fireOnLineCountChange method

void fireOnLineCountChange(String text, { required BoxConstraints constraints, required TextStyle effectiveTextStyle, required TextScaler textScaler, required double effectiveCursorWidth, })

Implementation

void fireOnLineCountChange(
  String text, {
  required BoxConstraints constraints,
  required TextStyle effectiveTextStyle,
  required TextScaler textScaler,
  required double effectiveCursorWidth,
}) {
  // Do nothing if the callback is null
  if (widget.onLineCountChange == null) {
    return;
  }
  final span = TextSpan(
    text: text,
    style: effectiveTextStyle,
  );
  final tp = TextPainter(
    text: span,
    textDirection: Directionality.of(
      context,
    ),
    textScaler: textScaler,
    maxLines: widget.maxLines,
    textAlign: widget.textAlign,
    textWidthBasis: widget.expands
        ? TextWidthBasis.parent
        : TextWidthBasis.longestLine,
  );
  // The default caret gap is 1 pixel, so we need to account for that
  const caretGap = 1;
  // default of TextField constructor
  tp.layout(
    maxWidth: constraints.maxWidth - caretGap - effectiveCursorWidth,
  );
  final numLines = tp.computeLineMetrics().length;
  // Only fire callback if line count changed
  if (numLines != _previousLineCount) {
    _previousLineCount = numLines;
    widget.onLineCountChange!(
      numLines,
    );
  }
}