From 1197d5ed95e244e88dfa4cd6f15f662707707147 Mon Sep 17 00:00:00 2001
From: Craig Jennings <c@cjennings.net>
Date: Mon, 19 Oct 2026 14:32:03 -0500
Subject: feat(reveal): fit dense slides to the canvas instead of clipping them

reveal.js lays each slide out on a fixed canvas and clips whatever runs past the bottom. At the stock 42px font a slide held about six lines. Anything past that vanished with no sign it was missing.

I made three changes in org-reveal-config.el. The canvas is now 16:9 (1280x720), so lines wrap later. The head preamble sets a 30px base font and smaller headings through the theme's CSS variables, so any reveal 4+ theme picks them up. A script spliced in after Reveal.initialize measures every slide once reveal is ready and shrinks any that still overflows, down to a floor of half size. A slide that overflows even there gets a console warning. A slide that fits stays at full size. The script stays out of overview and print view, where reveal lays slides out differently and a measurement means nothing.

The header template now emits the same init options as the global default and turns off ^ markup, so snake_case identifiers in slide text stop exporting as subscripts. A file that already carries its own #+REVEAL_INIT_OPTIONS keeps them. The preamble and the fit script apply to every export.
---
 tests/test-org-reveal-config-header-template.el |   6 +
 tests/test-org-reveal-config-sizing.el          | 239 ++++++++++++++++++++++++
 2 files changed, 245 insertions(+)
 create mode 100644 tests/test-org-reveal-config-sizing.el

(limited to 'tests')

diff --git a/tests/test-org-reveal-config-header-template.el b/tests/test-org-reveal-config-header-template.el
index 9bda10db..b7ceff53 100644
--- a/tests/test-org-reveal-config-header-template.el
+++ b/tests/test-org-reveal-config-header-template.el
@@ -144,5 +144,11 @@
   "Nil title should signal an error rather than silently producing garbage."
   (should-error (test-reveal--header nil) :type 'user-error))
 
