Message: Add text streaming animation (#6834)

src/assets/localization/fallback.strings

@@ -708,6 +708,7 @@
 "SettingsPerformanceMessageBlur" = "Message Blur";
 "SettingsPerformanceRightColumn" = "Right Column Animation";
 "SettingsPerformanceThanos" = "Dust-effect deletion";
+"SettingsPerformanceTextStreaming" = "Text Streaming";
 "SettingsPerformanceAnimatedEmoji" = "Allow Animated Emoji";
 "SettingsPerformanceLoopStickers" = "Loop Animated Stickers";
 "SettingsPerformanceReactionEffects" = "Reaction Effects";

src/components/common/AnimatedIconWithPreview.tsx

@@ -1,10 +1,11 @@
-import { memo } from '../../lib/teact/teact';
+import { memo, useRef } from '../../lib/teact/teact';
 
 import type { OwnProps as AnimatedIconProps } from './AnimatedIcon';
 
 import buildClassName from '../../util/buildClassName';
 import buildStyle from '../../util/buildStyle';
 
+import useDynamicColorListener from '../../hooks/stickers/useDynamicColorListener';
 import useFlag from '../../hooks/useFlag';
 import useLastCallback from '../../hooks/useLastCallback';
 import useMediaTransitionDeprecated from '../../hooks/useMediaTransitionDeprecated';
@@ -15,7 +16,7 @@ import styles from './AnimatedIconWithPreview.module.scss';
 
 type OwnProps =
   Partial<AnimatedIconProps>
-  & { previewUrl?: string; thumbDataUri?: string; noPreviewTransition?: boolean };
+  & { previewUrl?: string; thumbDataUri?: string; noPreviewTransition?: boolean; shouldUseTextColor?: boolean };
 
 const ANIMATION_DURATION = 300;
 
@@ -23,9 +24,12 @@ const loadedPreviewUrls = new Set();
 
 function AnimatedIconWithPreview(props: OwnProps) {
   const {
-    previewUrl, thumbDataUri, className, ...otherProps
+    previewUrl, thumbDataUri, className, shouldUseTextColor, ...otherProps
   } = props;
 
+  const rootRef = useRef<HTMLDivElement>();
+  const customColor = useDynamicColorListener(rootRef, undefined, !shouldUseTextColor);
+
   const [isThumbOpen, , unmarkThumbOpen] = useFlag(Boolean(thumbDataUri));
   const thumbClassNames = useMediaTransitionDeprecated(isThumbOpen);
 
@@ -49,6 +53,7 @@ function AnimatedIconWithPreview(props: OwnProps) {
 
   return (
     <div
+      ref={rootRef}
       className={buildClassName(className, styles.root)}
       style={buildStyle(size !== undefined && `width: ${size}px; height: ${size}px;`)}
     >
@@ -65,7 +70,7 @@ function AnimatedIconWithPreview(props: OwnProps) {
           onLoad={handlePreviewLoad}
         />
       )}
-      <AnimatedIcon {...otherProps} onLoad={handleAnimationReady} />
+      <AnimatedIcon {...otherProps} color={customColor} onLoad={handleAnimationReady} />
     </div>
   );
 }

src/components/common/MessageText.tsx

@@ -40,6 +40,7 @@ interface OwnProps {
   canBeEmpty?: boolean;
   maxTimestamp?: number;
   shouldAnimateTyping?: boolean;
+  canAnimateTextStreaming?: boolean;
 }
 
 const MIN_CUSTOM_EMOJIS_FOR_SHARED_CANVAS = 3;
@@ -66,6 +67,7 @@ function MessageText({
   maxTimestamp,
   threadId,
   shouldAnimateTyping,
+  canAnimateTextStreaming,
 }: OwnProps) {
   const sharedCanvasRef = useRef<HTMLCanvasElement>();
   const sharedCanvasHqRef = useRef<HTMLCanvasElement>();
@@ -152,7 +154,12 @@ function MessageText({
         withSharedCanvas && <canvas key="shared-canvas" ref={sharedCanvasRef} className="shared-canvas" />,
         withSharedCanvas && <canvas key="shared-canvas-hq" ref={sharedCanvasHqRef} className="shared-canvas" />,
         shouldAnimateTyping ? (
-          <TypingWrapper key="typing-wrapper" text={textToRender}>{renderText}</TypingWrapper>
+          <TypingWrapper
+            key="typing-wrapper"
+            formattedText={textToRender}
+            renderText={renderText}
+            shouldAnimateMask={canAnimateTextStreaming}
+          />
         ) : renderText(textToRender),
       ].flat().filter(Boolean)}
     </>

