Function handle

packages/tailwindcss/src/utilities.ts:2678–2681

(value)

  staticUtility('bg-contain', [['background-size', 'contain']])
  functionalUtility('bg-size', {
    handle(value) {
      if (!value) return
      return [decl('background-size', value)]
    },
  })

  staticUtility('bg-fixed', [['background-attachment', 'fixed']])