1 files changed, 684 insertions, 0 deletions
diff --git a/extensions/spellcheck/src/mozSpellChecker.cpp b/extensions/spellcheck/src/mozSpellChecker.cpp
new file mode 100644
index 0000000000..3fc600adbb
--- /dev/null
+++ b/extensions/spellcheck/src/mozSpellChecker.cpp
@@ -0,0 +1,684 @@
+/* vim: set ts=2 sts=2 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/. */
+
+#include "mozSpellChecker.h"
+#include "nsIStringEnumerator.h"
+#include "nsICategoryManager.h"
+#include "nsISupportsPrimitives.h"
+#include "nsISimpleEnumerator.h"
+#include "mozEnglishWordUtils.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/Logging.h"
+#include "mozilla/PRemoteSpellcheckEngineChild.h"
+#include "mozilla/TextServicesDocument.h"
+#include "nsXULAppAPI.h"
+#include "RemoteSpellCheckEngineChild.h"
+
+using mozilla::AssertedCast;
+using mozilla::GenericPromise;
+using mozilla::LogLevel;
+using mozilla::RemoteSpellcheckEngineChild;
+using mozilla::TextServicesDocument;
+using mozilla::dom::ContentChild;
+
+#define DEFAULT_SPELL_CHECKER "@mozilla.org/spellchecker/engine;1"
+
+static mozilla::LazyLogModule sSpellChecker("SpellChecker");
+
+NS_IMPL_CYCLE_COLLECTION(mozSpellChecker, mTextServicesDocument,
+                         mPersonalDictionary)
+
+mozSpellChecker::mozSpellChecker() : mEngine(nullptr) {}
+
+mozSpellChecker::~mozSpellChecker() {
+  if (mPersonalDictionary) {
+    //    mPersonalDictionary->Save();
+    mPersonalDictionary->EndSession();
+  }
+  mSpellCheckingEngine = nullptr;
+  mPersonalDictionary = nullptr;
+
+  if (mEngine) {
+    MOZ_ASSERT(XRE_IsContentProcess());
+    RemoteSpellcheckEngineChild::Send__delete__(mEngine);
+    MOZ_ASSERT(!mEngine);
+  }
+}
+
+nsresult mozSpellChecker::Init() {
+  mSpellCheckingEngine = nullptr;
+  if (XRE_IsContentProcess()) {
+    mozilla::dom::ContentChild* contentChild =
+        mozilla::dom::ContentChild::GetSingleton();
+    MOZ_ASSERT(contentChild);
+    // mEngine is nulled in RemoteSpellcheckEngineChild(), so we don't need to
+    // worry about SendPRemoveSpellcheckEngineConstructor failing
+    mEngine = new RemoteSpellcheckEngineChild(this);
+    MOZ_ALWAYS_TRUE(
+        contentChild->SendPRemoteSpellcheckEngineConstructor(mEngine));
+  } else {
+    mPersonalDictionary =
+        do_GetService("@mozilla.org/spellchecker/personaldictionary;1");
+  }
+
+  return NS_OK;
+}
+
+TextServicesDocument* mozSpellChecker::GetTextServicesDocument() {
+  return mTextServicesDocument;
+}
+
+nsresult mozSpellChecker::SetDocument(
+    TextServicesDocument* aTextServicesDocument, bool aFromStartofDoc) {
+  MOZ_LOG(sSpellChecker, LogLevel::Debug, ("%s", __FUNCTION__));
+
+  mTextServicesDocument = aTextServicesDocument;
+  mFromStart = aFromStartofDoc;
+  return NS_OK;
+}
+
+nsresult mozSpellChecker::NextMisspelledWord(nsAString& aWord,
+                                             nsTArray<nsString>& aSuggestions) {
+  if (NS_WARN_IF(!mConverter)) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  int32_t selOffset;
+  nsresult result;
+  result = SetupDoc(&selOffset);
+  if (NS_FAILED(result)) return result;
+
+  bool done;
+  while (NS_SUCCEEDED(mTextServicesDocument->IsDone(&done)) && !done) {
+    int32_t begin, end;
+    nsAutoString str;
+    mTextServicesDocument->GetCurrentTextBlock(str);
+    while (mConverter->FindNextWord(str, selOffset, &begin, &end)) {
+      const nsDependentSubstring currWord(str, begin, end - begin);
+      bool isMisspelled;
+      result = CheckWord(currWord, &isMisspelled, &aSuggestions);
+      if (NS_WARN_IF(NS_FAILED(result))) {
+        return result;
+      }
+      if (isMisspelled) {
+        aWord = currWord;
+        MOZ_KnownLive(mTextServicesDocument)
+            ->SetSelection(AssertedCast<uint32_t>(begin),
+                           AssertedCast<uint32_t>(end - begin));
+        // After ScrollSelectionIntoView(), the pending notifications might
+        // be flushed and PresShell/PresContext/Frames may be dead.
