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Change jump compensation logic to maintain visible position always #207

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merged 1 commit into from
Oct 12, 2023
Merged

Change jump compensation logic to maintain visible position always #207

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22 changes: 8 additions & 14 deletions src/core/store.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,7 @@ export const createVirtualStore = (
let jumpCount = 0;
let jump: ScrollJump = 0;
let _scrollDirection: ScrollDirection = SCROLL_IDLE;
let _isShifting = false;
let _isManualScrollPremeasuring = false;
let _isManualScrolling = false;
let _resized = false;
let _prevRange: ItemsRange = [0, initialItemCount];
Expand Down Expand Up @@ -211,8 +211,8 @@ export const createVirtualStore = (

// Calculate jump
let diff = 0;
if (_isShifting || _isManualScrolling) {
// Should maintain visible position under specific situations
if (!_isManualScrollPremeasuring) {
// Should maintain visible position to minimize junks in appearance
const [startIndex] = _prevRange;

if (scrollOffset === 0) {
Expand All @@ -230,12 +230,8 @@ export const createVirtualStore = (
updated.filter(([index]) => index < startIndex)
);
}
} else if (_scrollDirection === SCROLL_UP) {
// We can assume jumps occurred on the upper outside during reverse scrolling
diff = calculateJump(cache, updated);
} else {
// Do nothing
}

if (diff) {
jump = diff;
jumpCount++;
Expand Down Expand Up @@ -286,7 +282,6 @@ export const createVirtualStore = (
jumpCount++;

mutated = UPDATE_SCROLL + UPDATE_JUMP;
_isShifting = true;
} else {
updateCacheLength(cache as Writeable<Cache>, payload[0]);
}
Expand Down Expand Up @@ -324,10 +319,8 @@ export const createVirtualStore = (
shouldSync = abs(delta) > viewportSize;

mutated += UPDATE_SCROLL_WITH_EVENT;

if (!isJustResized) {
_isShifting = false;
}
} else {
_isManualScrollPremeasuring = true;
}

scrollOffset = clampScrollOffset(payload);
Expand All @@ -338,10 +331,11 @@ export const createVirtualStore = (
if (updateScrollDirection(SCROLL_IDLE)) {
mutated = UPDATE_SCROLL_DIRECTION;
}
_isShifting = _isManualScrolling = false;
_isManualScrolling = _isManualScrollPremeasuring = false;
break;
}
case ACTION_MANUAL_SCROLL: {
_isManualScrollPremeasuring = false;
_isManualScrolling = true;
break;
}
Expand Down
6 changes: 1 addition & 5 deletions stories/advanced/Feed.stories.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,6 @@ type ImageData = {
type: "image";
id: number;
src: string;
size: number;
};

type Data = TextData | ImageData;
Expand All @@ -58,7 +57,6 @@ export const Default: StoryObj = {
type: "image",
id: id.current++,
src: faker.image.url(),
size: 100 * (Math.floor(Math.random() * 4) + 1),
};
};
const createItems = (num: number) => range(num, createItem);
Expand All @@ -84,9 +82,7 @@ export const Default: StoryObj = {
items.map((d) => (
<Item
key={d.id}
content={
d.type === "image" ? <img src={d.src} height={d.size} /> : d.value
}
content={d.type === "image" ? <img src={d.src} /> : d.value}
/>
)),
[items]
Expand Down
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