findStyleForFitHeight function

(double, int) findStyleForFitHeight({ required double maxWidth, required double maxHeight, required String text, required TextStyle style, })

Implementation

(double, int) findStyleForFitHeight({
  required double maxWidth,
  required double maxHeight,
  required String text,
  required TextStyle style,
}) {
  var lineHeight = maxHeight;
  var style0 = style.copyWith(fontSize: maxHeight);

  final textPainter = TextPainter(
    text: TextSpan(
      text: text,
      style: style0,
    ),
    textDirection: TextDirection.ltr,
  )..layout(maxWidth: maxWidth);

  var lines = textPainter.computeLineMetrics();
  var totalHeight = lines.fold(0.0, (prev, line) => prev + line.height);

  const decrement = -0.5;

  while (totalHeight > maxHeight) {
    lineHeight += decrement;
    style0 = style0.copyWith(fontSize: lineHeight);
    textPainter
      ..text = TextSpan(
        text: text,
        style: style0,
      )
      ..layout(maxWidth: maxWidth);
    lines = textPainter.computeLineMetrics();
    totalHeight = lines.fold(0.0, (prev, line) => prev + line.height);
  }

  return (style0.fontSize!, lines.length);
}