Merge pull request #3845 from Gazook89/Intersection-Observer

Intersection Observers for getting "Current Page(s)"

client/components/Anchored.jsx

@@ -7,6 +7,11 @@ import './Anchored.less';
 // **The Anchor Positioning API is not available in Firefox yet**
 // So in Firefox the positioning isn't perfect but is likely sufficient, and FF team seems to be working on the API quickly.
 
+// When Anchor Positioning is added to Firefox, this can also be rewritten using the Popover API-- add the `popover` attribute
+// to the container div, which will render the container in the *top level* and give it better interactions like
+// click outside to dismiss.  **Do not** add without Anchor, though, because positioning is very limited with the `popover`
+// attribute.
+
 
 const Anchored = ({ children })=>{
 	const [visible, setVisible] = useState(false);

client/homebrew/brewRenderer/brewRenderer.jsx

@@ -1,7 +1,7 @@
 /*eslint max-lines: ["warn", {"max": 300, "skipBlankLines": true, "skipComments": true}]*/
 require('./brewRenderer.less');
 const React = require('react');
-const { useState, useRef, useCallback, useMemo } = React;
+const { useState, useRef, useMemo, useEffect } = React;
 const _ = require('lodash');
 
 const MarkdownLegacy = require('naturalcrit/markdownLegacy.js');
@@ -36,8 +36,46 @@ const BrewPage = (props)=>{
 		index    : 0,
 		...props
 	};
+	const pageRef = useRef(null);
 	const cleanText = safeHTML(props.contents);
-	return <div className={props.className} id={`p${props.index + 1}`} style={props.style}>
+
+	useEffect(()=>{
+		if(!pageRef.current) return;
+
+		// Observer for tracking pages within the `.pages` div
+		const visibleObserver = new IntersectionObserver(
+			(entries)=>{
+				entries.forEach((entry)=>{
+					if(entry.isIntersecting)
+						props.onVisibilityChange(props.index + 1, true, false); // add page to array of visible pages.
+					else
+						props.onVisibilityChange(props.index + 1, false, false);
+				}
+			)},
+			{ threshold: .3, rootMargin: '0px 0px 0px 0px'  } // detect when >30% of page is within bounds.
+		);
+
+		// Observer for tracking the page at the center of the iframe.
+		const centerObserver = new IntersectionObserver(
+			(entries)=>{
+				entries.forEach((entry)=>{
+					if(entry.isIntersecting)
+						props.onVisibilityChange(props.index + 1, true, true); // Set this page as the center page
+				}
+			)},
+			{ threshold: 0, rootMargin: '-50% 0px -50% 0px' } // Detect when the page is at the center
+		);
+
+		// attach observers to each `.page`
+		visibleObserver.observe(pageRef.current);
+		centerObserver.observe(pageRef.current);
+		return ()=>{
+			visibleObserver.disconnect();
+			centerObserver.disconnect();
+		};
+	}, []);
+
+	return <div className={props.className} id={`p${props.index + 1}`} data-index={props.index} ref={pageRef} style={props.style}>
 	         <div className='columnWrapper' dangerouslySetInnerHTML={{ __html: cleanText }} />
 	       </div>;
 };
@@ -64,8 +102,10 @@ const BrewRenderer = (props)=>{
 	};
 
 	const [state, setState] = useState({
-		isMounted  : false,
-		visibility : 'hidden'
+		isMounted    : false,
+		visibility   : 'hidden',
+		visiblePages : [],
+		centerPage   : 1
 	});
 
 	const [displayOptions, setDisplayOptions] = useState({
@@ -83,34 +123,23 @@ const BrewRenderer = (props)=>{
 		rawPages = props.text.split(/^\\page$/gm);
 	}
 
-	const scrollToHash = (hash)=>{
-		if(!hash) return;
+	const handlePageVisibilityChange = (pageNum, isVisible, isCenter)=>{
+		setState((prevState)=>{
+			const updatedVisiblePages = new Set(prevState.visiblePages);
+			if(!isCenter)
+				isVisible ? updatedVisiblePages.add(pageNum) : updatedVisiblePages.delete(pageNum);
 
-		const iframeDoc = document.getElementById('BrewRenderer').contentDocument;
-		let anchor = iframeDoc.querySelector(hash);
+			return {
+				...prevState,
+				visiblePages : [...updatedVisiblePages].sort((a, b)=>a - b),
+				centerPage   : isCenter ? pageNum : prevState.centerPage
+			};
+		});
 
