Media pager with a mouse: the wheel pages, ctrl+wheel zooms, arrows for the pointer. Adam reached for the scroll wheel in the pager on his laptop and nothing useful happened: a notch scrolled the snap container a hundred pixels and the glide's snap put it straight back (a headless probe of the live pager: scrollTop stays 0), so the arrow keys were the only desktop way through. Now a wheel notch is a step — down the next post, up the one before, a sideways notch (a trackpad's, or shift+wheel) along the post's pictures — with a 220 ms breath between steps so a spin of the wheel is a step or two, not five; a trackpad's run of small deltas is one step per run (its first 40 px, the rest until a pause is spent). Ctrl+wheel zooms the picture at the cursor, which is also what a trackpad's pinch arrives as in Chrome (attachZoom's new wheel: 'ctrl' mode, 0.004 per unit); while zoomed the plain wheel pans it, and at 1× it is the pager's again. And where there is a pointer to hover with (hover: hover and pointer: fine), arrows: up and down at the right edge, left and right when the post has a picture that way (has-left/has-right, set as the slide on screen changes), faint until the pointer is over the pager. The keys, the wheel and the arrows share one step (pagerStep). No mouse drag-flick: discrete steps suit a pager. tools/pager-wheel-test.js (CDP mouseWheel is always a 120-unit notch to Chrome, so a trackpad run is dispatched page-side; headless has no hovering pointer, so one is given with --blink-settings); feed-picture-pager and image-zoom tests pass.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01J1Kon8bxJoHRpJdSzshCkp

5 files changed, 276 insertions, 19 deletions

diff --git a/src/app.js b/src/app.js
index 3cdb59e..7f6baa3 100644
--- a/src/app.js
+++ b/src/app.js
@@ -695,9 +695,16 @@ function attachZoom(box, img, { wheel = true } = {}) {
     if (e.target.closest('.lightbox-x')) return;
     if (moved) { moved = false; e.stopImmediatePropagation(); e.preventDefault(); return; }
   }, true);
+  // The wheel. true: a turn zooms (the lightbox, a picture on its own).
+  // 'ctrl': ctrl+wheel zooms — a trackpad's pinch arrives in Chrome as
+  // exactly that — and a plain wheel pans the picture while it is zoomed;
+  // at 1× a plain wheel is left to whoever owns the box (the pager pages).
   if (wheel) box.addEventListener('wheel', (e) => {
+    const zoom = wheel !== 'ctrl' || e.ctrlKey || e.metaKey;
+    if (!zoom && s <= 1) return;
     e.preventDefault();
-    zoomAt(s * Math.exp(-e.deltaY * 0.002), e.clientX, e.clientY);
+    if (zoom) zoomAt(s * Math.exp(-e.deltaY * (wheel === 'ctrl' ? 0.004 : 0.002)), e.clientX, e.clientY);
+    else { x -= e.deltaX; y -= e.deltaY; }
     clamp(); apply(false);
   }, { passive: false });
 }
diff --git a/src/features/messages.js b/src/features/messages.js
index a8815b0..7760654 100644
--- a/src/features/messages.js
+++ b/src/features/messages.js
@@ -12177,7 +12177,7 @@ export function messagesFeature(ctx) {
     slide._ev = ev;
     slide._rowId = it.row ? it.row.id : ev.id; // the feed row to land on (a repost's wrapper, not its inner post)
     // pinch to zoom a picture (drag pans it zoomed; the wheel is the pager's)
-    if (!video && ctx.attachZoom) ctx.attachZoom(slide, media, { wheel: false });
+    if (!video && ctx.attachZoom) ctx.attachZoom(slide, media, { wheel: 'ctrl' }); // ctrl+wheel (a pinch) zooms; the plain wheel is the pager's
     if (video) {
       guardPicture(media, url);
       media.muted = !pagerLoud;
@@ -12470,6 +12470,33 @@ export function messagesFeature(ctx) {
     return y ? box.scrollTop + r.top - b.top : box.scrollLeft + r.left - b.left;
   };
   const pagerHold = (box) => { if (box && box._glide) { cancelAnimationFrame(box._glide); box._glide = 0; } };
+  // the slide on screen — named, not "a screen further", which from a
+  // scroll still settling landed short
+  const pagerHere = () => pager && (pagerSlides().find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.left) < r.width / 2 && Math.abs(r.top) < r.height / 2; }) || pager.cur);
+  // A step: v up or down the posts (-1/1), hz along the post's pictures.
