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.esm suffix for module bundle, marked/highlight.js are installed via npm
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Hakim El Hattab
414
plugin/highlight/plugin.js
Normal file
414
plugin/highlight/plugin.js
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import hljs from 'highlight.js'
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import './highlight-line-numbers.js'
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/*!
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* reveal.js plugin that adds syntax highlight support.
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*/
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const Plugin = {
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id: 'highlight',
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HIGHLIGHT_STEP_DELIMITER: '|',
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HIGHLIGHT_LINE_DELIMITER: ',',
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HIGHLIGHT_LINE_RANGE_DELIMITER: '-',
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/**
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* Highlights code blocks withing the given deck.
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*
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* Note that this can be called multiple times if
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* there are multiple presentations on one page.
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*
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* @param {Reveal} reveal the reveal.js instance
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*/
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init: function( reveal ) {
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// Read the plugin config options and provide fallbacks
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var config = reveal.getConfig().highlight || {};
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config.highlightOnLoad = typeof config.highlightOnLoad === 'boolean' ? config.highlightOnLoad : true;
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config.escapeHTML = typeof config.escapeHTML === 'boolean' ? config.escapeHTML : true;
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[].slice.call( reveal.getRevealElement().querySelectorAll( 'pre code' ) ).forEach( function( block ) {
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// Trim whitespace if the "data-trim" attribute is present
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if( block.hasAttribute( 'data-trim' ) && typeof block.innerHTML.trim === 'function' ) {
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block.innerHTML = betterTrim( block );
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}
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// Escape HTML tags unless the "data-noescape" attrbute is present
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if( config.escapeHTML && !block.hasAttribute( 'data-noescape' )) {
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block.innerHTML = block.innerHTML.replace( /</g,"<").replace(/>/g, '>' );
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}
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// Re-highlight when focus is lost (for contenteditable code)
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block.addEventListener( 'focusout', function( event ) {
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hljs.highlightBlock( event.currentTarget );
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}, false );
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if( config.highlightOnLoad ) {
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Plugin.highlightBlock( block );
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}
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} );
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// If we're printing to PDF, scroll the code highlights of
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// all blocks in the deck into view at once
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reveal.on( 'pdf-ready', function() {
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[].slice.call( reveal.getRevealElement().querySelectorAll( 'pre code[data-line-numbers].current-fragment' ) ).forEach( function( block ) {
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Plugin.scrollHighlightedLineIntoView( block, {}, true );
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} );
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} );
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},
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/**
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* Highlights a code block. If the <code> node has the
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* 'data-line-numbers' attribute we also generate slide
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* numbers.
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*
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* If the block contains multiple line highlight steps,
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* we clone the block and create a fragment for each step.
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*/
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highlightBlock: function( block ) {
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hljs.highlightBlock( block );
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// Don't generate line numbers for empty code blocks
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if( block.innerHTML.trim().length === 0 ) return;
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if( block.hasAttribute( 'data-line-numbers' ) ) {
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hljs.lineNumbersBlock( block, { singleLine: true } );
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var scrollState = { currentBlock: block };
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// If there is at least one highlight step, generate
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// fragments
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var highlightSteps = Plugin.deserializeHighlightSteps( block.getAttribute( 'data-line-numbers' ) );
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if( highlightSteps.length > 1 ) {
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// If the original code block has a fragment-index,
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// each clone should follow in an incremental sequence
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var fragmentIndex = parseInt( block.getAttribute( 'data-fragment-index' ), 10 );
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if( typeof fragmentIndex !== 'number' || isNaN( fragmentIndex ) ) {
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fragmentIndex = null;
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}
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// Generate fragments for all steps except the original block
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highlightSteps.slice(1).forEach( function( highlight ) {
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var fragmentBlock = block.cloneNode( true );
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fragmentBlock.setAttribute( 'data-line-numbers', Plugin.serializeHighlightSteps( [ highlight ] ) );
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fragmentBlock.classList.add( 'fragment' );
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block.parentNode.appendChild( fragmentBlock );
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Plugin.highlightLines( fragmentBlock );
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if( typeof fragmentIndex === 'number' ) {
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fragmentBlock.setAttribute( 'data-fragment-index', fragmentIndex );
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fragmentIndex += 1;
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}
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else {
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fragmentBlock.removeAttribute( 'data-fragment-index' );
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}
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// Scroll highlights into view as we step through them
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fragmentBlock.addEventListener( 'visible', Plugin.scrollHighlightedLineIntoView.bind( Plugin, fragmentBlock, scrollState ) );
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fragmentBlock.addEventListener( 'hidden', Plugin.scrollHighlightedLineIntoView.bind( Plugin, fragmentBlock.previousSibling, scrollState ) );
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} );
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block.removeAttribute( 'data-fragment-index' )
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block.setAttribute( 'data-line-numbers', Plugin.serializeHighlightSteps( [ highlightSteps[0] ] ) );
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}
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// Scroll the first highlight into view when the slide
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// becomes visible. Note supported in IE11 since it lacks
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// support for Element.closest.
