46 lines
1.6 KiB
Plaintext
46 lines
1.6 KiB
Plaintext
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/**
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* Copyright (c) 2013-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @providesModule getScrollPosition
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* @typechecks
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*/
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'use strict';
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const getDocumentScrollElement = require('./getDocumentScrollElement');
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const getUnboundedScrollPosition = require('./getUnboundedScrollPosition');
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/**
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* Gets the scroll position of the supplied element or window.
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*
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* The return values are bounded. This means that if the scroll position is
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* negative or exceeds the element boundaries (which is possible using inertial
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* scrolling), you will get zero or the maximum scroll position, respectively.
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*
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* If you need the unbound scroll position, use `getUnboundedScrollPosition`.
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*
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* @param {DOMWindow|DOMElement} scrollable
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* @return {object} Map with `x` and `y` keys.
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*/
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function getScrollPosition(scrollable) {
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const documentScrollElement = getDocumentScrollElement(scrollable.ownerDocument || scrollable.document);
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if (scrollable.Window && scrollable instanceof scrollable.Window) {
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scrollable = documentScrollElement;
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}
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const scrollPosition = getUnboundedScrollPosition(scrollable);
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const viewport = scrollable === documentScrollElement ? scrollable.ownerDocument.documentElement : scrollable;
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const xMax = scrollable.scrollWidth - viewport.clientWidth;
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const yMax = scrollable.scrollHeight - viewport.clientHeight;
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scrollPosition.x = Math.max(0, Math.min(scrollPosition.x, xMax));
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scrollPosition.y = Math.max(0, Math.min(scrollPosition.y, yMax));
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return scrollPosition;
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}
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module.exports = getScrollPosition;
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