+        // See bug 418470.
+        mTextServicesDocument->ScrollSelectionIntoView();
+        return NS_OK;
+      }
+      selOffset = end;
+    }
+    mTextServicesDocument->NextBlock();
+    selOffset = 0;
+  }
+  return NS_OK;
+}
+
+RefPtr<mozilla::CheckWordPromise> mozSpellChecker::CheckWords(
+    const nsTArray<nsString>& aWords) {
+  if (XRE_IsContentProcess()) {
+    return mEngine->CheckWords(aWords);
+  }
+
+  nsTArray<bool> misspells;
+  misspells.SetCapacity(aWords.Length());
+  for (auto& word : aWords) {
+    bool misspelled;
+    nsresult rv = CheckWord(word, &misspelled, nullptr);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return mozilla::CheckWordPromise::CreateAndReject(rv, __func__);
+    }
+    misspells.AppendElement(misspelled);
+  }
+  return mozilla::CheckWordPromise::CreateAndResolve(std::move(misspells),
+                                                     __func__);
+}
+
+nsresult mozSpellChecker::CheckWord(const nsAString& aWord, bool* aIsMisspelled,
+                                    nsTArray<nsString>* aSuggestions) {
+  if (XRE_IsContentProcess()) {
+    // Use async version (CheckWords or Suggest) on content process
+    return NS_ERROR_FAILURE;
+  }
+
+  nsresult result;
+  bool correct;
+
+  if (!mSpellCheckingEngine) {
+    return NS_ERROR_NULL_POINTER;
+  }
+  *aIsMisspelled = false;
+  result = mSpellCheckingEngine->Check(aWord, &correct);
+  NS_ENSURE_SUCCESS(result, result);
+  if (!correct) {
+    if (aSuggestions) {
+      result = mSpellCheckingEngine->Suggest(aWord, *aSuggestions);
+      NS_ENSURE_SUCCESS(result, result);
+    }
+    *aIsMisspelled = true;
+  }
+  return NS_OK;
+}
+
+RefPtr<mozilla::SuggestionsPromise> mozSpellChecker::Suggest(
+    const nsAString& aWord, uint32_t aMaxCount) {
+  if (XRE_IsContentProcess()) {
+    return mEngine->SendSuggest(aWord, aMaxCount)
+        ->Then(
+            mozilla::GetCurrentSerialEventTarget(), __func__,
+            [](nsTArray<nsString>&& aSuggestions) {
+              return mozilla::SuggestionsPromise::CreateAndResolve(
+                  std::move(aSuggestions), __func__);
+            },
+            [](mozilla::ipc::ResponseRejectReason&& aReason) {
+              return mozilla::SuggestionsPromise::CreateAndReject(
+                  NS_ERROR_NOT_AVAILABLE, __func__);
+            });
+  }
+
+  if (!mSpellCheckingEngine) {
+    return mozilla::SuggestionsPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE,
+                                                        __func__);
+  }
+
+  bool correct;
+  nsresult rv = mSpellCheckingEngine->Check(aWord, &correct);
+  if (NS_FAILED(rv)) {
+    return mozilla::SuggestionsPromise::CreateAndReject(rv, __func__);
+  }
+  nsTArray<nsString> suggestions;
+  if (!correct) {
+    rv = mSpellCheckingEngine->Suggest(aWord, suggestions);
