[Tex/LaTex] \f@size and how can I convert the value between units

fontsizefontspec

What is \f@size?

Why doesn't \convertto{\f@size bp}{pt} work?

Microsoft Word uses big points to measure fonts according to a comment to this answer: https://tex.stackexchange.com/a/274609/13552

I went about converting the points to big points in the most logical way I could think of, using \convertto{bp}{1pt} to convert 1pt into bp.

Code

\documentclass[12pt]{article}
\usepackage{fontspec}
\usepackage[margin=2cm]{geometry}
\usepackage{xparse} % For \NewDocumentCommand (LaTeX3)
\makeatletter
\NewDocumentCommand\thefontsizePoint{m}{{#1 The current font size is: \f@size pt\hfill{\string#1}}\par}
\NewDocumentCommand\thefontsizeBigPoint{m}{{#1 The current font size is: \convertto{bp}{\f@size pt} bp\hfill{\string#1}}\par}
\makeatother

\makeatletter
\def\convertto#1#2{\strip@pt\dimexpr #2*65536/\number\dimexpr 1#1}
\makeatother

\NewDocumentCommand{\fontsizes}{m}{%
    \begingroup
    #1
    \offinterlineskip
    \setlength{\lineskip}{4pt}
    \thefontsizeBigPoint\tiny
    \thefontsizeBigPoint\scriptsize
    \thefontsizeBigPoint\footnotesize
    \thefontsizeBigPoint\small
    \thefontsizeBigPoint\normalsize
    \thefontsizeBigPoint\large
    \thefontsizeBigPoint\Large
    \thefontsizeBigPoint\LARGE
    \thefontsizeBigPoint\huge
    \thefontsizeBigPoint\Huge
    \endgroup
    \begingroup
    \offinterlineskip
    \setlength{\lineskip}{4pt}
    \thefontsizeBigPoint\tiny
    \thefontsizePoint\scriptsize
    \thefontsizePoint\footnotesize
    \thefontsizePoint\small
    \thefontsizePoint\normalsize
    \thefontsizePoint\large
    \thefontsizePoint\Large
    \thefontsizePoint\LARGE
    \thefontsizePoint\huge
    \thefontsizePoint\Huge
    \endgroup
}%

\begin{document}
\fontsizes{}
\end{document}

Updated Code that David Carlisle's Answer Implies

Hopefully this is correct:

\documentclass[12pt]{article}
\usepackage{fontspec}
\usepackage[margin=2cm]{geometry}
\usepackage{xparse} % For \NewDocumentCommand (LaTeX3)
\setlength{\parindent}{0pt}
\makeatletter
\NewDocumentCommand\thefontsizeBigPoint{m}{{#1 Current font size: \f@size\ pt (1/72.27 in)\hfill{\string#1}}\par}
\ExplSyntaxOn
\NewDocumentCommand\thefontsizePoint{m}{{#1 Current~font~size:~\dim_to_decimal_in_unit:nn { \f@size bp }{ 1 pt }~bp~(1/72~in)\hfill{\string#1}}\par}
\ExplSyntaxOff
\makeatother
\NewDocumentCommand{\fontsizes}{m}{%
\textbf{\TeX\ Point}

(1 pt in TeX) equals 1/72.27 in (= 2540/7227 mm ≈ 0.35145980351 mm) % https://tex.stackexchange.com/questions/21758/globally-redefining-1-pt-to-1-72-in-postscript-point-and-other-similar-changes
\bigskip

    \begingroup
    #1
    \offinterlineskip
    \setlength{\lineskip}{4pt}
    \thefontsizeBigPoint\tiny
    \thefontsizeBigPoint\scriptsize
    \thefontsizeBigPoint\footnotesize
    \thefontsizeBigPoint\small
    \thefontsizeBigPoint\normalsize
    \thefontsizeBigPoint\large
    \thefontsizeBigPoint\Large
    \thefontsizeBigPoint\LARGE
    \thefontsizeBigPoint\huge
    \thefontsizeBigPoint\Huge
    \endgroup

\bigskip\textbf{PostScript Point}

(1 bp in TeX) equals 1/72 in (= 127/360 mm = 0.352(7) mm). It is commonly used unit in DTP nowadays. % https://tex.stackexchange.com/questions/21758/globally-redefining-1-pt-to-1-72-in-postscript-point-and-other-similar-changes
\bigskip

    \begingroup
    \offinterlineskip
    \setlength{\lineskip}{4pt}
    \thefontsizePoint\tiny
    \thefontsizePoint\scriptsize
    \thefontsizePoint\footnotesize
    \thefontsizePoint\small
    \thefontsizePoint\normalsize
    \thefontsizePoint\large
    \thefontsizePoint\Large
    \thefontsizePoint\LARGE
    \thefontsizePoint\huge
    \thefontsizePoint\Huge
    \endgroup
}%

\begin{document}
\thispagestyle{empty}
\fontsizes{}
\end{document}

Best Answer

\show will stop tex (as if for an error message) and show the meaning of any command.

\makeatletter
\show\f@size

Produces

*\show\f@size
> \f@size=macro:
->10.

\f@size is the current nominal font size, in pt (not bp).

The posted code produces the error

! Undefined control sequence.
\thefontsizePoint ...ent font size is: \convertto

and you give no indication of its intended behaviour, so hard to comment on that.

