resolveCssSize

import { resolveCssSize } from 'ngwr/utils';

resolveCssSize(48);       // { cssValue: '48px',  pxValue: 48 }
resolveCssSize('3rem');   // { cssValue: '3rem',  pxValue: 3 * rootFont }
resolveCssSize('80%');    // { cssValue: '80%',   pxValue: null }
resolveCssSize(null, { defaultValue: '6rem' }); // falls back

// Native — you need to handle every shape yourself.
function pxForCss(raw: number | string | null): number | null {
  if (raw == null) return null;
  if (typeof raw === 'number') return raw;
  if (raw.endsWith('px')) return parseFloat(raw);
  if (raw.endsWith('rem')) {
    const root = parseFloat(getComputedStyle(document.documentElement).fontSize);
    return parseFloat(raw) * root;
  }
  return null; // '%', 'vh', 'em', … ignored — bug surface
}

// ngwr — one call, returns both the CSS value and the px equivalent.
const { cssValue, pxValue } = resolveCssSize(raw);