110 lines
3.5 KiB
TypeScript
110 lines
3.5 KiB
TypeScript
import clsx from 'clsx';
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import throttle from 'lodash/throttle';
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import React, { useState, useEffect, useCallback } from 'react';
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import { useIntl, MessageDescriptor } from 'react-intl';
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import Icon from 'pl-fe/components/ui/icon';
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import Text from 'pl-fe/components/ui/text';
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import { useSettings } from 'pl-fe/hooks/use-settings';
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interface IScrollTopButton {
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/** Callback when clicked, and also when scrolled to the top. */
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onClick: () => void;
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/** Number of unread items. */
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count: number;
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/** Message to display in the button (should contain a `{count}` value). */
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message: MessageDescriptor;
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/** Distance from the top of the screen (scrolling down) before the button appears. */
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threshold?: number;
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/** Distance from the top of the screen (scrolling up) before the action is triggered. */
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autoloadThreshold?: number;
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}
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/** Floating new post counter above timelines, clicked to scroll to top. */
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const ScrollTopButton: React.FC<IScrollTopButton> = ({
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onClick,
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count,
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message,
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threshold = 240,
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autoloadThreshold = 50,
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}) => {
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const intl = useIntl();
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const { autoloadTimelines } = useSettings();
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// Whether we are scrolled past the `threshold`.
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const [scrolled, setScrolled] = useState<boolean>(false);
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// Whether we are scrolled above the `autoloadThreshold`.
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const [scrolledTop, setScrolledTop] = useState<boolean>(false);
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const visible = count > 0 && scrolled;
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/** Number of pixels scrolled down from the top of the page. */
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const getScrollTop = (): number => (document.scrollingElement || document.documentElement).scrollTop;
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/** Unload feed items if scrolled to the top. */
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const maybeUnload = useCallback(() => {
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if (autoloadTimelines && scrolledTop && count) {
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onClick();
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}
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}, [autoloadTimelines, scrolledTop, count, onClick]);
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/** Set state while scrolling. */
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const handleScroll = useCallback(throttle(() => {
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const scrollTop = getScrollTop();
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setScrolled(scrollTop > threshold);
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setScrolledTop(scrollTop <= autoloadThreshold);
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}, 40, { trailing: true }), [threshold, autoloadThreshold]);
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/** Scroll to top and trigger `onClick`. */
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const handleClick: React.MouseEventHandler = useCallback(() => {
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window.scrollTo({ top: 0 });
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onClick();
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}, [onClick]);
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useEffect(() => {
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// Delay adding the scroll listener so navigating back doesn't
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// unload feed items before the feed is rendered.
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setTimeout(() => {
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window.addEventListener('scroll', handleScroll);
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handleScroll();
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}, 250);
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return () => {
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window.removeEventListener('scroll', handleScroll);
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};
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}, [handleScroll]);
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useEffect(() => {
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maybeUnload();
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}, [maybeUnload]);
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return (
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<div
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className={clsx(
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'fixed left-1/2 z-50 -translate-x-1/2 transition-all', {
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'top-2 opacity-100': visible,
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'-top-4 opacity-0': !visible,
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})}
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aria-hidden={!visible}
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>
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<button
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className='flex cursor-pointer items-center space-x-1.5 whitespace-nowrap rounded-full bg-primary-600/80 px-4 py-2 text-white backdrop-blur-md transition-transform hover:scale-105 hover:bg-primary-700/80 active:scale-100'
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onClick={handleClick}
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tabIndex={visible ? 0 : -1}
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>
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<Icon
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className='size-4'
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src={require('@tabler/icons/outline/arrow-bar-to-up.svg')}
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/>
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<Text theme='inherit' size='sm'>
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{intl.formatMessage(message, { count })}
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</Text>
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</button>
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</div>
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);
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};
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export { ScrollTopButton as default };
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