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	 * Highlights code blocks within the given deck.
	 *
	 * Note that this can be called multiple times if
	 * there are multiple presentations on one page.
	 *
	 * @param {Reveal} reveal the reveal.js instance
	 */
	init: function( reveal ) {

		// Read the plugin config options and provide fallbacks
		let config = reveal.getConfig().highlight || {};

		config.highlightOnLoad = typeof config.highlightOnLoad === 'boolean' ? config.highlightOnLoad : true;
		config.escapeHTML = typeof config.escapeHTML === 'boolean' ? config.escapeHTML : true;

		Array.from( reveal.getRevealElement().querySelectorAll( 'pre code' ) ).forEach( block => {

			block.parentNode.classList.add('code-wrapper');

			// Code can optionally be wrapped in script template to avoid
			// HTML being parsed by the browser (i.e. when you need to
			// include <, > or & in your code).
			let substitute = block.querySelector( 'script[type="text/template"]' );
			if( substitute ) {
				// textContent handles the HTML entity escapes for us
				block.textContent = substitute.innerHTML;
			}

			// Trim whitespace if the "data-trim" attribute is present
			if( block.hasAttribute( 'data-trim' ) && typeof block.innerHTML.trim === 'function' ) {
				block.innerHTML = betterTrim( block );
			}

			// Escape HTML tags unless the "data-noescape" attrbute is present
			if( config.escapeHTML && !block.hasAttribute( 'data-noescape' )) {
				block.innerHTML = block.innerHTML.replace( /</g,"&lt;").replace(/>/g, '&gt;' );
			}

			// Re-highlight when focus is lost (for contenteditable code)
			block.addEventListener( 'focusout', function( event ) {
				hljs.highlightElement( event.currentTarget );
			}, false );

		} );

		// Triggers a callback function before we trigger highlighting
		if( typeof config.beforeHighlight === 'function' ) {
			config.beforeHighlight( hljs );
		}

		// Run initial highlighting for all code
		if( config.highlightOnLoad ) {
			Array.from( reveal.getRevealElement().querySelectorAll( 'pre code' ) ).forEach( block => {
				Plugin.highlightBlock( block );
			} );
		}

		// If we're printing to PDF, scroll the code highlights of
		// all blocks in the deck into view at once
		reveal.on( 'pdf-ready', function() {
			[].slice.call( reveal.getRevealElement().querySelectorAll( 'pre code[data-line-numbers].current-fragment' ) ).forEach( function( block ) {
				Plugin.scrollHighlightedLineIntoView( block, {}, true );
			} );
		} );

	},

	/**
	 * Highlights a code block. If the <code> node has the
	 * 'data-line-numbers' attribute we also generate slide
	 * numbers.
	 *
	 * If the block contains multiple line highlight steps,
	 * we clone the block and create a fragment for each step.
	 */
	highlightBlock: function( block ) {

		hljs.highlightElement( block );

		// Don't generate line numbers for empty code blocks
		if( block.innerHTML.trim().length === 0 ) return;

		if( block.hasAttribute( 'data-line-numbers' ) ) {
			hljs.lineNumbersBlock( block, { singleLine: true } );

			var scrollState = { currentBlock: block };

			// If there is more than one highlight step, generate
			// fragments
			var highlightSteps = Plugin.deserializeHighlightSteps( block.getAttribute( 'data-line-numbers' ) );
			if( highlightSteps.length > 1 ) {

				// If the original code block has a fragment-index,
				// each clone should follow in an incremental sequence
				var fragmentIndex = parseInt( block.getAttribute( 'data-fragment-index' ), 10 );

				if( typeof fragmentIndex !== 'number' || isNaN( fragmentIndex ) ) {
					fragmentIndex = null;
				}

