Fix items disappear when zooming VirtualizedList (facebook#33765)

Summary:
fix facebook#33705
Fixed the disappearance of items when scrolling after zooming VirtualizedList.
example https://github.com/islandryu/zoomVirtualizedList

Before modification

https://user-images.githubusercontent.com/65934663/166849127-9fc3ba84-5172-4ae1-bd44-dd6312f283ec.mov

After modification

https://user-images.githubusercontent.com/65934663/166868632-2f78e118-f705-442d-b94e-ff165bed26c7.mov

## Changelog

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[General] [Fixed] - Fixed the disappearance of items when scrolling after zooming VirtualizedList.

Pull Request resolved: facebook#33765

Test Plan:
Make the VirtualizedList zoomable with a prop such as maximumZoomScale.
Apply the patch and make sure that items in the VirtualizedList do not disappear when you scroll after zooming the VirtualizedList.

Or apply the patch from this repository and check it.
https://github.com/islandryu/zoomVirtualizedList

Reviewed By: javache

Differential Revision: D36169686

Pulled By: yungsters

fbshipit-source-id: 0f86255c2864be13f6d2dc5a58af1d11c9eedac3

Author: islandryu

Libraries/Lists/VirtualizeUtils.js

@@ -25,12 +25,13 @@ export function elementsThatOverlapOffsets(
     offset: number,
     ...
   },
+  zoomScale: number,
 ): Array<number> {
   const out = [];
   let outLength = 0;
   for (let ii = 0; ii < itemCount; ii++) {
     const frame = getFrameMetrics(ii);
-    const trailingOffset = frame.offset + frame.length;
+    const trailingOffset = (frame.offset + frame.length) * zoomScale;
     for (let kk = 0; kk < offsets.length; kk++) {
       if (out[kk] == null && trailingOffset >= offsets[kk]) {
         out[kk] = ii;
@@ -104,6 +105,7 @@ export function computeWindowedRenderLimits(
     offset: number,
     velocity: number,
     visibleLength: number,
+    zoomScale: number,
     ...
   },
 ): {
@@ -115,7 +117,7 @@ export function computeWindowedRenderLimits(
   if (itemCount === 0) {
     return prev;
   }
-  const {offset, velocity, visibleLength} = scrollMetrics;
+  const {offset, velocity, visibleLength, zoomScale} = scrollMetrics;
 
   // Start with visible area, then compute maximum overscan region by expanding from there, biased
   // in the direction of scroll. Total overscan area is capped, which should cap memory consumption
@@ -136,7 +138,8 @@ export function computeWindowedRenderLimits(
   );
   const overscanEnd = Math.max(0, visibleEnd + leadFactor * overscanLength);
 
-  const lastItemOffset = getFrameMetricsApprox(itemCount - 1).offset;
+  const lastItemOffset =
+    getFrameMetricsApprox(itemCount - 1).offset * zoomScale;
   if (lastItemOffset < overscanBegin) {
     // Entire list is before our overscan window
     return {
@@ -150,6 +153,7 @@ export function computeWindowedRenderLimits(
     [overscanBegin, visibleBegin, visibleEnd, overscanEnd],
     itemCount,
     getFrameMetricsApprox,
+    zoomScale,
   );
   overscanFirst = overscanFirst == null ? 0 : overscanFirst;
   first = first == null ? Math.max(0, overscanFirst) : first;

Libraries/Lists/VirtualizedList.js

@@ -1228,6 +1228,7 @@ class VirtualizedList extends React.PureComponent<Props, State> {
     timestamp: 0,
     velocity: 0,
     visibleLength: 0,
+    zoomScale: 1,
   };
   _scrollRef: ?React.ElementRef<any> = null;
   _sentEndForContentLength = 0;
@@ -1624,6 +1625,9 @@ class VirtualizedList extends React.PureComponent<Props, State> {
       );
       this._hasWarned.perf = true;
     }
+
+    const zoomScale = e.nativeEvent.zoomScale;
+
     this._scrollMetrics = {
       contentLength,
       dt,
@@ -1632,6 +1636,7 @@ class VirtualizedList extends React.PureComponent<Props, State> {
       timestamp,
       velocity,
       visibleLength,
+      zoomScale,
     };
     this._updateViewableItems(this.props.data);
     if (!this.props) {

