adjustFontWeight function

FontWeight? adjustFontWeight(FontWeight? weight, int adjustment)

按 adjustment 偏移字重，对应 Android Compose 平台自动施加的 Configuration.fontWeightAdjustment（跟随系统字体粗细度）。

adjustment 为权重数值，100 为一档（与 Flutter FontWeight 步进一致）： +100 时 w400→w500、w600→w700、w700→w800。weight 为 null 时按 w400 处理。

adjustment == 0 时原样返回（含 null），保证零行为回归。

Implementation

FontWeight? adjustFontWeight(FontWeight? weight, int adjustment) {
  if (adjustment == 0) return weight;
  final base = weight ?? FontWeight.w400;
  final target = base.value + adjustment;
  final idx = ((target / 100).round() - 1).clamp(0, FontWeight.values.length - 1);
  return FontWeight.values[idx];
}