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var slide = typeof block.closest === 'function' ? block.closest( 'section:not(.stack)' ) : null;
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if( slide ) {
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var scrollFirstHighlightIntoView = function() {
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Plugin.scrollHighlightedLineIntoView( block, scrollState, true );
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slide.removeEventListener( 'visible', scrollFirstHighlightIntoView );
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}
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slide.addEventListener( 'visible', scrollFirstHighlightIntoView );
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}
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Plugin.highlightLines( block );
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}
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},
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/**
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* Animates scrolling to the first highlighted line
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* in the given code block.
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*/
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scrollHighlightedLineIntoView: function( block, scrollState, skipAnimation ) {
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cancelAnimationFrame( scrollState.animationFrameID );
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// Match the scroll position of the currently visible
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// code block
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if( scrollState.currentBlock ) {
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block.scrollTop = scrollState.currentBlock.scrollTop;
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}
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// Remember the current code block so that we can match
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// its scroll position when showing/hiding fragments
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scrollState.currentBlock = block;
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var highlightBounds = this.getHighlightedLineBounds( block )
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var viewportHeight = block.offsetHeight;
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// Subtract padding from the viewport height
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var blockStyles = getComputedStyle( block );
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viewportHeight -= parseInt( blockStyles.paddingTop ) + parseInt( blockStyles.paddingBottom );
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// Scroll position which centers all highlights
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var startTop = block.scrollTop;
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var targetTop = highlightBounds.top + ( Math.min( highlightBounds.bottom - highlightBounds.top, viewportHeight ) - viewportHeight ) / 2;
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// Account for offsets in position applied to the
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// <table> that holds our lines of code
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var lineTable = block.querySelector( '.hljs-ln' );
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if( lineTable ) targetTop += lineTable.offsetTop - parseInt( blockStyles.paddingTop );
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// Make sure the scroll target is within bounds
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targetTop = Math.max( Math.min( targetTop, block.scrollHeight - viewportHeight ), 0 );
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if( skipAnimation === true || startTop === targetTop ) {
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block.scrollTop = targetTop;
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}
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else {
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// Don't attempt to scroll if there is no overflow
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if( block.scrollHeight <= viewportHeight ) return;
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var time = 0;
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var animate = function() {
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time = Math.min( time + 0.02, 1 );
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// Update our eased scroll position
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block.scrollTop = startTop + ( targetTop - startTop ) * Plugin.easeInOutQuart( time );
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// Keep animating unless we've reached the end
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if( time < 1 ) {
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scrollState.animationFrameID = requestAnimationFrame( animate );
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}
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};
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animate();
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}
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},
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/**
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* The easing function used when scrolling.
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*/
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easeInOutQuart: function( t ) {
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// easeInOutQuart
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return t<.5 ? 8*t*t*t*t : 1-8*(--t)*t*t*t;
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},
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getHighlightedLineBounds: function( block ) {
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var highlightedLines = block.querySelectorAll( '.highlight-line' );
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if( highlightedLines.length === 0 ) {
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return { top: 0, bottom: 0 };
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}
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else {
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var firstHighlight = highlightedLines[0];
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var lastHighlight = highlightedLines[ highlightedLines.length -1 ];
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return {
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top: firstHighlight.offsetTop,
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bottom: lastHighlight.offsetTop + lastHighlight.offsetHeight
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}
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}
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},
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/**
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* Visually emphasize specific lines within a code block.
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* This only works on blocks with line numbering turned on.
