perf(app): window emoji picker rows by offset instead of observers (#1870)

fluxer_app/src/features/channel/components/EmojiPicker.module.css

@@ -236,6 +236,7 @@
 .headerIcon {
 	height: 1rem;
 	width: 1rem;
+	color: var(--text-primary-muted);
 }
 
 .caretIcon {
@@ -384,6 +385,11 @@
 	width: 100%;
 }
 
+.emojiGridFixedTrack {
+	grid-auto-flow: column;
+	justify-content: start;
+}
+
 .emojiGridCategory {
 	margin-bottom: 1rem;
 }
@@ -437,6 +443,15 @@
 	object-fit: contain;
 }
 
+.emojiImageLoading {
+	color: transparent;
+	object-position: 6.25rem;
+	background-color: var(--background-modifier-accent);
+	background-repeat: no-repeat;
+	background-size: 100% 100%;
+	border-radius: 0.125rem;
+}
+
 .spriteEmoji {
 	width: 2rem;
 	height: 2rem;

fluxer_app/src/features/channel/components/EmojiPicker.tsx

@@ -1,11 +1,20 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
+import Accessibility from '@app/features/accessibility/state/Accessibility';
 import {PREMIUM_PRODUCT_NAME} from '@app/features/app/config/I18nDisplayConstants';
 import {useSearchInputAutofocus} from '@app/features/app/hooks/useSearchInputAutofocus';
 import {useShouldAnimate} from '@app/features/app/hooks/useShouldAnimate';
 import styles from '@app/features/channel/components/EmojiPicker.module.css';
 import {EmojiPickerCategoryList} from '@app/features/channel/components/emoji_picker/EmojiPickerCategoryList';
-import {getEmojiGridColumns} from '@app/features/channel/components/emoji_picker/EmojiPickerConstants';
+import {
+	buildEmojiRowOffsets,
+	EMOJI_GRID_TRACK_WIDTH,
+	EMOJI_ROW_HEIGHT,
+	EMOJI_SECTION_GAP,
+	type EmojiRowKind,
+	getEmojiGridColumns,
+	getEmojiRowWindow,
+} from '@app/features/channel/components/emoji_picker/EmojiPickerConstants';
 import {EmojiPickerInspector} from '@app/features/channel/components/emoji_picker/EmojiPickerInspector';
 import {EmojiPickerSearchBar} from '@app/features/channel/components/emoji_picker/EmojiPickerSearchBar';
 import {useEmojiCategories} from '@app/features/channel/components/emoji_picker/hooks/useEmojiCategories';
@@ -27,18 +36,28 @@ import {
 	shouldShowEmojiPremiumUpsell,
 } from '@app/features/expressions/utils/ExpressionPermissionUtils';
 import {getEmojiDisplayDataWithSkinTone} from '@app/features/expressions/utils/SkinToneUtils';
+import {getEmojiRenderUrl} from '@app/features/messaging/utils/markdown/EmojiDetector';
 import Permission from '@app/features/permissions/state/Permission';
 import {ComponentBus} from '@app/features/platform/utils/ComponentBus';
 import {usePremiumUpsellData} from '@app/features/premium/hooks/usePremiumUpsellData';
 import {shouldShowPremiumFeatures} from '@app/features/premium/utils/PremiumUtils';
 import {Scroller, type ScrollerHandle} from '@app/features/ui/components/Scroller';
-import * as AvatarUtils from '@app/features/user/utils/AvatarUtils';
+import {getAppRemScale} from '@app/features/ui/utils/AppZoomUtils';
 import {msg} from '@lingui/core/macro';
 import {Plural, Trans, useLingui} from '@lingui/react/macro';
 import {SmileySadIcon} from '@phosphor-icons/react';
 import {observer} from 'mobx-react-lite';
 import type React from 'react';
-import {useCallback, useContext, useEffect, useMemo, useRef, useState, useSyncExternalStore} from 'react';
+import {
+	useCallback,
+	useContext,
+	useEffect,
+	useLayoutEffect,
+	useMemo,
+	useRef,
+	useState,
+	useSyncExternalStore,
+} from 'react';
 
