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use-max-width-observer.js
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use-max-width-observer.js
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/**
* WordPress dependencies
*/
import { cloneElement, useRef, useMemo } from '@wordpress/element';
import { useResizeObserver } from '@wordpress/compose';
function useMaxWidthObserver() {
const [ contentResizeListener, { width } ] = useResizeObserver();
const observerRef = useRef();
const maxWidthObserver = (
<div
// Some themes set max-width on blocks.
className="wp-block"
aria-hidden="true"
style={ {
position: 'absolute',
inset: 0,
width: '100%',
height: 0,
margin: 0,
} }
ref={ observerRef }
>
{ cloneElement( contentResizeListener, {
style: {
...contentResizeListener.props.style,
position: 'relative',
},
} ) }
</div>
);
const maxWidth = useMemo( () => {
const observer = observerRef.current;
if ( ! observer ) {
return width;
}
const win = observer.ownerDocument.defaultView;
const observerStyle = win.getComputedStyle( observer );
const parentStyle = win.getComputedStyle( observer.parentElement );
const isParentBorderBox = parentStyle.boxSizing === 'border-box';
const paddingInline = isParentBorderBox
? 0
: parseFloat( parentStyle.paddingLeft ) +
parseFloat( parentStyle.paddingRight );
const observerMaxWidth = parseFloat( observerStyle.maxWidth );
const contentWidth =
width - ( Number.isNaN( paddingInline ) ? 0 : paddingInline );
return Number.isNaN( observerMaxWidth )
? contentWidth
: Math.min( contentWidth, observerMaxWidth );
}, [ width ] );
return [ maxWidthObserver, maxWidth ];
}
export { useMaxWidthObserver };