cff2hintorder.md

title	date	author	mainfont	geometry	output	mainfontoptions
Ordering and overlap between variable CFF2 stem hints	February 9, 2024	Skef Iterum	LibertinusSerif-Regular.otf	margin=1.4in	pdf_document md_extensions +fancy_lists	BoldFont=LibertinusSerif-Bold.otf ItalicFont=LibertinusSerif-Italic.otf BoldItalicFont=LibertinusSerif-BoldItalic.otf

\noindent The following unnumbered section is added to the end of the current CFF2 section "Hints":

Variable hints {-}

As with other CharString values, the values of hstem, hstemhm, vstem and vstemhm operators can be blended so that they vary across a design space. The requirements on stem hints are relaxed in the following two ways in the context of a variable font:

• Although horizontal and vertical stems must always be sorted according to their values in the default instance, their relative ordering can change in other instances.
• Any instance, including the default instance, can have more than one stem with exactly the same position and width.

Any pair of stems that overlap with one another at any point in design space—and therefore any pair of stems that change order or are identical in some instance—must be treated as overlapping when choosing between the stem and stemhm operator variants and when constructing hintmasks for the CharString.