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fix(frontend): stop trimming the file grid while scrolling

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The grid windowed to ~4 viewports, dropping off-screen rows as it grew.
That broke large multi-selects: range/drag selection could not span past
trimmed cards, which silently vanished mid-scroll. Accumulate all loaded
rows for the visit instead; the grid is still cleared on sort/filter
change and on leaving the page (reset effect + section cache). Removes
the now-dead trim/anchor-refill fallbacks in loadMore/loadPrev.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Masahiko AMANO
2026-06-15 23:27:19 +03:00
parent 95db88388b
commit 97d6daaa13
1 changed files with 21 additions and 100 deletions
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frontend/src/routes/files/+page.svelte
+21 -100
View File
@@ -484,32 +484,14 @@
// between) so there's no visible jump. Shares the `loading` guard with loadMore
// so the two never mutate files concurrently.
async function loadPrev() {
if (loading || !hasPrev) return;
if (loading || !hasPrev || !prevCursor) return;
loading = true;
try {
let items: File[];
let newPrevCursor: string | null;
if (prevCursor) {
const params = baseListParams();
params.set('cursor', prevCursor);
params.set('direction', 'backward');
const res = await api.get<FileCursorPage>(`/files?${params}`);
items = res.items ?? [];
newPrevCursor = res.prev_cursor ?? null;
} else {
// The head cursor was dropped when the window trimmed its top. Refetch
// the rows just before the current first file from an anchored window.
const firstId = files[0]?.id;
if (!firstId) {
hasPrev = false;
return;
}
const res = await fetchAnchorWindow(firstId);
const all = res.items ?? [];
const idx = all.findIndex((f) => f.id === firstId);
items = idx > 0 ? all.slice(0, idx) : [];
newPrevCursor = res.prev_cursor ?? null;
}
const params = baseListParams();
params.set('cursor', prevCursor);
params.set('direction', 'backward');
const res = await api.get<FileCursorPage>(`/files?${params}`);
const items = res.items ?? [];
if (items.length === 0) {
hasPrev = false;
return;
@@ -522,13 +504,11 @@
const beforeHeight = scroller.scrollHeight;
files = [...items, ...files];
prevCursor = newPrevCursor;
hasPrev = !!newPrevCursor;
prevCursor = res.prev_cursor ?? null;
hasPrev = !!prevCursor;
flushSync(); // apply the prepend now, before the browser paints
scroller.scrollTop = beforeTop + (scroller.scrollHeight - beforeHeight);
trimTail();
} catch {
hasPrev = false;
} finally {
@@ -550,85 +530,26 @@
return (document.scrollingElement as HTMLElement | null) ?? document.documentElement;
}
// ---- Windowing -----------------------------------------------------------
// The grid keeps at most ~4 viewports of rows in memory. As it grows past the
// cap on one end, the off-screen rows on the other end are trimmed; the cursor
// for the trimmed boundary is dropped (set null) and the opposite `has*` flag
// is raised, so scrolling back refills that side from an anchored window.
// ---- Loaded grid -----------------------------------------------------------
// The grid accumulates every loaded row for the lifetime of the visit. It is
// only cleared on a sort/filter change or when leaving the page (the reset
// effect above; the section cache restores it on return). Rows are never
// trimmed while scrolling, so a long drag- or shift-select can span the whole
// loaded list without earlier cards disappearing underneath it.
const CARD_PITCH = 162; // 160px thumbnail + 2px grid gap
function windowCap(): number {
const scroller = getScroller();
const w = scroller.clientWidth || 390;
const h = scroller.clientHeight || 700;
const cols = Math.max(1, Math.floor(w / CARD_PITCH));
const rows = Math.max(1, Math.ceil(h / CARD_PITCH));
return Math.max(4 * cols * rows, 2 * LIMIT);
}
// Fetch a window centred on a file (with its boundary cursors), used to refill
// a trimmed edge where the original cursor is no longer held.
function fetchAnchorWindow(anchorId: string): Promise<FileCursorPage> {
const a = baseListParams();
a.set('anchor', anchorId);
return api.get<FileCursorPage>(`/files?${a}`);
}
// Drop the off-screen rows above the viewport once the grid grew past the cap.
// Run after appended rows have painted so the height delta measures only the
// removed top; scroll is compensated so the visible rows don't jump.
function trimHead() {
const cap = windowCap();
if (files.length <= cap) return;
flushSync(); // paint the just-appended (below-fold) rows before measuring
const scroller = getScroller();
const beforeTop = scroller.scrollTop;
const beforeHeight = scroller.scrollHeight;
files = files.slice(files.length - cap);
prevCursor = null;
hasPrev = true;
flushSync();
scroller.scrollTop = beforeTop + (scroller.scrollHeight - beforeHeight);
}
// Symmetric to trimHead for upward growth: drop the off-screen rows below the
// viewport. No scroll compensation — the removed rows are past the fold.
function trimTail() {
const cap = windowCap();
if (files.length <= cap) return;
files = files.slice(0, cap);
nextCursor = null;
hasMore = true;
}
const CARD_PITCH = 162; // 160px thumbnail + 2px grid gap (used for grid math)
async function loadMore() {
if (loading || !hasMore) return;
loading = true;
error = '';
try {
let newItems: File[];
let newNextCursor: string | null;
if (nextCursor == null && files.length > 0) {
// The tail cursor was dropped when the window trimmed its bottom.
// Refetch the rows after the current last file from an anchored window.
const lastId = files[files.length - 1]?.id;
const res = await fetchAnchorWindow(lastId!);
const all = res.items ?? [];
const idx = all.findIndex((f) => f.id === lastId);
newItems = idx >= 0 ? all.slice(idx + 1) : [];
newNextCursor = res.next_cursor ?? null;
} else {
const params = baseListParams();
if (nextCursor) params.set('cursor', nextCursor);
const res = await api.get<FileCursorPage>(`/files?${params}`);
newItems = res.items ?? [];
newNextCursor = res.next_cursor ?? null;
}
files = [...files, ...newItems];
nextCursor = newNextCursor;
hasMore = !!newNextCursor;
trimHead();
const params = baseListParams();
if (nextCursor) params.set('cursor', nextCursor);
const res = await api.get<FileCursorPage>(`/files?${params}`);
files = [...files, ...(res.items ?? [])];
nextCursor = res.next_cursor ?? null;
hasMore = !!nextCursor;
} catch (err) {
error = err instanceof ApiError ? err.message : 'Failed to load files';
hasMore = false;