             nsAString& aEncodedString) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocumentEncoder::SetNodeFixup(nsIDocumentEncoderNodeFixup* aFixup) {
+  mNodeFixup = aFixup;
+  return NS_OK;
+}
+
+bool do_getDocumentTypeSupportedForEncoding(const char* aContentType) {
+  if (!nsCRT::strcmp(aContentType, "text/xml") ||
+      !nsCRT::strcmp(aContentType, "application/xml") ||
+      !nsCRT::strcmp(aContentType, "application/xhtml+xml") ||
+      !nsCRT::strcmp(aContentType, "image/svg+xml") ||
+      !nsCRT::strcmp(aContentType, "text/html") ||
+      !nsCRT::strcmp(aContentType, "text/plain")) {
+    return true;
+  }
+  return false;
+}
+
+already_AddRefed<nsIDocumentEncoder> do_createDocumentEncoder(
+    const char* aContentType) {
+  if (do_getDocumentTypeSupportedForEncoding(aContentType)) {
+    return do_AddRef(new nsDocumentEncoder);
+  }
+  return nullptr;
+}
+
+class nsHTMLCopyEncoder : public nsDocumentEncoder {
+ private:
+  class RangeNodeContext final : public nsDocumentEncoder::RangeNodeContext {
+    bool IncludeInContext(nsINode& aNode) const final;
+
+    int32_t GetImmediateContextCount(
+        const nsTArray<nsINode*>& aAncestorArray) const final;
+  };
+
+ public:
+  nsHTMLCopyEncoder();
+  ~nsHTMLCopyEncoder();
+
+  NS_IMETHOD Init(Document* aDocument, const nsAString& aMimeType,
+                  uint32_t aFlags) override;
+
+  // overridden methods from nsDocumentEncoder
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  NS_IMETHOD SetSelection(Selection* aSelection) override;
+  NS_IMETHOD EncodeToStringWithContext(nsAString& aContextString,
+                                       nsAString& aInfoString,
+                                       nsAString& aEncodedString) override;
+  NS_IMETHOD EncodeToString(nsAString& aOutputString) override;
+
+ protected:
+  enum Endpoint { kStart, kEnd };
+
+  nsresult PromoteRange(nsRange* inRange);
+  nsresult PromoteAncestorChain(nsCOMPtr<nsINode>* ioNode,
+                                int32_t* ioStartOffset, int32_t* ioEndOffset);
+  nsresult GetPromotedPoint(Endpoint aWhere, nsINode* aNode, int32_t aOffset,
+                            nsCOMPtr<nsINode>* outNode, int32_t* outOffset,
+                            nsINode* aCommon);
+  static nsCOMPtr<nsINode> GetChildAt(nsINode* aParent, int32_t aOffset);
+  static bool IsMozBR(Element* aNode);
+  static nsresult GetNodeLocation(nsINode* inChild,
+                                  nsCOMPtr<nsINode>* outParent,
+                                  int32_t* outOffset);
+  bool IsRoot(nsINode* aNode);
+  static bool IsFirstNode(nsINode* aNode);
+  static bool IsLastNode(nsINode* aNode);
+
+  bool mIsTextWidget;
+};
+
+nsHTMLCopyEncoder::nsHTMLCopyEncoder()
+    : nsDocumentEncoder{MakeUnique<nsHTMLCopyEncoder::RangeNodeContext>()} {
+  mIsTextWidget = false;
+}
+
+nsHTMLCopyEncoder::~nsHTMLCopyEncoder() = default;
+
+NS_IMETHODIMP
+nsHTMLCopyEncoder::Init(Document* aDocument, const nsAString& aMimeType,
+                        uint32_t aFlags) {
+  if (!aDocument) return NS_ERROR_INVALID_ARG;
+
+  mIsTextWidget = false;
+  Initialize();
+
+  mIsCopying = true;
+  mDocument = aDocument;
+
+  // Hack, hack! Traditionally, the caller passes text/plain, which is
+  // treated as "guess text/html or text/plain" in this context. (It has a
+  // different meaning in other contexts. Sigh.) From now on, "text/plain"
+  // means forcing text/plain instead of guessing.
