What does this error mean and why does it keep moving?

Question

The following MWE gives me an error:

%Page layout here
\documentclass[letterpaper]{article}
\usepackage{kantlipsum}

%Font stuff here
\usepackage{tgtermes}


\begin{document}
\kant
\oldstylenums{314159} %This is line 11
\kant
\end{document}

LaTeX Font Info: Try loading font information for OML+qtm on input line 11. LaTeX Font Info: No file OMLqtm.fd. on input line 11.

LaTeX Font Warning: Font shape OML/qtm/m/it' undefined (Font)
usingOML/cmm/m/it' instead on input line 11.

[2] [3] [4] (./MWE.aux)

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

Now, this seems pretty obvious that it is a problem using \oldstylenums{314159} with tgterms. However, I had to edit out everything but this code to find that: In this MWE (based on my original document)

%Page layout here
\documentclass[letterpaper]{article}
\usepackage{kantlipsum}

%Font stuff here
\usepackage{tgtermes}

\usepackage{fancyhdr}
\pagestyle{fancyplain}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt} % remove lines as well
\setlength{\headheight}{30pt}
\chead{\oldstylenums{314159}}

\begin{document}
Here is some normal text
\kant
More normal text %This is line 18
\end{document}

The error points to the last line before the end of the document, line 18.

However, I made another MWE, where I pasted a couple of pages of the lipsum in manually and got something strange that seems replicate my original problem: The error message moves seemingly randomly (In this case it is on the first blank line after a command; in my more complex document... I have no idea, it is line 97, which is the first blank line on the second page, but there are lots of commands on the first page. Possibly the first blank line after \emph{}?

%Page layout here
\documentclass[letterpaper]{article}
\usepackage{kantlipsum}

%Font stuff here
\usepackage{tgtermes}

\usepackage{fancyhdr}
\pagestyle{fancyplain}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt} % remove lines as well
\setlength{\headheight}{30pt}
\chead{\oldstylenums{314159}}

\begin{document}
   Here is some normal text As any dedicated reader can clearly see, the Ideal of practical
   reason is a representation of, as far as I know, the things in themselves; as I have
   shown elsewhere, the phenomena should only be used as a canon for our understanding.
   The paralogisms of practical reason are what first give rise to the architectonic of
   practical reason. 

   Kant here

\kant %This is line 23, error occures on next line unless I put a comment there

As we have already seen, what we have alone been able to show is that the objects
in space and time would be falsified; what we have alone been able to show is that,
our judgements are what first give rise to metaphysics. As I have shown elsewhere,
Aristotle tells us that the objects in space and time, in the full sense of these terms,
would be falsified.
\end{document}

That one puts the error on the first blank line after \kant. Can someone explain what this error is and why the heck it keeps moving around?

Answer 1

You don't get an error but a warning. The default definition of \oldstylenums switch to the OML-encoding. As tgtermes doesn't know it, LaTeX falls back to the cm fonts and warns you when the oldstyle numbers are used the first time.

Load the textcomp package to get oldstyle numbers with tgtermes.

Answer 2

\oldstylenums as defined in the base LaTeX format is really designed to extract the numbers from the eccentric encoding layouts of the original TeX fonts. Specifically it does

 \usefont{OML}{\rmdefault}{\f@series}{it}

using the OML encoding which is the encoding used for the original 7bit TeX fonts such as computer modern math italic.

So LaTeX is telling you that for the font family you have, there is no font defined for the math letters encoding:

OML/qtm/m/it'

so it is going to use cmmi (computer modern math italic instead.)

Note it's not an error, "just" a warning.

If there is a font matching tgtermes that has old style figures, then either you need to encode that in OML encoding and tell LaTeX about it in an fd file, or you need to locally redefine \oldstylenums to get the digits from wherever they are in the font set you are using.

---

In your longer example the command is in the page head so you get the warning when the output routine assembles the first page. A common trigger for the output routine is a blank line (\par) which most likely accounts for your remark "first blank line on second page" .