Re-vendor the theme from the trantor fork

Syncs with the stack now open upstream as pull requests: the progress bar
extracted into a shared command, \subsectionpage, \appendix, the dark
title band, and the metropolis-style dividers.

Two local changes are reapplied on top, as before: the licence notice in
the header, and font selection left to the document so this template can
use OpenSans and RobotoMono.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

slides_template/trantor.sty

@@ -13,12 +13,8 @@
 \RequirePackage{tikz}
 \RequirePackage{pifont}
 
-% -- Fonts. Upstream sets Libertinus here and loads lum-euler for maths.
+% -- Fonts. Upstream sets Libertinus and loads lum-euler; both are left to the
-% Both are left to the document instead: this template ships OpenSans and
+% document, which must \setsansfont, \setmonofont and load a maths font.
-% RobotoMono, and lum-euler is not packaged in Debian's TeX Live. The document
-% is expected to \setsansfont, \setmonofont and load a Unicode maths font
-% before using anything below. \headerfont is what the theme uses for titles
-% and other display text; redefine it if you want titles in a second face.
 \renewcommand{\familydefault}{\sfdefault}
 \linespread{1.18}
 \providecommand\headerfont{\sffamily}
@@ -34,17 +30,15 @@
   \setlength\belowdisplayshortskip{5pt plus 2pt minus 1pt}%
 }
 
-% -- Palette. Four colours drive everything the theme draws. Override any of
+% -- Colours. Set your own accent anywhere in the preamble with, e.g.,
-% them in the preamble, before or after loading trantor:
-%
 %      \definecolor{accent}{HTML}{BF1238}
-%   \colorlet{TrantorDark}{makopurple1}
+%      \definecolor{TrantorDark}{HTML}{23373B}
-%
+% Four colour palette:
-% accent      progress bars and emphasis
+%   1. accent       progress bars, title rule
-% TrantorDark header band, section dividers, standout panels, frame numbers
+%   2. TrantorDark  headings, section dividers, standout panels, frame numbers
-% TrantorLight text on dark, and anything that has to read against it
+%   3. TrantorLight text set against TrantorDark
-% TrantorMuted affiliations, footlines, arxiv tags. This is the lightest grey
+%   4. TrantorMuted affiliation, footline, arxiv. Lightest grey that still meets
-%              that still meets WCAG AA contrast (4.5:1) on white (~4.54:1).
+%                   WCAG AA contrast (4.5:1) on white (~4.54:1).
 \providecolor{accent}{HTML}{2A7AE2}
 \providecolor{TrantorDark}{HTML}{000000}
 \providecolor{TrantorLight}{HTML}{FFFFFF}
@@ -55,11 +49,8 @@
 \AddToHook{begindocument}{\colorlet{structure}{TrantorDark}}
 
 % -- Header bar carrying the frame title (hidden on plain pages).
-% The band is a rule of height (header height - headsep) with depth headsep, so
+% headsep is what pads under the title; the height key alone only pads above.
-% headsep is the only thing that puts space under the title. geometry owns it.
 \geometry{headsep=10pt}
-
-
 \AddToHook{begindocument}{%
   \EditInstance{header}{std}{
     background-color  = TrantorDark,
@@ -105,28 +96,21 @@
   \href{https://arxiv.org/abs/#1}{{\headerfont\scriptsize\color{TrantorMuted}arXiv:#1}}%
 }
 
-% -- \appendix, which ltx-talk does not provide. Frames after it keep counting
+% -- \appendix: frames after it are numbered among themselves and left out of
-% but are left out of the total, so the denominator is the last frame of the
+% the total. The count travels through the aux file, so it settles on the
-% talk proper. This is what appendixnumberbeamer does for beamer. The count is
+% second run.
-% carried through the aux file, so it settles on the second run.
 \newif\iftrantorAppendix
 \trantorAppendixfalse
 \newcommand\trantorMainFrames{\@totalframes}
 
-% Appendix frames are numbered among themselves, as appendixnumberbeamer does,
-% but by subtracting an offset rather than resetting the counter. The class
-% records a property per frame keyed on that counter, so resetting it collides
-% with ltx-talk's own frame.<n> labels and breaks \ref to a frame. Properly
-% this belongs in the class, which could renumber and relabel together.
 \NewDocumentCommand \appendix { } {%
   \global\trantorAppendixtrue
   \protected@write\@auxout{}{%
     \string\gdef\string\trantorMainFrames{\the\value{frame}}}%
 }
 
