eraseRange method

void eraseRange(int start, int end, CursorStyle style, { bool respectProtected = false, })

Erase cells whose index satisfies start <= index < end. Erased cells are filled with style.

Implementation

void eraseRange(
  int start,
  int end,
  CursorStyle style, {
  bool respectProtected = false,
}) {
  // reset cell one to the left if start is second cell of a wide char.
  // Guarded by start < end (a non-empty range): if nothing is erased at
  // start, its lead must be left alone too, or an intact wide pair gets
  // torn apart by an empty-range call.
  if (start > 0 &&
      start < end &&
      getWidth(start - 1) == 2 &&
      _canErase(start - 1, respectProtected)) {
    eraseCell(start - 1, style);
  }

  // If end lands on the placeholder half of a wide char whose lead (at
  // end - 1) is inside the erased range, erase the placeholder too -
  // otherwise the lead below gets cleared and this placeholder is left
  // behind as an orphaned width-0 cell with no lead. end - 1 >= start
  // guards an empty range (start == end): the lead isn't erased below in
  // that case, so the placeholder must be left alone too.
  if (end > 0 &&
      end < _length &&
      end - 1 >= start &&
      getWidth(end - 1) == 2 &&
      _canErase(end, respectProtected)) {
    eraseCell(end, style);
  }

  end = min(end, _length);
  for (var i = start; i < end; i++) {
    if (!_canErase(i, respectProtected)) continue;
    eraseCell(i, style);
  }
}