parseDoubleWithUnits method

double? parseDoubleWithUnits(String? rawDouble, { bool tryParse = false, })

Parses a rawDouble String to a double taking into account absolute and relative units (px, em or ex).

Passing an em value will calculate the result relative to the provided fontSize: 1 em = 1 * fontSize.

Passing an ex value will calculate the result relative to the provided xHeight: 1 ex = 1 * xHeight.

The rawDouble might include a unit which is stripped off when parsed to a double.

Passing null will return null.

Implementation

double? parseDoubleWithUnits(
  String? rawDouble, {
  bool tryParse = false,
}) {
  if (rawDouble == null) {
    return null;
  }

  double unit = 1.0;
  // 1 rem unit is equal to the root font size.
  // 1 em unit is equal to the current font size.
  // 1 ex unit is equal to the current x-height.
  if (rawDouble.contains('pt')) {
    unit = kPointsToPixelFactor;
  } else if (rawDouble.contains('rem')) {
    _compatibilityTester.usesFontSize = true;
    unit = theme.fontSize;
  } else if (rawDouble.contains('em')) {
    _compatibilityTester.usesFontSize = true;
    unit = theme.fontSize;
  } else if (rawDouble.contains('ex')) {
    _compatibilityTester.usesFontSize = true;
    unit = theme.xHeight;
  }

  final double? value = parseDouble(
    rawDouble,
    tryParse: tryParse,
  );

  return value != null ? value * unit : null;
}