-% Numerator and denominator for the frame counter and the progress bars. These
+% Count registers, not macros: pgfmath expands while parsing, and a macro
-% are count registers rather than macros because pgfmath expands its argument
+% carrying a conditional loops.
-% while parsing, and a macro carrying a conditional sends it into a loop.
 \newcount\trantor@n
 \newcount\trantor@d
 
@@ -140,10 +124,11 @@
   \fi
 }
 
-\newcommand\trantorFrameNumber{\trantor@setcounts\the\trantor@n}
+% Fraction of the way through the talk, shared by the footer bar and
-\newcommand\trantorTotalFrames{\trantor@setcounts\the\trantor@d}
+% \trantorProgressBar. The zero test must stay outside pgfmath, which
-
+% evaluates both arms of a ternary.
 \newcommand\trantor@setratio{%
+  \trantor@setcounts
   \ifnum\trantor@d>0
     \pgfmathsetmacro{\trantorratio}{min(\the\trantor@n / \the\trantor@d, 1)}%
   \else
@@ -151,6 +136,21 @@
   \fi
 }
 
+% \trantorProgressBar{<width>}: a rule of the given width, filled to the
+% current position and grey the rest of the way.
+\newlength\trantor@barwidth
+\newlength\trantor@barfill
+
+\NewDocumentCommand \trantorProgressBar { m } {%
+  \setlength\trantor@barwidth{#1}%
+  \trantor@setratio
+  % dimen = <factor><dimen>, so \trantorratio scales the width
+  \setlength\trantor@barfill{\trantorratio\trantor@barwidth}%
+  \textcolor{TrantorAccent}{\rule{\trantor@barfill}{0.6pt}}%
+  \textcolor{TrantorDark!20}{%
+    \rule{\dimexpr\trantor@barwidth-\trantor@barfill\relax}{0.6pt}}%
+}
+
 % -- Bottom progress bar + frame counter (hidden on plain pages).
 \newif\iftrantorPlainPage
 \trantorPlainPagefalse
@@ -159,22 +159,20 @@
   \iftrantorPlainPage\else
   \trantorArtifactBegin
   \begin{tikzpicture}[remember picture, overlay]
-    \trantor@setcounts
     \trantor@setratio
     \fill[TrantorAccent]
       (current page.south west)
       rectangle
       ([xshift=\trantorratio\paperwidth, yshift=1pt] current page.south west);
-    \node[anchor=south east, inner sep=5pt, font=\scriptsize, text=TrantorDark]
+    \node[anchor=south east, inner sep=5pt, font=\tiny, text=TrantorDark]
-      at (current page.south east)
+      at (current page.south east) {\the\trantor@n\,/\,\the\trantor@d};
-      {\the\trantor@n\,/\,\the\trantor@d};
   \end{tikzpicture}%
   \trantorArtifactEnd
   \fi
   \global\trantorPlainPagefalse
 }
 
-% -- Remember the current section title, and dim the others in the mini-TOC.
+% -- Remember the section and subsection titles, for the dividers.
 \ExplSyntaxOn
 \tl_new:N \g__trantor_section_tl
 
@@ -187,8 +185,8 @@
 \cs_new_protected:Npn \__trantor_print_section: { \tl_use:N \g__trantor_section_tl }
 \cs_set_eq:NN \trantorSectionTitle \__trantor_print_section:
 
-% Likewise the subsection, for \subsectionpage. Cleared at each new section so
+% Likewise the subsection, for \subsectionpage. Cleared when a new section
-% that a stale subsection title cannot leak into the next one.
+% starts so a stale title cannot leak into the next one.
 \tl_new:N \g__trantor_subsection_tl
 
 \AddToHook{section/begin}{ \tl_gclear:N \g__trantor_subsection_tl }
@@ -209,29 +207,9 @@
   { \cs_if_exist:NT \tag_suspend:n { \tag_suspend:n { trantor } } }
 \cs_new_protected:Npn \trantorArtifactEnd
   { \cs_if_exist:NT \tag_resume:n { \tag_resume:n { trantor } } }
-
-% Soften the dimming of inactive TOC entries on the section page (0.2 -> 0.7).
-% ltx-talk exposes no key for this yet, so we override the class-private
-% \__talk_toc_dest:w. Revisit if a supported interface appears or the internal
-% changes.
-\cs_set_protected:Npn \__talk_toc_dest:w #1 . #2 . #3 . #4 . #5 \q_stop #6
-  {
-    \bool_lazy_or:nnTF
-      {
-        \bool_lazy_and_p:nn
-          { \int_compare_p:nNn { \value { section } } = {#2} }
-          { \int_compare_p:nNn { \value { subsection } } = 0 }
-       }
-       {
-         \bool_lazy_and_p:nn
-           { \int_compare_p:nNn { \value { section } } = {#2} }
-           { \int_compare_p:nNn { \value { subsection } } = {#3} }
-      }
-      {#6}
-      { \opacity_begin:n { 0.7 } #6 \opacity_end: }
-  }
 \ExplSyntaxOff
 
