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Fix "Flatlist is not scrollable" #2772

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Original file line number Diff line number Diff line change
Expand Up @@ -453,35 +453,41 @@ class VirtualizedList extends StateSafePureComponent<Props, State> {

// REACT-NATIVE-WEB patch to preserve during future RN merges: Support inverted wheel scroller.
// For issue https://github.com/necolas/react-native-web/issues/995
this.invertedWheelEventHandler = (ev: any) => {
const scrollOffset = this.props.horizontal ? ev.target.scrollLeft : ev.target.scrollTop;
const scrollLength = this.props.horizontal ? ev.target.scrollWidth : ev.target.scrollHeight;
const clientLength = this.props.horizontal ? ev.target.clientWidth : ev.target.clientHeight;
const isEventTargetScrollable = scrollLength > clientLength;
const delta = this.props.horizontal
? ev.deltaX || ev.wheelDeltaX
: ev.deltaY || ev.wheelDeltaY;
let leftoverDelta = delta;
if (isEventTargetScrollable) {
leftoverDelta = delta < 0
? Math.min(delta + scrollOffset, 0)
: Math.max(delta - (scrollLength - clientLength - scrollOffset), 0);
}
const targetDelta = delta - leftoverDelta;

if (this.props.inverted && this._scrollRef && this._scrollRef.getScrollableNode) {
const node = (this._scrollRef: any).getScrollableNode();
if (this.props.horizontal) {
ev.target.scrollLeft += targetDelta;
const nextScrollLeft = node.scrollLeft - leftoverDelta;
node.scrollLeft = !this.props.getItemLayout ? Math.min(nextScrollLeft, this._totalCellLength) : nextScrollLeft;
} else {
ev.target.scrollTop += targetDelta;
const nextScrollTop = node.scrollTop - leftoverDelta;
node.scrollTop = !this.props.getItemLayout ? Math.min(nextScrollTop, this._totalCellLength) : nextScrollTop;
this.invertedWheelEventHandler = (ev) => {
const isHorizontal = this.props.horizontal;
const deltaX = ev.deltaX || ev.wheelDeltaX || 0;
const deltaY = ev.deltaY || ev.wheelDeltaY || 0;

const scrollOffset = isHorizontal ? ev.target.scrollLeft : ev.target.scrollTop;
const scrollLength = isHorizontal ? ev.target.scrollWidth : ev.target.scrollHeight;
const clientLength = isHorizontal ? ev.target.clientWidth : ev.target.clientHeight;
const isEventTargetScrollable = scrollLength > clientLength;
const delta = isHorizontal ? deltaX : deltaY;
let leftoverDelta = delta;
if (isEventTargetScrollable) {
leftoverDelta = delta < 0 ? Math.min(delta + scrollOffset, 0) : Math.max(delta - (scrollLength - clientLength - scrollOffset), 0);
}
const targetDelta = delta - leftoverDelta;
if (this.props.inverted && this._scrollRef && this._scrollRef.getScrollableNode) {
const node = this._scrollRef.getScrollableNode();
if (isHorizontal) {
ev.target.scrollLeft += targetDelta;
const nextScrollLeft = node.scrollLeft - leftoverDelta;
node.scrollLeft = !this.props.getItemLayout ? Math.min(nextScrollLeft, this._totalCellLength) : nextScrollLeft;

if (Math.abs(deltaX) > Math.abs(deltaY)) {
ev.preventDefault();
}
} else {
ev.target.scrollTop += targetDelta;
const nextScrollTop = node.scrollTop - leftoverDelta;
node.scrollTop = !this.props.getItemLayout ? Math.min(nextScrollTop, this._totalCellLength) : nextScrollTop;

if (Math.abs(deltaY) > Math.abs(deltaX)) {
ev.preventDefault();
}
}
}
ev.preventDefault();
}
};
}

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