third_party/WebKit/Source/core/editing/SurroundingText.cpp

/*
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#include "core/editing/SurroundingText.h"

#include "core/dom/Document.h"
#include "core/dom/Element.h"
#include "core/dom/Range.h"
#include "core/editing/Position.h"
#include "core/editing/iterators/BackwardsCharacterIterator.h"
#include "core/editing/iterators/CharacterIterator.h"

namespace blink {

SurroundingText::SurroundingText(const Range& range, unsigned maxLength)
    : m_startOffsetInContent(0), m_endOffsetInContent(0) {
  initialize(range.startPosition(), range.endPosition(), maxLength);
}

SurroundingText::SurroundingText(const Position& position, unsigned maxLength)
    : m_startOffsetInContent(0), m_endOffsetInContent(0) {
  initialize(position, position, maxLength);
}

void SurroundingText::initialize(const Position& startPosition,
                                 const Position& endPosition,
                                 unsigned maxLength) {
  DCHECK_EQ(startPosition.document(), endPosition.document());

  const unsigned halfMaxLength = maxLength / 2;

  Document* document = startPosition.document();
  // The position will have no document if it is null (as in no position).
  if (!document || !document->documentElement())
    return;
  DCHECK(!document->needsLayoutTreeUpdate());

  // The forward range starts at the selection end and ends at the document's
  // end. It will then be updated to only contain the text in the text in the
  // right range around the selection.
  CharacterIterator forwardIterator(
      endPosition, Position::lastPositionInNode(document->documentElement())
                       .parentAnchoredEquivalent(),
      TextIteratorStopsOnFormControls);
  // FIXME: why do we stop going trough the text if we were not able to select
  // something on the right?
  if (!forwardIterator.atEnd())
    forwardIterator.advance(maxLength - halfMaxLength);

  EphemeralRange forwardRange = forwardIterator.range();
  if (forwardRange.isNull() ||
      !Range::create(*document, endPosition, forwardRange.startPosition())
           ->text()
           .length())
    return;

  // Same as with the forward range but with the backward range. The range
  // starts at the document's start and ends at the selection start and will
  // be updated.
  BackwardsCharacterIterator backwardsIterator(
      Position::firstPositionInNode(document->documentElement())
          .parentAnchoredEquivalent(),
      startPosition, TextIteratorStopsOnFormControls);
  if (!backwardsIterator.atEnd())
    backwardsIterator.advance(halfMaxLength);

  m_startOffsetInContent =
      Range::create(*document, backwardsIterator.endPosition(), startPosition)
          ->text()
          .length();
  m_endOffsetInContent =
      Range::create(*document, backwardsIterator.endPosition(), endPosition)
          ->text()
          .length();
  m_contentRange = Range::create(*document, backwardsIterator.endPosition(),
                                 forwardRange.startPosition());
  DCHECK(m_contentRange);
}

String SurroundingText::content() const {
  if (m_contentRange)
    return m_contentRange->text();
  return String();
}

unsigned SurroundingText::startOffsetInContent() const {
  return m_startOffsetInContent;
}

unsigned SurroundingText::endOffsetInContent() const {
  return m_endOffsetInContent;
}

}  // namespace blink