+    if (NS_FAILED(rv)) {
+      return mozilla::SuggestionsPromise::CreateAndReject(rv, __func__);
+    }
+    if (suggestions.Length() > aMaxCount) {
+      suggestions.TruncateLength(aMaxCount);
+    }
+  }
+  return mozilla::SuggestionsPromise::CreateAndResolve(std::move(suggestions),
+                                                       __func__);
+}
+
+nsresult mozSpellChecker::Replace(const nsAString& aOldWord,
+                                  const nsAString& aNewWord,
+                                  bool aAllOccurrences) {
+  if (NS_WARN_IF(!mConverter)) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  if (!aAllOccurrences) {
+    MOZ_KnownLive(mTextServicesDocument)->InsertText(aNewWord);
+    return NS_OK;
+  }
+
+  int32_t selOffset;
+  int32_t startBlock;
+  int32_t begin, end;
+  bool done;
+  nsresult result;
+
+  // find out where we are
+  result = SetupDoc(&selOffset);
+  if (NS_WARN_IF(NS_FAILED(result))) {
+    return result;
+  }
+  result = GetCurrentBlockIndex(mTextServicesDocument, &startBlock);
+  if (NS_WARN_IF(NS_FAILED(result))) {
+    return result;
+  }
+
+  // start at the beginning
+  result = mTextServicesDocument->FirstBlock();
+  if (NS_WARN_IF(NS_FAILED(result))) {
+    return result;
+  }
+  int32_t currOffset = 0;
+  int32_t currentBlock = 0;
+  int32_t wordLengthDifference =
+      AssertedCast<int32_t>(static_cast<int64_t>(aNewWord.Length()) -
+                            static_cast<int64_t>(aOldWord.Length()));
+  while (NS_SUCCEEDED(mTextServicesDocument->IsDone(&done)) && !done) {
+    nsAutoString str;
+    mTextServicesDocument->GetCurrentTextBlock(str);
+    while (mConverter->FindNextWord(str, currOffset, &begin, &end)) {
+      if (aOldWord.Equals(Substring(str, begin, end - begin))) {
+        // if we are before the current selection point but in the same
+        // block move the selection point forwards
+        if (currentBlock == startBlock && begin < selOffset) {
+          selOffset += wordLengthDifference;
+          if (selOffset < begin) {
+            selOffset = begin;
+          }
+        }
+        // Don't keep running if selecting or inserting text fails because
+        // it may cause infinite loop.
+        if (NS_WARN_IF(NS_FAILED(
+                MOZ_KnownLive(mTextServicesDocument)
+                    ->SetSelection(AssertedCast<uint32_t>(begin),
+                                   AssertedCast<uint32_t>(end - begin))))) {
+          return NS_ERROR_FAILURE;
+        }
+        if (NS_WARN_IF(NS_FAILED(
+                MOZ_KnownLive(mTextServicesDocument)->InsertText(aNewWord)))) {
+          return NS_ERROR_FAILURE;
+        }
+        mTextServicesDocument->GetCurrentTextBlock(str);
+        end += wordLengthDifference;  // recursion was cute in GEB, not here.