+  if (aMimeType.EqualsLiteral("text/plain")) {
+    mMimeType.AssignLiteral("text/plain");
+  } else {
+    mMimeType.AssignLiteral("text/html");
+  }
+
+  // Make all links absolute when copying
+  // (see related bugs #57296, #41924, #58646, #32768)
+  mFlags = aFlags | OutputAbsoluteLinks;
+
+  if (!mDocument->IsScriptEnabled()) mFlags |= OutputNoScriptContent;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsHTMLCopyEncoder::SetSelection(Selection* aSelection) {
+  // check for text widgets: we need to recognize these so that
+  // we don't tweak the selection to be outside of the magic
+  // div that ender-lite text widgets are embedded in.
+
+  if (!aSelection) return NS_ERROR_NULL_POINTER;
+
+  const uint32_t rangeCount = aSelection->RangeCount();
+
+  // if selection is uninitialized return
+  if (!rangeCount) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // we'll just use the common parent of the first range.  Implicit assumption
+  // here that multi-range selections are table cell selections, in which case
+  // the common parent is somewhere in the table and we don't really care where.
+  //
+  // FIXME(emilio, bug 1455894): This assumption is already wrong, and will
+  // probably be more wrong in a Shadow DOM world...
+  //
+  // We should be able to write this as "Find the common ancestor of the
+  // selection, then go through the flattened tree and serialize the selected
+  // nodes", effectively serializing the composed tree.
+  RefPtr<nsRange> range = aSelection->GetRangeAt(0);
+  nsINode* commonParent = range->GetClosestCommonInclusiveAncestor();
+
+  for (nsCOMPtr<nsIContent> selContent(
+           nsIContent::FromNodeOrNull(commonParent));
+       selContent; selContent = selContent->GetParent()) {
+    // checking for selection inside a plaintext form widget
+    if (selContent->IsAnyOfHTMLElements(nsGkAtoms::input,
+                                        nsGkAtoms::textarea)) {
+      mIsTextWidget = true;
+      break;
+    }
+  }
+
+  // normalize selection if we are not in a widget
+  if (mIsTextWidget) {
+    mEncodingScope.mSelection = aSelection;
+    mMimeType.AssignLiteral("text/plain");
+    return NS_OK;
+  }
+
+  // XXX We should try to get rid of the Selection object here.
+  // XXX bug 1245883
+
+  // also consider ourselves in a text widget if we can't find an html document
+  if (!(mDocument && mDocument->IsHTMLDocument())) {
+    mIsTextWidget = true;
+    mEncodingScope.mSelection = aSelection;
+    // mMimeType is set to text/plain when encoding starts.
+    return NS_OK;
+  }
+
+  // there's no Clone() for selection! fix...
+  // nsresult rv = aSelection->Clone(getter_AddRefs(mSelection);
+  // NS_ENSURE_SUCCESS(rv, rv);
+  mEncodingScope.mSelection = new Selection(SelectionType::eNormal, nullptr);
+
+  // loop thru the ranges in the selection
+  for (const uint32_t rangeIdx : IntegerRange(rangeCount)) {
+    MOZ_ASSERT(aSelection->RangeCount() == rangeCount);
+    range = aSelection->GetRangeAt(rangeIdx);
+    NS_ENSURE_TRUE(range, NS_ERROR_FAILURE);
+    RefPtr<nsRange> myRange = range->CloneRange();
+    MOZ_ASSERT(myRange);
+
+    // adjust range to include any ancestors who's children are entirely
+    // selected
+    nsresult rv = PromoteRange(myRange);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    ErrorResult result;
+    RefPtr<Selection> selection(mEncodingScope.mSelection);
+    RefPtr<Document> document(mDocument);
+    selection->AddRangeAndSelectFramesAndNotifyListenersInternal(
+        *myRange, document, result);
+    rv = result.StealNSResult();
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsHTMLCopyEncoder::EncodeToString(nsAString& aOutputString) {
+  if (mIsTextWidget) {
+    mMimeType.AssignLiteral("text/plain");
+  }
+  return nsDocumentEncoder::EncodeToString(aOutputString);
+}
+
+NS_IMETHODIMP
+nsHTMLCopyEncoder::EncodeToStringWithContext(nsAString& aContextString,
+                                             nsAString& aInfoString,
+                                             nsAString& aEncodedString) {
+  nsresult rv = EncodeToString(aEncodedString);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // do not encode any context info or range hints if we are in a text widget.
