fontspec + xelatex: won't use small caps TTF

Question

I wanted to use the Cormorant font family in my LaTeX document.

I later learned that a Geramond variety of this family appears in the TeXLive distribution, but I was unaware at the time, and anyway I believe that these families are not identical, the Geramond lacking letter definitions for small caps.

I downloaded and unpacked the font files from the release download page (archive name Cormorant_Install_v3.601.zip) into the folder containing my document, and inserted the following lines into my LaTeX file:

    \usepackage{fontspec}
    \setmainfont{Cormorant-Regular.ttf}[
      BoldFont = Cormorant-Bold.ttf ,
      ItalicFont = Cormorant-Italic.ttf ,
      BoldItalicFont = Cormorant-BoldItalic.ttf,
    ]

I created some small caps formatting, which looked reasonable after running through XeLaTeX, but as I understood that LaTeX would not have a source of correct small caps lettering, it must be faking the small caps based on the regular style font. I wanted to achieve a superior appearance from the correct source for this letter appearance, which is given in a separate font file.

I added the additional field to the optional parameter list:

SmallCapsFont = CormorantSC-Regular.ttf

Yet, I discovered no difference in the output.

I tried a variety of further additions to the list, dealing with font features, based on my frustrated attempt to benefit from the fontspec documentation, but I found no variation that produced output with a different effect.

I looked at the results under magnification, and began to wonder whether somehow the effect I was seeing was actually correct small caps. However, after inspecting the font file as best I could, I came to understand that a TTF-format file cannot embed both regular letters and small caps.

As such, the small caps output I have now is either fake, or the font is somehow being found in another source. Yet I have no evidence of either.

I can prove that the option has some effect because I can make LaTeX generate italics from the \textsc command by using the following form:

SmallCapsFont = Cormorant-Italics.ttf

I created an overall test case, as follows.

\documentclass{article}

\usepackage{fontspec}
\usepackage{geometry}
\geometry{landscape,a5paper}

\setmainfont{Cormorant-Regular.ttf}[
   BoldFont = Cormorant-Bold.ttf ,
    ItalicFont = Cormorant-Italic.ttf ,
    BoldItalicFont = Cormorant-BoldItalic.ttf,
]

\begin{document}

\Large

\noindent The Quick Brown Fox Jumped Over The Lazy Dog. \vspace{1em}

\noindent \textbf{The Quick Brown Fox Jumped Over The Lazy Dog.} \vspace{1em}

\noindent \textit{The Quick Brown Fox Jumped Over The Lazy Dog.} \vspace{1em}

\noindent \textsc{The Quick Brown Fox Jumped Over The Lazy Dog.} \vspace{1em}

\end{document}

Adding the following line to the optional parameter list of \setmainfont should have an effect, but has none.

SmallCapsFont = CormorantSC-Regular.ttf

---

Results

Without use of small caps font file

With use of small caps font file

Answer 1

You do not need to change anything since Cormorant-Regular.ttf does contain the smcp feature necessary for fontspec to use real small caps:

$ otfinfo -f  Cormorant_Install_v3.601/1.\ TrueType\ Font\ Files/Cormorant-Regular.ttf | grep smcp
smcp    Small Capitals 

An alternative way to see this is provided by fontforge that you mention in the comments. With Metrics -> New Metrics Window you can not only test font metrics but also many font features. Typing some text gives you:

Activating the smcp feature in the left hand column gives:

While the typed characters at the top stay the same, the glyphs used to represent these characters have changed: /h has been replaced with /h.sc etc.

If the feature where not there, fontspec would not fake small caps all by itself. The CormorantSC-Regular.ttf font present in the distribution is meant as a convenience feature for people having to use software that does not understand OpenType features like smcp.

Concerning your (implicit) question how a TrueType font can contain both regular and small caps glyphs. This has been possible for a long time. "Palatino Linotype" is an example for such a font. One has to remember that OpenType is TrueType plus the abbility to store glyphs as cubic splines and additional font features like smcp. A TrueType font with glyphs stored as quadratic splines but OpenType font features can still be treated as normal TrueType font by applications that do not understand OpenType.