 const NO_EMOJIS_MATCH_YOUR_SEARCH_DESCRIPTOR = msg({
 	message: 'No emojis match that search',
@@ -58,14 +77,15 @@ export const EmojiPicker = observer(
 		const [selectedColumn, setSelectedColumn] = useState(-1);
 		const [shouldScrollOnSelection, setShouldScrollOnSelection] = useState(false);
 		const scrollerRef = useRef<ScrollerHandle>(null);
-		const {viewportSize, handleResize} = useScrollerViewport(scrollerRef);
+		const {viewportSize, scrollTop, handleScroll, handleResize} = useScrollerViewport(scrollerRef);
 		const gridColumns = useMemo(() => getEmojiGridColumns(viewportSize.width), [viewportSize.width]);
 		const searchInputRef = useRef<HTMLInputElement>(null);
 		const emojiRefs = useRef<Map<string, HTMLButtonElement>>(new Map());
 		const normalizedSearchTerm = useMemo(() => normalizeEmojiSearchQuery(searchTerm), [searchTerm]);
 		const {i18n} = useLingui();
 		const channel = channelId ? (Channels.getChannel(channelId) ?? null) : null;
-		const categoryRefs = useRef<Map<string, HTMLDivElement>>(new Map());
+		const rowListRef = useRef<HTMLDivElement>(null);
+		const [listMetrics, setListMetrics] = useState({origin: 0, viewportHeight: 0});
 		const [emojiDataVersion, setEmojiDataVersion] = useState(0);
 		const permissionVersion = useSyncExternalStore(Permission.subscribe.bind(Permission), () => Permission.version);
 		const skinTone = Emoji.skinTone;
@@ -80,15 +100,16 @@ export const EmojiPicker = observer(
 				const key = emoji.id ?? emoji.uniqueName ?? emoji.name ?? `${emoji.guildId ?? 'unicode'}-preview`;
 				const {url: fallbackDisplayUrl} = getEmojiDisplayDataWithSkinTone(emoji, skinTone);
 				const displayUrl = emoji.id
-					? AvatarUtils.getEmojiURL({id: emoji.id, animated: Boolean(emoji.animated) && shouldAnimateEmoji})
+					? getEmojiRenderUrl({
+							id: emoji.id,
+							surrogateUrl: null,
+							isAnimatable: Boolean(emoji.animated),
+							animated: shouldAnimateEmoji,
+							jumbo: false,
+						})
 					: fallbackDisplayUrl;
 				const content = displayUrl ? (
-					<img
-						src={displayUrl}
-						alt={emoji.name}
-						loading="lazy"
-						data-flx="channel.emoji-picker.render-emoji-preview-item.img"
-					/>
+					<img src={displayUrl} alt={emoji.name} data-flx="channel.emoji-picker.render-emoji-preview-item.img" />
 				) : (
 					<span
 						className={premiumStyles.previewEmojiText}
@@ -184,17 +205,54 @@ export const EmojiPicker = observer(
 			}
 			return result;
 		}, [pickerRows]);
+		const {emojiRowIndexes, emojiRowStarts, categoryRowIndexes} = useMemo(() => {
+			const indexes = new Array<number>(pickerRows.length);
+			const starts: Array<number> = [];
+			const categories = new Map<string, number>();
+			let emojiRowIndex = 0;
+			for (let rowIndex = 0; rowIndex < pickerRows.length; rowIndex += 1) {
+				const row = pickerRows[rowIndex];
+				indexes[rowIndex] = emojiRowIndex;
+				if (row.type === 'emoji-row') {
+					starts.push(rowIndex);
+					emojiRowIndex += 1;
+				} else {
+					categories.set(row.category, rowIndex);
+				}
+			}
+			return {emojiRowIndexes: indexes, emojiRowStarts: starts, categoryRowIndexes: categories};
+		}, [pickerRows]);
+		const zoomLevel = Accessibility.zoomLevel;
+		const remScale = getAppRemScale();
+		const rowOffsets = useMemo(() => {
+			const rowKinds = pickerRows.map((row): EmojiRowKind => row.type);
+			return buildEmojiRowOffsets(rowKinds, {remScale, sectionGap: EMOJI_SECTION_GAP});
+		}, [pickerRows, remScale, zoomLevel]);
+		const contentHeight = rowOffsets[rowOffsets.length - 1]!;
+		useLayoutEffect(() => {
+			const rowListNode = rowListRef.current;
+			const scrollerNode = scrollerRef.current?.getViewportElement();
+			if (!rowListNode || !scrollerNode) {
+				return;
+			}
+			const origin = Math.round(
+				rowListNode.getBoundingClientRect().top - scrollerNode.getBoundingClientRect().top + scrollerNode.scrollTop,
+			);
+			const viewportHeight = scrollerNode.clientHeight;
+			setListMetrics((current) =>
+				current.origin === origin && current.viewportHeight === viewportHeight ? current : {origin, viewportHeight},
+			);
+		});
+		const rowWindow = useMemo(
+			() => getEmojiRowWindow(rowOffsets, scrollTop - listMetrics.origin, listMetrics.viewportHeight),
+			[rowOffsets, scrollTop, listMetrics],
+		);
 		const handleCategoryClick = (category: string) => {
-			const element = categoryRefs.current.get(category);
-			if (element) {
-				scrollerRef.current?.revealElement({node: element, preferStartEdge: true});
-			}
-		};
