Message List: Fix scroll animation

src/components/middle/MessageList.scss

@@ -1,8 +1,6 @@
 .MessageList {
   --action-message-bg: var(--pattern-color);
 
-  scroll-snap-type: y proximity;
-
   overflow-x: hidden;
   overflow-y: scroll;
   flex: 1;
@@ -38,8 +36,8 @@
     display: none;
   }
 
-  &.no-bottom-snap {
-    scroll-snap-type: none;
+  &.with-bottom-snap {
+    scroll-snap-type: y proximity;
   }
 
   .messages-container {

src/components/middle/MessageList.tsx

@@ -1,4 +1,3 @@
-import type { FC } from '@teact';
 import { beginHeavyAnimation, memo, useEffect, useMemo, useRef } from '@teact';
 import { addExtraClass, removeExtraClass } from '@teact/teact-dom';
 import { getActions, getGlobal, withGlobal } from '../../global';
@@ -170,7 +169,7 @@ const MESSAGE_FACT_CHECK_UPDATE_INTERVAL = 5 * 1000;
 const MESSAGE_STORY_POLLING_INTERVAL = 5 * 60 * 1000;
 
 const BOTTOM_THRESHOLD = 50;
-const BOTTOM_SNAP_THRESHOLD = 10;
+const BOTTOM_SNAP_THRESHOLD = 7;
 
 const UNREAD_DIVIDER_TOP = 10;
 const SCROLL_DEBOUNCE = 200;
@@ -180,11 +179,11 @@ const SELECT_MODE_ANIMATION_DURATION = 200;
 
 const UNREAD_DIVIDER_CLASS = 'unread-divider';
 const FORCE_MESSAGES_SCROLL_CLASS = 'force-messages-scroll';
-const NO_BOTTOM_SNAP_CLASS = 'no-bottom-snap';
+const BOTTOM_SNAP_CLASS = 'with-bottom-snap';
 
 const runDebouncedForScroll = debounce((cb) => cb(), SCROLL_DEBOUNCE, false);
 
-const MessageList: FC<OwnProps & StateProps> = ({
+const MessageList = ({
   chatId,
   threadId,
   type,
@@ -243,7 +242,7 @@ const MessageList: FC<OwnProps & StateProps> = ({
   onIntersectPinnedMessage,
   onScrollDownToggle,
   onNotchToggle,
-}) => {
+}: OwnProps & StateProps) => {
   const {
     loadViewportMessages, setScrollOffset, loadSponsoredMessages, loadMessageReactions, copyMessagesByIds,
     loadMessageViews, loadPeerStoriesByIds, loadFactChecks, requestChatTranslation,
@@ -471,6 +470,33 @@ const MessageList: FC<OwnProps & StateProps> = ({
 
   const { isScrolled, updateStickyDates } = useStickyDates();
 
+  const updateBottomSnapClass = useLastCallback(() => {
+    const container = containerRef.current;
+    const bottomTrigger = container?.querySelector<HTMLDivElement>('.fab-trigger');
+    if (!container || !bottomTrigger) return;
+
+    // Check if fab-trigger + threshold are entering the viewport
+    const viewportBottom = container.scrollTop + container.offsetHeight;
+    const triggerPosition = bottomTrigger.offsetTop;
+    // Scroll is near fab-trigger + threshold. Prevents snap on sponsored message
+    const shouldSnapBeActive = triggerPosition - BOTTOM_SNAP_THRESHOLD <= viewportBottom
+      && viewportBottom <= triggerPosition + BOTTOM_SNAP_THRESHOLD * 2;
+
+    const hasSnap = container.classList.contains(BOTTOM_SNAP_CLASS);
+    if (hasSnap === shouldSnapBeActive) return;
+
+    if (shouldSnapBeActive) {
+      requestMutation(() => {
+        addExtraClass(container, BOTTOM_SNAP_CLASS);
+      });
+    } else {
+      clearTimeout(scrollSnapDisabledTimerRef.current);
+      requestMutation(() => {
+        removeExtraClass(container, BOTTOM_SNAP_CLASS);
+      });
+    }
+  });
+
   const handleScroll = useLastCallback(() => {
     if (isScrollTopJustUpdatedRef.current) {
       isScrollTopJustUpdatedRef.current = false;
@@ -486,6 +512,8 @@ const MessageList: FC<OwnProps & StateProps> = ({
       updateStickyDates(container);
     }
 
+    updateBottomSnapClass();
+
     runDebouncedForScroll(() => {
       const global = getGlobal();
 
