Implement hot mode invocation for idle time spell checker

third_party/WebKit/Source/core/editing/spellcheck/HotModeSpellCheckRequester.cpp

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/editing/spellcheck/HotModeSpellCheckRequester.h"
+
+#include "core/editing/EditingUtilities.h"
+#include "core/editing/Editor.h"
+#include "core/editing/VisiblePosition.h"
+#include "core/editing/commands/CompositeEditCommand.h"
+#include "core/editing/commands/TypingCommand.h"
+#include "core/editing/iterators/BackwardsCharacterIterator.h"
+#include "core/editing/iterators/CharacterIterator.h"
+#include "core/editing/spellcheck/SpellCheckRequester.h"
+#include "core/editing/spellcheck/SpellChecker.h"
+
+namespace blink {
+
+namespace {
+
+const int kHotModeChunkSize = 1024;
+
+bool isInOrAdjacentToWord(const Position& pos) {
+  const VisiblePosition& visiblePos = createVisiblePosition(pos);
+  const VisiblePosition& wordStart = previousWordPosition(visiblePos);
+  if (wordStart.isNull())
+    return false;
+  const VisiblePosition& wordEnd = endOfWord(wordStart);
+  if (wordEnd.isNull())
+    return false;
+  return comparePositions(visiblePos, wordEnd) <= 0;
+}
+
+bool isTypingInPartialWord(const Element& editable) {
+  const LocalFrame& frame = *editable.document().frame();
+  const SelectionInDOMTree& selection = frame.selection().selectionInDOMTree();
+  if (!selection.isCaret())
+    return false;
+  if (rootEditableElementOf(selection.base()) != &editable)
+    return false;
+
+  CompositeEditCommand* typingCommand =
+      frame.editor().lastTypingCommandIfStillOpenForTyping();
+  if (!typingCommand)
+    return false;
+  if (typingCommand->endingSelection().asSelection() != selection)
+    return false;
+  return isInOrAdjacentToWord(selection.base());
+}
+
+bool shouldCheckRootEditableInHotMode(const Element& editable,
+                                      const Position& position) {
+  if (!editable.isSpellCheckingEnabled() &&
+      !SpellChecker::isSpellCheckingEnabledAt(position))
+    return false;
+  if (editable.visibleBoundsInVisualViewport().isEmpty())
+    return false;
+  // TODO(xiaochengh): Design more aggressive strategies to reduce checking when
+  // we are just moving selection around without modifying anything.
+  return !isTypingInPartialWord(editable);
+}
+
+EphemeralRange calculateHotModeCheckingRange(const Element& editable,
+                                             const Position& position) {
+  const EphemeralRange& fullRange = EphemeralRange::rangeOfContents(editable);
+  const int fullLength = TextIterator::rangeLength(fullRange.startPosition(),
+                                                   fullRange.endPosition());
+  if (fullLength <= kHotModeChunkSize)
+    return fullRange;
+
+  TextIteratorBehavior behavior = TextIteratorBehavior::Builder()
+                                      .setEmitsObjectReplacementCharacter(true)
+                                      .build();
+  BackwardsCharacterIterator backwardIterator(fullRange.startPosition(),
+                                              position, behavior);
+  backwardIterator.advance(kHotModeChunkSize / 2);
+  const Position& chunkStart = backwardIterator.endPosition();
+  CharacterIterator forwardIterator(position, fullRange.endPosition(),
+                                    behavior);
+  forwardIterator.advance(kHotModeChunkSize / 2);
+  const Position& chunkEnd = forwardIterator.endPosition();
+  return expandRangeToSentenceBoundary(EphemeralRange(chunkStart, chunkEnd));
+}
+
+}  // namespace
+
+HotModeSpellCheckRequester::HotModeSpellCheckRequester(
+    SpellCheckRequester& requester)
+    : m_requester(requester) {}
+
+void HotModeSpellCheckRequester::checkSpellingAt(const Position& position) {
+  const Element* rootEditable = rootEditableElementOf(position);
+  if (!rootEditable || !rootEditable->isConnected())
+    return;
+
+  if (m_processedRootEditables.contains(rootEditable))
+    return;
+  m_processedRootEditables.push_back(rootEditable);
+
+  if (!shouldCheckRootEditableInHotMode(*rootEditable, position))
+    return;
+
+  SpellCheckRequest* request = SpellCheckRequest::create(
+      calculateHotModeCheckingRange(*rootEditable, position));
+  m_requester->requestCheckingFor(request);
+}
+
+}  // namespace blink