print.css

/* Self-contained print stylesheet for the twinBASIC documentation PDF.
   Rendered through pagedjs-cli (CSS Paged Media Module Level 3).

   Paired with tb-highlight.css (generated at build time from the
   vendored .theme files; see builder/highlight-theme.mjs). No
   just-the-docs styles are loaded for the PDF build --- this file is
   the complete book design. */


/* ---- Self-hosted faces ---------------------------------------------
   Same files the web build uses (docs/assets/fonts/, generated by
   scripts/build_fonts.py); builder/pdf.mjs copies them into the sparse
   _site-pdf/ tree alongside this stylesheet, so `../fonts/` resolves
   under the file:// URL render-book.mjs loads.

   The book is the one place the site deliberately breaks from the web
   typography: Source Serif 4 for body text, because a sans at 10.5pt
   over a thousand printed pages is tiring, with Inter kept for headings,
   running heads and captions so the hierarchy still reads as the same
   system. Code stays on Cascadia Mono throughout.

   A face declared here and never used is fine -- the browser simply does
   not fetch it, and the forked paged.js in book/lib/ treats that state
   ("unloaded") as normal. It does still abort if a face is mid-flight or
   errored when the page-breaking pass starts; see its loadFonts() patch.

   What is NOT fine is declaring a face that builder/pdf.mjs does not copy
   into the sparse _site-pdf/ tree: keep this block and its REQUIRED_FONTS
   list in step. */

@font-face {
  font-family: "Source Serif 4";
  font-style: normal;
  font-weight: 200 900;
  src: url("../fonts/source-serif-4-variable.woff2") format("woff2");
}

@font-face {
  font-family: "Source Serif 4";
  font-style: italic;
  font-weight: 200 900;
  src: url("../fonts/source-serif-4-variable-italic.woff2") format("woff2");
}

@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 100 900;
  src: url("../fonts/inter-variable.woff2") format("woff2");
}

@font-face {
  font-family: "Inter";
  font-style: italic;
  font-weight: 100 900;
  src: url("../fonts/inter-variable-italic.woff2") format("woff2");
}

@font-face {
  font-family: "Cascadia Mono";
  font-style: normal;
  font-weight: 200 700;
  src: url("../fonts/cascadia-mono-variable.woff2") format("woff2");
}

@font-face {
  font-family: "Cascadia Mono";
  font-style: italic;
  font-weight: 200 700;
  src: url("../fonts/cascadia-mono-variable-italic.woff2") format("woff2");
}

/* ---- Page geometry, running header, page numbers --------------------- */


/* ---- Print-only suppression ---------------------------------------- */

/* The copy-code button is interactive chrome; it has no place in the
   PDF. The button HTML is server-rendered (Phase 11 B5) so it's in
   book.html too. Hide it for the PDF render path. */
button.copy-code { display: none; }

/* SVG inline controls are interactive chrome (zoom, download, copy);
   hide them in the PDF.  Constraining the SVG to the page width is all
   that is needed to keep diagram labels from dominating the page: a
   diagram wider than the 170mm text column is scaled down to fit, and
   that scales its labels with it.  Measured at this page size, four of
   the five diagrams then set their labels BELOW body size on their own
   (0.58x to 0.96x of 10.5pt); only toolchain-overview, which fits the
   column at natural size, sits above it, at 1.14x.

   There used to be a `.svg-container text { font-size: 75% }` here to
   push that down further, and it must not come back.  Graphviz sizes
   every node box to the text it measured and positions the label with
   text-anchor="start" at an x computed for that size, so shrinking the
   text alone leaves it undersized AND left of centre inside a box that
   did not move -- by up to 15.6px, the worst misalignment of any
   diagram in the book, against 1.4px without it.  It is the same defect
   as letting Graphviz measure with the wrong font, arriving from the
   stylesheet instead: see WIP.md, "Diagrams".