@@ -509,28 +537,14 @@ const MessageList: FC<OwnProps & StateProps> = ({
   const [getContainerHeight, prevContainerHeightRef] = useContainerHeight(containerRef, canPost && !isSelectModeActive);
 
   const handleWheel = useLastCallback((e: React.WheelEvent<HTMLDivElement>) => {
-    // Firefox is finicky about bottom scroll snapping, so we enable it only when nearing the bottom
+    // Remove snap when scrolling up to avoid scroll bug
     // https://bugzilla.mozilla.org/show_bug.cgi?id=1753188
-    if (!IS_FIREFOX) return;
+    if (IS_FIREFOX && e.deltaY < 0) {
+      const container = containerRef.current;
+      if (!container) return;
 
-    const container = containerRef.current;
-    if (!container) return;
-
-    const scrollTop = container.scrollTop;
-    const scrollHeight = container.scrollHeight;
-    const offsetHeight = container.offsetHeight;
-    const isNearBottomForSnap = scrollTop >= scrollHeight - offsetHeight - BOTTOM_SNAP_THRESHOLD;
-    if (!isNearBottomForSnap) return;
-
-    if (e.deltaY < 0) {
-      clearTimeout(scrollSnapDisabledTimerRef.current);
       requestMutation(() => {
-        addExtraClass(container, NO_BOTTOM_SNAP_CLASS);
-        container.scrollBy(0, -BOTTOM_SNAP_THRESHOLD); // Manually scroll to prevent ignoring first event
-      });
-    } else {
-      requestMutation(() => {
-        removeExtraClass(container, NO_BOTTOM_SNAP_CLASS);
+        removeExtraClass(container, BOTTOM_SNAP_CLASS);
       });
     }
   });
@@ -645,10 +659,12 @@ const MessageList: FC<OwnProps & StateProps> = ({
     if (wasMessageAdded) {
       clearTimeout(scrollSnapDisabledTimerRef.current);
 
-      addExtraClass(container, NO_BOTTOM_SNAP_CLASS);
+      removeExtraClass(container, BOTTOM_SNAP_CLASS);
 
       scrollSnapDisabledTimerRef.current = window.setTimeout(() => {
-        removeExtraClass(container, NO_BOTTOM_SNAP_CLASS);
+        requestMutation(() => {
+          addExtraClass(container, BOTTOM_SNAP_CLASS);
+        });
       }, MESSAGE_ANIMATION_DURATION);
     }
 
@@ -768,7 +784,6 @@ const MessageList: FC<OwnProps & StateProps> = ({
     !isReady && 'is-animating',
     hasOpenChatButton && 'saved-dialog',
     isChatProtected && 'hide-on-print',
-    IS_FIREFOX && NO_BOTTOM_SNAP_CLASS,
   );
 
   const hasMessages = Boolean((messageIds && messageGroups) || lastMessage);

src/components/middle/MessageListBottomMarker.tsx

@@ -1,7 +1,5 @@
 import { memo, useRef } from '@teact';
 
-import { FocusDirection } from '../../types';
-
 import buildClassName from '../../util/buildClassName';
 
 import useFocusMessageListElement from './message/hooks/useFocusMessageListElement';
@@ -19,7 +17,6 @@ const MessageListBottomMarker = ({ isFocused, className }: OwnProps) => {
     isJustAdded: true,
     isFocused,
     noFocusHighlight: true,
-    focusDirection: FocusDirection.Down,
   });
 
   return (

src/util/animateScroll.ts

@@ -1,3 +1,4 @@
+import { setExtraStyles } from '@teact/teact-dom';
 import { beginHeavyAnimation } from '../lib/teact/teact';
 import { getGlobal } from '../global';
 
@@ -140,6 +141,10 @@ function createMutateFunction(args: AnimateScrollArgs) {
 
     isAnimating = true;
 
+    setExtraStyles(container, {
+      scrollSnapType: 'none',
+    });
+
     const prevOnHeavyAnimationEnd = onHeavyAnimationEnd;
     onHeavyAnimationEnd = beginHeavyAnimation(undefined, true);
     prevOnHeavyAnimationEnd?.();
@@ -155,6 +160,9 @@ function createMutateFunction(args: AnimateScrollArgs) {
 
       if (!isAnimating) {
         currentArgs = undefined;
+        setExtraStyles(container, {
+          scrollSnapType: '',
+        });
 
         onHeavyAnimationEnd?.();
         onHeavyAnimationEnd = undefined;
@@ -170,7 +178,13 @@ export function isAnimatingScroll() {
 }
 
 export function cancelScrollBlockingAnimation() {
-  onHeavyAnimationEnd!();
+  if (currentArgs?.container) {
+    setExtraStyles(currentArgs.container, {
+      scrollSnapType: '',
+    });
+  }
+
+  onHeavyAnimationEnd?.();
   onHeavyAnimationEnd = undefined;
 }