-		const handleHover = (emoji: FlatEmoji | null, row?: number, column?: number) => {
-			setHoveredEmoji(emoji);
-			if (emoji && row !== undefined && column !== undefined) {
-				handleSelectionChange(row, column, false);
+			const rowIndex = categoryRowIndexes.get(category);
+			if (rowIndex == null) {
+				return;
 			}
+			scrollerRef.current?.scrollTo({to: listMetrics.origin + rowOffsets[rowIndex]!});
 		};
 		const handleEmojiSelect = useCallback(
 			(emoji: FlatEmoji, shiftKey?: boolean) => {
@@ -229,11 +287,31 @@ export const EmojiPicker = observer(
 			},
 			[pickerRows],
 		);
+		const handleHover = useCallback(
+			(emoji: FlatEmoji | null, row?: number, column?: number) => {
+				setHoveredEmoji(emoji);
+				if (emoji && row !== undefined && column !== undefined) {
+					handleSelectionChange(row, column, false);
+				}
+			},
+			[handleSelectionChange],
+		);
 		useEffect(() => {
 			if (renderedEmojis.length > 0 && selectedRow === 0 && selectedColumn === 0 && !hoveredEmoji) {
 				handleSelectionChange(0, 0, false);
 			}
 		}, [renderedEmojis, selectedRow, selectedColumn, hoveredEmoji, handleSelectionChange]);
+		useEffect(() => {
+			if (!shouldScrollOnSelection || selectedRow < 0) {
+				return;
+			}
+			const rowIndex = emojiRowStarts[selectedRow];
+			if (rowIndex == null) {
+				return;
+			}
+			const start = listMetrics.origin + rowOffsets[rowIndex]!;
+			scrollerRef.current?.revealRange({start, end: start + EMOJI_ROW_HEIGHT * remScale});
+		}, [shouldScrollOnSelection, selectedRow, emojiRowStarts, rowOffsets, listMetrics.origin, remScale]);
 		const handleSelectEmoji = useCallback(
 			(row: number | null, column: number | null, event?: React.KeyboardEvent) => {
 				if (row === null || column === null) {
@@ -281,8 +359,8 @@ export const EmojiPicker = observer(
 								className={`${styles.list} ${styles.listWrapper}`}
 								fade={false}
 								key="emoji_picker-scroller"
+								onScroll={handleScroll}
 								onResize={handleResize}
-								data-emoji-picker-scroll-root="true"
 								data-flx="channel.emoji-picker.list"
 							>
 								{showPremiumUpsell && (
@@ -294,22 +372,22 @@ export const EmojiPicker = observer(
 										data-flx="channel.emoji-picker.premium-upsell-banner"
 									/>
 								)}
-								{pickerRows.map((row, index) => {
-									const emojiRowIndex = pickerRows.slice(0, index).filter((r) => r.type === 'emoji-row').length;
-									const needsSpacingAfter = row.type === 'emoji-row' && pickerRows[index + 1]?.type === 'header';
+								<div
+									ref={rowListRef}
+									style={{position: 'relative', flexShrink: 0, height: `${contentHeight}px`}}
+									data-flx="channel.emoji-picker.row-list"
+								>
+									{pickerRows.slice(rowWindow.firstRow, rowWindow.lastRow + 1).map((row, windowIndex) => {
+										const rowIndex = rowWindow.firstRow + windowIndex;
 										return (
 											<div
 												key={`${row.type}-${row.index}`}
-											ref={
-												row.type === 'header'
-													? (el) => {
-															if (el && 'category' in row) {
-																categoryRefs.current.set(row.category, el);
-															}
-														}
-													: undefined
-											}
-											style={row.type === 'emoji-row' && needsSpacingAfter ? {marginBottom: '12px'} : undefined}
+												style={{
+													position: 'absolute',
+													left: 0,
+													right: 0,
+													transform: `translateY(${rowOffsets[rowIndex]!}px)`,
+												}}
 												data-flx="channel.emoji-picker.div"
 											>
 												<VirtualizedRow
@@ -320,10 +398,10 @@ export const EmojiPicker = observer(
 													channel={channel}
 													allowAnimation={shouldAnimateEmoji}
 													gridColumns={gridColumns}
-												hoveredEmoji={hoveredEmoji}
+													cellTrackWidth={EMOJI_GRID_TRACK_WIDTH}
 													selectedRow={selectedRow}
 													selectedColumn={selectedColumn}
-												emojiRowIndex={emojiRowIndex}
+													emojiRowIndex={emojiRowIndexes[rowIndex]!}
 													shouldScrollOnSelection={shouldScrollOnSelection}
 													emojiRefs={emojiRefs}
 													data-flx="channel.emoji-picker.virtualized-row"
@@ -331,6 +409,7 @@ export const EmojiPicker = observer(
 											</div>
 										);
 									})}
+								</div>
 							</Scroller>
 							{renderedEmojis.length === 0 && (
 								<div className={styles.emptyState} data-flx="channel.emoji-picker.empty-state">