+  // The keys, the wheel and the desktop arrows all come here.
+  function pagerStep(v, hz) {
+    if (!pager) return false;
+    const here = pagerHere();
+    if (v) {
+      const from = pager.onTail || !here ? pager.tail : here.closest('.mp-group');
+      const to = from && (v > 0 ? from.nextElementSibling : from.previousElementSibling);
+      if (to) pagerGlide(pager.scroller, 'y', pagerAt(pager.scroller, to, true));
+      return !!to;
+    }
+    if (hz) {
+      const to = !pager.onTail && here && (hz > 0 ? here.nextElementSibling : here.previousElementSibling);
+      if (to) pagerGlide(here.parentElement, 'x', pagerAt(here.parentElement, to, false));
+      return !!to;
+    }
+    return false;
+  }
+  // the sideways arrows show only where the post has a picture that way
+  function pagerArrows(slide) {
+    if (!pager || !slide) return;
+    pager.el.classList.toggle('has-left', !!slide.previousElementSibling);
+    pager.el.classList.toggle('has-right', !!slide.nextElementSibling);
+  }
 
   function buildPager(want) {
     const video = want.kind === 'videos';
@@ -12479,7 +12506,48 @@ export function messagesFeature(ctx) {
       h('div', { class: 'mp-top' },
         h('button', { class: 'mp-x', type: 'button', 'aria-label': t('close'), onClick: (e) => { e.stopPropagation(); dismissPager(); } }, '×'),
         video ? h('button', { class: 'mp-sound', type: 'button', onClick: (e) => { e.stopPropagation(); pagerSound(!pagerLoud); } },
-          h('span', { class: 'on' }, '\u{1F50A}'), h('span', { class: 'off' }, '\u{1F507} ' + t('videoUnmute'))) : null));
+          h('span', { class: 'on' }, '\u{1F50A}'), h('span', { class: 'off' }, '\u{1F507} ' + t('videoUnmute'))) : null),
+      // a mouse's way through (shown where there is a pointer to hover with,
+      // style.css): up and down the posts at the right edge, left and right
+      // along a post's pictures when it has more than one (has-left/right)
+      h('div', { class: 'mp-arrows' }, ...[['mp-up', 'pagerPrevPost', 'M6 15l6-6 6 6', -1, 0], ['mp-down', 'pagerNextPost', 'M6 9l6 6 6-6', 1, 0],
+        ['mp-ar-left', 'pagerPrevPic', 'M15 6l-6 6 6 6', 0, -1], ['mp-ar-right', 'pagerNextPic', 'M9 6l6 6-6 6', 0, 1]].map(([cls, label, d, v, hz]) =>
+        h('button', { class: 'mp-arrow ' + cls, type: 'button', 'aria-label': t(label), title: t(label), onClick: (e) => { e.stopPropagation(); pagerStep(v, hz); } },
+          h('span', { style: 'display:flex', html: '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round"><path d="' + d + '"/></svg>' })))));
+    // A mouse wheel pages: a notch down is the next post, a notch up the one
+    // before, a breath between steps so a spin of the wheel doesn't skip
+    // five. A trackpad's run of small deltas is one step per run (its first
+    // 40px; the rest of the run, until a pause, is spent), and a sideways
+    // run — or shift+wheel — walks along the post's pictures. Ctrl+wheel (a
+    // trackpad's pinch comes the same way) zooms the picture and the wheel
+    // pans it while zoomed: attachZoom takes those first (defaultPrevented).
+    // Left to the browser, a notch scrolled the snap container a hundred
+    // pixels and the glide's snap put it straight back: the wheel did nothing.
