@shopify/flash-list
Version:
FlashList is a more performant FlatList replacement
68 lines • 2.93 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.Cancellable = exports.autoScroll = void 0;
/**
* This method can be used to trigger scroll events that can be forwarded to an element. Anything that implements scrollable can leverage this.
* @param scroll The scrollable element
* @param fromX The x offset to start from
* @param fromY The y offset to start from
* @param toX the x offset to end scroll at
* @param toY the y offset to end scroll at
* @param speedMultiplier the speed multiplier to use
* @param cancellable can be used to cancel the scroll
* @returns Promise that resolves when the scroll is complete
*/
function autoScroll(scroll, fromX, fromY, toX, toY, speedMultiplier, cancellable) {
if (speedMultiplier === void 0) { speedMultiplier = 1; }
if (cancellable === void 0) { cancellable = new Cancellable(); }
return new Promise(function (resolve) {
scroll(fromX, fromY, false);
// Very fast scrolls on Android/iOS typically move content 7px every millisecond.
var incrementPerMs = 7 * speedMultiplier;
var directionMultiplierX = toX > fromX ? 1 : -1;
var directionMultiplierY = toY > fromY ? 1 : -1;
var comparatorX = toX > fromX ? Math.min : Math.max;
var comparatorY = toY > fromY ? Math.min : Math.max;
var startTime = Date.now();
var startX = fromX;
var startY = fromY;
// Computes the number of pixels to scroll in the given time
// Also invokes the scrollable to update the scroll position
var animationLoop = function () {
requestAnimationFrame(function () {
if (cancellable.isCancelled()) {
resolve(false);
return;
}
var currentTime = Date.now();
var timeElapsed = currentTime - startTime;
var distanceToCover = incrementPerMs * timeElapsed;
startX += distanceToCover * directionMultiplierX;
startY += distanceToCover * directionMultiplierY;
scroll(comparatorX(toX, startX), comparatorY(toY, startY), false);
startTime = currentTime;
if (comparatorX(toX, startX) !== toX ||
comparatorY(toY, startY) !== toY) {
return animationLoop();
}
resolve(true);
});
};
animationLoop();
});
}
exports.autoScroll = autoScroll;
var Cancellable = /** @class */ (function () {
function Cancellable() {
this._isCancelled = false;
}
Cancellable.prototype.cancel = function () {
this._isCancelled = true;
};
Cancellable.prototype.isCancelled = function () {
return this._isCancelled;
};
return Cancellable;
}());
exports.Cancellable = Cancellable;
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