fluxer_app/src/features/channel/components/MobileEmojiPicker.tsx

@@ -5,6 +5,11 @@ import {PREMIUM_PRODUCT_NAME} from '@app/features/app/config/I18nDisplayConstant
 import {useSearchInputAutofocus} from '@app/features/app/hooks/useSearchInputAutofocus';
 import {useShouldAnimate} from '@app/features/app/hooks/useShouldAnimate';
 import {EmojiPickerCategoryList} from '@app/features/channel/components/emoji_picker/EmojiPickerCategoryList';
+import {
+	buildEmojiRowOffsets,
+	type EmojiRowKind,
+	getEmojiRowWindow,
+} from '@app/features/channel/components/emoji_picker/EmojiPickerConstants';
 import {EmojiPickerSearchBar} from '@app/features/channel/components/emoji_picker/EmojiPickerSearchBar';
 import {useEmojiCategories} from '@app/features/channel/components/emoji_picker/hooks/useEmojiCategories';
 import {useVirtualRows} from '@app/features/channel/components/emoji_picker/hooks/useVirtualRows';
@@ -26,16 +31,17 @@ import {
 	shouldShowEmojiPremiumUpsell,
 } from '@app/features/expressions/utils/ExpressionPermissionUtils';
 import {getEmojiDisplayDataWithSkinTone} from '@app/features/expressions/utils/SkinToneUtils';
+import {getEmojiRenderUrl} from '@app/features/messaging/utils/markdown/EmojiDetector';
 import Permission from '@app/features/permissions/state/Permission';
 import {ComponentBus} from '@app/features/platform/utils/ComponentBus';
 import {usePremiumUpsellData} from '@app/features/premium/hooks/usePremiumUpsellData';
 import {shouldShowPremiumFeatures} from '@app/features/premium/utils/PremiumUtils';
 import {Scroller, type ScrollerHandle} from '@app/features/ui/components/Scroller';
-import * as AvatarUtils from '@app/features/user/utils/AvatarUtils';
+import {getAppRemScale} from '@app/features/ui/utils/AppZoomUtils';
 import {Plural, Trans, useLingui} from '@lingui/react/macro';
 import {observer} from 'mobx-react-lite';
 import type React from 'react';
-import {useCallback, useEffect, useMemo, useRef, useState, useSyncExternalStore} from 'react';
+import {useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState, useSyncExternalStore} from 'react';
 
