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/** |
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* The tab bar. |
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* |
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* Built by hand rather than with TabPanel, because the address has to carry |
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* the tab: a bookmark, a reload and a link shared with a colleague should all |
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* arrive in the same place. TabPanel keeps that state to itself. |
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* |
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* On a narrow screen the bar scrolls sideways instead of wrapping, which keeps |
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* the tabs on one line and the content where the eye expects it. |
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*/ |
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|
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import { useEffect, useRef, useState } from '@wordpress/element'; |
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|
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export default function Tabs( { tabs, active, onSelect } ) { |
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const listRef = useRef( null ); |
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const [ atEnd, setAtEnd ] = useState( false ); |
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|
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// Keep the selected tab in view. Arriving with ?tab=advanced on a phone |
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// otherwise showed the first tab underlined off-screen and the last one cut |
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// in half, with nothing to say the bar could be scrolled at all. |
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useEffect( () => { |
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const list = listRef.current; |
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|
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if ( ! list ) { |
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return undefined; |
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} |
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|
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// scrollLeft by hand rather than scrollIntoView: the latter walks up the |
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// ancestors and scrolls whatever it finds, which on a phone dragged the |
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// whole admin page a few pixels sideways every time a tab was picked. |
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// This touches nothing but the bar itself. |
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const activeTab = list.querySelector( '.is-active' ); |
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|
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if ( activeTab ) { |
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const overflowRight = |
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activeTab.offsetLeft + |
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activeTab.offsetWidth - |
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( list.scrollLeft + list.clientWidth ); |
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const overflowLeft = list.scrollLeft - activeTab.offsetLeft; |
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|
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if ( overflowRight > 0 ) { |
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list.scrollLeft += overflowRight + 16; |
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} else if ( overflowLeft > 0 ) { |
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list.scrollLeft -= overflowLeft + 16; |
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} |
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} |
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|
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// The fade at the right edge announces "there is more". Once the end is |
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// reached it would be announcing something untrue, so it is dropped. |
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const update = () => { |
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const remaining = |
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list.scrollWidth - list.scrollLeft - list.clientWidth; |
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setAtEnd( remaining <= 1 ); |
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}; |
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|
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update(); |
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list.addEventListener( 'scroll', update, { passive: true } ); |
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window.addEventListener( 'resize', update ); |
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|
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return () => { |
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list.removeEventListener( 'scroll', update ); |
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window.removeEventListener( 'resize', update ); |
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}; |
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}, [ active, tabs ] ); |
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|
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/** |
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* Left and right move between tabs, as the tab pattern expects. |
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* |
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* @param {Object} event The keyboard event. |
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* @param {number} index Position of the focused tab. |
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*/ |
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const onKeyDown = ( event, index ) => { |
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let next = null; |
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|
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if ( event.key === 'ArrowRight' ) { |
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next = ( index + 1 ) % tabs.length; |
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} else if ( event.key === 'ArrowLeft' ) { |
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next = ( index - 1 + tabs.length ) % tabs.length; |
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} else if ( event.key === 'Home' ) { |
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next = 0; |
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} else if ( event.key === 'End' ) { |
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next = tabs.length - 1; |
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} |
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|
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if ( next === null ) { |
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return; |
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} |
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|
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event.preventDefault(); |
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onSelect( tabs[ next ].id ); |
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listRef.current?.querySelectorAll( '[role="tab"]' )[ next ]?.focus(); |
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}; |
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|
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return ( |
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<div |
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className={ 'cryptx-tabs' + ( atEnd ? ' is-scrolled-end' : '' ) } |
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role="tablist" |
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ref={ listRef } |
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> |
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{ tabs.map( ( tab, index ) => { |
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const isActive = tab.id === active; |
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|
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return ( |
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<button |
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key={ tab.id } |
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type="button" |
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role="tab" |
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id={ `cryptx-tab-${ tab.id }` } |
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aria-selected={ isActive } |
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aria-controls={ `cryptx-panel-${ tab.id }` } |
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tabIndex={ isActive ? 0 : -1 } |
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className={ |
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'cryptx-tabs__tab' + |
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( isActive ? ' is-active' : '' ) |
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} |
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onClick={ () => onSelect( tab.id ) } |
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onKeyDown={ ( event ) => onKeyDown( event, index ) } |
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> |
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{ tab.label } |
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</button> |
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); |
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} ) } |
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</div> |
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); |
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} |
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|