+      }
+      currOffset = end;
+    }
+    mTextServicesDocument->NextBlock();
+    currentBlock++;
+    currOffset = 0;
+  }
+
+  // We are done replacing.  Put the selection point back where we found  it
+  // (or equivalent);
+  result = mTextServicesDocument->FirstBlock();
+  if (NS_WARN_IF(NS_FAILED(result))) {
+    return result;
+  }
+  currentBlock = 0;
+  while (NS_SUCCEEDED(mTextServicesDocument->IsDone(&done)) && !done &&
+         currentBlock < startBlock) {
+    mTextServicesDocument->NextBlock();
+  }
+
+  // After we have moved to the block where the first occurrence of replace
+  // was done, put the selection to the next word following it. In case there
+  // is no word following it i.e if it happens to be the last word in that
+  // block, then move to the next block and put the selection to the first
+  // word in that block, otherwise when the Setupdoc() is called, it queries
+  // the LastSelectedBlock() and the selection offset of the last occurrence
+  // of the replaced word is taken instead of the first occurrence and things
+  // get messed up as reported in the bug 244969
+
+  if (NS_SUCCEEDED(mTextServicesDocument->IsDone(&done)) && !done) {
+    nsAutoString str;
+    mTextServicesDocument->GetCurrentTextBlock(str);
+    if (mConverter->FindNextWord(str, selOffset, &begin, &end)) {
+      MOZ_KnownLive(mTextServicesDocument)
+          ->SetSelection(AssertedCast<uint32_t>(begin), 0);
+      return NS_OK;
+    }
+    mTextServicesDocument->NextBlock();
+    mTextServicesDocument->GetCurrentTextBlock(str);
+    if (mConverter->FindNextWord(str, 0, &begin, &end)) {
+      MOZ_KnownLive(mTextServicesDocument)
+          ->SetSelection(AssertedCast<uint32_t>(begin), 0);
+    }
+  }
+  return NS_OK;
+}
+
+nsresult mozSpellChecker::IgnoreAll(const nsAString& aWord) {
+  if (mPersonalDictionary) {
+    mPersonalDictionary->IgnoreWord(aWord);
+  }
+  return NS_OK;
+}
+
+nsresult mozSpellChecker::AddWordToPersonalDictionary(const nsAString& aWord) {
+  nsresult res;
+  if (NS_WARN_IF(!mPersonalDictionary)) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+  res = mPersonalDictionary->AddWord(aWord);
+  return res;
+}
+
+nsresult mozSpellChecker::RemoveWordFromPersonalDictionary(
+    const nsAString& aWord) {
+  nsresult res;
+  if (NS_WARN_IF(!mPersonalDictionary)) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+  res = mPersonalDictionary->RemoveWord(aWord);
+  return res;
+}
+
+nsresult mozSpellChecker::GetPersonalDictionary(nsTArray<nsString>* aWordList) {
+  if (!aWordList || !mPersonalDictionary) return NS_ERROR_NULL_POINTER;
+
+  nsCOMPtr<nsIStringEnumerator> words;
+  mPersonalDictionary->GetWordList(getter_AddRefs(words));
+
+  bool hasMore;
+  nsAutoString word;
+  while (NS_SUCCEEDED(words->HasMore(&hasMore)) && hasMore) {
+    words->GetNext(word);
+    aWordList->AppendElement(word);
+  }
+  return NS_OK;
+}
+
+nsresult mozSpellChecker::GetDictionaryList(
+    nsTArray<nsCString>* aDictionaryList) {
+  MOZ_ASSERT(aDictionaryList->IsEmpty());
+  if (XRE_IsContentProcess()) {
+    ContentChild* child = ContentChild::GetSingleton();
+    child->GetAvailableDictionaries(*aDictionaryList);
+    return NS_OK;
+  }
+
+  nsresult rv;
+
+  // For catching duplicates
+  nsTHashSet<nsCString> dictionaries;
+
+  nsCOMArray<mozISpellCheckingEngine> spellCheckingEngines;
+  rv = GetEngineList(&spellCheckingEngines);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  for (int32_t i = 0; i < spellCheckingEngines.Count(); i++) {
+    nsCOMPtr<mozISpellCheckingEngine> engine = spellCheckingEngines[i];
+
+    nsTArray<nsCString> dictNames;
+    engine->GetDictionaryList(dictNames);
+    for (auto& dictName : dictNames) {
+      // Skip duplicate dictionaries. Only take the first one
+      // for each name.