-		if(anchor) {
-			anchor.scrollIntoView({ behavior: 'smooth' });
-		} else {
-			// Use MutationObserver to wait for the element if it's not immediately available
-			new MutationObserver((mutations, obs)=>{
-				anchor = iframeDoc.querySelector(hash);
-				if(anchor) {
-					anchor.scrollIntoView({ behavior: 'smooth' });
-					obs.disconnect();
-				}
-			}).observe(iframeDoc, { childList: true, subtree: true });
-		}
+		if(isCenter)
+			props.onPageChange(pageNum);
 	};
 
-	const updateCurrentPage = useCallback(_.throttle((e)=>{
-		const { scrollTop, clientHeight, scrollHeight } = e.target;
-		const totalScrollableHeight = scrollHeight - clientHeight;
-		const currentPageNumber = Math.max(Math.ceil((scrollTop / totalScrollableHeight) * rawPages.length), 1);
-
-		props.onPageChange(currentPageNumber);
-	}, 200), []);
-
 	const isInView = (index)=>{
 		if(!state.isMounted)
 			return false;
@@ -137,19 +166,21 @@ const BrewRenderer = (props)=>{
 	};
 
 	const renderPage = (pageText, index)=>{
+
+		const styles = {
+			...(!displayOptions.pageShadows ? { boxShadow: 'none' } : {})
+			// Add more conditions as needed
+		};
+
 		if(props.renderer == 'legacy') {
 			const html = MarkdownLegacy.render(pageText);
-			return <BrewPage className='page phb' index={index} key={index} contents={html} />;
+
+			return <BrewPage className='page phb' index={index} key={index} contents={html} style={styles} onVisibilityChange={handlePageVisibilityChange} />;
 		} else {
 			pageText += `\n\n&nbsp;\n\\column\n&nbsp;`; //Artificial column break at page end to emulate column-fill:auto (until `wide` is used, when column-fill:balance will reappear)
 			const html = Markdown.render(pageText, index);
 
-			const styles = {
-				...(!displayOptions.pageShadows ? { boxShadow: 'none' } : {})
-				// Add more conditions as needed
-			};
-
-			return <BrewPage className='page' index={index} key={index} contents={html} style={styles} />;
+			return <BrewPage className='page' index={index} key={index} contents={html} style={styles} onVisibilityChange={handlePageVisibilityChange} />;
 		}
 	};
 
@@ -182,6 +213,26 @@ const BrewRenderer = (props)=>{
 		}
 	};
 
+	const scrollToHash = (hash)=>{
+		if(!hash) return;
+
+		const iframeDoc = document.getElementById('BrewRenderer').contentDocument;
+		let anchor = iframeDoc.querySelector(hash);
+
+		if(anchor) {
+			anchor.scrollIntoView({ behavior: 'smooth' });
+		} else {
+			// Use MutationObserver to wait for the element if it's not immediately available
+			new MutationObserver((mutations, obs)=>{
+				anchor = iframeDoc.querySelector(hash);
+				if(anchor) {
+					anchor.scrollIntoView({ behavior: 'smooth' });
+					obs.disconnect();
+				}
+			}).observe(iframeDoc, { childList: true, subtree: true });
+		}
+	};
+
 	const frameDidMount = ()=>{	//This triggers when iFrame finishes internal "componentDidMount"
 		scrollToHash(window.location.hash);
 
@@ -217,13 +268,13 @@ const BrewRenderer = (props)=>{
 	}
 
 	const renderedStyle = useMemo(()=>renderStyle(), [props.style, props.themeBundle]);
-	renderedPages = useMemo(()=>renderPages(), [displayOptions.pageShadows, props.text]);
+	renderedPages = useMemo(()=>renderPages(), [props.text, displayOptions]);
 
 	return (
 		<>
 			{/*render dummy page while iFrame is mounting.*/}
 			{!state.isMounted
-				? <div className='brewRenderer' onScroll={updateCurrentPage}>
+				? <div className='brewRenderer'>
 					<div className='pages'>
 						{renderDummyPage(1)}
 					</div>
@@ -236,7 +287,7 @@ const BrewRenderer = (props)=>{
 				<NotificationPopup />
 			</div>
 
