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import React from 'react';
import PropTypes from 'prop-types';
import scheduleIdleTask from '../features/ui/util/schedule_idle_task';
import getRectFromEntry from '../features/ui/util/get_rect_from_entry';
// Diff these props in the "unrendered" state
const updateOnPropsForUnrendered = ['id', 'index', 'listLength', 'cachedHeight'];
export default class IntersectionObserverArticle extends React.Component {
static propTypes = {
intersectionObserverWrapper: PropTypes.object.isRequired,
id: PropTypes.oneOfType([PropTypes.string, PropTypes.number]),
index: PropTypes.oneOfType([PropTypes.string, PropTypes.number]),
listLength: PropTypes.oneOfType([PropTypes.string, PropTypes.number]),
saveHeightKey: PropTypes.string,
cachedHeight: PropTypes.number,
onHeightChange: PropTypes.func,
children: PropTypes.node,
};
state = {
isHidden: false, // set to true in requestIdleCallback to trigger un-render
};
shouldComponentUpdate (nextProps, nextState) {
const isUnrendered = !this.state.isIntersecting && (this.state.isHidden || this.props.cachedHeight);
const willBeUnrendered = !nextState.isIntersecting && (nextState.isHidden || nextProps.cachedHeight);
if (!!isUnrendered !== !!willBeUnrendered) {
// If we're going from rendered to unrendered (or vice versa) then update
return true;
}
// If we are and remain hidden, diff based on props
if (isUnrendered) {
return !updateOnPropsForUnrendered.every(prop => nextProps[prop] === this.props[prop]);
}
// Else, assume the children have changed
return true;
}
componentDidMount () {
const { intersectionObserverWrapper, id } = this.props;
intersectionObserverWrapper.observe(
id,
this.node,
this.handleIntersection,
);
this.componentMounted = true;
}
componentWillUnmount () {
const { intersectionObserverWrapper, id } = this.props;
intersectionObserverWrapper.unobserve(id, this.node);
this.componentMounted = false;
}
handleIntersection = (entry) => {
this.entry = entry;
scheduleIdleTask(this.calculateHeight);
this.setState(this.updateStateAfterIntersection);
};
updateStateAfterIntersection = (prevState) => {
if (prevState.isIntersecting !== false && !this.entry.isIntersecting) {
scheduleIdleTask(this.hideIfNotIntersecting);
}
return {
isIntersecting: this.entry.isIntersecting,
isHidden: false,
};
};
calculateHeight = () => {
const { onHeightChange, saveHeightKey, id } = this.props;
// save the height of the fully-rendered element (this is expensive
// on Chrome, where we need to fall back to getBoundingClientRect)
this.height = getRectFromEntry(this.entry).height;
if (onHeightChange && saveHeightKey) {
onHeightChange(saveHeightKey, id, this.height);
}
};
hideIfNotIntersecting = () => {
if (!this.componentMounted) {
return;
}
// When the browser gets a chance, test if we're still not intersecting,
// and if so, set our isHidden to true to trigger an unrender. The point of
// this is to save DOM nodes and avoid using up too much memory.
// See: https://github.com/mastodon/mastodon/issues/2900
this.setState((prevState) => ({ isHidden: !prevState.isIntersecting }));
};
handleRef = (node) => {
this.node = node;
};
render () {
const { children, id, index, listLength, cachedHeight } = this.props;
const { isIntersecting, isHidden } = this.state;
const style = {};
if (!isIntersecting && (isHidden || cachedHeight)) {
style.height = `${this.height || cachedHeight || 150}px`;
style.opacity = 0;
style.overflow = 'hidden';
}
return (
<article
ref={this.handleRef}
aria-posinset={index + 1}
aria-setsize={listLength}
data-id={id}
tabIndex={0}
style={style}
>
{children && React.cloneElement(children, { hidden: !isIntersecting && (isHidden || !!cachedHeight) })}
</article>
);
}
}
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