+  if (mIsTextWidget) return NS_OK;
+
+  // now encode common ancestors into aContextString.  Note that the common
+  // ancestors will be for the last range in the selection in the case of
+  // multirange selections. encoding ancestors every range in a multirange
+  // selection in a way that could be understood by the paste code would be a
+  // lot more work to do.  As a practical matter, selections are single range,
+  // and the ones that aren't are table cell selections where all the cells are
+  // in the same table.
+
+  mSerializer->Init(mFlags, mWrapColumn, mEncoding, mIsCopying, false,
+                    &mNeedsPreformatScanning, aContextString);
+
+  // leaf of ancestors might be text node.  If so discard it.
+  int32_t count = mRangeSerializer.mCommonInclusiveAncestors.Length();
+  int32_t i;
+  nsCOMPtr<nsINode> node;
+  if (count > 0) {
+    node = mRangeSerializer.mCommonInclusiveAncestors.ElementAt(0);
+  }
+
+  if (node && IsTextNode(node)) {
+    mRangeSerializer.mCommonInclusiveAncestors.RemoveElementAt(0);
+    if (mRangeSerializer.mContextInfoDepth.mStart) {
+      --mRangeSerializer.mContextInfoDepth.mStart;
+    }
+    if (mRangeSerializer.mContextInfoDepth.mEnd) {
+      --mRangeSerializer.mContextInfoDepth.mEnd;
+    }
+    count--;
+  }
+
+  i = count;
+  while (i > 0) {
+    node = mRangeSerializer.mCommonInclusiveAncestors.ElementAt(--i);
+    rv = mNodeSerializer.SerializeNodeStart(*node, 0, -1);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+  // i = 0; guaranteed by above
+  while (i < count) {
+    node = mRangeSerializer.mCommonInclusiveAncestors.ElementAt(i++);
+    rv = mNodeSerializer.SerializeNodeEnd(*node);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  mSerializer->Finish();
+
+  // encode range info : the start and end depth of the selection, where the
+  // depth is distance down in the parent hierarchy.  Later we will need to add
+  // leading/trailing whitespace info to this.
+  nsAutoString infoString;
+  infoString.AppendInt(mRangeSerializer.mContextInfoDepth.mStart);
+  infoString.Append(char16_t(','));
+  infoString.AppendInt(mRangeSerializer.mContextInfoDepth.mEnd);
+  aInfoString = infoString;
+
+  return rv;
+}
+
+bool nsHTMLCopyEncoder::RangeNodeContext::IncludeInContext(
+    nsINode& aNode) const {
+  nsCOMPtr<nsIContent> content(nsIContent::FromNodeOrNull(&aNode));
+
+  if (!content) return false;
+
+  return content->IsAnyOfHTMLElements(
+      nsGkAtoms::b, nsGkAtoms::i, nsGkAtoms::u, nsGkAtoms::a, nsGkAtoms::tt,
+      nsGkAtoms::s, nsGkAtoms::big, nsGkAtoms::small, nsGkAtoms::strike,
+      nsGkAtoms::em, nsGkAtoms::strong, nsGkAtoms::dfn, nsGkAtoms::code,
+      nsGkAtoms::cite, nsGkAtoms::var, nsGkAtoms::abbr, nsGkAtoms::font,
+      nsGkAtoms::script, nsGkAtoms::span, nsGkAtoms::pre, nsGkAtoms::h1,
+      nsGkAtoms::h2, nsGkAtoms::h3, nsGkAtoms::h4, nsGkAtoms::h5,
+      nsGkAtoms::h6);
+}
+
+nsresult nsHTMLCopyEncoder::PromoteRange(nsRange* inRange) {
+  if (!inRange->IsPositioned()) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  nsCOMPtr<nsINode> startNode = inRange->GetStartContainer();
+  uint32_t startOffset = inRange->StartOffset();
+  nsCOMPtr<nsINode> endNode = inRange->GetEndContainer();
+  uint32_t endOffset = inRange->EndOffset();
+  nsCOMPtr<nsINode> common = inRange->GetClosestCommonInclusiveAncestor();
+
+  nsCOMPtr<nsINode> opStartNode;
+  nsCOMPtr<nsINode> opEndNode;
+  int32_t opStartOffset, opEndOffset;
+
+  // examine range endpoints.