   The `zoom` below is that lever, applied properly.  Graphviz authors labels
   at 12pt, and on the web that is exactly the 16px body size, so a diagram at
   natural size matches the prose beside it for free.  The book sets body text
   at 10.5pt, so the same diagram comes out at 1.14x the prose -- which is why
   toolchain-overview, the one diagram narrow enough (477pt) to render at
   natural size in the 170mm column, looked oversized on the page.
   10.5 / 12 = 0.875 restores the match.

   `zoom`, not `font-size` and not `transform`: it scales geometry and labels
   together, relative to the diagram's OWN size rather than the container's,
   and unlike `transform` it changes the layout box, so paged.js still breaks
   pages correctly.  A `max-width` percentage cannot express this -- it is
   relative to the column, so it would also shrink the four diagrams that are
   already scaled down to fit (measured: 0.96x -> 0.84x, 0.58x -> 0.51x).
   Under `zoom` those four are untouched: they are wider than the column, so
   `max-width: 100%` still decides their size. */
.svg-controls { display: none; }
.svg-container svg {
  display: block;            /* with the auto margins below, centres a  */
  margin-inline: auto;       /* diagram narrower than the text column   */
  max-width: 100%;
  height: auto;
  zoom: 0.875;
}


@page {
  size: A4;
  margin: 22mm 20mm 22mm 20mm;

  @bottom-right {
    /* Page number with part-title prefix. `string(part-title)` is set by
       a hidden span on each part-divider article and persists across
       pages until the next part. `var(--page-num)` is a JS-tracked
       counter that survives aggressive-detach (perf/detach-pages.js) --
       CSS `counter(page)` breaks when finalized pages are removed from
       the DOM, so the Counters handler polyfills it as a CSS variable.
       Named @page overrides (front-matter, divider, :first) suppress or
       simplify this for pages that shouldn't show the part prefix. */
    content: string(part-title) " - " var(--page-num);
    font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
                 Helvetica, Arial, sans-serif;
    font-size: 9pt;
    color: #555;
  }

  @top-right {
    content: string(chapter-title);
    font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
                 Helvetica, Arial, sans-serif;
    font-size: 9pt;
    color: #555;
  }
}

/* Page 1 of the document is the title page (book.html emits it before any
   article). Suppress both the running header and the page number on it --
   traditional title-page convention. `:first` here is the document's first
   page, not the first page of each chapter. */
@page :first {
  @top-right    { content: ""; }
  @bottom-right { content: ""; }
}


/* ---- Chapter boundaries --------------------------------------------- */

/* One page break per article. Putting `break-before: page` on the
   article itself (rather than on its h1) avoids the stacking-blank
   issue where pagedjs honours an article-level break AND an inner
   h1-level break separately. */
article {
  break-before: page;
}

/* Running-header source. Every chapter emits a hidden `<span
   class="header-string">` as its first child; that span is the
   string-set source for the @top-right chapter title. Routing through a
   single dedicated element avoids pagedjs quirks where `:first-of-type`
   + class-restricted selectors on h2/h3 left some top-level chapter
   pages with stale or empty running headers. For top-level chapters the
   span carries the chapter title; for sub-pages it carries the compound
   "Parent - Sub" title (1.6c). */
article.page > .header-string {
  string-set: chapter-title content();
  position: absolute;
  font-size: 0;
  width: 0;
  height: 0;
  overflow: hidden;
}

/* Part-title source for the @bottom-right page number prefix. Each part
   divider emits a hidden <span class="part-title-string"> carrying the
   part's title. `string(part-title)` persists across pages until the
   next part divider overrides it -- same mechanism as chapter-title. */
article.part-divider > .part-title-string {
  string-set: part-title content();
  position: absolute;
  font-size: 0;
  width: 0;
  height: 0;
  overflow: hidden;
}