+    let wheelStepAt = 0, run = null;
+    el.addEventListener('wheel', (e) => {
+      if (!pager || e.defaultPrevented || e.ctrlKey || e.metaKey) return;
+      if (e.target.closest && e.target.closest('.mp-caption.open, .mp-seek')) return;
+      e.preventDefault();
+      const k = e.deltaMode === 1 ? 40 : 1;
+      let dx = e.deltaX * k, dy = e.deltaY * k;
+      if (e.shiftKey && !dx) { dx = dy; dy = 0; }
+      const hz = Math.abs(dx) > Math.abs(dy), d = hz ? dx : dy;
+      if (!d) return;
+      const notch = e.deltaMode === 1 || (hz ? e.wheelDeltaX && e.wheelDeltaX % 120 === 0 : e.wheelDeltaY && e.wheelDeltaY % 120 === 0);
+      const now = e.timeStamp;
+      if (notch) {
+        if (now - wheelStepAt < 220) return;
+      } else {
+        if (!run || now - run.at > 150) run = { at: now, acc: 0, done: false };
+        run.at = now;
+        if (run.done) return;
+        run.acc += d;
+        if (Math.abs(run.acc) < 40) return;
+        run.done = true;
+      }
+      wheelStepAt = now;
+      pagerStep(hz ? 0 : Math.sign(d), hz ? Math.sign(d) : 0);
+    }, { passive: false });
     // A touch is the pager's to judge, not the browser's. Left to native
     // scrolling, a tap whose finger moved a few pixels was taken for a
     // scroll (no click: a tap meant to pause a clip did nothing), and a quick
@@ -12635,6 +12703,7 @@ export function messagesFeature(ctx) {
         }
         pager.cur = e.target;
         pager.curAt = Date.now();
+        pagerArrows(e.target);
         if (pager.fromFeed) { const row = feedNow().notes.find((x) => x.id === e.target._rowId); markSeen(row || e.target._ev); }
         playSlide(e.target);
         pagerCounts(e.target);
@@ -12749,22 +12818,7 @@ export function messagesFeature(ctx) {
       // up and down: the next post, or the one before; left and right: along this post's row
       const v = ['ArrowDown', 'j', 'PageDown'].includes(e.key) ? 1 : ['ArrowUp', 'k', 'PageUp'].includes(e.key) ? -1 : 0;
       const hz = ['ArrowRight', 'l'].includes(e.key) ? 1 : ['ArrowLeft', 'h'].includes(e.key) ? -1 : 0;
-      // to the slide (or post) next to the one on screen — named, not "a
-      // screen further", which from a scroll still settling landed short
-      const here = pagerSlides().find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.left) < r.width / 2 && Math.abs(r.top) < r.height / 2; }) || pager.cur;
-      if (v) {
-        e.preventDefault();
-        const from = pager.onTail || !here ? pager.tail : here.closest('.mp-group');
-        const to = from && (v > 0 ? from.nextElementSibling : from.previousElementSibling);
-        if (to) pagerGlide(pager.scroller, 'y', pagerAt(pager.scroller, to, true));
-        return;
-      }
-      if (hz) {
-        e.preventDefault();
-        const to = !pager.onTail && here && (hz > 0 ? here.nextElementSibling : here.previousElementSibling);
-        if (to) pagerGlide(here.parentElement, 'x', pagerAt(here.parentElement, to, false));
-        return;
-      }
+      if (v || hz) { e.preventDefault(); pagerStep(v, hz); return; }
       if (e.key === ' ' && pager.cur) {
         const v = pager.cur.querySelector('video.mp-media');
         if (v) { e.preventDefault(); if (v.paused) v.play().catch(() => {}); else v.pause(); }
diff --git a/src/i18n.js b/src/i18n.js
index 82004a2..fd192a1 100644
--- a/src/i18n.js
+++ b/src/i18n.js
@@ -274,6 +274,10 @@ const STR = {
     pagerFetchingVideo: "Fetching the next video…",
     pagerFetchingPictures: "Fetching more pictures…",
     pagerCaughtUp: "That’s everything for now",
+    pagerPrevPost: 'Previous post',
+    pagerNextPost: 'Next post',
+    pagerPrevPic: 'Previous picture',
+    pagerNextPic: 'Next picture',
     videoNoPicture: "This browser can’t show this video’s picture",
     videoOpenFile: "Open the file",
     videoLargeTitle: "Videos",
diff --git a/src/style.css b/src/style.css
index f908a05..c581535 100644
