perf(app): defer video embed metadata probes until hover (#1893)

fluxer_app/src/features/channel/components/embeds/media/EmbedVideo.tsx

@@ -24,7 +24,7 @@ import {useMediaFavorite} from '@app/features/messaging/hooks/useMediaFavorite';
 import {useNearViewport} from '@app/features/messaging/hooks/useNearViewport';
 import {createDownloadHandler} from '@app/features/messaging/utils/FileDownloadUtils';
 import * as ImageCacheUtils from '@app/features/messaging/utils/ImageCacheUtils';
-import {buildMediaProxyURL} from '@app/features/messaging/utils/MediaProxyUtils';
+import {buildMediaProxyURL, mediaDevicePixelRatio} from '@app/features/messaging/utils/MediaProxyUtils';
 import {attachmentsToViewerItems, findViewerItemIndex} from '@app/features/messaging/utils/MediaViewerItemUtils';
 import {decodeThumbHashDataURL} from '@app/features/messaging/utils/ThumbHashUtils';
 import {remFromPx} from '@app/features/theme/layout/RemFromPx';
@@ -33,6 +33,7 @@ import * as ContextMenuCommands from '@app/features/ui/commands/ContextMenuComma
 import * as MediaViewerCommands from '@app/features/ui/commands/MediaViewerCommands';
 import MobileLayout from '@app/features/ui/state/MobileLayout';
 import {
+	detachMediaElementSource,
 	VideoPlayer,
 	type VideoPlayerMetadata,
 } from '@app/features/voice/components/media_player/components/VideoPlayer';
@@ -45,7 +46,7 @@ import {PlayIcon, SpeakerHighIcon, SpeakerXIcon} from '@phosphor-icons/react';
 import {AnimatePresence, motion} from 'framer-motion';
 import {observer} from 'mobx-react-lite';
 import type {FC} from 'react';
-import {useCallback, useEffect, useMemo, useRef, useState} from 'react';
+import {useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState} from 'react';
 
