cs341book.sty

% cs341book.sty -- PDF-only layout that works with PDF tagging (issue
% #238, Part B). It replaces three packages the LaTeX tagging code does
% not support, keeping their look:
%   fncychap [Bjornstrup]  chapter heads (grey bars, big grey number)
%   titlesec               the section sizes and spacing in main.tex
% and settles two clashes with the tagging code (proof, hidelinks).
% pandoc never reads this file (it ignores \usepackage), so none of this
% reaches the EPUB or the wiki. prelude.tex loads it first, with
% \RequirePackage (pandoc does parse a local .sty named in \usepackage).
%
% With \DocumentMetadata (the default `make pdf`) chapter heads go through
% latex-lab's heading templates, which tag them as /H1; without it (`make
% pdf TAGGED=0`) through the class's \@makechapterhead. Both draw the
% same boxes with the same macros below.
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{cs341book}[2026/09/14 v1.0 CS341 coursebook layout]

% ---------------------------------------------------------------------
% Fonts. The book was set in Bitstream Charter from mathdesign (Type 1,
% T1 encoding). XCharter is the same design as OpenType, with math to
% match (XCharter-Math). Two reasons to switch: veraPDF's PDF/UA check
% fails the embedded Type 1 Charter (rule 8.4.5.6-1, glyph widths), and
% the T1 Charter has no ’ “ ” under LuaLaTeX, so every such character in
% the sources was silently dropped from the PDF (24 in background alone).
% Sans and mono stay Latin Modern (fontspec's default, the same design
% as the T1 fonts before). A code character Latin Modern Mono lacks falls
% back to DejaVu Sans Mono rather than to an empty .notdef glyph (which
% PDF/UA forbids): one block shows the replacement character U+FFFD.
\RequirePackage{fontspec}
\RequirePackage{unicode-math}
\directlua{luaotfload.add_fallback("cs341mono", {"file:DejaVuSansMono.ttf:mode=node;"})}
% fontspec's Latin Modern Mono has no bold, so \textbf{\texttt{..}} (in
% every \keyword) came out regular; the book set it in LM Mono Light Bold
% (lmtk10), whose OpenType version is named here.
\setmonofont{Latin Modern Mono}[
  BoldFont=lmmonolt10-bold.otf, BoldItalicFont=lmmonolt10-boldoblique.otf,
  BoldSlantedFont=lmmonolt10-boldoblique.otf,
  RawFeature={fallback=cs341mono}]
\setmainfont{XCharter}[
  Extension=.otf, UprightFont=*-Roman, BoldFont=*-Bold,
  ItalicFont=*-Italic, BoldItalicFont=*-BoldItalic,
  SlantedFont=*-Slanted, BoldSlantedFont=*-BoldSlanted]
% AUTHORS.md (\lstinputlisting, cs341code.sty) has a few CJK names.
% XCharter has no CJK, so they vanished from the PDF (as they did with
% mathdesign), and PDF/UA fails on the .notdef glyph. This family falls
% back to HaranoAji Mincho (in TeX Live), which has them all. Only that
% list uses it: a fallback font is loaded with every instance of the font
% that names it, and the CJK font is large. (Look it up by font name: the
% file: form fails to load.)
\directlua{luaotfload.add_fallback("cs341cjk", {"HaranoAjiMincho-Regular:mode=node;"})}
\newfontfamily\cs@cjkfamily{XCharter}[
  Extension=.otf, UprightFont=*-Roman, BoldFont=*-Bold,
  ItalicFont=*-Italic, BoldItalicFont=*-BoldItalic,
  RawFeature={fallback=cs341cjk}]
\def\cscodeinputfont{\cs@cjkfamily}
\setmathfont{XCharter-Math.otf}
% The chapter number: TeX Gyre Chorus, the OpenType version of the Zapf
% Chancery (pzc) that fncychap's Bjornstrup style used.
\newfontfamily\cs@chapnumfamily{texgyrechorus-mediumitalic.otf}
% mathdesign (like amssymb) had \square, which the proof box in
% prelude.tex ends with; unicode-math calls U+25A1 \mdlgwhtsquare.
\AtBeginDocument{\providecommand\square{\mdlgwhtsquare}}

% ---------------------------------------------------------------------
% Links: with \DocumentMetadata the class option hidelinks no longer
% reaches hyperref (links got coloured boxes), so set it here. The title
% is the window title (PDF/UA: DisplayDocTitle). prelude.tex loads this
% package before hyperref.
\AddToHook{package/hyperref/after}{%
  \hypersetup{hidelinks,
    pdftitle={CS341 System Programming Coursebook},
    pdfauthor={B. Venkatesh, L. Angrave, et al.},
    pdfdisplaydoctitle=true}}

% ---------------------------------------------------------------------
% proof: latex-lab's block module defines a proof environment, and then
% prelude.tex's \newenvironment{proof} (the shaded box) fails with
% "already defined". prelude.tex has to keep that plain \newenvironment,
% because pandoc expands it for the EPUB (pandoc does not expand
% \NewDocumentEnvironment or \DeclareDocumentEnvironment); so remove
% latex-lab's definition here, before prelude.tex makes its own.
\let\proof\@undefined
\let\endproof\@undefined

