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Remove hacks in web InvertedFlatList #31288

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Nov 14, 2023
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151 changes: 14 additions & 137 deletions src/components/InvertedFlatList/BaseInvertedFlatList.js
Original file line number Diff line number Diff line change
@@ -1,9 +1,6 @@
import PropTypes from 'prop-types';
import React, {forwardRef, useCallback, useRef} from 'react';
import {FlatList as NativeFlatlist, View} from 'react-native';
import _ from 'underscore';
import React, {forwardRef} from 'react';
import FlatList from '@components/FlatList';
import * as CollectionUtils from '@libs/CollectionUtils';

const AUTOSCROLL_TO_TOP_THRESHOLD = 128;

Expand All @@ -14,148 +11,28 @@ const propTypes = {

/** Same as FlatList although we wrap it in a measuring helper before passing to the actual FlatList component */
renderItem: PropTypes.func.isRequired,

/** This must be set to the minimum size of one of the renderItem rows. Web experiences issues when inaccurate. */
initialRowHeight: PropTypes.number.isRequired,

/** Passed via forwardRef so we can access the FlatList ref */
innerRef: PropTypes.oneOfType([PropTypes.func, PropTypes.shape({current: PropTypes.instanceOf(NativeFlatlist)})]).isRequired,

/** Should we measure these items and call getItemLayout? */
shouldMeasureItems: PropTypes.bool,
};

const defaultProps = {
data: [],
shouldMeasureItems: false,
};

function BaseInvertedFlatList(props) {
const {initialRowHeight, shouldMeasureItems, innerRef, renderItem} = props;

// Stores each item's computed height after it renders
// once and is then referenced for the life of this component.
// This is essential to getting FlatList inverted to work on web
// and also enables more predictable scrolling on native platforms.
const sizeMap = useRef({});

/**
* Return default or previously cached height for
* a renderItem row
*
* @param {*} data
* @param {Number} index
*
* @return {Object}
*/
const getItemLayout = (data, index) => {
const size = sizeMap.current[index];

if (size) {
return {
length: size.length,
offset: size.offset,
index,
};
}

// If we don't have a size yet means we haven't measured this
// item yet. However, we can still calculate the offset by looking
// at the last size we have recorded (if any)
const lastMeasuredItem = CollectionUtils.lastItem(sizeMap.current);

return {
// We haven't measured this so we must return the minimum row height
length: initialRowHeight,

// Offset will either be based on the lastMeasuredItem or the index +
// initialRowHeight since we can only assume that all previous items
// have not yet been measured
offset: _.isUndefined(lastMeasuredItem) ? initialRowHeight * index : lastMeasuredItem.offset + initialRowHeight,
index,
};
};

/**
* Measure item and cache the returned length (a.k.a. height)
*
* @param {React.NativeSyntheticEvent} nativeEvent
* @param {Number} index
*/
const measureItemLayout = useCallback((nativeEvent, index) => {
const computedHeight = nativeEvent.layout.height;

// We've already measured this item so we don't need to
// measure it again.
if (sizeMap.current[index]) {
return;
}

const previousItem = sizeMap.current[index - 1] || {};

// If there is no previousItem this can mean we haven't yet measured
// the previous item or that we are at index 0 and there is no previousItem
const previousLength = previousItem.length || 0;
const previousOffset = previousItem.offset || 0;
sizeMap.current[index] = {
length: computedHeight,
offset: previousLength + previousOffset,
};
}, []);

/**
* Render item method wraps the prop renderItem to render in a
* View component so we can attach an onLayout handler and
* measure it when it renders.
*
* @param {Object} params
* @param {Object} params.item
* @param {Number} params.index
*
* @return {React.Component}
*/
const renderItemFromProp = useCallback(
({item, index}) => {
if (shouldMeasureItems) {
return <View onLayout={({nativeEvent}) => measureItemLayout(nativeEvent, index)}>{renderItem({item, index})}</View>;
}

return renderItem({item, index});
},
[shouldMeasureItems, measureItemLayout, renderItem],
);

return (
<FlatList
// eslint-disable-next-line react/jsx-props-no-spreading
{...props}
ref={innerRef}
renderItem={renderItemFromProp}
// Native platforms do not need to measure items and work fine without this.
// Web requires that items be measured or else crazy things happen when scrolling.
getItemLayout={shouldMeasureItems ? getItemLayout : undefined}
windowSize={15}
maintainVisibleContentPosition={{
minIndexForVisible: 0,
autoscrollToTopThreshold: AUTOSCROLL_TO_TOP_THRESHOLD,
}}
inverted
/>
);
}

BaseInvertedFlatList.propTypes = propTypes;
BaseInvertedFlatList.defaultProps = defaultProps;
BaseInvertedFlatList.displayName = 'BaseInvertedFlatList';

const BaseInvertedFlatListWithRef = forwardRef((props, ref) => (
<BaseInvertedFlatList
const BaseInvertedFlatList = forwardRef((props, ref) => (
<FlatList
// eslint-disable-next-line react/jsx-props-no-spreading
{...props}
innerRef={ref}
ref={ref}
windowSize={15}
maintainVisibleContentPosition={{
minIndexForVisible: 0,
autoscrollToTopThreshold: AUTOSCROLL_TO_TOP_THRESHOLD,
}}
inverted
/>
));

BaseInvertedFlatListWithRef.displayName = 'BaseInvertedFlatListWithRef';
BaseInvertedFlatList.propTypes = propTypes;
BaseInvertedFlatList.defaultProps = defaultProps;
BaseInvertedFlatList.displayName = 'BaseInvertedFlatList';

export default BaseInvertedFlatListWithRef;
export default BaseInvertedFlatList;
4 changes: 0 additions & 4 deletions src/components/InvertedFlatList/index.js
Original file line number Diff line number Diff line change
Expand Up @@ -106,12 +106,8 @@ function InvertedFlatList(props) {
// eslint-disable-next-line react/jsx-props-no-spreading
{...props}
ref={innerRef}
shouldMeasureItems
contentContainerStyle={contentContainerStyle}
onScroll={handleScroll}
// We need to keep batch size to one to workaround a bug in react-native-web.
// This can be removed once https://github.com/Expensify/App/pull/24482 is merged.
maxToRenderPerBatch={1}
/>
);
}
Expand Down
1 change: 0 additions & 1 deletion src/pages/home/report/ReportActionsList.js
Original file line number Diff line number Diff line change
Expand Up @@ -420,7 +420,6 @@ function ReportActionsList({
renderItem={renderItem}
contentContainerStyle={contentContainerStyle}
keyExtractor={keyExtractor}
initialRowHeight={32}
initialNumToRender={initialNumToRender}
onEndReached={loadOlderChats}
onEndReachedThreshold={0.75}
Expand Down
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