+      if (!dictionaries.EnsureInserted(dictName)) continue;
+
+      aDictionaryList->AppendElement(dictName);
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult mozSpellChecker::GetCurrentDictionaries(
+    nsTArray<nsCString>& aDictionaries) {
+  if (XRE_IsContentProcess()) {
+    aDictionaries = mCurrentDictionaries.Clone();
+    return NS_OK;
+  }
+
+  if (!mSpellCheckingEngine) {
+    aDictionaries.Clear();
+    return NS_OK;
+  }
+
+  return mSpellCheckingEngine->GetDictionaries(aDictionaries);
+}
+
+nsresult mozSpellChecker::SetCurrentDictionary(const nsACString& aDictionary) {
+  if (XRE_IsContentProcess()) {
+    mCurrentDictionaries.Clear();
+    bool isSuccess;
+    mEngine->SendSetDictionary(aDictionary, &isSuccess);
+    if (!isSuccess) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+
+    mCurrentDictionaries.AppendElement(aDictionary);
+    return NS_OK;
+  }
+
+  // Calls to mozISpellCheckingEngine::SetDictionary might destroy us
+  RefPtr<mozSpellChecker> kungFuDeathGrip = this;
+
+  mSpellCheckingEngine = nullptr;
+
+  if (aDictionary.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsresult rv;
+  nsCOMArray<mozISpellCheckingEngine> spellCheckingEngines;
+  rv = GetEngineList(&spellCheckingEngines);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsTArray<nsCString> dictionaries;
+  dictionaries.AppendElement(aDictionary);
+  for (int32_t i = 0; i < spellCheckingEngines.Count(); i++) {
+    // We must set mSpellCheckingEngine before we call SetDictionaries, since
+    // SetDictionaries calls back to this spell checker to check if the
+    // dictionary was set
+    mSpellCheckingEngine = spellCheckingEngines[i];
+    rv = mSpellCheckingEngine->SetDictionaries(dictionaries);
+
+    if (NS_SUCCEEDED(rv)) {
+      nsCOMPtr<mozIPersonalDictionary> personalDictionary =
+          do_GetService("@mozilla.org/spellchecker/personaldictionary;1");
+      mSpellCheckingEngine->SetPersonalDictionary(personalDictionary);
+
+      mConverter = new mozEnglishWordUtils;
+      return NS_OK;
+    }
+  }
+
+  mSpellCheckingEngine = nullptr;
+
+  // We could not find any engine with the requested dictionary
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+RefPtr<GenericPromise> mozSpellChecker::SetCurrentDictionaries(
+    const nsTArray<nsCString>& aDictionaries) {
+  if (XRE_IsContentProcess()) {
+    if (!mEngine) {
+      mCurrentDictionaries.Clear();
+      return GenericPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE, __func__);
+    }
+
+    // mCurrentDictionaries will be set by RemoteSpellCheckEngineChild
+    return mEngine->SetCurrentDictionaries(aDictionaries);
+  }
+
+  // Calls to mozISpellCheckingEngine::SetDictionary might destroy us
+  RefPtr<mozSpellChecker> kungFuDeathGrip = this;
+
+  mSpellCheckingEngine = nullptr;
+
+  if (aDictionaries.IsEmpty()) {
+    return GenericPromise::CreateAndResolve(true, __func__);
+  }
+
+  nsresult rv;
+  nsCOMArray<mozISpellCheckingEngine> spellCheckingEngines;
+  rv = GetEngineList(&spellCheckingEngines);
+  if (NS_FAILED(rv)) {
+    return GenericPromise::CreateAndReject(rv, __func__);
+  }
+
+  for (int32_t i = 0; i < spellCheckingEngines.Count(); i++) {
