Method intern

src/ink/screen.ts:129–141

* Intern a style and return its ID. Bit 0 of the ID encodes whether the * style has a visible effect on space characters (background, inverse, * underline, etc.). Foreground-only styles get even IDs; styles visible * on spaces get odd IDs. This lets the renderer skip invisible spaces * w

(styles: AnsiCode[])

   * with a single bitmask check on the packed word.
   */
  intern(styles: AnsiCode[]): number {
    const key = styles.length === 0 ? '' : styles.map(s => s.code).join('\0')
    let id = this.ids.get(key)
    if (id === undefined) {
      const rawId = this.styles.length
      this.styles.push(styles.length === 0 ? [] : styles)
      id =
        (rawId << 1) |
        (styles.length > 0 && hasVisibleSpaceEffect(styles) ? 1 : 0)
      this.ids.set(key, id)
    }
    return id
  }

  /** Recover styles from an encoded ID. Strips the bit-0 flag via >>> 1. */
  get(id: number): AnsiCode[] {