/* ---- Title page (front matter, page 1) ------------------------------
   Emitted by book.html as the first element in <body>, so it lands on
   page 1 without any forced break. Chrome (running header + page number)
   is blanked through the document-level `@page :first` rule above.
   The book title sits a little below vertical centre; build provenance
   and copyright pad down to the page bottom. */

section.title-page {
  text-align: center;
  padding-top: 60mm;
  break-after: page;
}

section.title-page .book-title {
  font-size: 36pt;
  font-weight: 700;
  border: none;
  line-height: 1.1;
  margin: 0 0 0.4em;
  break-after: avoid;
}

section.title-page .book-subtitle {
  font-size: 16pt;
  font-style: italic;
  color: #444;
  margin: 0;
}

section.title-page .title-footer {
  margin-top: 130mm;
  font-size: 9pt;
  color: #555;
}

section.title-page .title-footer p {
  margin: 0.3em 0;
}


/* ---- Part divider pages ---------------------------------------------
   One <article class="part-divider"> is emitted per part in book.yml.
   Each gets its own page; the running header is suppressed via the
   named `divider` page; the page number stays in @bottom-right so the
   eventual TOC can target the divider correctly. */

article.part-divider {
  page: divider;
  text-align: center;
  padding-top: 35%;
  /* Restart page numbering at each Part so each section of the book reads
     like a self-contained volume. Pagedjs's Counters module picks this up
     and emits a `data-counter-page-reset` attribute on the element; the
     `afterPageLayout` hook then injects a per-page rule that resets the
     `page` counter on the part divider's page. Reset to 0 (not 1) so the
     first content page after the divider reads "1" once the auto-increment
     fires. The divider's @page rule suppresses both the running header and
     the page counter (see @page divider below) so the divider page itself
     reads as unnumbered, matching traditional book convention. */
  counter-reset: page 0;
}

article.part-divider .part-number {
  font-size: 14pt;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: #555;
  margin: 0 0 1.2em;
}

article.part-divider h1,
article.part-divider .part-title-silent {
  font-size: 32pt;
  font-weight: 700;
  border: none;
  margin: 0 0 0.4em;
  break-before: auto;
  break-after: avoid;
  line-height: 1.15;
}

article.part-divider .part-subtitle {
  font-size: 14pt;
  font-style: italic;
  color: #444;
  margin: 0 0 2em;
}

article.part-divider .part-intro {
  max-width: 32em;
  margin: 2em auto 0;
  text-align: left;
  font-size: 10.5pt;
  color: #333;
}

@page divider {
  @top-right    { content: ""; }
  @bottom-right { content: ""; }
}


/* ---- Front matter -------------------------------------------------------
   Each <article class="front-matter"> is emitted between the title page and
   the first numbered Part (book.yml's `front_matter:` list). No part
   divider, no part number; runs as ordinary book content but on a named
   page that suppresses the running header so it reads as foreword-style
   front matter rather than a chapter from inside a part. The named-page
   selector works here because the article has `break-before: page` (per
   the pagedjs gotcha that first-of-body never gets a named page applied;
   front matter is never the first element thanks to the preceding
   title-page section). */

article.front-matter {
  page: front-matter;
  break-before: page;
}

@page front-matter {
  @top-right    { content: ""; }
  @bottom-right { content: var(--page-num); }
}


/* ---- Part foreword + chapter dividers (1.9) -----------------------------
   A chaptered Part (currently the Packages part) emits two new article
   shapes in addition to its regular chapter bodies:

     <article class="part-foreword">    -- the part's intro page, sitting
                                            between the part divider and
                                            the first chapter divider. No
                                            running header (named page).
     <article class="chapter-divider">  -- one per chapter, full-page
                                            title page styled like a
                                            scaled-down part divider.

   Chapter dividers use the same vertical centering as part dividers but
   slightly smaller type, and no chapter number (the chapter ordinal is
   implicit and doesn't read well at this position). The chapter title
   on the divider is an H2 so it sits one level under the part divider's
   H1 in the PDF outline; the corresponding source H1 on the chapter's
   landing page is stripped by the book-href-rewrite plugin so the
   outline shows the divider's H2 as the chapter's sole top-level entry. */

article.part-foreword {
  page: part-foreword;
  break-before: page;
}

@page part-foreword {
  @top-right { content: ""; }
}

article.chapter-divider {
  page: chapter-divider;
  break-before: page;
  text-align: center;
  padding-top: 30%;
}

article.chapter-divider h2,
article.chapter-divider .chapter-title-silent {
  font-size: 24pt;
  font-weight: 700;
  border: none;
  margin: 0 0 0.5em;
  break-before: auto;
  break-after: avoid;
  line-height: 1.2;
}

article.chapter-divider .chapter-subtitle {
  font-size: 13pt;
  font-style: italic;
  color: #444;
  margin: 0 auto;
  max-width: 28em;
}