--- a/src/style.css
+++ b/src/style.css
@@ -1546,6 +1546,26 @@ body::after {
 }
 .mp-sound { font-size: 15px; }
 .mp-sound .off { display: none; }
+/* A mouse's way through the pager: arrows, where there is a pointer to
+   hover with (a phone swipes). Faint until the pointer is over the pager;
+   the sideways pair only when the post has a picture that way. */
+.mp-arrows { display: none; }
+@media (hover: hover) and (pointer: fine) {
+  .mp-arrows { display: contents; }
+  .mp-arrow {
+    position: absolute; z-index: 3; width: 44px; height: 44px; padding: 0; border: 0; border-radius: 50%;
+    display: flex; align-items: center; justify-content: center; cursor: pointer;
+    color: #fff; background: rgba(255, 255, 255, .14); opacity: .4; transition: opacity .15s, background .15s;
+  }
+  .mp-arrow svg { width: 26px; height: 26px; }
+  .media-pager:hover .mp-arrow { opacity: .8; }
+  .mp-arrow:hover { opacity: 1; background: rgba(255, 255, 255, .28); }
+  .mp-up { right: 14px; top: calc(50% - 50px); }
+  .mp-down { right: 14px; top: calc(50% + 6px); }
+  .mp-ar-left { left: 14px; top: calc(50% - 22px); }
+  .mp-ar-right { right: 72px; top: calc(50% - 22px); }
+  .media-pager:not(.has-left) .mp-ar-left, .media-pager:not(.has-right) .mp-ar-right { display: none; }
+}
 .media-pager.quiet .mp-sound .on { display: none; }
 .media-pager.quiet .mp-sound .off { display: inline; }
 /* muted against our will: the button stays up so the way to sound is plain */
diff --git a/tools/pager-wheel-test.js b/tools/pager-wheel-test.js
new file mode 100644
index 0000000..b73171b
--- /dev/null
+++ b/tools/pager-wheel-test.js
@@ -0,0 +1,172 @@
+// The media pager with a mouse (a laptop): a wheel notch is a step — down
+// the next post, up the one before, sideways (or shift+wheel) along a post's
+// pictures — a trackpad's run of small deltas one step per run, a spin of
+// the wheel not five; ctrl+wheel (a trackpad's pinch) zooms the picture,
+// the wheel pans it while zoomed and pages again at 1×; and arrows at the
+// edges for the pointer, the sideways pair only where the post has more.
+// Run: bun tools/pager-wheel-test.js
+import puppeteer from './puppeteer.js';
+import { cacheKeyFor } from '../src/wallet.js';
+import { generateSecretKey, getPublicKey, finalizeEvent } from 'nostr-tools/pure';
+import { buildHtml } from '../build.js';
+const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
+let ok = true;
+const check = (n, c, d = '') => { console.log(` ${c ? '✓' : '✗'} ${n}${d ? ' — ' + d : ''}`); if (!c) ok = false; };
+const png = (size) => Bun.spawnSync(['ffmpeg', '-loglevel', 'error', '-f', 'lavfi', '-i', 'testsrc=size=' + size, '-frames:v', '1', '-f', 'image2', '-c:v', 'png', 'pipe:1']).stdout;
+const PICS = { a1: png('400x300'), a2: png('300x400'), b: png('320x320'), d: png('360x240') };
+
+const SK = generateSecretKey(), AUTHOR = getPublicKey(SK);
+const now = Math.floor(Date.now() / 1000);
+const post = (content, ago) => finalizeEvent({ kind: 1, created_at: now - ago, tags: [], content }, SK);
+const html = await buildHtml({ minify: true, pwa: false });
+const server = Bun.serve({ port: 0, fetch: (req) => {
+  const path = new URL(req.url).pathname;
+  if (path.startsWith('/punks')) return new Response(Bun.file('dist' + path));
+  const m = /^\/(a1|a2|b|d)\.png$/.exec(path);
+  if (m) return new Response(PICS[m[1]], { headers: { 'content-type': 'image/png' } });
+  return new Response(html, { headers: { 'content-type': 'text/html' } });
+} });
+const U = (n) => server.url.origin + '/' + n + '.png';
+const seeded = [
+  post('two pictures ' + U('a1') + ' ' + U('a2'), 100),
+  post('one picture ' + U('b'), 200),
+  post('only words here, nothing to look at', 300),
+  post('a last picture ' + U('d'), 400),
+  ...Array.from({ length: 12 }, (_, i) => post('filler ' + i + ' ' + 'lorem ipsum dolor sit amet. '.repeat(5), 500 + i * 60)),
+];
+
