getPositionAbove method

@override TextPosition? getPositionAbove(TextPosition position)

Returns the position within the text which is on the line above the given position.

The position parameter must be relative to the node content.

Primarily used with multi-line or soft-wrapping text.

Can return null which indicates that the position is at the topmost line in the text already.

Implementation

@override
TextPosition? getPositionAbove(TextPosition position) {
  assert(position.offset < getContainer().length);

  final child = childAtPosition(position);
  final childLocalPosition =
      TextPosition(offset: position.offset - child.getContainer().offset);
  final result = child.getPositionAbove(childLocalPosition);
  if (result != null) {
    return TextPosition(offset: result.offset + child.getContainer().offset);
  }

  final sibling = childBefore(child);
  if (sibling == null) {
    return null;
  }

  final caretOffset = child.getOffsetForCaret(childLocalPosition);
  final testPosition =
      TextPosition(offset: sibling.getContainer().length - 1);
  final testOffset = sibling.getOffsetForCaret(testPosition);
  final finalOffset = Offset(caretOffset.dx, testOffset.dy);
  return TextPosition(
      offset: sibling.getContainer().offset +
          sibling.getPositionForOffset(finalOffset).offset);
}