+  nsresult rv =
+      GetPromotedPoint(kStart, startNode, static_cast<int32_t>(startOffset),
+                       address_of(opStartNode), &opStartOffset, common);
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = GetPromotedPoint(kEnd, endNode, static_cast<int32_t>(endOffset),
+                        address_of(opEndNode), &opEndOffset, common);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // if both range endpoints are at the common ancestor, check for possible
+  // inclusion of ancestors
+  if (opStartNode == common && opEndNode == common) {
+    rv = PromoteAncestorChain(address_of(opStartNode), &opStartOffset,
+                              &opEndOffset);
+    NS_ENSURE_SUCCESS(rv, rv);
+    opEndNode = opStartNode;
+  }
+
+  // set the range to the new values
+  ErrorResult err;
+  inRange->SetStart(*opStartNode, static_cast<uint32_t>(opStartOffset), err);
+  if (NS_WARN_IF(err.Failed())) {
+    return err.StealNSResult();
+  }
+  inRange->SetEnd(*opEndNode, static_cast<uint32_t>(opEndOffset), err);
+  if (NS_WARN_IF(err.Failed())) {
+    return err.StealNSResult();
+  }
+  return NS_OK;
+}
+
+// PromoteAncestorChain will promote a range represented by
+// [{*ioNode,*ioStartOffset} , {*ioNode,*ioEndOffset}] The promotion is
+// different from that found in getPromotedPoint: it will only promote one
+// endpoint if it can promote the other.  Thus, instead of having a
+// startnode/endNode, there is just the one ioNode.
+nsresult nsHTMLCopyEncoder::PromoteAncestorChain(nsCOMPtr<nsINode>* ioNode,
+                                                 int32_t* ioStartOffset,
+                                                 int32_t* ioEndOffset) {
+  if (!ioNode || !ioStartOffset || !ioEndOffset) return NS_ERROR_NULL_POINTER;
+
+  nsresult rv = NS_OK;
+  bool done = false;
+
+  nsCOMPtr<nsINode> frontNode, endNode, parent;
+  int32_t frontOffset, endOffset;
+
+  // save the editable state of the ioNode, so we don't promote an ancestor if
+  // it has different editable state
+  nsCOMPtr<nsINode> node = *ioNode;
+  bool isEditable = node->IsEditable();
+
+  // loop for as long as we can promote both endpoints
+  while (!done) {
+    node = *ioNode;
+    parent = node->GetParentNode();
+    if (!parent) {
+      done = true;
+    } else {
+      // passing parent as last param to GetPromotedPoint() allows it to promote
+      // only one level up the hierarchy.
+      rv = GetPromotedPoint(kStart, *ioNode, *ioStartOffset,
+                            address_of(frontNode), &frontOffset, parent);
+      NS_ENSURE_SUCCESS(rv, rv);
+      // then we make the same attempt with the endpoint
+      rv = GetPromotedPoint(kEnd, *ioNode, *ioEndOffset, address_of(endNode),
+                            &endOffset, parent);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      // if both endpoints were promoted one level and isEditable is the same as
+      // the original node, keep looping - otherwise we are done.
+      if ((frontNode != parent) || (endNode != parent) ||
+          (frontNode->IsEditable() != isEditable))
+        done = true;
+      else {
+        *ioNode = frontNode;
+        *ioStartOffset = frontOffset;
+        *ioEndOffset = endOffset;
+      }
+    }
+  }
+  return rv;
+}
+
+nsresult nsHTMLCopyEncoder::GetPromotedPoint(Endpoint aWhere, nsINode* aNode,
+                                             int32_t aOffset,
+                                             nsCOMPtr<nsINode>* outNode,
+                                             int32_t* outOffset,
+                                             nsINode* common) {
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsINode> node = aNode;
+  nsCOMPtr<nsINode> parent = aNode;
+  int32_t offset = aOffset;
+  bool bResetPromotion = false;
+
+  // default values
+  *outNode = node;
+  *outOffset = offset;
+
+  if (common == node) return NS_OK;
+
+  if (aWhere == kStart) {
+    // some special casing for text nodes
+    if (auto nodeAsText = aNode->GetAsText()) {
+      // if not at beginning of text node, we are done
+      if (offset > 0) {
+        // unless everything before us in just whitespace.  NOTE: we need a more
+        // general solution that truly detects all cases of non-significant
+        // whitesace with no false alarms.
