expansionLength static method

int expansionLength(int baseLength, int percent)

How many characters expandPercent adds to a value of baseLength: percent of the value's own ceiling, and the ceiling depends on how short it is.

A short string has proportionally the most room to grow — localisation guidance is unanimous that a 6-character button label can triple where a 70-character sentence grows by a third — and a flat ×2 ceiling was answering "at least 22" for an 11-character label whose real limit sits far higher. So the top rung (percent: 100) pads a value up to +300% at ≤10 characters, +200% at ≤20, +150% at ≤30, +120% at ≤50 and +100% beyond, and every rung below scales its key's own ceiling — the same ten passes probe every key as far as it plausibly goes.

Implementation

static int expansionLength(int baseLength, int percent) {
  var factor = switch (baseLength) {
    <= 10 => 3.0,
    <= 20 => 2.0,
    <= 30 => 1.5,
    <= 50 => 1.2,
    _ => 1.0,
  };
  return (baseLength * percent * factor / 100).ceil();
}