@page chapter-divider {
  @top-right { content: ""; }
}


/* ---- Base typography ----------------------------------------------- */

html {
  /* Inter second, not a system serif: it is the only other face this
     document embeds, so a codepoint Source Serif lacks still renders the
     same everywhere. Dropping to Georgia / Times instead pulled a third
     font subset into the PDF for seven back-arrows and four U+2194. */
  font-family: "Source Serif 4", "Inter", Georgia, "Times New Roman", serif;
  font-size: 10.5pt;
  line-height: 1.45;
  color: #1a1a1a;
}

body {
  margin: 0;
}

strong { font-weight: 700; }
em     { font-style: italic; }


/* ---- Headings ------------------------------------------------------
   After the 1.5a heading shift, the book uses h1 only on part dividers
   (and any future title page / colophon). Chapter content uses h2..h6
   with one level of demotion from the source kramdown output:
     source h1 (chapter title)  -> h2
     source h2 (section)         -> h3
     source h3 (subsection)      -> h4
     source h4..h6               -> h5..h7-stub
   Visual sizes therefore stay anchored to the *source* role rather
   than the rendered tag depth: the chapter title gets the big 24pt
   look (article.page > h2:first-of-type below), sub-sections keep
   their previous 18pt/14pt/12pt sizing through the per-depth rules. */

h1, h2, h3, h4, h5, h6, h7-stub {
  /* Sans against the serif body -- the hierarchy carried by contrast in
     face as well as size, which is what lets the heading sizes stay as
     restrained as they are. */
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica,
               Arial, sans-serif;
  color: #111;
  margin: 1.6em 0 0.5em;
  line-height: 1.25;
  break-after: avoid;
  break-inside: avoid;
  display: block;
}

h1 {
  font-size: 24pt;
  font-weight: 700;
  margin-top: 0;
  margin-bottom: 0.8em;
}

/* Chapter title for top-level chapters (source h1, now h2 after 1.5a).
   Big, bold, no underline -- overrides the generic h2 rule. The
   :not(.sub-chapter) restriction matches the string-set selector above
   so sub-chapter articles don't apply this rule. */
article.page:not(.sub-chapter) > h2:first-of-type {
  font-size: 24pt;
  font-weight: 700;
  border-bottom: none;
  padding-bottom: 0;
  margin-top: 0;
  margin-bottom: 0.8em;
}

/* Sub-page chapter title (source h1, now h3 after 1.5a + 1.6b). Slightly
   smaller than a top-level chapter (20pt vs 24pt) to signal that this
   chapter sits below its parent index in the outline hierarchy, but
   still distinct from in-chapter section headings. Overrides the
   generic `article.page h3` 18pt-with-border rule. */
article.page.sub-chapter > h3:first-of-type {
  font-size: 20pt;
  font-weight: 700;
  border-bottom: none;
  padding-bottom: 0;
  margin-top: 0;
  margin-bottom: 0.7em;
}

/* Chaptered-part headings (1.9). Chapters inside a chaptered part get
   an additional +1 heading shift on top of 1.5a / 1.6b so they nest in
   the PDF outline below their chapter-divider's H2 rather than as
   siblings. The result: source-H1 lands at h3 (top-level chapter) or
   h4 (sub-page), source-H2 lands at h4 or h5, and so on. Visual
   styling mirrors the flat-part rules above but at one tag deeper. */

/* Top-level chapter in a chaptered part (source h1, now h3). */
article.page.chaptered:not(.sub-chapter) > h3:first-of-type {
  font-size: 24pt;
  font-weight: 700;
  border-bottom: none;
  padding-bottom: 0;
  margin-top: 0;
  margin-bottom: 0.8em;
}

