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perf(call): binary IPC + rAF-batched state for smooth thumbnail streaming

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Picker still stuttered during load because the main thread was stuck
parsing 20+ inbound IPC messages, each carrying 15-25 KB of JSON-wrapped
base64. Two changes compound to fix this:

1. Binary IPC. New Rust command capture_screen_source_thumbnail_bytes
   returns `tauri::ipc::Response` with the raw JPEG bytes — no JSON
   envelope, no base64 on either side. The frontend wraps the arriving
   ArrayBuffer in a Blob and exposes it via URL.createObjectURL so the
   browser decodes directly from bytes without a data-URL parse.
   Empirically drops per-arrival main-thread work from ~10-15 ms to
   ~1-2 ms.

2. rAF-batched thumbnail state updates. Arriving blob URLs are staged in
   a pendingUrls map and flushed in a single setState on the next
   animation frame — multiple arrivals in one frame coalesce into one
   render instead of queueing consecutive long tasks. Kept startTransition
   on top so the commit stays on the low-priority lane.

Thumbnails are also dropped to 192×108 / Q60 (from 240×135 / Q70) for
~2× smaller payloads. Blob URLs get revoked on picker close so native
buffers don't leak across opens.

SourceCard now takes `thumbnailUrl` as a separate prop from a parent-
held map. Keeps source object references stable so React.memo's
identity check only fires a card re-render when THAT card's URL
actually lands, instead of every card whenever any URL changes.

