Media pager: a flick flies from an ordinary brisk swipe, and further. A flight took a hard fling (3 px/ms, coasting 500 ms) — Adam, 2026-10-16: "too hard to get it to fly". Now from 1.6 px/ms, coasting 800 ms (so a brisk swipe is two posts, a hard flick five or six), and the finger's speed is its average over its last 80 ms rather than its last five samples — at a phone's 120 Hz those were a third of that, and the finger slowing as it lifts hid the flick. tools/pager-swipe-fly-test.js: the quick flick is three big moves on a schedule from the start (a move's handling in a headless browser takes 30–50 ms, so a paced flick came out a stroll), flying three to six posts; a 320px swipe over 130ms is still one post; 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, 15 insertions, 12 deletions

diff --git a/tools/pager-swipe-fly-test.js b/tools/pager-swipe-fly-test.js
index 63af647..36fa816 100644
--- a/tools/pager-swipe-fly-test.js
+++ b/tools/pager-swipe-fly-test.js
@@ -35,9 +35,10 @@ const waitFor = async (fn, arg, ms = 10000) => { for (let i = 0; i < ms / 100; i
 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.
+// quick one is dispatched inside the page, as fast as the handlers take
+// the moves (about 30–50 ms each here, headless): the browser's own touch
+// simulation takes a round trip per move on top, 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);
@@ -49,9 +50,11 @@ const swipe = async (px, ms, steps = 6) => {
     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); };
+    // on a schedule from the start, not a pause after each move: a move's
+    // handling (the slides following the finger) takes its own time
+    const t0 = performance.now();
     fire('touchstart', 700);
-    for (let i = 1; i <= steps; i++) { spin(ms / steps); fire('touchmove', 700 - px * i / steps); }
+    for (let i = 1; i <= steps; i++) { while (performance.now() < t0 + ms * i / steps); fire('touchmove', 700 - px * i / steps); }
     fire('touchend', 700 - px, true);
   }, [px, ms, steps]);
 };
@@ -88,24 +91,24 @@ try {
 
   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 tr = await trace(() => swipe(600, 80, 3)); await settled(); // three big moves: 3–6 px/ms as their handling takes, three posts' worth of coast and up
   const landed = await at();
-  check('a 420px flick in 72ms flies three posts on', landed === 5, String(landed));
+  check('a 600px flick in a few frames flies three to six posts on', landed >= 5 && landed <= 8, 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();
+  while ((await at()) < 7) { 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();
+  await swipe(600, 80, 3); await settled();
+  check('from post ' + before + ' (a flight\'s worth would be past the end), a flick lands on the last post', before >= 7 && (await at()) === N, String(await at()));
+  await swipe(600, 80, 3); 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 swipe(600, 80, 3);
   await sleep(120);
   const mid = await page.evaluate(() => document.querySelector('.mp-scroll').scrollTop);
   await page.touchscreen.touchStart(195, 500);