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feat: preload the current chapter ahead of the reader

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Continuous mode eager-loaded only pages 0..=initialIndex; everything
below stayed `loading="lazy"`, so pages fetched and reflowed in as they
scrolled into view. Now a rolling window eager-loads a few pages ahead of
the reading position (PRELOAD_AHEAD) so they arrive — fetched and sized —
while still below the fold, then swap in without pop-in.

The window rolls forward off `scrollLeadIdx`, the top-of-viewport page
measured from live rects and guarded by `scrollY`. It deliberately does
not use the read-progress high-water mark: before images load they are
0-height and pile into the viewport, which would latch that mark to the
last page and eager-load the whole chapter on open. Pages past the window
stay lazy so opening a long chapter doesn't fetch every page at once.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
MechaCat02
2026-07-07 19:39:50 +02:00
parent 51ea254dde
commit c69ff502f7
6 changed files with 156 additions and 26 deletions
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2
backend/Cargo.lock generated
View File

@@ -1558,7 +1558,7 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
[[package]]
name = "mangalord"
version = "0.122.1"
version = "0.123.0"
dependencies = [
"anyhow",
"argon2",

2
backend/Cargo.toml
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@@ -1,6 +1,6 @@
[package]
name = "mangalord"
version = "0.122.1"
version = "0.123.0"
edition = "2021"
default-run = "mangalord"

40
frontend/e2e/reader-page-deep-link.spec.ts
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@@ -171,41 +171,39 @@ test.describe('reader ?page=N deep link', () => {
await expect(page.getByTestId('reader-continuous')).toBeVisible();
// Pages 1..=4 (1-indexed in the testid, 0-indexed in the
// template; initialIndex = 3 means we eager-load 0..=3, i.e.
// testids 1..4). Without this guard, page 2+ would be lazy
// template; initialIndex = 3 means we eager-load at least 0..=3,
// i.e. testids 1..4). Without this guard, page 2+ would be lazy
// and their 0×0 placeholders would let the scroll target
// appear far above its final position.
for (const n of [1, 2, 3, 4]) {
// appear far above its final position. The rolling preload window
// (PRELOAD_AHEAD) extends the eager set a few pages past the
// target, so on this 6-page chapter every page is eager.
for (const n of [1, 2, 3, 4, 5, 6]) {
await expect(page.getByTestId(`reader-page-${n}`)).toHaveAttribute(
'loading',
'eager'
);
}
// Pages beyond the target stay lazy.
for (const n of [5, 6]) {
await expect(page.getByTestId(`reader-page-${n}`)).toHaveAttribute(
'loading',
'lazy'
);
}
});
test('continuous mode: no ?page= eager-loads only the first two', async ({
test('continuous mode: no ?page= eager-loads a leading preload window, not the whole chapter', async ({
page
}) => {
await mockReader(page, 'continuous');
await page.goto(`/manga/${mangaId}/chapter/${chapterId}`);
await expect(page.getByTestId('reader-continuous')).toBeVisible();
await expect(page.getByTestId('reader-page-1')).toHaveAttribute(
'loading',
'eager'
);
await expect(page.getByTestId('reader-page-2')).toHaveAttribute(
'loading',
'eager'
);
await expect(page.getByTestId('reader-page-3')).toHaveAttribute(
// initialIndex = 0; the rolling window (PRELOAD_AHEAD = 3) eager-loads
// the first few pages ahead of the reader so they don't pop in on
// scroll ...
for (const n of [1, 2, 3]) {
await expect(page.getByTestId(`reader-page-${n}`)).toHaveAttribute(
'loading',
'eager'
);
}
// ... while the tail stays lazy so a long chapter doesn't fetch every
// page at once on open.
await expect(page.getByTestId('reader-page-6')).toHaveAttribute(
'loading',
'lazy'
);

