Refactor startOffset in WindowVirtualizer

inokawa · Mar 4, 2024 · 73f0066 · 73f0066
1 parent a04b6eb
commit 73f0066
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Showing 2 changed files with 20 additions and 15 deletions.
diff --git a/src/core/scroller.ts b/src/core/scroller.ts
@@ -13,6 +13,7 @@ import {
  ACTION_MANUAL_SCROLL,
  SCROLL_IDLE,
  ACTION_BEFORE_MANUAL_SMOOTH_SCROLL,
+ ACTION_START_OFFSET_CHANGE,
 } from "./store";
 import { ScrollToIndexOpts } from "./types";
 import { debounce, timeout, clamp, microtask } from "./utils";
@@ -42,7 +43,8 @@ const createScrollObserver = (
  value: number,
  shift: boolean,
  isMomentumScrolling: boolean
- ) => void
+ ) => void,
+ getStartOffset?: () => number
 ) => {
  const now = Date.now;
 
@@ -73,7 +75,11 @@ const createScrollObserver = (
  stillMomentumScrolling = true;
  }
 
+ if (getStartOffset) {
+ store._update(ACTION_START_OFFSET_CHANGE, getStartOffset());
+ }
  store._update(ACTION_SCROLL, getScrollOffset());
+
  onScrollEnd();
  };
 
@@ -353,8 +359,6 @@ export const createWindowScroller = (
 
  return {
  _observe(container) {
- let prevStartOffset = 0;
-
  const scrollOffsetKey = isHorizontal ? "scrollX" : "scrollY";
 
  const document = getCurrentDocument(container);
@@ -392,24 +396,18 @@ export const createWindowScroller = (
  store,
  window,
  isHorizontal,
- () =>
- normalizeOffset(window[scrollOffsetKey], isHorizontal) -
- (prevStartOffset = calcOffsetToViewport(
- container,
- documentBody,
- isHorizontal
- )),
+ () => normalizeOffset(window[scrollOffsetKey], isHorizontal),
  (jump, shift) => {
  // TODO support case two window scrollers exist in the same view
  if (shift) {
  window.scroll({
- [isHorizontal ? "left" : "top"]:
- store._getScrollOffset() + prevStartOffset + jump,
+ [isHorizontal ? "left" : "top"]: store._getScrollOffset() + jump,
  });
  } else {
  window.scrollBy(isHorizontal ? jump : 0, isHorizontal ? 0 : jump);
  }
- }
+ },
+ () => calcOffsetToViewport(container, documentBody, isHorizontal)
  );
  },
  _dispose() {

diff --git a/src/core/store.ts b/src/core/store.ts
@@ -53,9 +53,11 @@ export const ACTION_SCROLL = 4;
 /** @internal */
 export const ACTION_SCROLL_END = 5;
 /** @internal */
-export const ACTION_MANUAL_SCROLL = 6;
+export const ACTION_START_OFFSET_CHANGE = 6;
 /** @internal */
-export const ACTION_BEFORE_MANUAL_SMOOTH_SCROLL = 7;
+export const ACTION_MANUAL_SCROLL = 7;
+/** @internal */
+export const ACTION_BEFORE_MANUAL_SMOOTH_SCROLL = 8;
 
 type Actions =
  | [type: typeof ACTION_ITEM_RESIZE, entries: ItemResize[]]
@@ -66,6 +68,7 @@ type Actions =
  ]
  | [type: typeof ACTION_SCROLL, offset: number]
  | [type: typeof ACTION_SCROLL_END, dummy?: void]
+ | [type: typeof ACTION_START_OFFSET_CHANGE, offset: number]
  | [type: typeof ACTION_MANUAL_SCROLL, dummy?: void]
  | [type: typeof ACTION_BEFORE_MANUAL_SMOOTH_SCROLL, offset: number];
 
@@ -439,6 +442,10 @@ export const createVirtualStore = (
  _frozenRange = null;
  break;
  }
+ case ACTION_START_OFFSET_CHANGE: {
+ startSpacerSize = payload;
+ break;
+ }
  case ACTION_MANUAL_SCROLL: {
  _scrollMode = SCROLL_BY_MANUAL_SCROLL;
  break;