selectWordEdge method
- required SelectionChangedCause cause,
Move the selection to the beginning or end of a word.
This method is mainly used to translate user inputs in global positions into a TextSelection. When used in conjunction with a EditableText, the selection change is fed back into TextEditingController.selection.
If you have a TextEditingController, it's generally easier to
programmatically manipulate its value or selection directly.
Implementation
void selectWordEdge({required SelectionChangedCause cause}) {
  _computeTextMetricsIfNeeded();
  assert(_lastTapDownPosition != null);
  final TextPosition position = _textPainter.getPositionForOffset(
    globalToLocal(_lastTapDownPosition!) - _paintOffset,
  );
  final TextRange word = _textPainter.getWordBoundary(position);
  late TextSelection newSelection;
  if (position.offset <= word.start) {
    newSelection = TextSelection.collapsed(offset: word.start);
  } else {
    newSelection = TextSelection.collapsed(offset: word.end, affinity: TextAffinity.upstream);
  }
  _setSelection(newSelection, cause);
}