Replacement for copyright symbol within newtx package

Question

When compiling my document using newtx font I get the following error

LaTeX Font Warning: Font shape `OMS/ntxrx/m/n' undefined
(Font)              using `OMS/ntxsy/m/n' instead on input line 209.

LaTeX Font Warning: Some font shapes were not available, defaults substituted.

I did some research and concluded that this error is most probably due to the fact that LaTeX does not find \textcopyright symbol within normalfont part of newtx package. I also concluded that LaTeX then replaces it with the same symbol from some other part of newtx package. Since replacement is done by LaTeX automatically, I could probably ignore the error message altogether.

Still, for the curiosity and pedantic sake, I wonder if I could direct LaTeX to the right sub-font and avoid annoying error messages. Is that possible to do?

Answer 1

The default definition of \textcopyright in latex.ltx is

\DeclareTextCommandDefault{\textcopyright}{\textcircled{c}}

where \textcircled is

\DeclareTextAccentDefault{\textcircled}{OMS}

This means that \textcircled is taken, by default, from an OMS encoded font, provided it is defined. The standard font provides a substitution for \OMS/cmr/<series>/<shape>, precisely \OMS/cmsy/<series>/<shape>. You can find the substitution rules in the file omscmr.fd.

The newtxtext doesn't have a suitable omsntxrx.fd file, so there's a warning about the font substitution performed by default; LaTeX's rules say that when an OMS encoded font is requested and not available for the current font attributes, the one defined for the math symbols is used (with warning).

However, the textcomp package loads the definitions for TS1 encoded fonts and there a “real” copyright symbol is present. The newtxtext package has support for TS1, so not only

\usepackage{textcomp}

avoids the warning, but provides a better glyph.

Without textcomp

With textcomp