+(ert-deftest test-org-reveal-config-header-template-normal-keeps-underscores-literal ()
+  "Normal: #+OPTIONS: turns off ^ markup so snake_case identifiers in slide text stay literal.
+Without it a heading like event_payloads_ais exports as event with a subscript."
+  (let ((result (cj/--reveal-header-template "My Talk")))
+    (should (string-match-p "^#\\+OPTIONS:.*\\^:nil" result))))
+
 (provide 'test-org-reveal-config-header-template)
 ;;; test-org-reveal-config-header-template.el ends here
diff --git a/tests/test-org-reveal-config-sizing.el b/tests/test-org-reveal-config-sizing.el
new file mode 100644
index 00000000..ea27b718
--- /dev/null
+++ b/tests/test-org-reveal-config-sizing.el
@@ -0,0 +1,239 @@
+;;; test-org-reveal-config-sizing.el --- Tests for reveal.js slide sizing and auto-fit -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Dense slides overflowed reveal.js's 960x700 canvas at the theme's 42px
+;; base font and were clipped with no way to scroll.  The module now ships
+;; a 16:9 canvas with a smaller base font (via the head preamble) and a
+;; script, spliced in after Reveal.initialize, that shrinks any slide whose
+;; content still overflows.  These tests pin the three builders and run the
+;; fit algorithm under node against a stub Reveal API.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+(require 'json)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'keybindings)
+(require 'org-reveal-config)
+
+(defun test-org-reveal-config--count (regexp string)
+  "Return how many times REGEXP matches in STRING."
+  (let ((n 0) (start 0))
+    (while (string-match regexp string start)
+      (setq n (1+ n)
+            start (match-end 0)))
+    n))
+
+;; ------------------------------ Init options -------------------------------
+
+(ert-deftest test-org-reveal-config-init-options-normal-has-behaviour-and-canvas ()
+  "Normal: the shared init options carry slide numbers, hash, transition and the canvas size."
+  (let ((opts (cj/--reveal-init-options)))
+    (should (string-match-p "slideNumber:true" opts))
+    (should (string-match-p "hash:true" opts))
+    (should (string-match-p (format "transition:'%s'" cj/reveal-default-transition) opts))
+    (should (string-match-p (format "width:%d" cj/reveal-canvas-width) opts))
+    (should (string-match-p (format "height:%d" cj/reveal-canvas-height) opts))))
+
+(ert-deftest test-org-reveal-config-init-options-boundary-splices-into-initialize ()
+  "Boundary: one line, no trailing comma, so it splices into Reveal.initialize({...})."
+  (let ((opts (cj/--reveal-init-options)))
+    (should-not (string-match-p "\n" opts))
+    (should-not (string-suffix-p "," (string-trim opts)))))
+
+(ert-deftest test-org-reveal-config-init-options-normal-canvas-is-16-9 ()
+  "Normal: the canvas is a 16:9 frame, the shape of every projector and monitor the slides land on."
+  (should (= (* 9 cj/reveal-canvas-width) (* 16 cj/reveal-canvas-height))))
+
+(ert-deftest test-org-reveal-config-header-template-normal-uses-shared-init-options ()
+  "Normal: the header template emits the same init options as the global default, so a file never drifts from the module."
+  (let ((result (cj/--reveal-header-template "Sizing")))
+    (should (string-match-p
+             (format "^#\\+REVEAL_INIT_OPTIONS: %s$"
+                     (regexp-quote (cj/--reveal-init-options)))
+             result))))
+
+;; ------------------------------ Head preamble ------------------------------
+
+(ert-deftest test-org-reveal-config-head-preamble-normal-sets-font-sizes ()
+  "Normal: the preamble lowers the theme's base font and heading sizes through the theme variables."
+  (let ((css (cj/--reveal-head-preamble)))
+    (should (string-match-p (format "--r-main-font-size: *%s"
+                                    (regexp-quote cj/reveal-base-font-size))
+                            css))
+    (should (string-match-p "--r-heading1-size" css))
+    (should (string-match-p "--r-heading2-size" css))))
+
+(ert-deftest test-org-reveal-config-head-preamble-normal-keeps-no-caps-rule ()
+  "Normal: the rule that stops the theme upper-casing headings survives the rewrite."
+  (should (string-match-p "text-transform: *none" (cj/--reveal-head-preamble))))
+
+(ert-deftest test-org-reveal-config-head-preamble-boundary-one-style-element ()
+  "Boundary: exactly one <style> element, opened and closed."
+  (let ((css (cj/--reveal-head-preamble)))
+    (should (= 1 (test-org-reveal-config--count "<style" css)))
+    (should (= 1 (test-org-reveal-config--count "</style>" css)))))
+
+;; -------------------------------- Fit script -------------------------------
+
+(ert-deftest test-org-reveal-config-fit-script-normal-hooks-reveal-events ()
+  "Normal: the script fits every slide once reveal is ready and refits on each slide change."
+  (let ((js (cj/--reveal-fit-script)))
+    (should (string-match-p "Reveal\\.on('ready'" js))
+    (should (string-match-p "Reveal\\.on('slidechanged'" js))
+    (should (string-match-p "Reveal\\.on('overviewhidden'" js))
+    (should (string-match-p "isOverview" js))
+    (should (string-match-p "scrollHeight" js))
+    (should (string-match-p "getConfig()\\.height" js))))
+
+(ert-deftest test-org-reveal-config-fit-script-boundary-no-script-tags ()
+  "Boundary: ox-reveal splices the text inside its own <script> element, so it must carry no tags."
+  (let ((js (cj/--reveal-fit-script)))
+    (should-not (string-match-p "<script" js))
+    (should-not (string-match-p "</script" js))))
+
+(defconst test-org-reveal-config--fit-harness
+  "const MODE = '%s';
+let overview = false;
+const make = (base, fixed, inStack) => {
+  const s = { style: { fontSize: '', display: 'none' },
+              parentNode: { classList: { contains: (c) => inStack && c === 'stack' },
+                            style: { display: 'none' } } };
+  Object.defineProperty(s, 'scrollHeight', { get() {
+    const m = /^([\\d.]+)%%$/.exec(s.style.fontSize);
+    const h = fixed + Math.round(base * (m ? parseFloat(m[1]) / 100 : 1));
+    return overview ? Math.max(h, 720) : h; } });
+  return s;
+};
+const slides = [make(600, 0, false), make(684, 0, true), make(1368, 0, true),
+                make(100000, 0, false), make(900, 100, false), make(500, 450, true)];