 function getVisibleViewportWidth(): number {
 	if (typeof window === 'undefined') {
@@ -67,9 +73,10 @@ export const MobileEmojiPicker = observer(
 		const scrollerRef = useRef<ScrollerHandle>(null);
 		const searchInputRef = useRef<HTMLInputElement>(null);
 		const emojiRefs = useRef<Map<string, HTMLButtonElement>>(new Map());
-		const {viewportSize, handleResize} = useScrollerViewport(scrollerRef);
+		const {viewportSize, scrollTop, handleScroll, handleResize} = useScrollerViewport(scrollerRef);
 		const channel = channelId ? (Channels.getChannel(channelId) ?? null) : null;
-		const categoryRefs = useRef<Map<string, HTMLDivElement>>(new Map());
+		const rowListRef = useRef<HTMLDivElement>(null);
+		const [listMetrics, setListMetrics] = useState({origin: 0, viewportHeight: 0});
 		const [emojiDataVersion, setEmojiDataVersion] = useState(0);
 		const permissionVersion = useSyncExternalStore(Permission.subscribe.bind(Permission), () => Permission.version);
 		const getEmojiAvailability = useCallback(
@@ -119,7 +126,13 @@ export const MobileEmojiPicker = observer(
 				const key = emoji.id ?? emoji.uniqueName ?? emoji.name ?? `${emoji.guildId ?? 'unicode'}-mobile`;
 				const {url: fallbackDisplayUrl} = getEmojiDisplayDataWithSkinTone(emoji, skinTone);
 				const displayUrl = emoji.id
-					? AvatarUtils.getEmojiURL({id: emoji.id, animated: Boolean(emoji.animated) && shouldAnimateEmoji})
+					? getEmojiRenderUrl({
+							id: emoji.id,
+							surrogateUrl: null,
+							isAnimatable: Boolean(emoji.animated),
+							animated: shouldAnimateEmoji,
+							jumbo: false,
+						})
 					: fallbackDisplayUrl;
 				let content: React.ReactNode;
 				if (displayUrl) {
@@ -127,7 +140,6 @@ export const MobileEmojiPicker = observer(
 						<img
 							src={displayUrl}
 							alt={emoji.name}
-							loading="lazy"
 							data-flx="channel.mobile-emoji-picker.render-emoji-preview-item.img"
 						/>
 					);
@@ -220,15 +232,50 @@ export const MobileEmojiPicker = observer(
 			shouldShowEmojiPremiumUpsell(channel) &&
 			!normalizedSearchTerm &&
 			lockedEmojiCount > 0;
-		const handleCategoryClick = (category: string) => {
-			const element = categoryRefs.current.get(category);
-			if (element) {
-				scrollerRef.current?.revealElement({node: element, preferStartEdge: true});
+		const categoryRowIndexes = useMemo(() => {
+			const categories = new Map<string, number>();
+			for (let rowIndex = 0; rowIndex < pickerRows.length; rowIndex += 1) {
+				const row = pickerRows[rowIndex];
+				if (row.type === 'header') {
+					categories.set(row.category, rowIndex);
 				}
+			}
+			return categories;
+		}, [pickerRows]);
+		const remScale = getAppRemScale();
+		const rowOffsets = useMemo(() => {
+			const rowKinds = pickerRows.map((row): EmojiRowKind => row.type);
+			return buildEmojiRowOffsets(rowKinds, {remScale, sectionGap: 0});
+		}, [pickerRows, remScale, zoomLevel]);
+		const contentHeight = rowOffsets[rowOffsets.length - 1]!;
+		useLayoutEffect(() => {
+			const rowListNode = rowListRef.current;
+			const scrollerNode = scrollerRef.current?.getViewportElement();
+			if (!rowListNode || !scrollerNode) {
+				return;
+			}
+			const origin = Math.round(
+				rowListNode.getBoundingClientRect().top - scrollerNode.getBoundingClientRect().top + scrollerNode.scrollTop,
+			);
+			const viewportHeight = scrollerNode.clientHeight;
+			setListMetrics((current) =>
+				current.origin === origin && current.viewportHeight === viewportHeight ? current : {origin, viewportHeight},
+			);
+		});
+		const rowWindow = useMemo(
+			() => getEmojiRowWindow(rowOffsets, scrollTop - listMetrics.origin, listMetrics.viewportHeight),
+			[rowOffsets, scrollTop, listMetrics],
+		);
+		const handleCategoryClick = (category: string) => {
+			const rowIndex = categoryRowIndexes.get(category);
+			if (rowIndex == null) {
+				return;
+			}
+			scrollerRef.current?.scrollTo({to: listMetrics.origin + rowOffsets[rowIndex]!});
 		};
-		const handleHover = (emoji: FlatEmoji | null) => {
+		const handleHover = useCallback((emoji: FlatEmoji | null) => {
 			setHoveredEmoji(emoji);
-		};
+		}, []);
 		const searchBar = !hideSearchBar ? (
 			<EmojiPickerSearchBar
 				searchTerm={searchTerm}
@@ -256,7 +303,7 @@ export const MobileEmojiPicker = observer(
 								ref={scrollerRef}
 								className={`${mobileStyles.list} ${mobileStyles.listWrapper}`}
 								key="mobile-emoji_picker-scroller"
-								data-emoji-picker-scroll-root="true"
+								onScroll={handleScroll}
 								onResize={handleResize}
 								data-flx="channel.mobile-emoji-picker.scroller"
 							>
@@ -269,18 +316,20 @@ export const MobileEmojiPicker = observer(
 										data-flx="channel.mobile-emoji-picker.premium-upsell-banner"
 									/>
 								)}
-								{pickerRows.map((row) => (
+								<div
+									ref={rowListRef}
+									style={{position: 'relative', flexShrink: 0, height: `${contentHeight}px`}}
+									data-flx="channel.mobile-emoji-picker.row-list"
+								>
+									{pickerRows.slice(rowWindow.firstRow, rowWindow.lastRow + 1).map((row, windowIndex) => (
 										<div
 											key={`${row.type}-${row.index}`}
-										ref={
-											row.type === 'header'
-												? (el) => {
-														if (el && 'category' in row) {
-															categoryRefs.current.set(row.category, el);
-														}
-													}
-												: undefined
-										}
+											style={{
+												position: 'absolute',
+												left: 0,
+												right: 0,
+												transform: `translateY(${rowOffsets[rowWindow.firstRow + windowIndex]!}px)`,
+											}}
 											data-flx="channel.mobile-emoji-picker.div--4"
 										>
 											<VirtualizedRow
@@ -292,7 +341,6 @@ export const MobileEmojiPicker = observer(
 												allowAnimation={shouldAnimateEmoji}
 												gridColumns={gridColumns}
 												gridWidth={gridWidth}
-											hoveredEmoji={hoveredEmoji}
 												selectedRow={-1}
 												selectedColumn={-1}
 												emojiRowIndex={0}
@@ -301,6 +349,7 @@ export const MobileEmojiPicker = observer(
 											/>
 										</div>
 									))}
+								</div>
 							</Scroller>
 						</div>
 					</div>