+    // We must set mSpellCheckingEngine before we call SetDictionaries, since
+    // SetDictionaries calls back to this spell checker to check if the
+    // dictionary was set
+    mSpellCheckingEngine = spellCheckingEngines[i];
+    rv = mSpellCheckingEngine->SetDictionaries(aDictionaries);
+
+    if (NS_SUCCEEDED(rv)) {
+      mCurrentDictionaries = aDictionaries.Clone();
+
+      nsCOMPtr<mozIPersonalDictionary> personalDictionary =
+          do_GetService("@mozilla.org/spellchecker/personaldictionary;1");
+      mSpellCheckingEngine->SetPersonalDictionary(personalDictionary);
+
+      mConverter = new mozEnglishWordUtils;
+      return GenericPromise::CreateAndResolve(true, __func__);
+    }
+  }
+
+  mSpellCheckingEngine = nullptr;
+
+  // We could not find any engine with the requested dictionary
+  return GenericPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE, __func__);
+}
+
+RefPtr<GenericPromise> mozSpellChecker::SetCurrentDictionaryFromList(
+    const nsTArray<nsCString>& aList) {
+  if (aList.IsEmpty()) {
+    return GenericPromise::CreateAndReject(NS_ERROR_INVALID_ARG, __func__);
+  }
+
+  if (XRE_IsContentProcess()) {
+    if (!mEngine) {
+      mCurrentDictionaries.Clear();
+      return GenericPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE, __func__);
+    }
+
+    // mCurrentDictionaries will be set by RemoteSpellCheckEngineChild
+    return mEngine->SetCurrentDictionaryFromList(aList);
+  }
+
+  for (auto& dictionary : aList) {
+    nsresult rv = SetCurrentDictionary(dictionary);
+    if (NS_SUCCEEDED(rv)) {
+      return GenericPromise::CreateAndResolve(true, __func__);
+    }
+  }
+  // We could not find any engine with the requested dictionary
+  return GenericPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE, __func__);
+}
+
+nsresult mozSpellChecker::SetupDoc(int32_t* outBlockOffset) {
+  nsresult rv;
+
+  TextServicesDocument::BlockSelectionStatus blockStatus;
+  *outBlockOffset = 0;
+
+  if (!mFromStart) {
+    uint32_t selOffset, selLength;
+    rv = MOZ_KnownLive(mTextServicesDocument)
+             ->LastSelectedBlock(&blockStatus, &selOffset, &selLength);
+    if (NS_SUCCEEDED(rv) &&
+        blockStatus !=
+            TextServicesDocument::BlockSelectionStatus::eBlockNotFound) {
+      switch (blockStatus) {
+        // No TB in S, but found one before/after S.
+        case TextServicesDocument::BlockSelectionStatus::eBlockOutside:
+        // S begins or ends in TB but extends outside of TB.
+        case TextServicesDocument::BlockSelectionStatus::eBlockPartial:
+          // the TS doc points to the block we want.
+          if (NS_WARN_IF(selOffset == UINT32_MAX) ||
+              NS_WARN_IF(selLength == UINT32_MAX)) {
+            rv = mTextServicesDocument->FirstBlock();
+            *outBlockOffset = 0;
+            break;
+          }
+          *outBlockOffset = AssertedCast<int32_t>(selOffset + selLength);
+          break;
+
+        // S extends beyond the start and end of TB.
+        case TextServicesDocument::BlockSelectionStatus::eBlockInside:
+          // we want the block after this one.
+          rv = mTextServicesDocument->NextBlock();
+          *outBlockOffset = 0;
+          break;
+
+        // TB contains entire S.