Libraries/Lists/VirtualizedListContext.js

@@ -47,6 +47,7 @@ type Context = $ReadOnly<{
     timestamp: number,
     velocity: number,
     visibleLength: number,
+    zoomScale: number,
   },
   horizontal: ?boolean,
   getOutermostParentListRef: () => VirtualizedList,

Libraries/Lists/__tests__/VirtualizeUtils-test.js

@@ -48,9 +48,9 @@ describe('elementsThatOverlapOffsets', function () {
         offset: 100 * index,
       };
     }
-    expect(elementsThatOverlapOffsets(offsets, 100, getFrameMetrics)).toEqual([
-      0, 2, 3, 4,
-    ]);
+    expect(
+      elementsThatOverlapOffsets(offsets, 100, getFrameMetrics, 1),
+    ).toEqual([0, 2, 3, 4]);
   });
   it('handles variable length', function () {
     const offsets = [150, 250, 900];
@@ -62,7 +62,7 @@ describe('elementsThatOverlapOffsets', function () {
       {offset: 950, length: 150},
     ];
     expect(
-      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii]),
+      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii], 1),
     ).toEqual([1, 1, 3]);
   });
   it('handles out of bounds', function () {
@@ -73,7 +73,7 @@ describe('elementsThatOverlapOffsets', function () {
       {offset: 250, length: 100},
     ];
     expect(
-      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii]),
+      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii], 1),
     ).toEqual([1]);
   });
   it('errors on non-increasing offsets', function () {
@@ -84,7 +84,7 @@ describe('elementsThatOverlapOffsets', function () {
       {offset: 250, length: 100},
     ];
     expect(() => {
-      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii]);
+      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii], 1);
     }).toThrowErrorMatchingSnapshot();
   });
 });

Libraries/Lists/__tests__/VirtualizedList-test.js

@@ -384,7 +384,7 @@ describe('VirtualizedList', () => {
 
     const instance = component.getInstance();
 
-    instance._onLayout({nativeEvent: {layout}});
+    instance._onLayout({nativeEvent: {layout, zoomScale: 1}});
 
     const initialContentHeight = props.initialNumToRender * ITEM_HEIGHT;
 
@@ -1490,7 +1490,7 @@ it('calls _onCellLayout properly', () => {
   );
   const cell = virtualList._cellRefs.i4;
   const event = {
-    nativeEvent: {layout: {x: 0, y: 0, width: 50, height: 50}},
+    nativeEvent: {layout: {x: 0, y: 0, width: 50, height: 50}, zoomScale: 1},
   };
   cell._onLayout(event);
   expect(mock).toHaveBeenCalledWith(event, 'i4', 3);
@@ -1544,7 +1544,9 @@ function simulateLayout(component, args) {
 
 function simulateViewportLayout(component, dimensions) {
   lastViewportLayout = dimensions;
-  component.getInstance()._onLayout({nativeEvent: {layout: dimensions}});
+  component
+    .getInstance()
+    ._onLayout({nativeEvent: {layout: dimensions}, zoomScale: 1});
 }
 
 function simulateContentLayout(component, dimensions) {
@@ -1558,7 +1560,7 @@ function simulateCellLayout(component, items, itemIndex, dimensions) {
   const instance = component.getInstance();
   const cellKey = instance._keyExtractor(items[itemIndex], itemIndex);
   instance._onCellLayout(
-    {nativeEvent: {layout: dimensions}},
+    {nativeEvent: {layout: dimensions, zoomScale: 1}},
     cellKey,
     itemIndex,
   );
@@ -1570,6 +1572,7 @@ function simulateScroll(component, position) {
       contentOffset: position,
       contentSize: lastContentLayout,
       layoutMeasurement: lastViewportLayout,
+      zoomScale: 1,
     },
   });
 }