+const browser = await puppeteer.launch({ executablePath: '/usr/bin/google-chrome', headless: 'new', args: ['--no-sandbox', '--blink-settings=primaryHoverType=2,availableHoverTypes=2,primaryPointerType=4,availablePointerTypes=4'] /* a pointer that hovers: headless has none */ });
+const page = await browser.newPage();
+const errs = [];
+page.on('pageerror', (e) => errs.push(String(e)));
+const click = (t) => page.evaluate((x) => { const e = [...document.querySelectorAll('button')].find((n) => n.textContent.trim().toLowerCase().includes(x)); if (e) { e.click(); return true; } return false; }, t);
+const waitText = async (x, ms = 25000) => { for (let i = 0; i < ms / 250; i++) { if ((await page.evaluate(() => document.body.innerText)).toLowerCase().includes(x)) return true; await sleep(250); } return false; };
+const waitFor = async (fn, arg, ms = 10000) => { for (let i = 0; i < ms / 100; i++) { if (await page.evaluate(fn, arg)) return true; await sleep(100); } return false; };
+// the slide the pager rests on, by its picture
+const curPic = () => page.evaluate(() => {
+  const sc = document.querySelector('.mp-scroll'); if (!sc) return null;
+  const s = [...sc.querySelectorAll('.mp-slide')].find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.top) < 4 && Math.abs(r.left) < 4; });
+  return s ? s.getAttribute('data-k').split('|')[1].split('/').pop() : 'between';
+});
+const resting = async (name) => rested(name).then(async (r) => { await sleep(260); return r; }); // a breath after: the wheel's gate between steps
+const rested = async (name) => waitFor((n) => { const sc = document.querySelector('.mp-scroll'); if (!sc) return false; const s = [...sc.querySelectorAll('.mp-slide')].find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.top) < 4 && Math.abs(r.left) < 4; }); return !!s && s.getAttribute('data-k').endsWith('/' + n); }, name, 4000);
+const openPic = async (word) => {
+  await page.evaluate((w) => { const r = [...document.querySelectorAll('.notes-feed [data-key]')].find((n) => n.textContent.includes(w)); r.scrollIntoView({ block: 'center' }); }, word);
+  await sleep(400);
+  const at = await page.evaluate((w) => { const r = [...document.querySelectorAll('.notes-feed [data-key]')].find((n) => n.textContent.includes(w)); const i = r.querySelector('img.note-img').getBoundingClientRect(); return { x: i.x + i.width / 2, y: i.y + i.height / 2, y0: window.scrollY }; }, word);
+  await page.mouse.click(at.x, at.y);
+  await waitFor(() => !!document.querySelector('.media-pager'), null, 4000);
+  return at.y0;
+};
+const tapPager = async () => { const at = await page.evaluate(() => { const sc = document.querySelector('.mp-scroll'); const s = [...sc.querySelectorAll('.mp-slide')].find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.top) < 4 && Math.abs(r.left) < 4; }) || sc.firstChild; const r = s.querySelector('img.mp-media').getBoundingClientRect(); return { x: r.x + r.width / 2, y: r.y + r.height / 2 }; }); await page.mouse.click(at.x, at.y); };
+const rowTop = (word) => page.evaluate((w) => { const r = [...document.querySelectorAll('.notes-feed [data-key]')].find((n) => n.textContent.includes(w)); return r ? Math.round(r.getBoundingClientRect().top) : null; }, word);
+
+try {
+  await page.setViewport({ width: 1280, height: 900 });
+  await page.goto(server.url.href, { waitUntil: 'domcontentloaded' });
+  await page.evaluate(() => localStorage.setItem('btc-wallet-network', 'regtest'));
+  await page.reload({ waitUntil: 'domcontentloaded' });
+  await sleep(400);
+  await click('create a new wallet'); await sleep(600);
+  await page.waitForSelector('.words .w .t');
+  const mn = (await page.$$eval('.words .w .t', (l) => l.map((e) => e.textContent.trim()))).join(' ');
+  await click('skip verification');
+  await waitText('receive', 20000);
+  const base = cacheKeyFor(mn + '\n');
+  await page.evaluate(([k, pk, ns]) => {