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*
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* @param {HTMLElement} block a <code> block
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* @param {String} [linesToHighlight] The lines that should be
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* highlighted in this format:
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* "1" = highlights line 1
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* "2,5" = highlights lines 2 & 5
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* "2,5-7" = highlights lines 2, 5, 6 & 7
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*/
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highlightLines: function( block, linesToHighlight ) {
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var highlightSteps = Plugin.deserializeHighlightSteps( linesToHighlight || block.getAttribute( 'data-line-numbers' ) );
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if( highlightSteps.length ) {
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highlightSteps[0].forEach( function( highlight ) {
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var elementsToHighlight = [];
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// Highlight a range
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if( typeof highlight.end === 'number' ) {
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elementsToHighlight = [].slice.call( block.querySelectorAll( 'table tr:nth-child(n+'+highlight.start+'):nth-child(-n+'+highlight.end+')' ) );
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}
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// Highlight a single line
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else if( typeof highlight.start === 'number' ) {
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elementsToHighlight = [].slice.call( block.querySelectorAll( 'table tr:nth-child('+highlight.start+')' ) );
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}
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if( elementsToHighlight.length ) {
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elementsToHighlight.forEach( function( lineElement ) {
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lineElement.classList.add( 'highlight-line' );
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} );
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block.classList.add( 'has-highlights' );
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}
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} );
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}
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},
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/**
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* Parses and formats a user-defined string of line
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* numbers to highlight.
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*
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* @example
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* Plugin.deserializeHighlightSteps( '1,2|3,5-10' )
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* // [
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* // [ { start: 1 }, { start: 2 } ],
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* // [ { start: 3 }, { start: 5, end: 10 } ]
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* // ]
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*/
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deserializeHighlightSteps: function( highlightSteps ) {
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// Remove whitespace
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highlightSteps = highlightSteps.replace( /\s/g, '' );
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// Divide up our line number groups
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highlightSteps = highlightSteps.split( Plugin.HIGHLIGHT_STEP_DELIMITER );
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return highlightSteps.map( function( highlights ) {
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return highlights.split( Plugin.HIGHLIGHT_LINE_DELIMITER ).map( function( highlight ) {
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// Parse valid line numbers
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if( /^[\d-]+$/.test( highlight ) ) {
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highlight = highlight.split( Plugin.HIGHLIGHT_LINE_RANGE_DELIMITER );
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var lineStart = parseInt( highlight[0], 10 ),
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lineEnd = parseInt( highlight[1], 10 );
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if( isNaN( lineEnd ) ) {
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return {
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start: lineStart
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};
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}
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else {
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return {
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start: lineStart,
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end: lineEnd
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};
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}
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}
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// If no line numbers are provided, no code will be highlighted
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else {
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return {};
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}
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} );
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} );
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},
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/**
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* Serializes parsed line number data into a string so
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* that we can store it in the DOM.
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*/
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serializeHighlightSteps: function( highlightSteps ) {
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return highlightSteps.map( function( highlights ) {
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return highlights.map( function( highlight ) {
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// Line range
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if( typeof highlight.end === 'number' ) {
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return highlight.start + Plugin.HIGHLIGHT_LINE_RANGE_DELIMITER + highlight.end;
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}
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// Single line
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else if( typeof highlight.start === 'number' ) {
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return highlight.start;
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}
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// All lines
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else {
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return '';
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}
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} ).join( Plugin.HIGHLIGHT_LINE_DELIMITER );
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} ).join( Plugin.HIGHLIGHT_STEP_DELIMITER );
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}
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}
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// Function to perform a better "data-trim" on code snippets
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// Will slice an indentation amount on each line of the snippet (amount based on the line having the lowest indentation length)
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function betterTrim(snippetEl) {
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// Helper functions
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function trimLeft(val) {
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// Adapted from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim#Polyfill
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return val.replace(/^[\s\uFEFF\xA0]+/g, '');
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}
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function trimLineBreaks(input) {
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var lines = input.split('\n');
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// Trim line-breaks from the beginning
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for (var i = 0; i < lines.length; i++) {
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if (lines[i].trim() === '') {
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lines.splice(i--, 1);
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} else break;
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}
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// Trim line-breaks from the end
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for (var i = lines.length-1; i >= 0; i--) {
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if (lines[i].trim() === '') {
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lines.splice(i, 1);
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} else break;
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}
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return lines.join('\n');
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}
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// Main function for betterTrim()
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return (function(snippetEl) {
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var content = trimLineBreaks(snippetEl.innerHTML);
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var lines = content.split('\n');
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// Calculate the minimum amount to remove on each line start of the snippet (can be 0)
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var pad = lines.reduce(function(acc, line) {
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if (line.length > 0 && trimLeft(line).length > 0 && acc > line.length - trimLeft(line).length) {
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return line.length - trimLeft(line).length;
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}
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return acc;
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}, Number.POSITIVE_INFINITY);
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// Slice each line with this amount
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return lines.map(function(line, index) {
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return line.slice(pad);
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})
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.join('\n');
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})(snippetEl);
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}
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export default () => Plugin;
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