Media pager: a fast flick on the phone flies past several posts and lands snapped on one. A swipe went one post, however hard it was flung (Adam, 2026-10-16: "can we make images coast on the phone too when I swipe?"). Now a flick of FLY_V (3 px/ms) or more flies as many posts as the fling would have coasted — its speed times FLY_TAU (500 ms), in screens, up to six — in a glide, the pictures passing, to land square on the last (pagerFlyTo, the flight factored out of the wheel's pagerFly, paced a little slower per screen for a finger); only the landing is arrived at. A gentler swipe is the one post it was. A fling that would go past the end lands on the last post (or the first), and a swipe from there wraps by one post as before (a fling's whole count no longer picks the wrap target); a finger put down mid-flight catches it where it is. tools/pager-swipe-fly-test.js (a 320px swipe over 130ms is one post; a 420px flick in 72ms is three; the counter agrees; near the end it lands on the last and the next flick wraps to the first; a finger catches a flight) — the quick flick is dispatched inside the page, since the browser's touch simulation takes a round trip per move; pager-tap-slop and profile-pager tests pass.

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

1 files changed, 121 insertions, 0 deletions

diff --git a/tools/pager-swipe-fly-test.js b/tools/pager-swipe-fly-test.js
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+// On a phone, a fast flick up or down in the media pager flies past several
+// posts and lands snapped on one, the way a spin of the wheel does; a
+// gentler swipe is one post, as before; a fling at the end lands on the
+// last post rather than wrapping past it; a finger put down mid-flight
+// catches it. Run: bun tools/pager-swipe-fly-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 N = 9, PIC = png('360x360');
+const SK = generateSecretKey(), AUTHOR = getPublicKey(SK);
+const now = Math.floor(Date.now() / 1000);
+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));
+  if (/^\/p\d+\.png$/.test(path)) return new Response(PIC, { headers: { 'content-type': 'image/png' } });
+  return new Response(html, { headers: { 'content-type': 'text/html' } });
+} });
+const U = (n) => server.url.origin + '/p' + n + '.png';
+const seeded = Array.from({ length: N }, (_, i) => finalizeEvent({ kind: 1, created_at: now - 100 - i * 100, tags: [], content: 'picture post ' + (i + 1) + ' ' + U(i + 1) }, SK));
+
+const browser = await puppeteer.launch({ executablePath: '/usr/bin/google-chrome', headless: 'new', args: ['--no-sandbox'] });
+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 post the pager rests square on (its number), or 'between'
+const at = () => page.evaluate(() => { const s = [...document.querySelectorAll('.mp-slide')].find((x) => { const r = x.getBoundingClientRect(); return Math.abs(r.top) < 1 && Math.abs(r.left) < 1; }); return s ? Number(/p(\d+)\.png/.exec(s.getAttribute('data-k'))[1]) : 'between'; });
+const settled = async () => { let last = null; for (let i = 0; i < 40; i++) { const t = await page.evaluate(() => document.querySelector('.mp-scroll').scrollTop); if (t === last) { await sleep(100); if (await page.evaluate(() => document.querySelector('.mp-scroll').scrollTop) === t) return; } last = t; await sleep(50); } };
+// a swipe up the screen: px of travel over about `ms` milliseconds. A
+// quick one is dispatched inside the page, paced to the millisecond: the
+// browser's own touch simulation takes a round trip per move, so a flick
+// through it is never faster than a stroll.
+const swipe = async (px, ms, steps = 6) => {
+  if (ms >= 100) {
+    await page.touchscreen.touchStart(195, 700);
+    for (let i = 1; i <= steps; i++) { await page.touchscreen.touchMove(195, 700 - px * i / steps); await sleep(ms / steps); }
+    await page.touchscreen.touchEnd();
+    return;
+  }
+  await page.evaluate(([px, ms, steps]) => {
+    const el = document.querySelector('.mp-scroll'), target = document.elementFromPoint(195, 700) || el;