src/components/common/TypingWrapper.module.scss

@@ -0,0 +1,29 @@
+.root {
+  --typing-draft-progress: 0%;
+  --typing-draft-spread: 10%;
+
+  display: inline;
+
+  mask-image:
+    linear-gradient(
+      to right,
+      black var(--typing-draft-progress),
+      transparent calc(var(--typing-draft-progress) + var(--typing-draft-spread))
+    );
+
+  &:dir(rtl) {
+    mask-image:
+      linear-gradient(
+        to left,
+        black var(--typing-draft-progress),
+        transparent calc(var(--typing-draft-progress) + var(--typing-draft-spread))
+      );
+  }
+}
+
+.placeholder {
+  display: inline-block;
+  width: 1.25rem;
+  height: 1.25rem;
+  vertical-align: text-top;
+}

src/components/common/TypingWrapper.tsx

@@ -1,71 +1,223 @@
+import type { TeactNode } from '../../lib/teact/teact';
 import {
-  memo, useEffect, useRef, useSignal, useUnmountCleanup,
+  memo, useEffect, useLayoutEffect, useMemo, useRef, useState, useUnmountCleanup,
 } from '../../lib/teact/teact';
 
-import {
-  type ApiFormattedText,
-} from '../../api/types';
+import type { ApiFormattedText } from '../../api/types';
+
+import { requestMutation } from '../../lib/fasterdom/fasterdom';
+import { LOCAL_TGS_URLS } from './helpers/animatedAssets';
+import { REM } from './helpers/mediaDimensions';
 
-import useDerivedState from '../../hooks/useDerivedState';
 import useLastCallback from '../../hooks/useLastCallback';
 
+import AnimatedIconWithPreview from './AnimatedIconWithPreview';
+
+import styles from './TypingWrapper.module.scss';
+
 type OwnProps = {
-  text: ApiFormattedText;
-  duration?: number;
-  children: (text: ApiFormattedText) => React.ReactNode;
+  formattedText: ApiFormattedText;
+  shouldAnimateMask?: boolean;
+  renderText: (text: ApiFormattedText) => TeactNode;
 };
 
-const DEFAULT_HEADWAY_DURATION = 1000;
-const MIN_TIMEOUT_DURATION = 1000 / 60; // 60 FPS
-const MAX_SYMBOLS_BATCH = 10;
+const CHUNK_SIZE = 67;
+const CHUNK_SPREAD_DURATION = 500;
+const HEADWAY_DURATION = 750;
+const PLACEHOLDER_SIZE = 1.25 * REM;
+const SPREAD_CHARS = 20;
+const PROGRESS_CSS_PROPERTY = '--typing-draft-progress';
+const SPREAD_CSS_PROPERTY = '--typing-draft-spread';
 
-const TypingWrapper = ({
-  text,
-  duration = DEFAULT_HEADWAY_DURATION,
-  children,
-}: OwnProps) => {
-  const [getCurrentTextLength, setCurrentTextLength] = useSignal(text.text.length);
-  const intervalRef = useRef<number>();
+try {
+  window.CSS.registerProperty({
+    name: PROGRESS_CSS_PROPERTY,
+    syntax: '<percentage>',
+    inherits: false,
+    initialValue: '0%',
+  });
+} catch (_) {
+  // Ignore duplicate registrations
+}
 