+const handlers = {};
+let layouts = 0;
+let warnings = 0;
+console.warn = () => { warnings++; };
+global.Reveal = {
+  getConfig: () => ({ height: 720 }),
+  getSlides: () => slides,
+  getCurrentSlide: () => slides[2],
+  layout: () => { layouts++;
+                  if (MODE === 'reentrant' && handlers.slidechanged) {
+                    handlers.slidechanged({ currentSlide: slides[2] }); } },
+  isReady: () => MODE === 'ready',
+  isPrintView: () => false,
+  isOverview: () => overview,
+  on: (name, fn) => { handlers[name] = fn; } };
+%s
+const readyHandler = Boolean(handlers.ready);
+if (handlers.ready) { handlers.ready(); }
+if (MODE === 'overview') {
+  overview = true;
+  handlers.slidechanged({ currentSlide: slides[0] });
+  overview = false;
+  handlers.overviewhidden();
+}
+if (MODE === 'reentrant') {
+  slides[4].style.fontSize = '';
+  handlers.slidechanged({ currentSlide: slides[4] });
+}
+handlers.slidechanged({ currentSlide: slides[2] });
+handlers.slidechanged({ currentSlide: null });
+process.stdout.write(JSON.stringify({
+  sizes: slides.map(s => s.style.fontSize),
+  displays: slides.map(s => s.style.display),
+  parents: slides.map(s => s.parentNode.style.display),
+  overflow: slides.map(s => s.scrollHeight > 684),
+  readyHandler, overviewHandler: Boolean(handlers.overviewhidden),
+  layouts, warnings }));
+"
+  "Node harness: a stub Reveal API around the fit script.
+The first %s is the harness MODE (normal, ready, overview, reentrant) and
+the second is the script.  Each stub slide's scrollHeight is a fixed part
+plus a text part that scales with the font-size the script sets, so a
+later measuring pass sees the effect of the earlier one.  Slides 1, 2 and
+5 sit in a .stack parent, as every ox-reveal content slide does.  The
+canvas is 720px, so the usable limit with the 5% margin is 684px.  In
+overview the stub floors scrollHeight at the 720px box, the way reveal's
+overview CSS does.")
+
+(defun test-org-reveal-config--run-fit-harness (&optional mode)
+  "Run the fit script under node in harness MODE; return the parsed result."
+  (let ((file (make-temp-file "reveal-fit-" nil ".js"))
+        (out (generate-new-buffer " *fit-harness*")))
+    (unwind-protect
+        (progn
+          (with-temp-file file
+            (insert (format test-org-reveal-config--fit-harness
+                            (or mode "normal")
+                            (cj/--reveal-fit-script))))
+          (let ((status (call-process "node" nil out nil file)))
+            (unless (eq status 0)
+              (error "node exited %s: %s" status
+                     (with-current-buffer out (buffer-string))))
+            (with-current-buffer out
+              (goto-char (point-min))
+              (json-parse-buffer :object-type 'alist :array-type 'list))))
+      (delete-file file)
+      (kill-buffer out))))
+
+(ert-deftest test-org-reveal-config-fit-script-normal-shrinks-only-overflowing-slides ()
+  "Normal: a slide twice the usable height is scaled to 50%; slides that fit are left alone."
+  (skip-unless (executable-find "node"))
+  (let-alist (test-org-reveal-config--run-fit-harness)
+    (should (equal "" (nth 0 .sizes)))
+    (should (equal "" (nth 1 .sizes)))
+    (should (equal "50.0%" (nth 2 .sizes)))))
+
+(ert-deftest test-org-reveal-config-fit-script-normal-converges-with-fixed-height-content ()
+  "Normal: content with a fixed-height part needs several passes and still lands inside the limit."
+  (skip-unless (executable-find "node"))
+  (let-alist (test-org-reveal-config--run-fit-harness)
+    (should (string-match-p "\\`6[0-9]\\.[0-9]%\\'" (nth 4 .sizes)))
+    (should (eq :false (nth 4 .overflow)))))
+
+(ert-deftest test-org-reveal-config-fit-script-boundary-floors-at-half-size ()
+  "Boundary: content that would need less than half size stops at the floor, and only those slides are reported."
+  (skip-unless (executable-find "node"))
+  (let-alist (test-org-reveal-config--run-fit-harness)
+    (should (equal "50.0%" (nth 3 .sizes)))
+    (should (equal "50.0%" (nth 5 .sizes)))
+    (should (eq t (nth 3 .overflow)))
+    (should (eq t (nth 5 .overflow)))
+    (should (= 2 .warnings))))
+
+(ert-deftest test-org-reveal-config-fit-script-boundary-restores-display-and-relayouts ()
+  "Boundary: measuring hidden slides and their stack parents leaves display as reveal set it, and layout runs afterwards."
+  (skip-unless (executable-find "node"))
+  (let-alist (test-org-reveal-config--run-fit-harness)
+    (should (equal '("none" "none" "none" "none" "none" "none") .displays))
+    (should (equal '("none" "none" "none" "none" "none" "none") .parents))
+    (should (> .layouts 0))))
+
+(ert-deftest test-org-reveal-config-fit-script-normal-fits-at-once-when-reveal-is-ready ()
+  "Normal: when reveal is already ready the slides are fitted immediately instead of waiting for an event."
+  (skip-unless (executable-find "node"))
+  (let-alist (test-org-reveal-config--run-fit-harness "ready")
+    (should (eq :false .readyHandler))
+    (should (equal "50.0%" (nth 2 .sizes)))))
+
+(ert-deftest test-org-reveal-config-fit-script-boundary-overview-is-left-alone ()
+  "Boundary: in overview every slide measures as the full box, so nothing is refitted until the overview closes."
+  (skip-unless (executable-find "node"))
+  (let-alist (test-org-reveal-config--run-fit-harness "overview")
+    (should (equal "" (nth 0 .sizes)))
+    (should (eq t .overviewHandler))))
+
+(ert-deftest test-org-reveal-config-fit-script-error-null-slide-is-ignored ()
+  "Error: a slidechanged event without a current slide is ignored rather than thrown."
+  (skip-unless (executable-find "node"))
+  (should (test-org-reveal-config--run-fit-harness)))
+
+(ert-deftest test-org-reveal-config-fit-script-error-reentrant-layout-does-not-recurse ()
+  "Error: a layout that fires slidechanged again (reveal's scroll view does) must not recurse without end."
+  (skip-unless (executable-find "node"))
+  (let-alist (test-org-reveal-config--run-fit-harness "reentrant")
+    (should (>= .layouts 2))))
+
+(provide 'test-org-reveal-config-sizing)
+;;; test-org-reveal-config-sizing.el ends here
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