fluxer_app/src/features/channel/components/emoji_picker/EmojiPickerConstants.ts

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
 import {convertToCodePoints} from '@app/features/expressions/utils/EmojiCodepointUtils';
-import {REM_BASE_PX, remFromPx} from '@app/features/theme/layout/RemFromPx';
+import {getRemScaleForDocument, remFromPx} from '@app/features/theme/layout/RemFromPx';
 import sprite1f3fb2x from '@app/media/images/emoji-sprites/[email protected]';
 import sprite1f3fb1x from '@app/media/images/emoji-sprites/spritesheet-1f3fb.png';
 import sprite1f3fc2x from '@app/media/images/emoji-sprites/[email protected]';
@@ -23,28 +23,90 @@ export const EMOJI_PICKER_CUSTOM_EMOJI_SIZE = 48;
 export const CATEGORY_HEADER_HEIGHT = 32;
 export const EMOJIS_PER_ROW = 9;
 const EMOJIS_PER_ROW_MIN = 5;
-export const OVERSCAN_ROWS = 5;
+export const EMOJI_SECTION_GAP = 12;
+const CATEGORY_HEADER_GAP = 8;
 
-const EMOJI_GRID_INLINE_PADDING = 16;
 const EMOJI_GRID_MIN_CELL_WIDTH = EMOJI_ROW_HEIGHT;
-
-function getRemScale(): number {
-	if (typeof document === 'undefined') return 1;
-	const rootFontSize = Number.parseFloat(getComputedStyle(document.documentElement).fontSize);
-	if (Number.isFinite(rootFontSize) && rootFontSize > 0) {
-		return rootFontSize / REM_BASE_PX;
-	}
-	return 1;
-}
+export const EMOJI_GRID_TRACK_WIDTH = EMOJI_GRID_MIN_CELL_WIDTH;
+export const EMOJI_GRID_SCROLLER_PADDING_WIDTH = 8;
 
 export function getEmojiGridColumns(containerWidth: number): number {
 	if (containerWidth <= 0) return EMOJIS_PER_ROW;
-	const remScale = getRemScale();
-	const availableWidth = Math.max(0, containerWidth - EMOJI_GRID_INLINE_PADDING * remScale);
-	const columns = Math.floor(availableWidth / (EMOJI_GRID_MIN_CELL_WIDTH * remScale));
+	const remScale = getRemScaleForDocument(typeof document === 'undefined' ? null : document);
+	const columns = Math.floor(containerWidth / (EMOJI_GRID_MIN_CELL_WIDTH * remScale));
 	return Math.max(EMOJIS_PER_ROW_MIN, columns);
 }
 
+export type EmojiRowKind = 'header' | 'emoji-row';
+
+export interface EmojiRowMetrics {
+	remScale: number;
+	sectionGap: number;
+}
+
+export interface EmojiRowWindow {
+	firstRow: number;
+	lastRow: number;
+}
+
+export function buildEmojiRowOffsets(
+	rowKinds: ReadonlyArray<EmojiRowKind>,
+	{remScale, sectionGap}: EmojiRowMetrics,
+): Array<number> {
+	const rowOffsets = new Array<number>(rowKinds.length + 1);
+	rowOffsets[0] = 0;
+	let runningOffset = 0;
+	for (let rowIndex = 0; rowIndex < rowKinds.length; rowIndex += 1) {
+		if (rowKinds[rowIndex] === 'header') {
+			runningOffset += (CATEGORY_HEADER_HEIGHT + CATEGORY_HEADER_GAP) * remScale;
+		} else {
+			runningOffset += EMOJI_ROW_HEIGHT * remScale;
+			if (rowKinds[rowIndex + 1] === 'header') {
+				runningOffset += sectionGap;
+			}
+		}
+		rowOffsets[rowIndex + 1] = runningOffset;
+	}
+	return rowOffsets;
+}
+
+export function findEmojiRowForOffset(rowOffsets: ReadonlyArray<number>, pixel: number): number {
+	const lastRow = rowOffsets.length - 2;
+	if (lastRow < 0 || pixel <= 0) {
+		return 0;
+	}
+	if (pixel >= rowOffsets[lastRow + 1]!) {
+		return lastRow;
+	}
+	let low = 0;
+	let high = lastRow;
+	while (low < high) {
+		const mid = (low + high + 1) >> 1;
+		if (rowOffsets[mid]! <= pixel) {
+			low = mid;
+		} else {
+			high = mid - 1;
+		}
+	}
+	return low;
+}
+
+export function getEmojiRowWindow(
+	rowOffsets: ReadonlyArray<number>,
+	scrollTop: number,
+	viewportHeight: number,
+): EmojiRowWindow {
+	const totalRows = rowOffsets.length - 1;
+	if (totalRows <= 0 || !(viewportHeight > 0)) {
+		return {firstRow: 0, lastRow: -1};
+	}
+	const safeScrollTop = Number.isFinite(scrollTop) ? Math.max(0, scrollTop) : 0;
+	return {
+		firstRow: findEmojiRowForOffset(rowOffsets, safeScrollTop),
+		lastRow: findEmojiRowForOffset(rowOffsets, safeScrollTop + viewportHeight),
+	};
+}
+
 export const getEmojiSpriteSheetLayout = (index: number, perRow: number, rows: number): CSSProperties => {
 	const column = index % perRow;
 	const row = Math.floor(index / perRow);