-  const animate = useLastCallback(() => {
-    const msPerSymbol = duration / text.text.length;
-    const timeoutDuration = Math.max(msPerSymbol, MIN_TIMEOUT_DURATION);
-    const nextSymbolBatchLength = Math.min(Math.ceil(timeoutDuration / msPerSymbol), MAX_SYMBOLS_BATCH);
+function getRunningProgress(animation: Animation | undefined, baseProgress: number) {
+  const timing = animation?.effect?.getComputedTiming().progress;
+  if (typeof timing !== 'number') return baseProgress;
+  return baseProgress + (100 - baseProgress) * timing;
+}
 
-    intervalRef.current = window.setTimeout(() => {
-      if (getCurrentTextLength() >= text.text.length) {
-        clearTimeout(intervalRef.current);
-        return;
-      }
+const TypingWrapper = ({ formattedText, shouldAnimateMask, renderText }: OwnProps) => {
+  const ref = useRef<HTMLSpanElement>();
+  const animationRef = useRef<Animation>();
+  const progressRef = useRef(0);
+  const prevRevealedRef = useRef(0);
 
-      setCurrentTextLength(getCurrentTextLength() + nextSymbolBatchLength);
-    }, timeoutDuration);
+  const [revealedLength, setRevealedLength] = useState(0);
+  const revealedLengthRef = useRef(0);
+  const chunkTimerRef = useRef<number>();
+  const prevFullTextRef = useRef('');
+
+  const fullText = formattedText.text;
+
+  const stopAnimation = useLastCallback(() => {
+    animationRef.current?.cancel();
+    animationRef.current = undefined;
   });
 
+  const scheduleChunks = useLastCallback((from: number, to: number) => {
+    window.clearTimeout(chunkTimerRef.current);
+
+    const delta = to - from;
+    if (delta <= 0) return;
+
+    const numChunks = Math.ceil(delta / CHUNK_SIZE);
+    const chunkInterval = numChunks > 1 ? CHUNK_SPREAD_DURATION / (numChunks - 1) : 0;
+
+    let position = from;
+
+    const addChunk = () => {
+      position = Math.min(position + CHUNK_SIZE, to);
+      revealedLengthRef.current = position;
+      setRevealedLength(position);
+
+      if (position < to) {
+        chunkTimerRef.current = window.setTimeout(addChunk, chunkInterval);
+      } else {
+        chunkTimerRef.current = undefined;
+      }
+    };
+
+    addChunk();
+  });
+
+  const resetChunking = useLastCallback(() => {
+    window.clearTimeout(chunkTimerRef.current);
+    chunkTimerRef.current = undefined;
+    revealedLengthRef.current = 0;
+    prevRevealedRef.current = 0;
+    progressRef.current = 0;
+    stopAnimation();
+    setRevealedLength(0);
+  });
+
+  // --- Chunking: spread incoming text over time ---
   useEffect(() => {
-    // Text got shorter, skip animation
-    if (text.text.length < getCurrentTextLength()) {
-      clearTimeout(intervalRef.current);
-      setCurrentTextLength(text.text.length);
+    if (fullText === prevFullTextRef.current) return;
+    prevFullTextRef.current = fullText;
+
+    const fullLen = fullText.length;
+    const revealed = revealedLengthRef.current;
+
+    if (fullLen < revealed) {
+      resetChunking();
+      scheduleChunks(0, fullLen);
       return;
     }
 
-    clearTimeout(intervalRef.current);
-    animate();
-  }, [getCurrentTextLength, setCurrentTextLength, text.text.length]);
-
-  useUnmountCleanup(() => {
-    clearTimeout(intervalRef.current);
+    scheduleChunks(revealed, fullLen);
   });
 
-  const displayedText = useDerivedState(() => {
-    return {
-      ...text,
-      text: text.text.slice(0, getCurrentTextLength()),
-    };
-  }, [getCurrentTextLength, text]);
+  // --- Mask animation: smooth reveal of rendered content (layout effect to prevent flash) ---
+  useLayoutEffect(() => {
+    const element = ref.current;
+    if (!element) return;
 