 const OPEN_VIDEO_DESCRIPTOR = msg({
 	message: 'Open video',
@@ -137,7 +138,8 @@ const MobileVideoOverlay: FC<{
 							exit={{opacity: 0}}
 							transition={{duration: Accessibility.useReducedMotion ? 0 : 0.2}}
 							src={thumbHashURL}
-							alt={title ? i18n._(THUMBNAIL_FOR_DESCRIPTOR, {title}) : i18n._(VIDEO_THUMBNAIL_DESCRIPTOR)}
+							alt=""
+							aria-hidden={true}
 							className={styles.thumbHashPlaceholder}
 							data-flx="channel.embeds.media.embed-video.mobile-video-overlay.thumbnail-placeholder"
 						/>
@@ -213,7 +215,12 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 		const messageViewContext = useMaybeMessageViewContext();
 		const effectiveSrc = buildMediaProxyURL(src);
 		const isBlob = src.startsWith('blob:');
-		const posterSrc = isBlob ? null : buildMediaProxyURL(src, {format: 'webp'});
+		const declaredLayout = resolveVideoLayout(getEffectiveVideoLayoutDimensions({width, height}, null), {
+			maxWidth,
+			maxHeight,
+		});
+		const posterRequestWidth = Math.max(1, Math.round(declaredLayout.renderDimensions.width * mediaDevicePixelRatio()));
+		const posterSrc = isBlob ? null : buildMediaProxyURL(src, {format: 'webp', width: posterRequestWidth});
 		const {ref: visibilityRef, isNearViewport} = useNearViewport<HTMLDivElement>({
 			rememberKey: posterSrc ?? effectiveSrc,
 		});
@@ -231,8 +238,16 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 		const [isPlayingInline, setIsPlayingInline] = useState(false);
 		const [decodedVideoDimensions, setDecodedVideoDimensions] = useState<DecodedVideoDimensions | null>(null);
 		const [posterNaturalDimensions, setPosterNaturalDimensions] = useState<DecodedVideoDimensions | null>(null);
+		const [metadataProbeArmed, setMetadataProbeArmed] = useState(false);
 		const inlineVideoRef = useRef<HTMLVideoElement>(null);
 		useInAppMediaSoundCapture(inlineVideoRef);
+		useLayoutEffect(() => {
+			if (!isPlayingInline) return;
+			const inlineVideo = inlineVideoRef.current;
+			return () => {
+				detachMediaElementSource(inlineVideo);
+			};
+		}, [isPlayingInline]);
 		const {shouldBlur, gateReason, canReveal, reveal: revealSensitiveMedia} = useMatureMedia(nsfw, channelId);
 		const shouldLoadMedia = isNearViewport && !shouldBlur;
 		const defaultName =
@@ -313,6 +328,8 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 				? !hasDifferentAspectRatio(decodedDimensionsForSrc, posterDimensionsForSrc, 0.05)
 				: true;
 		const effectivePosterSrc = posterMatchesVideo ? posterSrc : null;
+		const posterKnownLoaded = posterLoaded && posterMatchesVideo;
+		const presentedPosterSrc = shouldLoadMedia || posterKnownLoaded ? effectivePosterSrc : null;
 		const updateDecodedVideoDimensions = useCallback(
 			(nextWidth: number, nextHeight: number) => {
 				const nextDimensions = normalizeVideoDimensions({width: nextWidth, height: nextHeight});
@@ -481,6 +498,9 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 		const handleInitialPlay = useCallback(() => {
 			setHasPlayed(true);
 		}, []);
+		const handleMediaPointerEnter = useCallback(() => {
+			setMetadataProbeArmed(true);
+		}, []);
 		const containerStyles: React.CSSProperties = isMobile
 			? {
 					aspectRatio,
@@ -514,6 +534,7 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 								<img
 									src={thumbHashUrl}
 									alt=""
+									aria-hidden={true}
 									className={styles.blurThumbnail}
 									style={{filter: 'blur(40px)'}}
 									data-flx="channel.embeds.media.embed-video.blur-thumbnail"
@@ -537,7 +558,7 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 			{disableDelete: !!isPreview || snapshotIndex !== undefined},
 		);
 		const metadataProbe =
-			shouldLoadMedia && !fillContainer && !isBlob && !hasPlayed && !isPlayingInline ? (
+			metadataProbeArmed && shouldLoadMedia && !fillContainer && !isBlob && !hasPlayed && !isPlayingInline ? (
 				<video
 					aria-hidden="true"
 					className={styles.metadataProbe}
@@ -567,6 +588,7 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 					showDeleteButton={showDeleteButton}
 					onDeleteClick={handleDeleteClick}
 					onContextMenu={handleContextMenu}
+					onMouseEnter={handleMediaPointerEnter}
 					renderedWidth={dimensions.width}
 					renderedHeight={dimensions.height}
 					data-flx="channel.embeds.media.embed-video.media-container.context-menu"
@@ -579,6 +601,7 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 									ref={inlineVideoRef}
 									className={styles.inlineVideo}
 									src={effectiveSrc}
+									poster={presentedPosterSrc ?? undefined}
 									autoPlay
 									playsInline
 									muted={VideoVolume.isMuted}
@@ -613,9 +636,9 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 						) : (
 							<MobileVideoOverlay
 								thumbHashURL={thumbHashUrl}
-								posterSrc={shouldLoadMedia ? effectivePosterSrc : null}
-								posterLoaded={shouldLoadMedia && posterLoaded && posterMatchesVideo}
-								posterCachedOnMount={shouldLoadMedia && posterCachedOnMount && posterMatchesVideo}
+								posterSrc={presentedPosterSrc}
+								posterLoaded={posterKnownLoaded}
+								posterCachedOnMount={posterCachedOnMount && posterMatchesVideo}
 								onTap={handleMobileTap}
 								onPlayInline={handlePlayInline}
 								title={title}
@@ -641,6 +664,7 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 				showDeleteButton={showDeleteButton}
 				onDeleteClick={handleDeleteClick}
 				onContextMenu={handleContextMenu}
+				onMouseEnter={handleMediaPointerEnter}
 				renderedWidth={dimensions.width}
 				renderedHeight={dimensions.height}
 				data-flx="channel.embeds.media.embed-video.media-container.context-menu--2"
@@ -649,7 +673,7 @@ const EmbedVideo: FC<EmbedVideoProps> = observer(
 				<div className={styles.videoPlayerWrapper} data-flx="channel.embeds.media.embed-video.video-player-wrapper">
 					<VideoPlayer
 						src={effectiveSrc}
-						poster={shouldLoadMedia ? (effectivePosterSrc ?? undefined) : undefined}
+						poster={presentedPosterSrc ?? undefined}
 						placeholder={placeholder}
 						duration={duration}
 						width={dimensions.width}