55 lines
1.3 KiB
TypeScript
55 lines
1.3 KiB
TypeScript
// Copyright 2020-2021 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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import type { Ref } from 'react';
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import { useEffect, useState } from 'react';
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import { first, last, noop } from 'lodash';
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function getTop(element: Readonly<Element>): number {
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return element.getBoundingClientRect().top;
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}
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function isWrapped(element: Readonly<null | HTMLElement>): boolean {
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if (!element) {
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return false;
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}
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const { children } = element;
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const firstChild = first(children);
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const lastChild = last(children);
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return Boolean(
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firstChild &&
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lastChild &&
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firstChild !== lastChild &&
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getTop(firstChild) !== getTop(lastChild)
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);
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}
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/**
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* A hook that returns a ref (to put on your element) and a boolean. The boolean will be
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* `true` if the element's children have different `top`s, and `false` otherwise.
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*/
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export function useHasWrapped<T extends HTMLElement>(): [Ref<T>, boolean] {
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const [element, setElement] = useState<null | T>(null);
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const [hasWrapped, setHasWrapped] = useState(isWrapped(element));
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useEffect(() => {
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if (!element) {
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return noop;
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}
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const observer = new ResizeObserver(() => {
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setHasWrapped(isWrapped(element));
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});
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observer.observe(element);
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return () => {
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observer.disconnect();
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};
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}, [element]);
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return [setElement, hasWrapped];
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}
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