+    localStorage.setItem(k + ':follows', JSON.stringify({ tags: [['p', pk]], c: '', at: Math.floor(Date.now() / 1000) }));
+    localStorage.setItem(k + ':feedNotes', JSON.stringify(ns));
+    localStorage.setItem(k + ':profiles', JSON.stringify({ [pk]: { name: 'Picture Poster', t: Date.now() } }));
+    localStorage.setItem('btc-wallet-feed:' + k, 'following');
+  }, [base, AUTHOR, seeded]);
+  await page.reload({ waitUntil: 'domcontentloaded' });
+  await waitText('receive', 20000);
+  await page.evaluate(() => document.querySelector('.app-nav-button[aria-label="Feed"]').click());
+  check('the pictures are in the feed', await waitFor(() => document.querySelectorAll('.notes-feed img.note-img').length >= 4, null, 20000));
+  const cdp = await page.target().createCDPSession();
+  // a trackpad's run: small deltas, page-side — a CDP mouseWheel is always a 120-unit notch to Chrome
+  const pad = (dy, n) => page.evaluate(async ([dy, n]) => { const sc = document.querySelector('.mp-scroll'); for (let i = 0; i < n; i++) { const s = [...sc.querySelectorAll('.mp-slide')].find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.top) < 4 && Math.abs(r.left) < 4; }) || sc.firstChild; const ev = new WheelEvent('wheel', { deltaY: dy, deltaX: 0, deltaMode: 0, bubbles: true, cancelable: true, clientX: 640, clientY: 450 }); Object.defineProperty(ev, 'wheelDeltaY', { value: -Math.round(dy * 1.2) }); s.querySelector('img.mp-media').dispatchEvent(ev); await new Promise((r) => setTimeout(r, 16)); } }, [dy, n]);
+  const pos = () => page.evaluate(() => { const sc = document.querySelector('.mp-scroll'); return sc ? Math.round(sc.scrollTop) + '/' + sc.clientHeight + ' glide:' + !!sc._glide + ' snap:' + sc.style.scrollSnapType : 'none'; });
+  const wheel = (dy, { dx = 0, mods = 0 } = {}) => cdp.send('Input.dispatchMouseEvent', { type: 'mouseWheel', x: 640, y: 450, deltaX: dx, deltaY: dy, modifiers: mods });
+  const zoomOf = () => page.evaluate(() => { const sc = document.querySelector('.mp-scroll'); const s = [...sc.querySelectorAll('.mp-slide')].find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.top) < 4 && Math.abs(r.left) < 4; }); const m = /scale\(([\d.]+)\)/.exec(s.querySelector('img.mp-media').style.transform || ''); return m ? Number(m[1]) : 1; });
+  const shiftOf = () => page.evaluate(() => { const sc = document.querySelector('.mp-scroll'); const s = [...sc.querySelectorAll('.mp-slide')].find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.top) < 4 && Math.abs(r.left) < 4; }); const m = /translate\(([-\d.]+)px, ([-\d.]+)px\)/.exec(s.querySelector('img.mp-media').style.transform || ''); return m ? [Number(m[1]), Number(m[2])] : [0, 0]; });
+
+  console.log('\n[a wheel notch is a step]');
+  await openPic('two pictures');
+  check('the picture opens in the pager', await resting('a1.png'), await curPic());
+  await page.mouse.move(640, 450);
+  await wheel(100);
+  check('a notch down: the next post\'s picture', await resting('b.png'), await curPic());
+  await wheel(100);
+  check('another: the next, past a post with none', await resting('d.png'), await curPic());
+  await wheel(-100);
+  check('a notch up: back one post', await resting('b.png'), await curPic());
+  await wheel(-100);
+  check('up again: the first post', await resting('a1.png'), await curPic());
+  await wheel(0, { dx: 100 });
+  check('sideways: the post\'s second picture', await resting('a2.png'), await curPic());
+  await wheel(0, { dx: 100 }); await sleep(300);
+  check('sideways at the post\'s last: stays', (await curPic()) === 'a2.png', await curPic());
+  await wheel(-100, { mods: 8 });
+  check('shift+wheel up: back to its first picture', await resting('a1.png'), await curPic());
+  await wheel(-100, { mods: 8 }); await sleep(300);
+  check('shift+wheel at the first: stays', (await curPic()) === 'a1.png', await curPic());
+  await wheel(100, { mods: 8 }); await resting('a2.png');
+  await sleep(300);
+  for (let i = 0; i < 5; i++) { await wheel(100); await sleep(10); }