+        nsAutoString text;
+        nodeAsText->SubstringData(0, offset, text, IgnoreErrors());
+        text.CompressWhitespace();
+        if (!text.IsEmpty()) return NS_OK;
+        bResetPromotion = true;
+      }
+      // else
+      rv = GetNodeLocation(aNode, address_of(parent), &offset);
+      NS_ENSURE_SUCCESS(rv, rv);
+    } else {
+      node = GetChildAt(parent, offset);
+    }
+    if (!node) node = parent;
+
+    // finding the real start for this point.  look up the tree for as long as
+    // we are the first node in the container, and as long as we haven't hit the
+    // body node.
+    if (!IsRoot(node) && (parent != common)) {
+      rv = GetNodeLocation(node, address_of(parent), &offset);
+      NS_ENSURE_SUCCESS(rv, rv);
+      if (offset == -1) return NS_OK;  // we hit generated content; STOP
+      while ((IsFirstNode(node)) && (!IsRoot(parent)) && (parent != common)) {
+        if (bResetPromotion) {
+          nsCOMPtr<nsIContent> content = nsIContent::FromNodeOrNull(parent);
+          if (content && content->IsHTMLElement()) {
+            if (nsHTMLElement::IsBlock(
+                    nsHTMLTags::AtomTagToId(content->NodeInfo()->NameAtom()))) {
+              bResetPromotion = false;
+            }
+          }
+        }
+
+        node = parent;
+        rv = GetNodeLocation(node, address_of(parent), &offset);
+        NS_ENSURE_SUCCESS(rv, rv);
+        if (offset == -1)  // we hit generated content; STOP
+        {
+          // back up a bit
+          parent = node;
+          offset = 0;
+          break;
+        }
+      }
+      if (bResetPromotion) {
+        *outNode = aNode;
+        *outOffset = aOffset;
+      } else {
+        *outNode = parent;
+        *outOffset = offset;
+      }
+      return rv;
+    }
+  }
+
+  if (aWhere == kEnd) {
+    // some special casing for text nodes
+    if (auto nodeAsText = aNode->GetAsText()) {
+      // if not at end of text node, we are done
+      uint32_t len = aNode->Length();
+      if (offset < (int32_t)len) {
+        // unless everything after us in just whitespace.  NOTE: we need a more
+        // general solution that truly detects all cases of non-significant
+        // whitespace with no false alarms.
+        nsAutoString text;
+        nodeAsText->SubstringData(offset, len - offset, text, IgnoreErrors());
+        text.CompressWhitespace();
+        if (!text.IsEmpty()) return NS_OK;
+        bResetPromotion = true;
+      }
+      rv = GetNodeLocation(aNode, address_of(parent), &offset);
+      NS_ENSURE_SUCCESS(rv, rv);
+    } else {
+      if (offset) offset--;  // we want node _before_ offset
+      node = GetChildAt(parent, offset);
+    }
+    if (!node) node = parent;
+
+    // finding the real end for this point.  look up the tree for as long as we
+    // are the last node in the container, and as long as we haven't hit the
+    // body node.
+    if (!IsRoot(node) && (parent != common)) {
+      rv = GetNodeLocation(node, address_of(parent), &offset);
+      NS_ENSURE_SUCCESS(rv, rv);
+      if (offset == -1) return NS_OK;  // we hit generated content; STOP
+      while ((IsLastNode(node)) && (!IsRoot(parent)) && (parent != common)) {
+        if (bResetPromotion) {
+          nsCOMPtr<nsIContent> content = nsIContent::FromNodeOrNull(parent);
+          if (content && content->IsHTMLElement()) {
+            if (nsHTMLElement::IsBlock(
+                    nsHTMLTags::AtomTagToId(content->NodeInfo()->NameAtom()))) {
+              bResetPromotion = false;
+            }
+          }
+        }
+
+        node = parent;
+        rv = GetNodeLocation(node, address_of(parent), &offset);
+        NS_ENSURE_SUCCESS(rv, rv);
+        if (offset == -1)  // we hit generated content; STOP
+        {
+          // back up a bit
+          parent = node;
+          offset = 0;
+          break;
+        }
+      }
+      if (bResetPromotion) {
+        *outNode = aNode;
+        *outOffset = aOffset;
+      } else {
+        *outNode = parent;
+        offset++;  // add one since this in an endpoint - want to be AFTER node.