-			<ToolBar displayOptions={displayOptions} currentPage={props.currentBrewRendererPageNum} totalPages={rawPages.length} onDisplayOptionsChange={handleDisplayOptionsChange} />
+			<ToolBar displayOptions={displayOptions} onDisplayOptionsChange={handleDisplayOptionsChange} visiblePages={state.visiblePages.length > 0 ? state.visiblePages : [state.centerPage]} totalPages={rawPages.length}/>
 
 			{/*render in iFrame so broken code doesn't crash the site.*/}
 			<Frame id='BrewRenderer' initialContent={INITIAL_CONTENT}
@@ -245,18 +296,17 @@ const BrewRenderer = (props)=>{
 				onClick={()=>{emitClick();}}
 			>
 				<div className={`brewRenderer ${global.config.deployment && 'deployment'}`}
-					onScroll={updateCurrentPage}
 					onKeyDown={handleControlKeys}
 					tabIndex={-1}
-					style={ styleObject }>
+					style={ styleObject }
+				>
 
 					{/* Apply CSS from Style tab and render pages from Markdown tab */}
 					{state.isMounted
 						&&
 						<>
 							{renderedStyle}
-							<div lang={`${props.lang || 'en'}`} style={pagesStyle} className={
-								`pages ${displayOptions.startOnRight ? 'recto' : 'verso'}	${displayOptions.spread}` } >
+							<div className={`pages ${displayOptions.startOnRight ? 'recto' : 'verso'}	${displayOptions.spread}`} lang={`${props.lang || 'en'}`} style={pagesStyle}>
 								{renderedPages}
 							</div>
 						</>

client/homebrew/brewRenderer/brewRenderer.less

@@ -17,7 +17,7 @@
 			grid-template-columns: repeat(2, auto); 
 			grid-template-rows: repeat(3, auto); 
 			gap: 10px 10px; 
-			justify-content: center;
+			justify-content: safe center;
 			&.recto .page:first-child {
 				// sets first page on 'right' ('recto') of the preview, as if for a Cover page.  
 				// todo: add a checkbox to toggle this setting
@@ -33,7 +33,7 @@
 			display: flex;
 			flex-wrap: wrap;
 			gap: 10px;
-			justify-content: flex-start;
+			justify-content: safe center;
 			& :where(.page) {
 				flex: 0 0 auto;
 				margin-left: unset !important;

client/homebrew/brewRenderer/toolBar/toolBar.jsx

@@ -1,29 +1,30 @@
+/* eslint-disable max-lines */
 require('./toolBar.less');
 const React = require('react');
 const { useState, useEffect } = React;
 const _ = require('lodash');
 
 import { Anchored, AnchoredBox, AnchoredTrigger } from '../../../components/Anchored.jsx';
-// import * as ZoomIcons from '../../../icons/icon-components/zoomIcons.jsx';
 
 const MAX_ZOOM = 300;
 const MIN_ZOOM = 10;
 
-const ToolBar = ({ displayOptions, currentPage, totalPages, onDisplayOptionsChange })=>{
+const ToolBar = ({ displayOptions, onDisplayOptionsChange, visiblePages, totalPages })=>{
 
-	const [pageNum, setPageNum] = useState(currentPage);
+	const [pageNum, setPageNum]     = useState(1);
 	const [toolsVisible, setToolsVisible] = useState(true);
 
 	useEffect(()=>{
-		setPageNum(currentPage);
-	}, [currentPage]);
+		// format multiple visible pages as a range (e.g. "150-153")
+		const pageRange = visiblePages.length === 1 ? `${visiblePages[0]}` : `${visiblePages[0]} - ${visiblePages.at(-1)}`;
+		setPageNum(pageRange);
+	}, [visiblePages]);
 
 	const handleZoomButton = (zoom)=>{
 		handleOptionChange('zoomLevel', _.round(_.clamp(zoom, MIN_ZOOM, MAX_ZOOM)));
 	};
 
 	const handleOptionChange = (optionKey, newValue)=>{
-		//setDisplayOptions(prevOptions => ({ ...prevOptions, [optionKey]: newValue }));
 		onDisplayOptionsChange({ ...displayOptions, [optionKey]: newValue });
 	};
 
@@ -32,16 +33,16 @@ const ToolBar = ({ displayOptions, currentPage, totalPages, onDisplayOptionsChan
 			setPageNum(parseInt(pageInput)); // input type is 'text', so `page` comes in as a string, not number.
 	};
 