+  await sleep(700);
+  check('a spin of five notches in a blink is a step or two, not five', ['b.png', 'd.png'].includes(await curPic()), await curPic());
+  await wheel(-100); await resting('b.png'); await wheel(-100); await resting('a2.png'); await wheel(100); await resting('b.png');
+
+  console.log('\n[a trackpad\'s run is one step]');
+  await sleep(300);
+  await pad(9, 14);
+  check('a run of small deltas steps once', await resting('d.png'), await curPic() + ' ' + await pos());
+  await sleep(400);
+  check('…and only once', (await curPic()) === 'd.png', await curPic());
+  await sleep(300);
+  await pad(-9, 14);
+  check('a run back steps back', await resting('b.png'), await curPic());
+
+  console.log('\n[ctrl+wheel zooms, the wheel pans, 1× pages]');
+  await sleep(400);
+  await wheel(-100, { mods: 2 }); await sleep(100);
+  const z1 = await zoomOf();
+  check('ctrl + a notch up zooms the picture in', z1 > 1.2, 'scale ' + z1);
+  await wheel(-100, { mods: 2 }); await sleep(100);
+  check('…and more', (await zoomOf()) > z1, 'scale ' + await zoomOf());
+  const before = await shiftOf();
+  await wheel(100); await sleep(300);
+  check('a plain notch while zoomed pans, it does not page', (await curPic()) === 'b.png' && JSON.stringify(await shiftOf()) !== JSON.stringify(before), await curPic() + ' ' + JSON.stringify(before) + ' → ' + JSON.stringify(await shiftOf()));
+  for (let i = 0; i < 6; i++) { await wheel(100, { mods: 2 }); await sleep(30); }
+  await sleep(100);
+  check('ctrl + notches down zoom back out to 1×', (await zoomOf()) === 1, 'scale ' + await zoomOf());
+  await sleep(300);
+  await wheel(100);
+  check('at 1× the wheel pages again', await resting('d.png'), await curPic());
+
+  console.log('\n[arrows for the pointer]');
+  const shown = (sel) => page.evaluate((s) => { const b = document.querySelector(s); return !!b && getComputedStyle(b).display !== 'none' && b.getBoundingClientRect().width > 0; }, sel);
+  check('up and down arrows are on the pager', await shown('.mp-arrow.mp-up') && await shown('.mp-arrow.mp-down'));
+  check('a post with one picture shows no sideways arrows', !(await shown('.mp-arrow.mp-ar-left')) && !(await shown('.mp-arrow.mp-ar-right')));
+  await page.click('.mp-arrow.mp-up');
+  check('the up arrow: back one post', await resting('b.png'), await curPic());
+  await page.click('.mp-arrow.mp-up');
+  check('up again: the first post, on the picture it was left at', await resting('a2.png'), await curPic());
+  await sleep(200);
+  check('on its last picture: a left arrow, no right', await shown('.mp-arrow.mp-ar-left') && !(await shown('.mp-arrow.mp-ar-right')));
+  await page.click('.mp-arrow.mp-ar-left');
+  check('the left arrow: its first picture', await resting('a1.png'), await curPic());
+  await sleep(200);
+  check('on its first: a right arrow, no left', await shown('.mp-arrow.mp-ar-right') && !(await shown('.mp-arrow.mp-ar-left')));
+  await page.click('.mp-arrow.mp-ar-right');
+  check('the right arrow: its second picture', await resting('a2.png'), await curPic());
+  check('an arrow\'s click is not a tap on the picture (no details, still open)', await page.evaluate(() => { const p = document.querySelector('.media-pager'); return !!p && !p.classList.contains('show'); }));
+  await page.click('.mp-arrow.mp-down');
+  check('the down arrow: the next post', await resting('b.png'), await curPic());
+  await page.keyboard.press('Escape');
+  check('Escape still closes it', await waitFor(() => !document.querySelector('.media-pager') && !!document.querySelector('.notes-feed'), null, 3000));
+  check('no page errors', errs.length === 0, errs.slice(0, 2).join(' | '));
+} catch (e) { console.error(e); ok = false; } finally { await browser.close(); server.stop(true); }
+console.log(ok ? '\n✅ pager: wheel steps, ctrl+wheel zooms, arrows for the pointer' : '\n❌ failed');
+process.exit(ok ? 0 : 1);