@shopify/flash-list
Version:
FlashList is a more performant FlatList replacement
67 lines • 3.52 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.useBlankAreaTracker = void 0;
var react_1 = require("react");
/**
* Can be used to track visible blank area in production
* @param flashListRef Ref to the FlashList component
* @param onBlankAreaChange This event handler will be called when the blank area changes
* @param config additional configuration for the blank area tracker
* @returns blankAreaTrackerResult - maxBlankArea, cumulativeBlankArea this object is mutated and kept up to date. Also returns a callback that needs to be forwarded to FlashList.
*/
function useBlankAreaTracker(flashListRef, onBlankAreaChange, config) {
var _a;
var startDelay = (_a = config === null || config === void 0 ? void 0 : config.startDelayInMs) !== null && _a !== void 0 ? _a : 1000;
var blankAreaResult = (0, react_1.useRef)({
maxBlankArea: 0,
cumulativeBlankArea: 0,
}).current;
var waitOperations = (0, react_1.useRef)({ inProgress: false, complete: false }).current;
var onBlankAreaChangeRef = (0, react_1.useRef)(onBlankAreaChange);
onBlankAreaChangeRef.current = onBlankAreaChange;
var blankAreaTracker = (0, react_1.useCallback)(function (event) {
var _a, _b;
// we're ignoring some of the events that will be fired on list load
// initial events are fired on mount and thus, this won't lead to missing events during scroll
if (!waitOperations.complete && startDelay > 0) {
if (!waitOperations.inProgress) {
waitOperations.inProgress = true;
setTimeout(function () {
waitOperations.complete = true;
}, startDelay);
}
return;
}
var rlv = (_a = flashListRef.current) === null || _a === void 0 ? void 0 : _a.recyclerlistview_unsafe;
var horizontal = Boolean((_b = flashListRef.current) === null || _b === void 0 ? void 0 : _b.props.horizontal);
if (rlv) {
processBlankAreaChange(rlv, horizontal, blankAreaResult, event, onBlankAreaChangeRef.current, config);
}
},
// eslint-disable-next-line react-hooks/exhaustive-deps
[flashListRef]);
return [blankAreaResult, blankAreaTracker];
}
exports.useBlankAreaTracker = useBlankAreaTracker;
function processBlankAreaChange(rlv, horizontal, blankAreaResult, event, onBlankAreaChange, config) {
var listSize = horizontal
? rlv.getRenderedSize().width
: rlv.getRenderedSize().height;
var contentSize = horizontal
? rlv.getContentDimension().width
: rlv.getContentDimension().height;
// ignores blank events when there isn't enough content to fill the list
if (contentSize > listSize) {
var lastMaxBlankArea = blankAreaResult.maxBlankArea;
var lastCumulativeBlankArea = blankAreaResult.cumulativeBlankArea;
blankAreaResult.maxBlankArea = Math.max(blankAreaResult.maxBlankArea, event.blankArea, 0);
blankAreaResult.cumulativeBlankArea += (config === null || config === void 0 ? void 0 : config.sumNegativeValues)
? event.blankArea
: Math.max(event.blankArea, 0);
if (lastCumulativeBlankArea !== blankAreaResult.cumulativeBlankArea ||
lastMaxBlankArea !== blankAreaResult.maxBlankArea) {
onBlankAreaChange === null || onBlankAreaChange === void 0 ? void 0 : onBlankAreaChange(blankAreaResult);
}
}
}
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