74
frontend/e2e/reader-preload-window.spec.ts Normal file
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@@ -0,0 +1,74 @@
import { test, expect, type Page } from './fixtures';
// Continuous mode eager-loads a rolling window of pages ahead of the reading
// position, so pages are fetched (and sized) before they scroll into view
// instead of popping in / reflowing on scroll. Pages far beyond the window
// stay lazy so opening a long chapter doesn't fire every request at once.
const MANGA_ID = 'm1';
const CH1 = 'c1';
const PAGE_COUNT = 10;
function pages(prefix: string, n: number) {
return Array.from({ length: n }, (_, i) => ({
id: `${prefix}p${i + 1}`,
chapter_id: prefix,
page_number: i + 1,
storage_key: `${prefix}/${i + 1}`,
content_type: 'image/svg+xml'
}));
}
function chapter(id: string, number: number, count: number) {
return { id, manga_id: MANGA_ID, number, title: null, page_count: count, created_at: '2026-01-01T00:00:00Z', size_bytes: 0 };
}
async function mockReader(page: Page) {
await page.route('**/api/v1/**', async (route) => {
const { pathname } = new URL(route.request().url());
const json = (status: number, body: unknown) =>
route.fulfill({ status, contentType: 'application/json', body: JSON.stringify(body) });
if (pathname.includes('/files/')) {
// A viewBox + rect gives the <img> a real intrinsic size so pages
// get real (tall) heights — offscreen pages then stay below the
// fold instead of collapsing to 0 and piling into the viewport.
return route.fulfill({ status: 200, contentType: 'image/svg+xml', body: '<svg xmlns="http://www.w3.org/2000/svg" width="800" height="1200" viewBox="0 0 800 1200"><rect width="800" height="1200" fill="#888"/></svg>' });
}
if (pathname.endsWith('/auth/config')) return json(200, { self_register_enabled: true, private_mode: false });
if (pathname.endsWith('/auth/me')) return json(401, { error: { code: 'unauthenticated', message: 'no' } });
if (pathname.endsWith('/auth/me/preferences')) return json(401, { error: { code: 'unauthenticated', message: 'no' } });
if (pathname.endsWith(`/chapters/${CH1}/pages`)) return json(200, { pages: pages(CH1, PAGE_COUNT) });
if (pathname.endsWith(`/chapters/${CH1}`)) return json(200, chapter(CH1, 1, PAGE_COUNT));
if (pathname.includes(`/mangas/${MANGA_ID}/chapters`)) {
return json(200, { items: [chapter(CH1, 1, PAGE_COUNT)], page: { limit: 200, offset: 0, total: 1 } });
}
if (pathname.endsWith(`/mangas/${MANGA_ID}`)) return json(200, { id: MANGA_ID, title: 'Berserk', status: 'ongoing', alt_titles: [], description: null, cover_image_path: null, created_at: '2026-01-01T00:00:00Z', updated_at: '2026-01-01T00:00:00Z', authors: [], genres: [], tags: [], content_warnings: [], chapter_storage_bytes: 0 });
if (pathname.includes('/me/read-progress')) return json(401, { error: { code: 'unauthenticated', message: 'no' } });
return json(503, { error: { code: 'e2e_unmocked', message: pathname } });
});
}
async function goContinuous(page: Page, path: string) {
await page.addInitScript(() => localStorage.setItem('mangalord-reader-mode', 'continuous'));
await page.goto(path);
await expect(page.getByTestId('reader-continuous')).toBeVisible();
}
test('opening at page 1 eager-loads the leading window but leaves far pages lazy', async ({ page }) => {
await mockReader(page);
await goContinuous(page, `/manga/${MANGA_ID}/chapter/${CH1}`);
// The first page is always eager (it's on screen).
await expect(page.getByTestId('reader-page-1')).toHaveAttribute('loading', 'eager');
// A page far past the leading window is not fetched up front.
await expect(page.getByTestId('reader-page-10')).toHaveAttribute('loading', 'lazy');
});
test('opening deep in the chapter eager-loads the pages around that position', async ({ page }) => {
await mockReader(page);
// Deep-link to page 8: the window now covers the tail, so page 10 is eager.
await goContinuous(page, `/manga/${MANGA_ID}/chapter/${CH1}?page=8`);
await expect(page.getByTestId('reader-page-10')).toHaveAttribute('loading', 'eager');
});