-  return children(displayedText);
+    const revealed = revealedLength;
+    const prevRevealed = prevRevealedRef.current;
+    if (revealed === prevRevealed) return;
+
+    prevRevealedRef.current = revealed;
+
+    if (!shouldAnimateMask) {
+      stopAnimation();
+      progressRef.current = 100;
+      element.style.setProperty(PROGRESS_CSS_PROPERTY, '100%');
+      return;
+    }
+
+    let progress = animationRef.current
+      ? getRunningProgress(animationRef.current, progressRef.current)
+      : progressRef.current;
+
+    stopAnimation();
+
+    if (revealed < prevRevealed) {
+      progress = 0;
+    } else if (prevRevealed && revealed) {
+      progress = Math.min((prevRevealed * progress) / revealed, 100);
+    } else if (!prevRevealed) {
+      progress = 0;
+    }
+
+    if (!revealed) {
+      progress = 100;
+    }
+
+    progressRef.current = progress;
+    const remaining = 100 - progress;
+    const spread = revealed ? (SPREAD_CHARS / revealed) * 100 : 0;
+
+    if (!revealed || remaining <= 0) {
+      progressRef.current = 100;
+      element.style.setProperty(PROGRESS_CSS_PROPERTY, '100%');
+      return;
+    }
+
+    element.style.setProperty(SPREAD_CSS_PROPERTY, `${spread}%`);
+    element.style.setProperty(PROGRESS_CSS_PROPERTY, `${progress}%`);
+
+    const animation = element.animate([
+      { [PROGRESS_CSS_PROPERTY]: `${progress}%` },
+      { [PROGRESS_CSS_PROPERTY]: '100%' },
+    ] as Keyframe[], {
+      duration: HEADWAY_DURATION,
+      easing: 'linear',
+      fill: 'forwards',
+    });
+
+    animationRef.current = animation;
+
+    animation.onfinish = () => {
+      if (animationRef.current !== animation) return;
+
+      progressRef.current = 100;
+      animationRef.current = undefined;
+
+      requestMutation(() => {
+        element.style.setProperty(PROGRESS_CSS_PROPERTY, '100%');
+      });
+    };
+
+    animation.oncancel = () => {
+      if (animationRef.current !== animation) return;
+      animationRef.current = undefined;
+    };
+  });
+
+  useUnmountCleanup(() => {
+    window.clearTimeout(chunkTimerRef.current);
+    stopAnimation();
+  });
+
+  const truncatedText = useMemo(() => ({
+    text: fullText.slice(0, revealedLength),
+    entities: formattedText.entities,
+  }), [fullText, formattedText.entities, revealedLength]);
+
+  return (
+    <span ref={ref} className={styles.root}>
+      {renderText(truncatedText)}
+      <span key="typing-placeholder" className={styles.placeholder}>
+        <AnimatedIconWithPreview
+          tgsUrl={LOCAL_TGS_URLS.Typing}
+          size={PLACEHOLDER_SIZE}
+          play
+          noLoop={false}
+          shouldUseTextColor
+        />
+      </span>
+    </span>
+  );
 };
 
 export default memo(TypingWrapper);

src/components/common/helpers/animatedAssets.ts

@@ -20,6 +20,7 @@ import PartyPopper from '../../../assets/tgs/general/PartyPopper.tgs';
 import Invite from '../../../assets/tgs/invites/Invite.tgs';
 import JoinRequest from '../../../assets/tgs/invites/Requests.tgs';
 import LastSeen from '../../../assets/tgs/LastSeen.tgs';
+import Typing from '../../../assets/tgs/message/Typing.tgs';
 import MonkeyClose from '../../../assets/tgs/monkeys/TwoFactorSetupMonkeyClose.tgs';
 import MonkeyIdle from '../../../assets/tgs/monkeys/TwoFactorSetupMonkeyIdle.tgs';
 import MonkeyPeek from '../../../assets/tgs/monkeys/TwoFactorSetupMonkeyPeek.tgs';
@@ -97,4 +98,5 @@ export const LOCAL_TGS_URLS = {
   Passkeys,
   DuckCake,
   HandStop,
+  Typing,
 };

