[Perf] Fix heavy animation event for fastSmoothScroll, refactoring

src/hooks/useHeavyAnimationCheck.ts

@@ -6,7 +6,7 @@ const ANIMATION_END_EVENT = 'tt-event-heavy-animation-end';
 let timeout: number | undefined;
 let isAnimating = false;
 
-export const dispatchHeavyAnimationEvent = (duration: number) => {
+export const dispatchHeavyAnimationEvent = (duration?: number) => {
   if (!isAnimating) {
     isAnimating = true;
     document.dispatchEvent(new Event(ANIMATION_START_EVENT));
@@ -17,11 +17,18 @@ export const dispatchHeavyAnimationEvent = (duration: number) => {
     timeout = undefined;
   }
 
+  if (duration) {
     timeout = window.setTimeout(() => {
       isAnimating = false;
       document.dispatchEvent(new Event(ANIMATION_END_EVENT));
       timeout = undefined;
     }, duration);
+  }
+
+  return () => {
+    isAnimating = false;
+    document.dispatchEvent(new Event(ANIMATION_END_EVENT));
+  };
 };
 
 export default (

src/util/fastSmoothScroll.ts

@@ -8,7 +8,6 @@ import {
   FAST_SMOOTH_SHORT_TRANSITION_MAX_DISTANCE,
 } from '../config';
 import { dispatchHeavyAnimationEvent } from '../hooks/useHeavyAnimationCheck';
-import { fastRaf } from './schedulers';
 import { animateSingle } from './animation';
 
 let isAnimating = false;
@@ -37,92 +36,104 @@ export default function fastSmoothScroll(
     return;
   }
 
-  const { offsetTop } = element;
-
-  if (forceDirection === undefined) {
-    const offset = offsetTop - container.scrollTop;
-
-    if (offset < -maxDistance) {
-      container.scrollTop += (offset + maxDistance);
-    } else if (offset > maxDistance) {
-      container.scrollTop += (offset - maxDistance);
-    }
-  } else if (forceDirection === FocusDirection.Up) {
-    container.scrollTop = offsetTop + maxDistance;
-  } else if (forceDirection === FocusDirection.Down) {
-    container.scrollTop = Math.max(0, offsetTop - maxDistance);
-  }
+  const scrollFrom = calculateScrollFrom(container, element, maxDistance, forceDirection);
 
   if (getGlobal().settings.byKey.animationLevel === ANIMATION_LEVEL_MIN) {
     forceDuration = 0;
   }
 
-  isAnimating = true;
-  fastRaf(() => {
-    scrollWithJs(container, element, position, margin, forceDuration, forceCurrentContainerHeight);
-  });
+  scrollWithJs(container, element, scrollFrom, position, margin, forceDuration, forceCurrentContainerHeight);
 }
 
 export function isAnimatingScroll() {
   return isAnimating;
 }
 
+function calculateScrollFrom(
+  container: HTMLElement,
+  element: HTMLElement,
+  maxDistance = FAST_SMOOTH_MAX_DISTANCE,
+  forceDirection?: FocusDirection,
+) {
+  const { offsetTop: elementTop } = element;
+  const { scrollTop } = container;
+
+  if (forceDirection === undefined) {
+    const offset = elementTop - container.scrollTop;
+
+    if (offset < -maxDistance) {
+      return scrollTop + (offset + maxDistance);
+    } else if (offset > maxDistance) {
+      return scrollTop + (offset - maxDistance);
+    }
+  } else if (forceDirection === FocusDirection.Up) {
+    return elementTop + maxDistance;
+  } else if (forceDirection === FocusDirection.Down) {
+    return Math.max(0, elementTop - maxDistance);
+  }
+
+  return scrollTop;
+}
+
 function scrollWithJs(
   container: HTMLElement,
   element: HTMLElement,
+  scrollFrom: number,
   position: ScrollLogicalPosition | 'centerOrTop',
   margin = 0,
   forceDuration?: number,
   forceCurrentContainerHeight?: boolean,
 ) {
   const { offsetTop: elementTop, offsetHeight: elementHeight } = element;
-  const { scrollTop, offsetHeight: containerHeight, scrollHeight } = container;
+  const { scrollTop: currentScrollTop, offsetHeight: containerHeight, scrollHeight } = container;
   const targetContainerHeight = !forceCurrentContainerHeight && container.dataset.normalHeight
     ? Number(container.dataset.normalHeight)
     : containerHeight;
 