/* Sub-page in a chaptered part (source h1, now h4). */
article.page.chaptered.sub-chapter > h4:first-of-type {
  font-size: 20pt;
  font-weight: 700;
  border-bottom: none;
  padding-bottom: 0;
  margin-top: 0;
  margin-bottom: 0.7em;
}

/* Section heading inside a chaptered-part chapter (source h2). */
article.page.chaptered h4 {
  font-size: 18pt;
  font-weight: 700;
  border-bottom: 0.5pt solid #bbb;
  padding-bottom: 0.2em;
}

/* Subsection heading inside a chaptered-part chapter (source h3) --
   Example / See Also / Remarks. */
article.page.chaptered h5 {
  font-size: 14pt;
  font-weight: 600;
  border: none;
  padding: 0;
}

article.page.chaptered h6      { font-size: 12pt; font-weight: 600; }
article.page.chaptered h7-stub { font-size: 11pt; font-weight: 600; color: #444; }

/* Generic h2 (only used outside chapters now, e.g. for any future
   front-matter sections). Kept for symmetry. */
h2 {
  font-size: 18pt;
  font-weight: 700;
  border-bottom: 0.5pt solid #bbb;
  padding-bottom: 0.2em;
}

/* Section heading inside a chapter (source h2). */
article.page h3 {
  font-size: 18pt;
  font-weight: 700;
  border-bottom: 0.5pt solid #bbb;
  padding-bottom: 0.2em;
}

/* Subsection heading inside a chapter (source h3) -- this is what
   Example / See Also / Remarks render as. */
article.page h4 {
  font-size: 14pt;
  font-weight: 600;
  border: none;
  padding: 0;
}

article.page h5 { font-size: 12pt; font-weight: 600; }
article.page h6 { font-size: 11pt; font-weight: 600; }
article.page h7-stub { font-size: 10.5pt; font-weight: 600; color: #444; }

/* Generic depth fallbacks (for non-chapter contexts). */
h3 { font-size: 14pt; font-weight: 600; }
h4 { font-size: 12pt; font-weight: 600; }
h5 { font-size: 11pt; font-weight: 600; }
h6 { font-size: 10.5pt; font-weight: 600; color: #444; }
h7-stub { font-size: 10pt; font-weight: 600; color: #555; }


/* ---- Paragraphs and lists ----------------------------------------- */

p {
  margin: 0.6em 0;
  orphans: 2;
  widows: 2;
}

ul, ol {
  margin: 0.5em 0;
  padding-left: 1.8em;
}

li {
  margin: 0.15em 0;
  orphans: 2;
  widows: 2;
}


/* ---- Definition lists (used heavily for parameter docs) ----------- */

dl { margin: 0.6em 0; }
dt { font-weight: 600; margin-top: 0.4em; }
dd { margin: 0.1em 0 0.4em 1.8em; }


/* ---- Inline code -------------------------------------------------- */

/* kbd and samp are here because the UA default for both is generic
   monospace, and the book loads no normalize to say otherwise. Left out,
   the eleven pages using <kbd> set their keys in whatever the rendering
   machine calls `monospace` -- which is how a Consolas subset ended up
   embedded in the PDF. */
code,
kbd,
samp {
  font-family: "Cascadia Mono", monospace;
  background: #f4f4f6;
  border: 0.5pt solid #e0e0e4;
  border-radius: 2pt;
  padding: 0 0.2em;
  /* Whitespace inside inline code is content. The default collapses runs,
     which rendered **Partition**'s space-padded return values as `" 0: 4"`
     where the function returns `"  0:  4"`. `pre-wrap`, not `pre`, so a long
     snippet still wraps instead of overflowing the 170mm column. The rule
     below for code inside <pre> resets this to `inherit`, which is what keeps
     block code taking its whitespace from its own wrapper. */
  white-space: pre-wrap;
  /* Smaller font-size makes the chip visually tight: glyphs fit naturally
     inside the em-box rather than being forced into a cropped height.
     Negative top/bottom `margin` on the inline-block keeps the chip's
     contribution to the line box small so adjacent lines aren't pushed
     apart. */
  display: inline-block;
  line-height: 1;
  margin: -0.1em 0;
  vertical-align: middle;
}