+
 % -- Title page. Drop a logo.png next to your slides, or redefine \titlelogo.
 \newcommand{\titlelogo}{%
   \IfFileExists{logo.png}
@@ -277,52 +255,9 @@
   \end{frame}%
 }
 
-% -- Divider pages, following metropolis: on the ordinary light background, a
+% -- A full-bleed dark panel with the given body centred in a minipage of the
-% block set in the middle of the slide holding the section title over a
+% given width.
-% progress bar, and for a subsection the subsection title beneath that. The
+\NewDocumentCommand \trantor@panel { m +m } {%
-% bar is the same progress the footer bar shows, drawn at half width. The
-% footer bar and frame number stay, so these are not plain pages in the sense
-% the shipout hook means.
-\newlength\trantor@barwidth
-\newlength\trantor@barfill
-
-% \trantorProgressBar{<width>}: filled to the current position, grey after.
-\NewDocumentCommand \trantorProgressBar { m } {%
-  \setlength\trantor@barwidth{#1}%
-  \trantor@setcounts
-  \trantor@setratio
-  \setlength\trantor@barfill{\trantorratio\trantor@barwidth}%
-  \textcolor{TrantorDark}{\rule{\trantor@barfill}{0.6pt}}%
-  \textcolor{TrantorDark!20}{%
-    \rule{\dimexpr\trantor@barwidth-\trantor@barfill\relax}{0.6pt}}%
-}
-
-\NewDocumentCommand \trantor@divider { m } {%
-  \begin{frame}{}%
-    \thispagestyle{plain}%
-    \vfill
-    \centering
-    \begin{minipage}{0.52\linewidth}%
-      \raggedright
-      {\headerfont\Large\bfseries\trantorSectionTitle\par}%
-      \vspace{0.4em}%
-      \trantorProgressBar{\linewidth}%
-      \IfBlankF{#1}{%
-        \par\vspace{0.8em}%
-        {\headerfont\large\bfseries #1\par}%
-      }%
-    \end{minipage}%
-    \par
-    \vfill
-  \end{frame}%
-}
-
-\NewDocumentCommand \sectionpage    { } { \trantor@divider {} }
-\NewDocumentCommand \subsectionpage { } { \trantor@divider {\trantorSubsectionTitle} }
-
-% \standout{...}: a full frame with the same dark panel as \sectionpage,
-% and the given text centred on it.
-\NewDocumentCommand \standout { +m } {%
   \global\trantorPlainPagetrue
   \begin{frame}{}%
     \thispagestyle{plain}%
@@ -335,14 +270,47 @@
         (\dimexpr\paperwidth-\Gm@lmargin\relax, -\paperheight);
       \node[text=TrantorLight, anchor=center, inner sep=0pt]
         at (0.5\linewidth, -0.5\textheight) {%
-        \begin{minipage}{0.8\linewidth}
+        \begin{minipage}{#1}
           \centering
-          \headerfont\LARGE\bfseries
+          #2
-          #1
         \end{minipage}%
       };
     \end{tikzpicture}%
   \end{frame}%
 }
 
+% -- Divider pages: the section title over a progress bar, set on the ordinary
+% light background. Not plain pages: the footer bar and frame number stay.
+\NewDocumentCommand \trantor@divider { +m } {%
+  \begin{frame}{}%
+    \thispagestyle{plain}%
+    \vfill
+    \centering
+    \begin{minipage}{0.52\linewidth}%
+      \raggedright
+      {\headerfont\Large\bfseries\trantorSectionTitle\par}%
+      \vspace{0.4em}%
+      \trantorProgressBar{\linewidth}%
+      #1%
+    \end{minipage}%
+    \par
+    \vfill
+  \end{frame}%
+}
+
+\NewDocumentCommand \sectionpage { } { \trantor@divider{} }
+
+% The subsection divider is the same, naming the subsection under the bar.
+\NewDocumentCommand \subsectionpage { } {%
+  \trantor@divider{%
+    \par\vspace{0.8em}%
+    {\headerfont\large\bfseries\trantorSubsectionTitle\par}%
+  }%
+}
+
+% \standout{...}: a full-bleed dark panel with the given text centred on it.
+\NewDocumentCommand \standout { +m } {%
+  \trantor@panel{0.8\linewidth}{\headerfont\LARGE\bfseries #1}%
+}
+
 \makeatother