class PDF::Reader::WidthCalculator::TypeZero

Type0 (or Composite) fonts are a “root font” that rely on a “descendant font” to do the heavy lifting. The “descendant font” is a CID-Keyed font. see Section 9.7.1, PDF 32000-1:2008, pp 267 so if we are calculating a Type0 font width, we just pass off to the descendant font