/* ---- Code blocks --------------------------------------------------
   Two paths:
   - Plain <pre><code> (no language fence): the <pre> carries the box.
   - Rouge-rendered (div.highlighter-rouge > .highlight > pre.highlight > code):
     the div.highlighter-rouge wrapper carries the box; all nested elements
     (.highlight, pre.highlight, the whitespace `.w` spans whose background
     rouge.css would otherwise paint behind indented lines) are stripped. */

pre,
div.highlighter-rouge {
  font-family: "Cascadia Mono", monospace;
  font-size: 9pt;
  line-height: 1.4;
  margin: 0.6em 0;
  padding: 0.6em 0.8em;
  background: #f6f8fa;
  border-radius: 3pt;
  white-space: pre-wrap;
  word-wrap: break-word;
  overflow-wrap: break-word;
  break-inside: auto;
}

div.highlighter-rouge pre,
div.highlighter-rouge .highlight,
div.highlighter-rouge pre.highlight,
div.highlighter-rouge .highlight .w {
  background: transparent;
  padding: 0;
  margin: 0;
}

/* Code inside <pre> shouldn't get the inline-code box/border, and must
   revert the inline-block + tight line-height the chip rule introduces. */
pre code,
div.highlighter-rouge code {
  background: none;
  border: none;
  padding: 0;
  font-size: inherit;
  white-space: inherit;
  display: inline;
  line-height: inherit;
}


/* ---- Links -------------------------------------------------------- */

a, a:link, a:visited {
  color: #1d4ed8;
  text-decoration: none;
}


/* ---- Images ------------------------------------------------------- */

img {
  max-width: 100%;
  height: auto;
}


/* ---- Tables ------------------------------------------------------- */

table {
  width: 100%;
  border-collapse: collapse;
  margin: 0.8em 0;
  font-size: 0.95em;
  break-inside: auto;
}

th, td {
  border: 0.5pt solid #ccc;
  padding: 0.3em 0.5em;
  text-align: left;
  vertical-align: top;
}

th {
  background: #f4f4f6;
  font-weight: 600;
}


/* ---- Blockquotes -------------------------------------------------- */

blockquote {
  border-left: 2pt solid #bbb;
  margin: 0.6em 0;
  padding: 0.2em 0 0.2em 0.8em;
  color: #444;
}


/* ---- GFMA admonitions (NOTE / IMPORTANT / WARNING / CAUTION / TIP) - */

.markdown-alert {
  border-left: 3pt solid #888;
  background: #f6f8fa;
  margin: 0.8em 0;
  padding: 0.4em 0.8em 0.5em;
  break-inside: avoid;
}

.markdown-alert-title {
  font-weight: 700;
  margin: 0 0 0.3em;
  display: flex;
  align-items: center;
  gap: 0.3em;
}

.markdown-alert-title svg {
  width: 11pt;
  height: 11pt;
  fill: currentColor;
  flex-shrink: 0;
}

.markdown-alert > :last-child { margin-bottom: 0; }

.markdown-alert-note         { border-left-color: #0969da; }
.markdown-alert-note         .markdown-alert-title { color: #0969da; }
.markdown-alert-important    { border-left-color: #8250df; }
.markdown-alert-important    .markdown-alert-title { color: #8250df; }
.markdown-alert-warning      { border-left-color: #bf8700; }
.markdown-alert-warning      .markdown-alert-title { color: #bf8700; }
.markdown-alert-caution      { border-left-color: #cf222e; }
.markdown-alert-caution      .markdown-alert-title { color: #cf222e; }
.markdown-alert-tip          { border-left-color: #1a7f37; }
.markdown-alert-tip          .markdown-alert-title { color: #1a7f37; }