src/components/left/settings/SettingsPerformance.tsx

@@ -64,6 +64,7 @@ const PERFORMANCE_OPTIONS: PerformanceSection[] = [
     { key: 'messageBlur', label: 'SettingsPerformanceMessageBlur', disabled: !IS_BACKDROP_BLUR_SUPPORTED },
     { key: 'rightColumnAnimations', label: 'SettingsPerformanceRightColumn' },
     { key: 'snapEffect', label: 'SettingsPerformanceThanos' },
+    { key: 'textStreaming', label: 'SettingsPerformanceTextStreaming' },
   ]],
   ['SettingsPerformanceStickers', [
     { key: 'animatedEmoji', label: 'SettingsPerformanceAnimatedEmoji' },

src/components/middle/message/Message.tsx

@@ -313,6 +313,7 @@ type StateProps = {
   requestedTranslationLanguage?: string;
   requestedChatTranslationLanguage?: string;
   withAnimatedEffects?: boolean;
+  canAnimateTextStreaming?: boolean;
   webPageStory?: ApiTypeStory;
   isConnected: boolean;
   isLoadingComments?: boolean;
@@ -440,6 +441,7 @@ const Message = ({
   requestedTranslationLanguage,
   requestedChatTranslationLanguage,
   withAnimatedEffects,
+  canAnimateTextStreaming,
   webPageStory,
   isConnected,
   getIsMessageListReady,
@@ -1073,6 +1075,7 @@ const Message = ({
         maxTimestamp={maxTimestamp}
         threadId={threadId}
         shouldAnimateTyping={isTypingDraft}
+        canAnimateTextStreaming={canAnimateTextStreaming}
       />
     );
   }
@@ -2221,6 +2224,7 @@ export default memo(withGlobal<OwnProps>(
       requestedChatTranslationLanguage,
       hasLinkedChat: Boolean(chatFullInfo?.linkedChatId),
       withAnimatedEffects: selectPerformanceSettingsValue(global, 'stickerEffects'),
+      canAnimateTextStreaming: selectPerformanceSettingsValue(global, 'textStreaming'),
       webPageStory,
       isConnected,
       isLoadingComments: repliesThreadInfo?.isCommentsInfo

src/components/test/demo/MessageTextStreamingTest.module.scss

@@ -0,0 +1,154 @@
+.root {
+  overflow-y: auto;
+  display: flex;
+
+  min-height: 100%;
+  padding: 2rem 1.5rem;
+
+  background:
+    radial-gradient(circle at top left, rgba(var(--color-primary-shade-rgb), 0.18), transparent 28rem),
+    linear-gradient(180deg, var(--color-background) 0%, var(--color-background-secondary) 100%);
+}
+
+.content {
+  display: flex;
+  flex: 1 1 auto;
+  flex-direction: column;
+  gap: 1rem;
+  align-items: center;
+
+  width: min(100%, 56rem);
+  min-height: 100%;
+  margin: 0 auto;
+}
+
+.header {
+  display: flex;
+  gap: 1rem;
+  align-items: flex-start;
+  justify-content: flex-end;
+}
+
+.restartButton {
+  flex-shrink: 0;
+}
+
+.meta {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.75rem;
+  align-items: center;
+}
+
+.statusBadge,
+.progress {
+  display: inline-flex;
+  align-items: center;
+
+  min-height: 2rem;
+  padding: 0.375rem 0.75rem;
+  border-radius: 999rem;
+
+  font-size: 0.875rem;
+  font-weight: var(--font-weight-medium);
+}
+
+.statusBadge {
+  color: var(--color-primary);
+  background: var(--color-primary-tint);
+}
+
+.progress {
+  color: var(--color-text-meta);
+  background: rgba(var(--color-text-meta-rgb), 0.08);
+}
+
+.stage {
+  display: flex;
+  flex: 1 1 auto;
+
+  max-width: 42rem;
+  min-height: 0;
+  padding: 1.25rem;
+  border-radius: 1.5rem;
+
+  background:
+    linear-gradient(180deg, rgba(var(--color-primary-shade-rgb), 0.08), transparent 45%),
+    var(--color-chat-hover);
+  box-shadow: 0 1rem 3rem rgba(0, 0, 0, 0.08);
+}
+
+.device {
+  display: flex;
+  flex: 1 1 auto;
+
+  width: min(100%, 38rem);
+  min-height: 0;
+  margin: 0 auto;
+  padding: 1rem;
+  border-radius: 1.75rem;
+
+  background: var(--color-background);
+  box-shadow: inset 0 0 0 1px rgba(var(--color-text-meta-rgb), 0.12);
+}
+
+.screen {
+  scroll-snap-type: y proximity;
+
+  overflow-y: auto;
+  overscroll-behavior: contain;
+  display: flex;
+  flex: 1 1 auto;
+  flex-direction: column;
+  gap: 0.75rem;
+
+  min-height: 0;
+  padding: 1rem;
+  border-radius: 1.25rem;
+
+  background:
+    radial-gradient(circle at top right, rgba(var(--color-primary-shade-rgb), 0.12), transparent 12rem),
+    var(--color-background-secondary);
+}
+
+.draftLabel {
+  align-self: center;
+
+  padding: 0.25rem 0.625rem;
+  border-radius: 999rem;
+
+  font-size: 0.75rem;
+  font-weight: var(--font-weight-medium);
+  color: var(--color-text-meta);
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+
+  background: rgba(var(--color-text-meta-rgb), 0.08);
+}
+
+.scrollSnapEnd {
+  scroll-snap-align: end;
+}
+
+.bubble {
+  flex-shrink: 0;
+  align-self: flex-end;
+
+  max-width: 100%;
+  min-height: 4.5rem;
+  margin-top: auto;
+  padding: 0.875rem 1rem;
+  border-radius: 1.25rem 1.25rem 0.375rem 1.25rem;
+
+  color: white;
+
+  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-shade));
+  box-shadow: 0 0.75rem 1.5rem rgba(var(--color-primary-shade-rgb), 0.22);
+}
+
+.bubbleText {
+  unicode-bidi: plaintext;
+  line-height: 1.35;
+  overflow-wrap: anywhere;
+  white-space: pre-wrap;
+}