2
frontend/package.json
View File

@@ -1,6 +1,6 @@
{
"name": "mangalord-frontend",
"version": "0.122.1",
"version": "0.123.0",
"private": true,
"type": "module",
"scripts": {

62
frontend/src/routes/manga/[id]/chapter/[chapter_id]/+page.svelte
View File

@@ -971,6 +971,61 @@
const furthestPage = $derived(mode === 'single' ? index + 1 : progressPage);
// ---- Current-chapter rolling preload window (continuous mode) ----
// Eager-load pages up to this index so they're fetched (and sized) a few
// pages ahead of the reading position — they arrive while still below the
// fold instead of popping in / reflowing as the user scrolls onto them.
// Pages past the window stay lazy so opening a long chapter doesn't fire
// every request at once.
//
// The window anchors on `initialIndex` (deterministic at open, and keeps
// the scroll-settle guarantee that pages `0..=initialIndex` are eager) and
// rolls forward by `scrollLeadIdx` — the page at the top of the viewport,
// measured from live geometry below. It deliberately does NOT use the
// read-progress high-water (`furthestPage`): before images load they're
// 0-height and pile into the viewport, which latches that mark to the last
// page and would eager-load the whole chapter on open.
const PRELOAD_AHEAD = 3;
let scrollLeadIdx = $state(0);
const eagerThrough = $derived(
Math.max(1, initialIndex, scrollLeadIdx) + PRELOAD_AHEAD
);
// Track the top-of-viewport page from live rects so the window rolls with
// actual scrolling. Guarded by `scrollY` so the pre-load 0-height pile-up
// (all rects collapsed near the top) can't inflate the lead at open.
$effect(() => {
if (!browser || mode !== 'continuous') return;
const measure = () => {
if (window.scrollY < 4) {
scrollLeadIdx = 0;
return;
}
const els = continuousPageEls;
for (let i = 0; i < els.length; i++) {
if (els[i] && els[i].getBoundingClientRect().bottom > 1) {
scrollLeadIdx = i;
return;
}
}
scrollLeadIdx = Math.max(0, els.length - 1);
};
measure();
let raf = 0;
const onScroll = () => {
if (raf) return;
raf = requestAnimationFrame(() => {
raf = 0;
measure();
});
};
window.addEventListener('scroll', onScroll, { passive: true });
return () => {
window.removeEventListener('scroll', onScroll);
if (raf) cancelAnimationFrame(raf);
};
});
$effect(() => {
const nc = nextChapter;
// Drop a previous chapter's warmed images once the next chapter
@@ -1308,12 +1363,15 @@
load scroll-to-`?page=N` effect fires. Without this,
`scrollIntoView(target)` lands while prior pages are
still 0×0 placeholders and the target gets pushed
past the viewport as they load. -->
past the viewport as they load. `eagerThrough` widens
that set into a rolling window a few pages ahead of the
reading position so pages load before they're scrolled
onto rather than filling in underneath the viewport. -->
<img
src={fileUrl(p.storage_key)}
alt={`${manga.title} chapter ${chapter.number} page ${i + 1}`}
class="page-image"
loading={i <= Math.max(1, initialIndex) ? 'eager' : 'lazy'}
loading={i <= eagerThrough ? 'eager' : 'lazy'}
oncontextmenu={(e) => onPageContextMenu(e, p.id)}
onpointerdown={(e) => onPagePointerDown(e, p.id)}
onpointermove={onPagePointerMove}