fluxer_app/src/features/channel/components/emoji_picker/VirtualRow.tsx

@@ -4,7 +4,6 @@ import styles from '@app/features/channel/components/EmojiPicker.module.css';
 import {
 	CATEGORY_HEADER_HEIGHT,
 	EMOJI_ROW_HEIGHT,
-	OVERSCAN_ROWS,
 } from '@app/features/channel/components/emoji_picker/EmojiPickerConstants';
 import {EmojiRenderer} from '@app/features/channel/components/emoji_picker/EmojiRenderer';
 import type {Channel} from '@app/features/channel/models/Channel';
@@ -13,11 +12,10 @@ import EmojiPicker from '@app/features/emoji/state/EmojiPicker';
 import type {FlatEmoji} from '@app/features/emoji/types/EmojiTypes';
 import {GuildIcon} from '@app/features/guild/components/popouts/GuildIcon';
 import Guilds from '@app/features/guild/state/Guilds';
-import {observeIntersection} from '@app/features/platform/utils/SharedIntersectionObserver';
 import {remFromPx} from '@app/features/theme/layout/RemFromPx';
 import {CaretDownIcon, ClockIcon, StarIcon} from '@phosphor-icons/react';
 import {observer} from 'mobx-react-lite';
-import React, {useEffect, useRef, useState} from 'react';
+import React from 'react';
 