src/components/test/demo/MessageTextStreamingTest.tsx

@@ -0,0 +1,211 @@
+import {
+  memo, useEffect, useMemo, useRef, useState,
+} from '../../../lib/teact/teact';
+
+import type { ApiMessage, ApiMessageEntity } from '../../../api/types';
+import { ApiMessageEntityTypes } from '../../../api/types';
+
+import buildClassName from '../../../util/buildClassName';
+
+import useLang from '../../../hooks/useLang';
+import useLastCallback from '../../../hooks/useLastCallback';
+
+import MessageText from '../../common/MessageText';
+import Button from '../../ui/Button';
+
+import styles from './MessageTextStreamingTest.module.scss';
+
+const MIN_CHUNK_DELAY_MS = 1500;
+const MAX_CHUNK_DELAY_MS = 1500;
+const MIN_CHUNK_SIZE = 1;
+const MAX_CHUNK_SIZE = 5;
+
+const MOCK_MESSAGE: ApiMessage = {
+  id: 1,
+  chatId: '1',
+  content: {
+    text: {
+      text: '',
+    },
+  },
+  date: 0,
+  isOutgoing: true,
+};
+
+function splitIntoSentences(text: string) {
+  return (text.match(/[^.!?]+[.!?]+(?:\s+|$)|[^.!?]+$/g) || [])
+    .map((sentence) => sentence.trim())
+    .filter(Boolean);
+}
+
+function pickRandomInteger(minValue: number, maxValue: number) {
+  return Math.floor(Math.random() * (maxValue - minValue + 1)) + minValue;
+}
+
+const ENTITY_TYPES = [ApiMessageEntityTypes.Bold, ApiMessageEntityTypes.Code] as const;
+const ENTITY_MIN_LEN = 5;
+const ENTITY_MAX_LEN = 60;
+const ENTITY_GAP = 10;
+const ENTITY_COUNT = 8;
+
+function generateRandomEntities(textLength: number): ApiMessageEntity[] {
+  const entities: ApiMessageEntity[] = [];
+  let cursor = pickRandomInteger(0, ENTITY_GAP);
+
+  for (let i = 0; i < ENTITY_COUNT && cursor < textLength; i++) {
+    const maxLen = Math.min(ENTITY_MAX_LEN, textLength - cursor);
+    if (maxLen < ENTITY_MIN_LEN) break;
+
+    const length = pickRandomInteger(ENTITY_MIN_LEN, maxLen);
+    const type = ENTITY_TYPES[i % ENTITY_TYPES.length];
+
+    entities.push({ type, offset: cursor, length });
+    cursor += length + pickRandomInteger(ENTITY_GAP, ENTITY_GAP * 3);
+  }
+
+  return entities;
+}
+
+const MessageTextStreamingTest = () => {
+  const lang = useLang();
+
+  const timeoutRef = useRef<number>();
+  const runIdRef = useRef(0);
+
+  const [displayedText, setDisplayedText] = useState('');
+  const [shownSentenceCount, setShownSentenceCount] = useState(0);
+  const [isFinished, setIsFinished] = useState(false);
+
+  const { sentences, entities } = useMemo(() => {
+    const chunks: string[] = [
+      lang('SuggestionBirthdaySetupTitle'),
+      lang('ProfileBirthdayTodayValue', { date: 'January 1' }),
+      lang('PremiumPreviewReactionsDescription'),
+      lang('SuggestedPostAgreementReached'),
+      lang('SuggestedPostPublishScheduleYou', { peer: 'Test', date: 'April 15' }),
+      lang('MonetizationInfoTONTitle'),
+      lang('PremiumPreviewAdvancedChatManagementDescription'),
+      lang('PremiumPreviewAnimatedProfilesDescription'),
+      lang('SponsoredMessageInfoDescription1'),
+      lang('SponsoredMessageInfoDescription3'),
+      lang('SuggestedPostChargedYou', { amount: '⭐️250' }),
+      lang('PremiumPreviewStickersDescription'),
+      lang('SuggestedPostRefundYou', { peer: 'Test', duration: '48 hours' }),
+      lang('PremiumPreviewNoAdsDescription'),
+      lang('AreYouSureShareMyContactInfoBot'),