+    const touch = (y) => new Touch({ identifier: 1, target, clientX: 195, clientY: y, pageX: 195, pageY: y });
+    const fire = (type, y, up) => target.dispatchEvent(new TouchEvent(type, { bubbles: true, cancelable: true, touches: up ? [] : [touch(y)], changedTouches: [touch(y)], targetTouches: up ? [] : [touch(y)] }));
+    const spin = (t) => { const t0 = performance.now(); while (performance.now() - t0 < t); };
+    fire('touchstart', 700);
+    for (let i = 1; i <= steps; i++) { spin(ms / steps); fire('touchmove', 700 - px * i / steps); }
+    fire('touchend', 700 - px, true);
+  }, [px, ms, steps]);
+};
+try {
+  await page.setViewport({ width: 390, height: 844, hasTouch: true, isMobile: true });
+  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 >= 3, null, 20000));
+  const pic = await page.evaluate(() => { const r = [...document.querySelectorAll('.notes-feed [data-key]')].find((n) => n.textContent.includes('picture post 1 ')); const i = r.querySelector('img.note-img').getBoundingClientRect(); return { x: i.x + i.width / 2, y: i.y + i.height / 2 }; });
+  await page.touchscreen.tap(pic.x, pic.y);
+  check('the first picture opens in the pager', await waitFor(() => !!document.querySelector('.media-pager'), null, 4000) && (await (async () => { await settled(); return at(); })()) === 1, String(await at()));
+  check('…with all the posts loaded', await waitFor((n) => document.querySelectorAll('.mp-group').length >= n, N, 8000));
+
+  console.log('\n[a gentle swipe: one post]');
+  await swipe(320, 130); await settled();
+  check('a 320px swipe over 130ms: the next post', (await at()) === 2, String(await at()));
+
+  console.log('\n[a fast flick: several posts, landing snapped]');
+  const trace = async (sw) => { await page.evaluate(() => { const sc = document.querySelector('.mp-scroll'); window.__tr = []; const t0 = performance.now(); const rec = () => { window.__tr.push(sc.scrollTop); if (performance.now() - t0 < 1500) requestAnimationFrame(rec); }; requestAnimationFrame(rec); }); await sw(); await sleep(1600); return page.evaluate(() => window.__tr); };
+  const tr = await trace(() => swipe(420, 72)); await settled(); // ~5.8 px/ms: three posts' worth of coast
+  const landed = await at();
+  check('a 420px flick in 72ms flies three posts on', landed === 5, String(landed));
+  check('…landing square on a post', landed !== 'between');
+  check('…in a glide, never back', tr.every((x, i) => !i || x >= tr[i - 1] - 0.5), tr.slice(0, 12).map((x) => Math.round(x)).join(' '));
+  const seen = await page.evaluate(() => document.querySelector('.mp-position').textContent);
+  check('the counter says where it landed', seen === landed + ' / ' + N, seen);
+
+  console.log('\n[a flick near the end: the last post, not past it]');
+  await page.keyboard.press('ArrowDown'); await settled(); await page.keyboard.press('ArrowDown'); await settled();
+  const before = await at();
+  await swipe(420, 72); await settled();
+  check('from post ' + before + ' (three posts\' worth would be past the end), a flick lands on the last post', before === 7 && (await at()) === N, String(await at()));
+  await swipe(420, 72); await settled();
+  check('…and one more flick at the end wraps to the first', (await at()) === 1, String(await at()));
+
+  console.log('\n[a finger down mid-flight catches it]');
+  await swipe(420, 72);
+  await sleep(120);
+  const mid = await page.evaluate(() => document.querySelector('.mp-scroll').scrollTop);
+  await page.touchscreen.touchStart(195, 500);
+  await page.touchscreen.touchMove(195, 480); await sleep(30);
+  await page.touchscreen.touchMove(195, 470); await sleep(200);
+  const held = await page.evaluate(() => document.querySelector('.mp-scroll').scrollTop);
+  await page.touchscreen.touchEnd(); await settled();
+  check('the flight stops under the finger', mid > 0 && Math.abs(held - mid) < 844, mid + ' → ' + held);
+  check('…and lands square on a post when it lifts', (await at()) !== 'between', String(await at()));
+  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✅ a fast flick flies through the pager' : '\n❌ failed');
+process.exit(ok ? 0 : 1);