+        *outOffset = offset;
+      }
+      return rv;
+    }
+  }
+
+  return rv;
+}
+
+nsCOMPtr<nsINode> nsHTMLCopyEncoder::GetChildAt(nsINode* aParent,
+                                                int32_t aOffset) {
+  nsCOMPtr<nsINode> resultNode;
+
+  if (!aParent) return resultNode;
+
+  nsCOMPtr<nsIContent> content = nsIContent::FromNodeOrNull(aParent);
+  MOZ_ASSERT(content, "null content in nsHTMLCopyEncoder::GetChildAt");
+
+  resultNode = content->GetChildAt_Deprecated(aOffset);
+
+  return resultNode;
+}
+
+bool nsHTMLCopyEncoder::IsMozBR(Element* aElement) {
+  HTMLBRElement* brElement = HTMLBRElement::FromNodeOrNull(aElement);
+  return brElement && brElement->IsPaddingForEmptyLastLine();
+}
+
+nsresult nsHTMLCopyEncoder::GetNodeLocation(nsINode* inChild,
+                                            nsCOMPtr<nsINode>* outParent,
+                                            int32_t* outOffset) {
+  NS_ASSERTION((inChild && outParent && outOffset), "bad args");
+  if (inChild && outParent && outOffset) {
+    nsCOMPtr<nsIContent> child = nsIContent::FromNodeOrNull(inChild);
+    if (!child) {
+      return NS_ERROR_NULL_POINTER;
+    }
+
+    nsIContent* parent = child->GetParent();
+    if (!parent) {
+      return NS_ERROR_NULL_POINTER;
+    }
+
+    *outParent = parent;
+    *outOffset = parent->ComputeIndexOf_Deprecated(child);
+    return NS_OK;
+  }
+  return NS_ERROR_NULL_POINTER;
+}
+
+bool nsHTMLCopyEncoder::IsRoot(nsINode* aNode) {
+  nsCOMPtr<nsIContent> content = nsIContent::FromNodeOrNull(aNode);
+  if (!content) {
+    return false;
+  }
+
+  if (mIsTextWidget) {
+    return content->IsHTMLElement(nsGkAtoms::div);
+  }
+
+  return content->IsAnyOfHTMLElements(nsGkAtoms::body, nsGkAtoms::td,
+                                      nsGkAtoms::th);
+}
+
+bool nsHTMLCopyEncoder::IsFirstNode(nsINode* aNode) {
+  // need to check if any nodes before us are really visible.
+  // Mike wrote something for me along these lines in nsSelectionController,
+  // but I don't think it's ready for use yet - revisit.
+  // HACK: for now, simply consider all whitespace text nodes to be
+  // invisible formatting nodes.
+  for (nsIContent* sibling = aNode->GetPreviousSibling(); sibling;
+       sibling = sibling->GetPreviousSibling()) {
+    if (!sibling->TextIsOnlyWhitespace()) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool nsHTMLCopyEncoder::IsLastNode(nsINode* aNode) {
+  // need to check if any nodes after us are really visible.
+  // Mike wrote something for me along these lines in nsSelectionController,
+  // but I don't think it's ready for use yet - revisit.
+  // HACK: for now, simply consider all whitespace text nodes to be
+  // invisible formatting nodes.
+  for (nsIContent* sibling = aNode->GetNextSibling(); sibling;
+       sibling = sibling->GetNextSibling()) {
+    if (sibling->IsElement() && IsMozBR(sibling->AsElement())) {
+      // we ignore trailing moz BRs.
+      continue;
+    }
+    if (!sibling->TextIsOnlyWhitespace()) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+already_AddRefed<nsIDocumentEncoder> do_createHTMLCopyEncoder() {
+  return do_AddRef(new nsHTMLCopyEncoder);
+}
+
+int32_t nsHTMLCopyEncoder::RangeNodeContext::GetImmediateContextCount(
+    const nsTArray<nsINode*>& aAncestorArray) const {
+  int32_t i = aAncestorArray.Length(), j = 0;
+  while (j < i) {
+    nsINode* node = aAncestorArray.ElementAt(j);
+    if (!node) {
+      break;
+    }
+    nsCOMPtr<nsIContent> content(nsIContent::FromNodeOrNull(node));
+    if (!content || !content->IsAnyOfHTMLElements(
+                        nsGkAtoms::tr, nsGkAtoms::thead, nsGkAtoms::tbody,
+                        nsGkAtoms::tfoot, nsGkAtoms::table)) {
+      break;
+    }
+    ++j;
+  }
+  return j;
+}