 export type VirtualRow =
 	| {type: 'header'; category: string; name: string; guildId?: string; index: number}
@@ -32,9 +30,8 @@ interface VirtualRowRendererProps {
 	shouldAnimate: boolean;
 	gridColumns?: number;
 	gridWidth?: number;
-	hoveredEmoji: FlatEmoji | null;
-	selectedRow: number;
-	selectedColumn: number;
+	cellTrackWidth?: number;
+	selectedColumnInRow: number;
 	emojiRowIndex: number;
 	shouldScrollOnSelection?: boolean;
 	emojiRefs: React.MutableRefObject<Map<string, HTMLButtonElement>>;
@@ -50,8 +47,8 @@ const VirtualRowRenderer: React.FC<VirtualRowRendererProps> = React.memo(
 		shouldAnimate,
 		gridColumns = 9,
 		gridWidth,
-		selectedRow,
-		selectedColumn,
+		cellTrackWidth,
+		selectedColumnInRow,
 		emojiRowIndex,
 		shouldScrollOnSelection = false,
 		emojiRefs,
@@ -98,7 +95,6 @@ const VirtualRowRenderer: React.FC<VirtualRowRendererProps> = React.memo(
 				<button
 					type="button"
 					onClick={handleToggleCategory}
-					className={styles.categoryTitle}
 					style={{
 						height: remFromPx(CATEGORY_HEADER_HEIGHT),
 						display: 'flex',
@@ -146,6 +142,7 @@ const VirtualRowRenderer: React.FC<VirtualRowRendererProps> = React.memo(
 				</button>
 			);
 		}
+		const hasFixedTrack = cellTrackWidth != null && cellTrackWidth > 0;
 		return (
 			<div
 				style={{
@@ -155,20 +152,22 @@ const VirtualRowRenderer: React.FC<VirtualRowRendererProps> = React.memo(
 				data-flx="channel.emoji-picker.virtual-row.virtual-row-renderer.div--2"
 			>
 				<div
-					className={styles.emojiGrid}
+					className={hasFixedTrack ? `${styles.emojiGrid} ${styles.emojiGridFixedTrack}` : styles.emojiGrid}
 					style={{
-						gridTemplateColumns: `repeat(${gridColumns}, minmax(0, 1fr))`,
+						gridTemplateColumns: hasFixedTrack
+							? `repeat(auto-fill, ${remFromPx(cellTrackWidth)})`
+							: `repeat(${gridColumns}, minmax(0, 1fr))`,
 						marginInline: gridWidth ? 'auto' : undefined,
 						width: gridWidth ? `${gridWidth}px` : undefined,
 					}}
 					data-flx="channel.emoji-picker.virtual-row.virtual-row-renderer.emoji-grid"
 				>
 					{row.emojis.map((emoji, colIndex) => {
-						const isSelected = emojiRowIndex === selectedRow && colIndex === selectedColumn;
+						const isSelected = colIndex === selectedColumnInRow;
 						const shouldHighlight = isSelected;
 						return (
 							<EmojiRenderer
-								key={emoji.name}
+								key={emoji.id ?? emoji.uniqueName}
 								emoji={emoji}
 								handleHover={(e) => handleHover(e, emojiRowIndex, colIndex)}
 								handleSelect={handleSelect}
@@ -204,7 +203,7 @@ interface VirtualizedRowProps {
 	allowAnimation: boolean;
 	gridColumns?: number;
 	gridWidth?: number;
-	hoveredEmoji: FlatEmoji | null;
+	cellTrackWidth?: number;
 	selectedRow: number;
 	selectedColumn: number;
 	emojiRowIndex: number;
@@ -222,79 +221,31 @@ export const VirtualizedRow: React.FC<VirtualizedRowProps> = observer(
 		allowAnimation,
 		gridColumns,
 		gridWidth,
-		hoveredEmoji,
+		cellTrackWidth,
 		selectedRow,
 		selectedColumn,
 		emojiRowIndex,
 		shouldScrollOnSelection = false,
 		emojiRefs,
 	}) => {
-		const [isVisible, setIsVisible] = useState(false);
-		const [isInViewport, setIsInViewport] = useState(false);
-		const placeholderRef = useRef<HTMLDivElement>(null);
-		useEffect(() => {
-			const placeholder = placeholderRef.current;
-			if (!placeholder) return;
-			const root = placeholder.closest('[data-emoji-picker-scroll-root]') as Element | null;
-			const overscanDistance = OVERSCAN_ROWS * EMOJI_ROW_HEIGHT;
-			const unobserveVisibility = observeIntersection(
-				placeholder,
-				(entry) => {
-					if (entry.isIntersecting) {
-						setIsVisible(true);
-					} else {
-						const rect = entry.boundingClientRect;
-						const rootTop = entry.rootBounds?.top ?? 0;
-						const rootBottom = entry.rootBounds?.bottom ?? window.innerHeight;
-						if (rect.bottom < rootTop - overscanDistance || rect.top > rootBottom + overscanDistance) {
-							setIsVisible(false);
-						}
-					}
-				},
-				{root, rootMargin: `${OVERSCAN_ROWS * EMOJI_ROW_HEIGHT}px 0px`, threshold: 0},
-			);
-			const unobserveAnimation = observeIntersection(
-				placeholder,
-				(entry) => {
-					setIsInViewport(entry.isIntersecting);
-				},
-				{root, rootMargin: '0px', threshold: 0},
-			);
-			return () => {
-				unobserveVisibility();
-				unobserveAnimation();
-			};
-		}, []);
-		const height = row.type === 'header' ? CATEGORY_HEADER_HEIGHT : EMOJI_ROW_HEIGHT;
-		if (!isVisible) {
+		const selectedColumnInRow = emojiRowIndex === selectedRow ? selectedColumn : -1;
 		return (
-				<div
-					ref={placeholderRef}
-					style={{height: remFromPx(height)}}
-					data-flx="channel.emoji-picker.virtual-row.virtualized-row.div"
-				/>
-			);
-		}
-		return (
-			<div ref={placeholderRef} data-flx="channel.emoji-picker.virtual-row.virtualized-row.div--2">
 			<VirtualRowRenderer
 				row={row}
 				handleHover={handleHover}
 				handleSelect={handleSelect}
 				skinTone={skinTone}
 				channel={channel}
-					shouldAnimate={allowAnimation && isInViewport}
+				shouldAnimate={allowAnimation}
 				gridColumns={gridColumns}
 				gridWidth={gridWidth}
-					hoveredEmoji={hoveredEmoji}
-					selectedRow={selectedRow}
-					selectedColumn={selectedColumn}
+				cellTrackWidth={cellTrackWidth}
+				selectedColumnInRow={selectedColumnInRow}
 				emojiRowIndex={emojiRowIndex}
 				shouldScrollOnSelection={shouldScrollOnSelection}
 				emojiRefs={emojiRefs}
 				data-flx="channel.emoji-picker.virtual-row.virtualized-row.virtual-row-renderer"
 			/>
-			</div>
 		);
 	},
 );