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fix: re-anchor stray iOS layout-viewport scroll that broke nav taps

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This commit is contained in:
Jonathan Sykes
2026-07-02 21:48:31 +08:00
parent a73781a048
commit 722457312c
2 changed files with 108 additions and 2 deletions
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43
frontend/app.js
View File

@@ -2303,6 +2303,40 @@ function setupPortraitPwaWatcher() {
});
}
// ============================================================================
// Layout-viewport anchor guard (iOS Safari / standalone PWA)
//
// The app is a fixed-viewport layout: body is overflow:hidden and only inner
// panes scroll, so the document itself must always sit at scroll position 0.
// iOS WebKit can still scroll the *layout viewport* behind our back — exiting
// native video fullscreen (webkitEnterFullscreen is the only fullscreen path
// on iPhone, and iOS enters it by itself when the phone rotates while a video
// plays), the on-screen keyboard revealing a focused input, or any
// scrollIntoView() walking up into <html>. Once that happens, fixed elements
// (bottom nav, mini-bar) are still *drawn* in place but their hit-testing
// regions are offset by the stray scroll amount, so taps on the nav buttons
// silently do nothing — and because the body isn't user-scrollable there is
// no gesture that can undo it. That is the "nav buttons stop working after
// playing a video" iPhone bug. Snap the document back to 0 whenever it ends
// up scrolled; skipped while an input is focused so we never fight the
// keyboard auto-scroll, then re-anchored once focus leaves the field.
function setupViewportAnchorGuard() {
const editing = () => {
const el = document.activeElement;
return !!el && (el.tagName === 'INPUT' || el.tagName === 'TEXTAREA' || el.isContentEditable);
};
const reanchor = () => {
if (editing()) return;
const doc = document.scrollingElement || document.documentElement;
if (window.scrollY || doc.scrollTop) window.scrollTo(0, 0);
};
window.addEventListener('scroll', reanchor);
document.addEventListener('focusout', () => setTimeout(reanchor, 50));
// Exiting native video fullscreen is the most reliable reproducer of the
// stray-scroll state; the scroll event alone doesn't always fire for it.
els.video.addEventListener('webkitendfullscreen', () => setTimeout(reanchor, 50));
}
// ============================================================================
// Events
// ============================================================================
@@ -2649,8 +2683,12 @@ document.querySelectorAll('.chip').forEach((c) => {
$('miniPlayBtn').addEventListener('click', (e) => { e.stopPropagation(); Player.toggle(); });
$('miniBar').addEventListener('click', () => {
hideMiniBar();
// Scroll the player into view if needed
els.playerPane.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
// Scroll the player into view if needed. In portrait PWA, scroll only the
// list-pane (the designated scroll container) — scrollIntoView() also
// scrolls overflow:hidden ancestors up to <html> on iOS, leaving the
// document offset and fixed-element hit testing broken.
if (isPortraitPWA()) scrollPlayerIntoViewPortrait();
else els.playerPane.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
});
$('miniCloseBtn').addEventListener('click', (e) => { e.stopPropagation(); hideMiniBar(); });
@@ -3104,6 +3142,7 @@ async function boot() {
wireUI();
wireShortcutHelp();
setupPortraitPwaWatcher();
setupViewportAnchorGuard();
try {
const loaded = await API.loadData();
if (loaded && typeof loaded === 'object') {

67
tests/viewport-anchor.smoke.spec.js Normal file
View File

@@ -0,0 +1,67 @@
/**
* Smoke test for the layout-viewport anchor guard.
*
* Bug: on an iPhone running the installed PWA, playing a video sometimes left
* the bottom-nav buttons unresponsive. iOS WebKit can scroll the document's
* layout viewport behind the app's back (exiting native video fullscreen,
* keyboard dismissal, scrollIntoView walking up into <html>) even though the
* body is overflow:hidden. Fixed elements are then still drawn in place but
* their hit-testing regions are offset by the stray scroll amount, so taps on
* the nav do nothing — and no user gesture can scroll the document back.
*
* The guard (setupViewportAnchorGuard in app.js) snaps the document back to 0
* whenever it ends up scrolled, except while an input is focused (so it never
* fights the on-screen keyboard); it re-anchors on blur instead.
*
* The static test page doesn't overflow, so each test injects a tall spacer
* and relaxes the overflow clamp — simulating the scrollable-document state
* iOS leaves behind.
*/
const { test, expect } = require('@playwright/test');
test.describe('Viewport anchor guard — stray document scroll', () => {
test.beforeEach(async ({ page }) => {
await page.goto('/');
await page.waitForSelector('.app', { state: 'attached' });
await page.evaluate(() => {
const spacer = document.createElement('div');
spacer.style.height = '3000px';
document.body.appendChild(spacer);
document.documentElement.style.overflow = 'visible';
document.body.style.overflow = 'visible';
});
});
test('snaps the document back to 0 after a stray window scroll', async ({ page }) => {
await page.evaluate(() => {
// boot() focuses the search input; release it so the guard is active.
if (document.activeElement) document.activeElement.blur();
window.scrollTo(0, 400);
});
await page.waitForFunction(() => window.scrollY === 0);
expect(await page.evaluate(() => window.scrollY)).toBe(0);
});
test('leaves the scroll alone while an input is focused (keyboard), re-anchors on blur', async ({ page }) => {
await page.evaluate(() => {
document.getElementById('searchInput').focus();
window.scrollTo(0, 300);
});
// Guard must not fight the keyboard-driven scroll while editing.
await page.waitForTimeout(200);
expect(await page.evaluate(() => window.scrollY)).toBeGreaterThan(0);
await page.evaluate(() => document.getElementById('searchInput').blur());
await page.waitForFunction(() => window.scrollY === 0);
});
test('re-anchors when native video fullscreen exits (webkitendfullscreen)', async ({ page }) => {
await page.evaluate(() => {
if (document.activeElement) document.activeElement.blur();
window.scrollTo(0, 250);
document.getElementById('video').dispatchEvent(new Event('webkitendfullscreen'));
});
await page.waitForFunction(() => window.scrollY === 0);
expect(await page.evaluate(() => window.scrollY)).toBe(0);
});
});