				// Generate fragments for all steps except the original block
				highlightSteps.slice(1).forEach( function( highlight ) {

					var fragmentBlock = block.cloneNode( true );
					fragmentBlock.setAttribute( 'data-line-numbers', Plugin.serializeHighlightSteps( [ highlight ] ) );
					fragmentBlock.classList.add( 'fragment' );
					block.parentNode.appendChild( fragmentBlock );
					Plugin.highlightLines( fragmentBlock );

					if( typeof fragmentIndex === 'number' ) {
						fragmentBlock.setAttribute( 'data-fragment-index', fragmentIndex );
						fragmentIndex += 1;
					}
					else {
						fragmentBlock.removeAttribute( 'data-fragment-index' );
					}

					// Scroll highlights into view as we step through them
					fragmentBlock.addEventListener( 'visible', Plugin.scrollHighlightedLineIntoView.bind( Plugin, fragmentBlock, scrollState ) );
					fragmentBlock.addEventListener( 'hidden', Plugin.scrollHighlightedLineIntoView.bind( Plugin, fragmentBlock.previousElementSibling, scrollState ) );

				} );

				block.removeAttribute( 'data-fragment-index' );
				block.setAttribute( 'data-line-numbers', Plugin.serializeHighlightSteps( [ highlightSteps[0] ] ) );

			}

			// Scroll the first highlight into view when the slide
			// becomes visible. Note supported in IE11 since it lacks
			// support for Element.closest.
			var slide = typeof block.closest === 'function' ? block.closest( 'section:not(.stack)' ) : null;
			if( slide ) {
				var scrollFirstHighlightIntoView = function() {
					Plugin.scrollHighlightedLineIntoView( block, scrollState, true );
					slide.removeEventListener( 'visible', scrollFirstHighlightIntoView );
				}
				slide.addEventListener( 'visible', scrollFirstHighlightIntoView );
			}

			Plugin.highlightLines( block );

		}

	},

	/**
	 * Animates scrolling to the first highlighted line
	 * in the given code block.
	 */
	scrollHighlightedLineIntoView: function( block, scrollState, skipAnimation ) {

		cancelAnimationFrame( scrollState.animationFrameID );

		// Match the scroll position of the currently visible
		// code block
		if( scrollState.currentBlock ) {
			block.scrollTop = scrollState.currentBlock.scrollTop;
		}

		// Remember the current code block so that we can match
		// its scroll position when showing/hiding fragments
		scrollState.currentBlock = block;

		var highlightBounds = this.getHighlightedLineBounds( block )
		var viewportHeight = block.offsetHeight;

		// Subtract padding from the viewport height
		var blockStyles = getComputedStyle( block );
		viewportHeight -= parseInt( blockStyles.paddingTop ) + parseInt( blockStyles.paddingBottom );

		// Scroll position which centers all highlights
		var startTop = block.scrollTop;
		var targetTop = highlightBounds.top + ( Math.min( highlightBounds.bottom - highlightBounds.top, viewportHeight ) - viewportHeight ) / 2;

		// Account for offsets in position applied to the
		// <table> that holds our lines of code
		var lineTable = block.querySelector( '.hljs-ln' );
		if( lineTable ) targetTop += lineTable.offsetTop - parseInt( blockStyles.paddingTop );

		// Make sure the scroll target is within bounds
		targetTop = Math.max( Math.min( targetTop, block.scrollHeight - viewportHeight ), 0 );

		if( skipAnimation === true || startTop === targetTop ) {
			block.scrollTop = targetTop;
		}
		else {

			// Don't attempt to scroll if there is no overflow
			if( block.scrollHeight <= viewportHeight ) return;

			var time = 0;
			var animate = function() {
				time = Math.min( time + 0.02, 1 );

				// Update our eased scroll position
				block.scrollTop = startTop + ( targetTop - startTop ) * Plugin.easeInOutQuart( time );

				// Keep animating unless we've reached the end
				if( time < 1 ) {
					scrollState.animationFrameID = requestAnimationFrame( animate );
				}
			};

			animate();

		}

	},

	/**
	 * The easing function used when scrolling.
	 */
	easeInOutQuart: function( t ) {

		// easeInOutQuart
		return t<.5 ? 8*t*t*t*t : 1-8*(--t)*t*t*t;

	},

	getHighlightedLineBounds: function( block ) {