Why the environment ttfamily is hyphenated, but macro ttfamily is not hyphenating?

Question

I tried copying the example from Example about hyphenation with ttfamily font and using the name ttfamily as \ttfamily{Some text} and \begin{ttfamily} & \end{ttfamily}.

However why the first line using the macro ttfamily is not hyphenated, but the second using the environment \begin{ttfamily} is hyphenated?

\documentclass[10pt,a5paper,twoside]{memoir}
\usepackage{lmodern}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage[main=english]{babel}
\usepackage[showframe,pass]{geometry}

%THIS IS THE IMPORTANT PART   % <=========================================
\usepackage{letltxmacro}
\LetLtxMacro\origttfamily\ttfamily
\DeclareRobustCommand*{\ttfamily}{%
  \origttfamily
  \hyphenchar\font=`\-\relax
  \fontdimen3\font=.25em\relax
  \fontdimen4\font=.167em\relax
  \fontdimen7\font=.167em\relax
}

\makeatletter
\DeclareRobustCommand\vttfamily{%
  \not@math@alphabet\vttfamily\relax
  \fontfamily{cmvtt}% cmvtt (Computer Modern) or lmvtt (Latin Modern)
  \selectfont
}
\DeclareTextFontCommand{\textvtt}{\vttfamily}
\makeatother % <=========================================================

\begin{document}

    \frenchspacing
    \ttfamily{Typewriter/teletype family - (encoding: T1, family: pcr, series: m,
    shape: n, size: 10.5, baseline: 11.0pt)}

    \bigskip

    \begin{ttfamily}
        Typewriter/teletype family - (encoding: T1, family: pcr, series: m,
        shape: n, size: 10.5, baseline: 11.0pt)
    \end{ttfamily}

\end{document}

On the question How can I use `\texttt{Some text}` with automatic hyphenation? we can see the same text without the tttext hyphenation, it causing Overfull \hbox:

test2.tex:182: Overfull \hbox (11.9992pt too wide) in paragraph at lines 182--183[]\T1/lmtt/m/n/10 Typewriter/teletype family - (encoding: T1, family:
test2.tex:182: Overfull \hbox (33.7491pt too wide) in paragraph at lines 182--183\T1/lmtt/m/n/10 pcr, series: m, shape: n, size: 10.5, baseline: 11.0pt)

First, proper group-limited syntax would be {\ttfamily Some text} and not \ttfamily{Some text}. That is, \ttfamily takes no argument (perhaps you are confusing it with \texttt{}). Not that that fixes your problem. — Steven B. Segletes, Aug 22 '17 at 18:27
If I comment out your redefinition of \ttfamily, the two examples typeset identically. — Steven B. Segletes, Aug 22 '17 at 18:31
If I comment out just the \fontdimen4\font=.167em\relax part of your redefinition, both paragraphs hyphenate. — Steven B. Segletes, Aug 22 '17 at 18:34

score 4 · Accepted Answer · answered Aug 22 '17 at 21:13

With your definitions, doing

{\ttfamily text}

and

\begin{ttfamily}text\end{ttfamily}

is exactly the same. Indeed the output of the following examples is exactly the same.

\documentclass[10pt,a5paper,twoside]{memoir}
\usepackage{lmodern}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage[main=english]{babel}
\usepackage[showframe,pass]{geometry}

\usepackage{letltxmacro}
\LetLtxMacro\origttfamily\ttfamily
\DeclareRobustCommand*{\ttfamily}{%
  \origttfamily
  \hyphenchar\font=`\-\relax
  \fontdimen3\font=.25em\relax
  \fontdimen4\font=.167em\relax
  \fontdimen7\font=.167em\relax
}

\begin{document}

\frenchspacing

{\ttfamily 
supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious}

\bigskip

\begin{ttfamily}
supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious
supercalifragilisticexpialidocious supercalifragilisticexpialidocious
\end{ttfamily}

\end{document}

Notes

\ttfamily{...} is wrong, in the sense that the font will be in typewriter type also after }.
The space after \begin{ttfamily} (the end-of-line, to be precise) is ignored because it is scanned when TeX is between paragraphs. It wouldn't be if \begin{ttfamily} is scanned in paragraph mode.
Avoid using pseudoenvironments like these.

Why the environment ttfamily is hyphenated, but macro ttfamily is not hyphenating?

1 Answers1