+    ];
+    const fullText = chunks.join(' ');
+    return {
+      sentences: splitIntoSentences(fullText),
+      entities: generateRandomEntities(fullText.length),
+    };
+  }, [lang]);
+
+  const clearStreamingTimeout = useLastCallback(() => {
+    if (timeoutRef.current === undefined) {
+      return;
+    }
+
+    clearTimeout(timeoutRef.current);
+    timeoutRef.current = undefined;
+  });
+
+  const appendNextChunk = useLastCallback((startIndex: number, runId: number) => {
+    if (runId !== runIdRef.current) {
+      return;
+    }
+
+    if (!sentences.length || startIndex >= sentences.length) {
+      setIsFinished(true);
+      timeoutRef.current = undefined;
+      return;
+    }
+
+    const nextIndex = Math.min(
+      startIndex + pickRandomInteger(MIN_CHUNK_SIZE, MAX_CHUNK_SIZE),
+      sentences.length,
+    );
+
+    setDisplayedText(sentences.slice(0, nextIndex).join(' '));
+    setShownSentenceCount(nextIndex);
+
+    if (nextIndex >= sentences.length) {
+      setIsFinished(true);
+      timeoutRef.current = undefined;
+      return;
+    }
+
+    timeoutRef.current = window.setTimeout(() => {
+      appendNextChunk(nextIndex, runId);
+    }, pickRandomInteger(MIN_CHUNK_DELAY_MS, MAX_CHUNK_DELAY_MS));
+  });
+
+  const restartStreaming = useLastCallback(() => {
+    clearStreamingTimeout();
+
+    runIdRef.current += 1;
+
+    setDisplayedText('');
+    setShownSentenceCount(0);
+    setIsFinished(false);
+
+    const runId = runIdRef.current;
+    appendNextChunk(0, runId);
+  });
+
+  useEffect(() => {
+    restartStreaming();
+
+    return () => {
+      clearStreamingTimeout();
+    };
+  }, [clearStreamingTimeout, restartStreaming, sentences]);
+
+  return (
+    <div className={buildClassName(styles.root, 'full-height')}>
+      <div className={styles.content}>
+        <div className={styles.header}>
+          <Button className={styles.restartButton} onClick={restartStreaming}>
+            {lang('BotRestart')}
+          </Button>
+        </div>
+
+        <div className={styles.meta}>
+          <span className={styles.statusBadge}>
+            {lang(isFinished ? 'GiftAuctionFinished' : 'Loading')}
+          </span>
+
+          <span className={styles.progress}>
+            {lang('FileTransferProgress', {
+              currentSize: lang.number(shownSentenceCount),
+              totalSize: lang.number(sentences.length),
+            })}
+          </span>
+        </div>
+
+        <div className={styles.stage}>
+          <div className={styles.device}>
+            <div className={styles.screen}>
+              <div className={styles.draftLabel}>{lang('Draft')}</div>
+
+              <div className={styles.bubble} dir="auto">
+                <div className={styles.bubbleText}>
+                  <MessageText
+                    messageOrStory={MOCK_MESSAGE}
+                    forcedText={{ text: displayedText, entities }}
+                    canBeEmpty
+                    shouldAnimateTyping
+                    canAnimateTextStreaming
+                  />
+                </div>
+              </div>
+              <div className={styles.scrollSnapEnd} />
+            </div>
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+};
+
+export default memo(MessageTextStreamingTest);

