determineLineHeights() {
    for (let k = 0; k < this.lines.length; k++) {
      const line = this.lines[k];

      // Looking for max height of blocks in line
      let height = 0;

      if (line.blocks !== undefined) {
        // Can happen if text contains e.g. '\n '
        for (let l = 0; l < line.blocks.length; l++) {
          const block = line.blocks[l];

          if (height < block.height) {
            height = block.height;
          }
        }
      }

      line.height = height;
    }
  }
Determine and set the heights of all the lines currently contained in this instance

Note that width has already been set.
@private