Strange latex font warnings with fontsize, tikz, fontspec

Question

This is mostly the same code as in:

• Problem with itemize indentation in minipage in tikz node

... but with a few changes - notably, it uses fontspec with Junicode font, and so needs to be compiled with xelatex. This is the MWE:

\documentclass[12pt,a4paper]{article}

\usepackage[pass]{geometry}
\usepackage{tikz,enumitem}

\usepackage{fontspec}
\defaultfontfeatures{Ligatures=TeX}
\setmainfont{Junicode}


\begin{document}

\pdfpagewidth=148mm \pdfpageheight=210mm % for PDF output
\paperwidth=148mm \paperheight=210mm     % for TikZ


\begin{tikzpicture}[overlay,remember picture,y=0.80pt,x=0.80pt,yscale=-1, inner sep=0pt, outer sep=0pt,anchor=north west]

  \begin{scope}[shift={(0,0.34461553)}]% layer1

  \fontspec[Scale=0.83]{Junicode}
  \fontsize{21}{27.3}\selectfont % introduces: "LaTeX Font Warning:"...

  \path[fill=blue] (10,10) node[below right] (text3134) {%
      \begin{minipage}{150pt}%
        \begin{itemize}[leftmargin=*,topsep=0pt,itemsep=0pt]%
          \setlength{\parskip}{0pt}%
          \item[\textcolor{red}{\textbullet}] Hello
          \item 2\textsuperscript{\fontsize{9}{11.7}\selectfont nd} {\scshape Entry}
        \end{itemize}%
      \end{minipage}
  }%path
  ;

  \end{scope}

\end{tikzpicture}
\end{document}

When I run xelatex test.tex; when the line \fontsize{21}{27.3}\selectfont the following warnings are generated:

[...]
*geometry* detected driver: xetex
ABD: EveryShipout initializing macros

LaTeX Font Warning: Font shape `OML/cmm/m/it' in size <10.5> not available
(Font)              size <10.95> substituted on input line 29.


LaTeX Font Warning: Font shape `OMS/cmsy/m/n' in size <10.5> not available
(Font)              size <10.95> substituted on input line 29.


LaTeX Font Warning: Font shape `OT1/cmr/m/n' in size <10.5> not available
(Font)              size <10.95> substituted on input line 29.

[1] (./test.aux)

LaTeX Font Warning: Size substitutions with differences
(Font)              up to 0.45pt have occurred.

 )
Output written on test.pdf (1 page).
Transcript written on test.log.

Now, as far as I can read font warnings, shapes like OT1/cmr/m/n would refer to Computer Modern font - and yet, I never requested that font; I though Junicode was now default? Where did this warning come from, then - and why does it appear only when the very first \fontsize{21}{27.3}\selectfont is enabled?

My idea with the code above was to specify a default font scale first (as in "global scale") with \fontspec[Scale=0.83]{Junicode}; then specify default font size with \fontsize{21}{27.3}\selectfont - then possibly override the default font size (like with \fontsize{9}{11.7}). (I'd expect both fontsize, 21 and 9, to be scaled by 0.83).

I'd say, the generated PDF does look like what I expect it to (though I haven't precisely measured whether the sizes are really scaled as I expect them) - however, these warnings confuse me - why do they appear and how to eliminate them?

Many thanks in advance for any answers,
Cheers!

Answer 1

For quite intricate reasons, the math fonts are still loaded (and at fixed sizes); the warnings are actually completely innocuous, but annoying. You can get rid of them by loading

\usepackage{fix-cm}

Note

I don't understand the line

\fontspec[Scale=0.83]{Junicode}\fontsize{21}{27.3}\selectfont

Wouldn't

\fontsize{17.5}{27.3}\selectfont

do just the same? In any case, \fontspec is a heavy macro to use and it's best to use \newfontfamily in the preamble; but, in this case, \addfontfeatures{Scale=0.83} would do the same.