+        case TextServicesDocument::BlockSelectionStatus::eBlockContains:
+          if (NS_WARN_IF(selOffset == UINT32_MAX) ||
+              NS_WARN_IF(selLength == UINT32_MAX)) {
+            rv = mTextServicesDocument->FirstBlock();
+            *outBlockOffset = 0;
+            break;
+          }
+          *outBlockOffset = AssertedCast<int32_t>(selOffset + selLength);
+          break;
+
+        // There is no text block (TB) in or before the selection (S).
+        case TextServicesDocument::BlockSelectionStatus::eBlockNotFound:
+        default:
+          MOZ_ASSERT_UNREACHABLE("Shouldn't ever get this status");
+      }
+    }
+    // Failed to get last sel block. Just start at beginning
+    else {
+      rv = mTextServicesDocument->FirstBlock();
+      *outBlockOffset = 0;
+    }
+
+  }
+  // We want the first block
+  else {
+    rv = mTextServicesDocument->FirstBlock();
+    mFromStart = false;
+  }
+  return rv;
+}
+
+// utility method to discover which block we're in. The TSDoc interface doesn't
+// give us this, because it can't assume a read-only document. shamelessly
+// stolen from nsTextServicesDocument
+nsresult mozSpellChecker::GetCurrentBlockIndex(
+    TextServicesDocument* aTextServicesDocument, int32_t* aOutBlockIndex) {
+  int32_t blockIndex = 0;
+  bool isDone = false;
+  nsresult result = NS_OK;
+
+  do {
+    aTextServicesDocument->PrevBlock();
+    result = aTextServicesDocument->IsDone(&isDone);
+    if (!isDone) {
+      blockIndex++;
+    }
+  } while (NS_SUCCEEDED(result) && !isDone);
+
+  *aOutBlockIndex = blockIndex;
+
+  return result;
+}
+
+nsresult mozSpellChecker::GetEngineList(
+    nsCOMArray<mozISpellCheckingEngine>* aSpellCheckingEngines) {
+  MOZ_ASSERT(!XRE_IsContentProcess());
+
+  nsresult rv;
+  bool hasMoreEngines;
+
+  nsCOMPtr<nsICategoryManager> catMgr =
+      do_GetService(NS_CATEGORYMANAGER_CONTRACTID);
+  if (!catMgr) return NS_ERROR_NULL_POINTER;
+
+  nsCOMPtr<nsISimpleEnumerator> catEntries;
+
+  // Get contract IDs of registrated external spell-check engines and
+  // append one of HunSpell at the end.
+  rv = catMgr->EnumerateCategory("spell-check-engine",
+                                 getter_AddRefs(catEntries));
+  if (NS_FAILED(rv)) return rv;
+
+  while (NS_SUCCEEDED(catEntries->HasMoreElements(&hasMoreEngines)) &&
+         hasMoreEngines) {
+    nsCOMPtr<nsISupports> elem;
+    rv = catEntries->GetNext(getter_AddRefs(elem));
+
+    nsCOMPtr<nsISupportsCString> entry = do_QueryInterface(elem, &rv);
+    if (NS_FAILED(rv)) return rv;
+
+    nsCString contractId;
+    rv = entry->GetData(contractId);
+    if (NS_FAILED(rv)) return rv;
+
+    // Try to load spellchecker engine. Ignore errors silently
+    // except for the last one (HunSpell).
+    nsCOMPtr<mozISpellCheckingEngine> engine =
+        do_GetService(contractId.get(), &rv);
+    if (NS_SUCCEEDED(rv)) {
+      aSpellCheckingEngines->AppendObject(engine);
+    }
+  }
+
+  // Try to load HunSpell spellchecker engine.
+  nsCOMPtr<mozISpellCheckingEngine> engine =
+      do_GetService(DEFAULT_SPELL_CHECKER, &rv);
+  if (NS_FAILED(rv)) {
+    // Fail if not succeeded to load HunSpell. Ignore errors
+    // for external spellcheck engines.
+    return rv;
+  }
+  aSpellCheckingEngines->AppendObject(engine);
+
+  return NS_OK;
+}