+  if (currentScrollTop !== scrollFrom) {
+    container.scrollTop = scrollFrom;
+  }
+
   let path!: number;
 
   switch (position) {
     case 'start':
-      path = (elementTop - margin) - scrollTop;
+      path = (elementTop - margin) - scrollFrom;
       break;
     case 'end':
-      path = (elementTop + elementHeight + margin) - (scrollTop + targetContainerHeight);
+      path = (elementTop + elementHeight + margin) - (scrollFrom + targetContainerHeight);
       break;
     // 'nearest' is not supported yet
     case 'nearest':
     case 'center':
     case 'centerOrTop':
       path = elementHeight < targetContainerHeight
-        ? (elementTop + elementHeight / 2) - (scrollTop + targetContainerHeight / 2)
-        : (elementTop - margin) - scrollTop;
+        ? (elementTop + elementHeight / 2) - (scrollFrom + targetContainerHeight / 2)
+        : (elementTop - margin) - scrollFrom;
       break;
   }
 
   if (path < 0) {
-    const remainingPath = -scrollTop;
+    const remainingPath = -scrollFrom;
     path = Math.max(path, remainingPath);
   } else if (path > 0) {
-    const remainingPath = scrollHeight - (scrollTop + targetContainerHeight);
+    const remainingPath = scrollHeight - (scrollFrom + targetContainerHeight);
     path = Math.min(path, remainingPath);
   }
 
   if (path === 0) {
-    isAnimating = false;
-
     return;
   }
 
-  const target = container.scrollTop + path;
+  const target = scrollFrom + path;
 
   if (forceDuration === 0) {
     container.scrollTop = target;
-    isAnimating = false;
-
     return;
   }
 
+  isAnimating = true;
+
   const absPath = Math.abs(path);
   const transition = absPath < FAST_SMOOTH_SHORT_TRANSITION_MAX_DISTANCE ? shortTransition : longTransition;
   const duration = forceDuration || (
@@ -130,16 +141,20 @@ function scrollWithJs(
     + (absPath / FAST_SMOOTH_MAX_DISTANCE) * (FAST_SMOOTH_MAX_DURATION - FAST_SMOOTH_MIN_DURATION)
   );
   const startAt = Date.now();
+  const onHeavyAnimationStop = dispatchHeavyAnimationEvent();
 
-  dispatchHeavyAnimationEvent(duration);
   animateSingle(() => {
     const t = Math.min((Date.now() - startAt) / duration, 1);
-
     const currentPath = path * (1 - transition(t));
+
     container.scrollTop = Math.round(target - currentPath);
 
     isAnimating = t < 1;
 
+    if (!isAnimating) {
+      onHeavyAnimationStop();
+    }
+
     return isAnimating;
   });
 }

src/util/fastSmoothScrollHorizontal.ts

@@ -1,9 +1,8 @@
 import { getGlobal } from '../lib/teact/teactn';
 
-import { fastRaf } from './schedulers';
-import { animate } from './animation';
-import { IS_IOS } from './environment';
 import { ANIMATION_LEVEL_MIN } from '../config';
+import { IS_IOS } from './environment';
+import { animate } from './animation';
 
 const DEFAULT_DURATION = 300;
 
@@ -19,9 +18,7 @@ export default function fastSmoothScrollHorizontal(container: HTMLElement, left:
       ...(duration && { behavior: 'smooth' }),
     });
   } else {
-    fastRaf(() => {
     scrollWithJs(container, left, duration);
-    });
   }
 }
 
@@ -41,10 +38,10 @@ function scrollWithJs(container: HTMLElement, left: number, duration: number) {
     return;
   }
 
-  const target = container.scrollLeft + path;
+  const target = scrollLeft + path;
 
   if (duration === 0) {
-    container.scrollTop = target;
+    container.scrollLeft = target;
     return;
   }