% ---------------------------------------------------------------------
% Chapter heads, as fncychap's Bjornstrup style drew them: a grey bar
% 40pt high with the chapter number in 76pt grey Zapf Chancery hanging off
% its right end, then the title flush right in a grey box. Only boxes and
% rules, no \parbox: in a tagged PDF a \parbox would put a Div and a
% paragraph inside the /H1, which PDF/UA-2 forbids. (fncychap used
% \parbox; the geometry here is the same.)
\newlength\cs@chapnumwd
\newcommand\cs@chapnumfont{\fontsize{76}{80}\cs@chapnumfamily}
\newcommand\cs@chapnumber[1]{%
  \settowidth\cs@chapnumwd{\cs@chapnumfont #1}%
  \addtolength\cs@chapnumwd{-10pt}%
  % A box exactly \textwidth wide, so the line is never overfull: the
  % number still hangs 10pt past the bar's right end, as with fncychap,
  % but TeX never breaks the line before the bar (in a tagged build the
  % heading starts with a link target, and a break there added a line).
  \makebox[\textwidth][l]{%
    {\color[gray]{.85}\rule{\textwidth}{40pt}}%
    \kern-\cs@chapnumwd\raise20pt\hbox{\color[gray]{.5}\cs@chapnumfont #1}}}
\newcommand\cs@chaptitle[1]{%
  \nointerlineskip\vskip-1ex
  {\fboxsep10pt\noindent
   \colorbox[gray]{.85}{\hbox to\dimexpr\textwidth-20pt\relax
     {\hfill\Large\sffamily\bfseries #1}}\par}}

% Tagged (latex-lab's heading templates are loaded) or not.
\newif\ifcs@headtemplates
\IfInstanceExistsTF{heading}{chapter}{\cs@headtemplatestrue}{\cs@headtemplatesfalse}
\ifcs@headtemplates
  % Tagged: latex-lab's chapter heading instance with our drawing. No
  % prefix, so there is no "Chapter" word, as with fncychap.
  \DeclareInstance{heading}{chapter}{display}
  {
    , name           = chapter
    , level          = 0
    , placement      = top
    , after-penalty-vspace = 50pt
    , after-vspace   = 40pt
    , prefix         = \NoValue
    , number-format  = \cs@chapnumber{\thechapter}
    , heading-decls  = \raggedright \parindent0pt
    , title-decls    =
    , headformat-instance = cs341chapter
    , mark-cmd       = \chaptermark {#1}
    , contents-extra = \addtocontents{lof}{\protect\addvspace{10\p@}}
                       \addtocontents{lot}{\protect\addvspace{10\p@}}
  }
  \DeclareInstance{headformat}{cs341chapter}{display}
  {
    , heading-indent   = 0pt
    , number-title-sep = 0pt
    , title-format     = \cs@chaptitle{#1}
  }
\else
  \def\@makechapterhead#1{%
    \vspace*{50\p@}%
    {\parindent\z@\raggedright\normalfont
     \ifnum\c@secnumdepth>\m@ne\if@mainmatter
       \cs@chapnumber{\thechapter}\par\nobreak
     \fi\fi
     \interlinepenalty\@M
     \cs@chaptitle{#1}\nobreak
     \vskip 40\p@}}
\fi

% ---------------------------------------------------------------------
% \tightlist (pandoc's idiom; prelude.tex \providecommand's it and 36 lists
% use it) zeroes \itemsep and \parskip after the list has begun. The
% kernel's list (untagged) has already set the space above the first item
% by then, but latex-lab's list (tagged) still uses \parskip for it, so
% each such list started 4pt higher in the tagged build: two pages over the
% book (B4a). Zero \parskip only once the first item has begun, so both
% builds keep the space above the first item, as the book always had. This
% definition comes first, so prelude.tex's \providecommand does nothing
% here, and pandoc (which never reads this file) keeps prelude.tex's.
\newcommand\tightlist{\setlength\itemsep{0pt}%
  \AddToHookNext{para/begin}{\setlength\parskip{0pt}}}

% ---------------------------------------------------------------------
% Section heads: the sizes and spacing main.tex used to set with titlesec
% (\titleformat*, \titlespacing*), as plain \@startsection calls, which
% latex-lab tags as /H2../H6. A negative space above means the paragraph
% after is not indented, like \titlespacing*.
\renewcommand\section{\@startsection{section}{1}{\z@}%
  {-5.5ex \@plus -1ex \@minus -.2ex}{4.3ex \@plus .2ex}{\normalfont\LARGE\bfseries}}
\renewcommand\subsection{\@startsection{subsection}{2}{\z@}%
  {-5.5ex \@plus -1ex \@minus -.2ex}{2.3ex \@plus .2ex}{\normalfont\Large\bfseries}}
\renewcommand\subsubsection{\@startsection{subsubsection}{3}{\z@}%
  {-5.5ex \@plus -1ex \@minus -.2ex}{2.3ex \@plus .2ex}{\normalfont\large\bfseries}}
\renewcommand\paragraph{\@startsection{paragraph}{4}{\z@}%
  {3.25ex \@plus 1ex \@minus .2ex}{-1em}{\normalfont\large\bfseries}}
\renewcommand\subparagraph{\@startsection{subparagraph}{5}{\parindent}%
  {3.25ex \@plus 1ex \@minus .2ex}{-1em}{\normalfont\large\bfseries}}