Analogous NFSS axes for petite caps as for small caps

[svenper]

Since petite capitals are practically identical in form (and opentype implementation) to small caps, they should be implemented as such. A real world use case for this would be persistent shape across language changes.

This would mean adding things like PetiteCapsFeatures, PetiteCapsFont, font changing command such as \pcshape and \textpc, and ensuring it combines with upright/italic/slanted, and conflicts with small caps.

MWE:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Coelacanth}
\usepackage{polyglossia}
\setmainlanguage{english}
\setotherlanguage{french}
\begin{document}
{\scshape hello \textfrench{salut}}
{\addfontfeature{Letters=PetiteCaps}hello \textfrench{salut}}
\end{document}

[wspr]

Sorry for the slow response. On some consideration, I don't think that it is fontspec's role to define additional axes here. Part of the concern is the proliferation of interaction between various options here. Since the 2e kernel added Swash as a "standard" shape, this would mean to support PetiteCaps as well we would have to potentially contruct things like SwashPetiteCaps …

Is there a precedent in typesetting terms for using both small caps and petite caps in the same document? I guess my assumption here has always been that you might load petite caps instead of small caps but never really need to use them both. (I guess maybe one could be used for acronyms and another used for running text…)