src/global/cache.ts

@@ -357,6 +357,10 @@ function unsafeMigrateCache(cached: GlobalState, initialState: GlobalState) {
     cachedSharedSettings.performance.messageBlur = false;
   }
 
+  if (cachedSharedSettings.performance.textStreaming === undefined) {
+    cachedSharedSettings.performance.textStreaming = true;
+  }
+
   if (!cachedSharedSettings.foldersPosition) {
     cachedSharedSettings.foldersPosition = FOLDERS_POSITION_DEFAULT;
   }

src/global/initialState.ts

@@ -35,6 +35,7 @@ export const INITIAL_PERFORMANCE_STATE_MAX: PerformanceType = {
   stickerEffects: true,
   storyRibbonAnimations: true,
   snapEffect: true,
+  textStreaming: true,
 };
 
 export const INITIAL_PERFORMANCE_STATE_MED: PerformanceType = {
@@ -54,6 +55,7 @@ export const INITIAL_PERFORMANCE_STATE_MED: PerformanceType = {
   stickerEffects: true,
   storyRibbonAnimations: true,
   snapEffect: false,
+  textStreaming: true,
 };
 
 export const INITIAL_PERFORMANCE_STATE_MIN: PerformanceType = {
@@ -73,6 +75,7 @@ export const INITIAL_PERFORMANCE_STATE_MIN: PerformanceType = {
   stickerEffects: false,
   storyRibbonAnimations: false,
   snapEffect: false,
+  textStreaming: false,
 };
 
 export const INITIAL_SHARED_STATE: SharedState = {

src/types/index.ts

@@ -112,7 +112,7 @@ export type PerformanceTypeKey = (
   'pageTransitions' | 'messageSendingAnimations' | 'mediaViewerAnimations'
   | 'messageComposerAnimations' | 'contextMenuAnimations' | 'contextMenuBlur' | 'messageBlur'
   | 'rightColumnAnimations' | 'animatedEmoji' | 'loopAnimatedStickers' | 'reactionEffects' | 'stickerEffects'
-  | 'autoplayGifs' | 'autoplayVideos' | 'storyRibbonAnimations' | 'snapEffect'
+  | 'autoplayGifs' | 'autoplayVideos' | 'storyRibbonAnimations' | 'snapEffect' | 'textStreaming'
 );
 export type PerformanceType = Record<PerformanceTypeKey, boolean>;
 

src/types/language.d.ts

@@ -628,6 +628,7 @@ export interface LangPair {
   'SettingsPerformanceMessageBlur': undefined;
   'SettingsPerformanceRightColumn': undefined;
   'SettingsPerformanceThanos': undefined;
+  'SettingsPerformanceTextStreaming': undefined;
   'SettingsPerformanceAnimatedEmoji': undefined;
   'SettingsPerformanceLoopStickers': undefined;
   'SettingsPerformanceReactionEffects': undefined;