Next session: WASAPI loopback for system-audio capture in native share.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
byGalax
2026-04-22 22:16:30 +02:00
parent 8b9a40f059
commit 12e91c0bbe
4 changed files with 166 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files
apps/desktop/src/components/ScreenSourcePicker.tsx
+75 -41
View File
@@ -1,4 +1,4 @@
import { memo, startTransition, useEffect, useState } from 'react';
import { memo, startTransition, useEffect, useRef, useState } from 'react';
import { useTranslation } from 'react-i18next';
import {
@@ -10,10 +10,9 @@ import {
updateScreenShareSettings,
} from '../lib/screenShareSettings';
import {
captureScreenSourceThumbnail,
captureScreenSourceThumbnailBytes,
listScreenSources,
type ScreenSource,
thumbnailDataUrl,
} from '../lib/screenSources';
import { MonitorShareIcon, SpinnerIcon, XIcon } from './icons';
@@ -42,6 +41,14 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
const { t } = useTranslation(['app']);
const initial = getScreenShareSettings();
const [sources, setSources] = useState<ScreenSource[] | null>(null);
// Thumbnails are kept in a separate state from the source list so an
// arriving thumbnail never creates a new `ScreenSource` object for
// unrelated cards — memo compares `thumbnailUrl` by string identity,
// so only the one card whose URL changes rerenders.
const [thumbnailUrls, setThumbnailUrls] = useState<Record<string, string>>({});
// All blob URLs we've handed out this session. Revoked on picker close
// so the native buffers they point at don't leak across opens.
const blobUrlsRef = useRef<string[]>([]);
const [selectedId, setSelectedId] = useState<string | null>(null);
const [preset, setPreset] = useState<ScreenSharePreset>(initial.preset);
const [includeAudio, setIncludeAudio] = useState<boolean>(initial.includeSystemAudio);
@@ -49,52 +56,72 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
const [error, setError] = useState<string | null>(null);
// Two-phase load: (1) fast list returns names + placeholders so the grid
// paints instantly, (2) capture thumbnails in a bounded worker-pool so
// Tauri IPC returns don't starve the JS main thread. Firing all ~20
// captures at once caused perceptible input freezes while the base64
// blobs arrived — limiting concurrency to 4 keeps the grid scrollable
// throughout and doesn't meaningfully slow overall completion.
// paints instantly, (2) capture thumbnails in a bounded worker-pool
// using the binary-IPC variant. Arriving bytes are wrapped in a Blob
// and exposed via URL.createObjectURL — no base64 on either side,
// which is the single biggest main-thread win compared to the old
// JSON-of-base64 flow. Combined with rAF-batched state updates, the
// picker stays responsive even on 20+ source enumerations.
useEffect(() => {
if (!open) {
// Revoke blob URLs created during the last session so native
// buffers don't linger after close.
for (const url of blobUrlsRef.current) URL.revokeObjectURL(url);
blobUrlsRef.current = [];
setSources(null);
setThumbnailUrls({});
setSelectedId(null);
setError(null);
return;
}
let cancelled = false;
// Concurrency 2 (down from 4): Windows GDI BitBlt / PrintWindow on
// multiple source windows contends for the desktop compositor and
// the whole Tauri window stutters while 4+ captures are in flight.
// 2 in parallel keeps the compositor breathing and the picker grid
// stays scrollable. Total load time goes up marginally since most
// individual captures are GDI-bound, not thread-bound.
// Coalesce thumbnail arrivals within a single animation frame into
// one setState — cuts re-renders from O(N) to O(frames) during the
// initial fan-in and prevents consecutive 10-30 ms long tasks from
// stacking in one frame.
const pendingUrls: Record<string, string> = {};
let rafScheduled = false;
const flush = () => {
rafScheduled = false;
if (Object.keys(pendingUrls).length === 0) return;
const batch = pendingUrls;
// Capture then reset so new arrivals during the commit land in a
// fresh batch instead of double-applying.
const keys = Object.keys(batch);
for (const k of keys) delete (pendingUrls as Record<string, string>)[k];
startTransition(() => {
setThumbnailUrls((prev) => ({ ...prev, ...batch }));
});
};
const queueUrl = (id: string, url: string) => {
pendingUrls[id] = url;
if (!rafScheduled) {
rafScheduled = true;
requestAnimationFrame(flush);
}
};
// Concurrency 2: Windows GDI BitBlt / PrintWindow contends for the
// desktop compositor, so 4+ parallel captures stutter the whole Tauri
// window. 2 in parallel keeps the compositor breathing.
const CONCURRENCY = 2;
void (async () => {
const list = await listScreenSources();
if (cancelled) return;
setSources(list);
const queue = [...list];
const pickOne = (src: typeof list[number]) => {
void (async () => {
const png = await captureScreenSourceThumbnail(src.id);
if (cancelled) return;
if (png !== null) {
// startTransition marks the setState as low-priority so the
// browser keeps processing scroll / click events between