Since you are using expl3 anyway you can use its functions to convert between units eg

\dim_to_decimal_in_unit:nn { 1bp } { 1mm }

will show 1bp in mm

see texdoc interface3 page 85

Related Solutions

[Tex/LaTex] Obtain the size between \huge and \Huge

The standard LaTeX document classes -- article, report, and book-- provide the following definitions of the directives \huge and \Huge:

If the main font size is either 10pt or 11pt,

\newcommand\huge{\@setfontsize\huge\@xxpt{25}}
\newcommand\Huge{\@setfontsize\Huge\@xxvpt{30}}

and if the main font size is 12pt, one finds
```
\newcommand\huge{\@setfontsize\huge\@xxvpt{30}}
\let\Huge=\huge
```
i.e., there's no difference between \huge and \Huge in this case.

Next, in the file latex.ltx (which contains the "LaTeX kernel"), one finds the following definitions of \@xxpt and \@xxvpt:

 \def\@xxpt{20.74}
 \def\@xxvpt{24.88}

The geometric mean of 20.74 and 24.88 is 22.72, and the geometric mean of 25 and 30 -- the baseline distances in effect for \huge and \Huge -- is 27.38. (See below for an explanation of why I choose the geometric mean.)

Thus, if you use either 10pt or 11pt as the size of the main text font, and if you use a font that's freely scalable, you could include the following instructions in your document's preamble to set up the directive \semiHuge:

\makeatletter 
\newcommand\semiHuge{\@setfontsize\semiHuge{22.72}{27.38}}}
\makeatother

This method of defining \@setfontsize is (marginally) safer than the more direct definition, viz., \newcommand\semiHuge{\fontsize{22.72}{27.38}\selectfont}, because \@setfontsize takes care not to mess with math font sizes.

Putting all this into an MWE, e.g.,

\RequirePackage{fix-cm} %% make CM font freely scalable
\documentclass{article}
\makeatletter 
\newcommand\semiHuge{\@setfontsize\semiHuge{22.72}{27.38}}
\makeatother 
\begin{document}
\huge The quick huge fox jumps \ldots

\semiHuge The quick semiHuge fox jumps \ldots

\Huge The quick Huge fox jumps \ldots
\end{document}

one gets:

enter image description here

Lastly, you may ask why I take the geometric mean of the \huge and \Huge font sizes to arrive at the font size for \semiHuge. For a main text font size ("\normalsize") of 10pt, LaTeX sets the ratio of adjoining font sizes -- \normalsize, \large, \Large, \LARGE, \huge, and \Huge -- is exactly 1.2. In addition, in LaTeX the exact font size for 11pt is not 11.00 but 10.95, i.e., the geometric mean of 10 and 12. LaTeX's evident preference for keeping relative font sizes in tidy geometric progressions is what swayed me to go with the geometric mean of the sizes for \huge and \Huge to obtain the size for \semiHuge.

Left as an exercise for the reader: Design macros named \semiLarge, \semiLARGE, and \semihuge. :-)

[Tex/LaTex] How to get the font sizes I need when they are in between the defaults? SAE Class progress

My solution to this problem was to first change the base class of my SAE class file from article to extarticle:

% The extarticle class allows for 9 pt font as the normalsize font.
\LoadClass[twocolumn,9pt]{extarticle}

This took care of most of the font sizes I needed, and allowed me to use a 9 pt. font as the \normalsize font in the document. For the fonts that were not available via the normal font size commands, I defined two additional font sizes in the following way:

% Define two additional exact font sizes to meet SAE guidelines. These font sizes are not included as part of the extarticle class, so we define them here. A 15pt font (baseline skip = 15*1.2 = 18), and an 11 pt font (baseline skip = 11*1.2 = 13.2). The general rule of thumb is that the baseline skip is 1.2 times the font point size. We will need to use \SAEtitlesize in the title definition, and SAEheadtwosize in the \subsection{} definition (heading level 2).
\newcommand\SAEtitlesize{\@setfontsize\SAEtitlesize{15pt}{18}}
\newcommand\SAEheadtwosize{\@setfontsize\SAEtwohead{11pt}{13.2}}

% A note about font sizes in this class: The class is based off the extarticle class, which supports 8-20pt font sizes as the default. Here we select 9pt fonts as the default \normalsize font. Thus in the SAE document class you will get the following font point sizes for each latex fontsize command:

% \tiny:         5 pt
% \scriptsize:   6 pt. 
% \footnotesize: 7 pt. SAE asks that text inside tables is 7 pt. Use \footnotesize before tables for this.
% \small:        8 pt. SAE asks for caption fonts to be 8 pt. Use \small for captions.
% \normalsize   9 pt. This should be the standard fontsize for the text body, as well as for 4th level headings (in bold/italic). This should also be the size of the paper number at the top of the page (in bold), and the size of the nomenclature/definitions/abbreviations at the end of the paper.
% \large        10 pt. This should be the size of 3rd level headings (in bold, \subsubsection{}), and the affiliations
% \Large        10.95 pt. 
% \SAEheadtwosize 11 pt. This custom font size should be the size of Heading level 2 (subsection{})
% \LARGE        12 pt. This should be the size of the author list (in bold), and all 1st level headings (in bold), including abstract, introduction, body headings, summary, references, contact info, acknowledgements, definitions/abbreviations, and the appendix heading.
% \huge         14.4 pt. 
% \SAEtitlesize 15 pt. This custom font size should be the size of the title.
% \Huge         17.28 pt.

[Tex/LaTex] \f@size and how can I convert the value between units

Code

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Updated Code that David Carlisle's Answer Implies

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