+	// scroll to a page, used in the Prev/Next Page buttons.
 	const scrollToPage = (pageNumber)=>{
+		if(typeof pageNumber !== 'number') return;
 		pageNumber = _.clamp(pageNumber, 1, totalPages);
 		const iframe = document.getElementById('BrewRenderer');
 		const brewRenderer = iframe?.contentWindow?.document.querySelector('.brewRenderer');
 		const page = brewRenderer?.querySelector(`#p${pageNumber}`);
 		page?.scrollIntoView({ block: 'start' });
-		setPageNum(pageNumber);
 	};
 
-
 	const calculateChange = (mode)=>{
 		const iframe = document.getElementById('BrewRenderer');
 		const iframeWidth = iframe.getBoundingClientRect().width;
@@ -57,8 +58,12 @@ const ToolBar = ({ displayOptions, currentPage, totalPages, onDisplayOptionsChan
 			desiredZoom = (iframeWidth / widestPage) * 100;
 
 		} else if(mode == 'fit'){
+			let minDimRatio;
 			// find the page with the largest single dim (height or width) so that zoom can be adapted to fit it.
-			const minDimRatio = [...pages].reduce((minRatio, page)=>Math.min(minRatio, iframeWidth / page.offsetWidth, iframeHeight / page.offsetHeight), Infinity);
+			if(displayOptions.spread === 'facing')
+				minDimRatio = [...pages].reduce((minRatio, page)=>Math.min(minRatio, iframeWidth / page.offsetWidth / 2), Infinity);    // if 'facing' spread, fit two pages in view
+			else 
+				minDimRatio = [...pages].reduce((minRatio, page)=>Math.min(minRatio, iframeWidth / page.offsetWidth, iframeHeight / page.offsetHeight), Infinity);
 
 			desiredZoom = minDimRatio * 100;
 		}
@@ -185,8 +190,8 @@ const ToolBar = ({ displayOptions, currentPage, totalPages, onDisplayOptionsChan
 					className='previousPage tool'
 					type='button'
 					title='Previous Page(s)'
-					onClick={()=>scrollToPage(pageNum - 1)}
-					disabled={pageNum <= 1}
+					onClick={()=>scrollToPage(_.min(visiblePages) - visiblePages.length)}
+					disabled={visiblePages.includes(1)}
 				>
 					<i className='fas fa-arrow-left'></i>
 				</button>
@@ -205,6 +210,7 @@ const ToolBar = ({ displayOptions, currentPage, totalPages, onDisplayOptionsChan
 						onChange={(e)=>handlePageInput(e.target.value)}
 						onBlur={()=>scrollToPage(pageNum)}
 						onKeyDown={(e)=>e.key == 'Enter' && scrollToPage(pageNum)}
+						style={{ width: `${pageNum.length}ch` }}
 					/>
 					<span id='page-count' title='Total Page Count'>/ {totalPages}</span>
 				</div>
@@ -214,8 +220,8 @@ const ToolBar = ({ displayOptions, currentPage, totalPages, onDisplayOptionsChan
 					className='tool'
 					type='button'
 					title='Next Page(s)'
-					onClick={()=>scrollToPage(pageNum + 1)}
-					disabled={pageNum >= totalPages}
+					onClick={()=>scrollToPage(_.max(visiblePages) + 1)}
+					disabled={visiblePages.includes(totalPages)}
 				>
 					<i className='fas fa-arrow-right'></i>
 				</button>

client/homebrew/brewRenderer/toolBar/toolBar.less

@@ -104,9 +104,9 @@
 		height         : 1.5em;
 		padding        : 2px 5px;
 		font-family    : 'Open Sans', sans-serif;
-		color          : #000000;
-		background     : #EEEEEE;
-		border         : 1px solid gray;
+		color          : inherit;
+		background     : #3B3B3B;
+		border         : none;
 		&:focus { outline : 1px solid #D3D3D3; }
 
 		// `.range-input` if generic to all range inputs, or `#zoom-slider` if only for zoom slider
@@ -141,7 +141,7 @@
 
 		// `.text-input` if generic to all range inputs, or `#page-input` if only for current page input
 		&#page-input {
-			width        : 4ch;
+			min-width    : 5ch;
 			margin-right : 1ch;
 			text-align   : center;
 		}