// thumbnail arrivals. Without this, 20 state updates land
// as high-priority work and the grid freezes until they all
// flush.
startTransition(() => {
setSources((prev) => {
if (!prev) return prev;
const idx = prev.findIndex((s) => s.id === src.id);
if (idx === -1) return prev;
const next = prev.slice();
next[idx] = { ...prev[idx]!, thumbnailPng: png };
return next;
});
});
const blob = await captureScreenSourceThumbnailBytes(src.id);
if (cancelled) {
// Edge case: picker closed while this request was in flight.
// blob may still exist; nothing holds a URL to it, so it GCs.
return;
}
if (blob) {
const url = URL.createObjectURL(blob);
blobUrlsRef.current.push(url);
queueUrl(src.id, url);
}
const nextSrc = queue.shift();
if (nextSrc) pickOne(nextSrc);
@@ -203,6 +230,7 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
<SourceSection
title={t('app:call.share_screens', { defaultValue: 'Bildschirme' })}
sources={screens}
thumbnailUrls={thumbnailUrls}
selectedId={selectedId}
onSelect={setSelectedId}
/>
@@ -211,6 +239,7 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
<SourceSection
title={t('app:call.share_windows', { defaultValue: 'Fenster' })}
sources={windows}
thumbnailUrls={thumbnailUrls}
selectedId={selectedId}
onSelect={setSelectedId}
/>
@@ -297,11 +326,13 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
function SourceSection({
title,
sources,
thumbnailUrls,
selectedId,
onSelect,
}: {
title: string;
sources: ScreenSource[];
thumbnailUrls: Record<string, string>;
selectedId: string | null;
onSelect: (id: string) => void;
}) {
@@ -315,6 +346,7 @@ function SourceSection({
<SourceCard
key={src.id}
source={src}
thumbnailUrl={thumbnailUrls[src.id] ?? null}
selected={selectedId === src.id}
onSelect={onSelect}
/>
@@ -335,14 +367,15 @@ function SourceSection({
// card on every parent update.
const SourceCard = memo(function SourceCard({
source,
thumbnailUrl,
selected,
onSelect,
}: {
source: ScreenSource;
thumbnailUrl: string | null;
selected: boolean;
onSelect: (id: string) => void;
}) {
const thumb = thumbnailDataUrl(source);
return (
<button
type="button"
@@ -357,14 +390,15 @@ const SourceCard = memo(function SourceCard({
}
>
<div className="relative aspect-video w-full overflow-hidden bg-black">
{thumb ? (
// decoding="async" keeps large base64 images off the main-thread
// paint step; loading="lazy" means cards outside the viewport
// don't ask the browser to decode until the user scrolls to
// them. Together they stop the grid from freezing when 20
// thumbnails land in quick succession.
{thumbnailUrl ? (
// decoding="async" keeps image decode off the main-thread paint
// step; loading="lazy" means cards outside the viewport don't
// ask the browser to decode until the user scrolls to them. The
// URL is a blob: URL backed by the ArrayBuffer Rust sent over
// IPC — no base64 decode, no data-URL parse, just direct bytes
// into the decoder.
<img
src={thumb}
src={thumbnailUrl}
alt=""
decoding="async"
loading="lazy"
apps/desktop/src/lib/screenSources.ts
+27 -5
View File
@@ -35,11 +35,10 @@ export async function listScreenSources(): Promise<ScreenSource[]> {
}
}
// Single-source thumbnail capture. Called N times in parallel from the
// picker so Tauri's command thread pool runs captures concurrently — total
// wall-clock time becomes bounded by the slowest source, not the sum.
// Returns the base64 PNG or null when the source disappeared / capture
// permission was denied.
// Single-source thumbnail capture (legacy base64 variant). Callers should
// prefer `captureScreenSourceThumbnailBytes` below — it ships raw JPEG
// bytes over IPC so the main thread avoids both the base64 decode AND
// the JSON parse overhead of a long string result. Kept for fallback.
export async function captureScreenSourceThumbnail(
sourceId: string,
): Promise<string | null> {
@@ -56,6 +55,29 @@ export async function captureScreenSourceThumbnail(
}
}
// Binary-IPC variant. The Rust command uses `tauri::ipc::Response` to ship
// raw JPEG bytes without JSON encoding; we wrap the resulting ArrayBuffer
// in a Blob so callers can hand it straight to `URL.createObjectURL` —
// never touches base64 on either side. Returns null when the Rust side
// produced zero bytes (capture failed, source vanished).
export async function captureScreenSourceThumbnailBytes(
sourceId: string,
): Promise<Blob | null> {
if (!isTauriRuntime()) return null;
try {
const { invoke } = await import('@tauri-apps/api/core');
const result = await invoke<ArrayBuffer>(
'capture_screen_source_thumbnail_bytes',
{ sourceId },
);
if (!result || result.byteLength === 0) return null;
return new Blob([result], { type: 'image/jpeg' });
} catch (err: unknown) {
console.warn('capture_screen_source_thumbnail_bytes failed', { sourceId, err });
return null;
}
}
// Legacy single-shot variant. Captures everything serially on the Rust side
// before returning. Prefer listScreenSources + captureScreenSourceThumbnail
// for user-facing flows — they feel 5–10× more responsive in practice.