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| 1 | +// Inspired by https://github.com/JorelAli/mdBook-pagetoc/tree/98ee241 (under WTFPL) |
| 2 | + |
| 3 | +let activeHref = location.href; |
| 4 | +function updatePageToc(elem = undefined) { |
| 5 | + let selectedPageTocElem = elem; |
| 6 | + const pagetoc = document.getElementById("pagetoc"); |
| 7 | + |
| 8 | + function getRect(element) { |
| 9 | + return element.getBoundingClientRect(); |
| 10 | + } |
| 11 | + |
| 12 | + function overflowTop(container, element) { |
| 13 | + return getRect(container).top - getRect(element).top; |
| 14 | + } |
| 15 | + |
| 16 | + function overflowBottom(container, element) { |
| 17 | + return getRect(container).bottom - getRect(element).bottom; |
| 18 | + } |
| 19 | + |
| 20 | + // We've not selected a heading to highlight, and the URL needs updating |
| 21 | + // so we need to find a heading based on the URL |
| 22 | + if (selectedPageTocElem === undefined && location.href !== activeHref) { |
| 23 | + activeHref = location.href; |
| 24 | + for (const pageTocElement of pagetoc.children) { |
| 25 | + if (pageTocElement.href === activeHref) { |
| 26 | + selectedPageTocElem = pageTocElement; |
| 27 | + } |
| 28 | + } |
| 29 | + } |
| 30 | + |
| 31 | + // We still don't have a selected heading, let's try and find the most |
| 32 | + // suitable heading based on the scroll position |
| 33 | + if (selectedPageTocElem === undefined) { |
| 34 | + const margin = window.innerHeight / 3; |
| 35 | + |
| 36 | + const headers = document.getElementsByClassName("header"); |
| 37 | + for (let i = 0; i < headers.length; i++) { |
| 38 | + const header = headers[i]; |
| 39 | + if (selectedPageTocElem === undefined && getRect(header).top >= 0) { |
| 40 | + if (getRect(header).top < margin) { |
| 41 | + selectedPageTocElem = header; |
| 42 | + } else { |
| 43 | + selectedPageTocElem = headers[Math.max(0, i - 1)]; |
| 44 | + } |
| 45 | + } |
| 46 | + // a very long last section's heading is over the screen |
| 47 | + if (selectedPageTocElem === undefined && i === headers.length - 1) { |
| 48 | + selectedPageTocElem = header; |
| 49 | + } |
| 50 | + } |
| 51 | + } |
| 52 | + |
| 53 | + // Remove the active flag from all pagetoc elements |
| 54 | + for (const pageTocElement of pagetoc.children) { |
| 55 | + pageTocElement.classList.remove("active"); |
| 56 | + } |
| 57 | + |
| 58 | + // If we have a selected heading, set it to active and scroll to it |
| 59 | + if (selectedPageTocElem !== undefined) { |
| 60 | + for (const pageTocElement of pagetoc.children) { |
| 61 | + if (selectedPageTocElem.href.localeCompare(pageTocElement.href) === 0) { |
| 62 | + pageTocElement.classList.add("active"); |
| 63 | + if (overflowTop(pagetoc, pageTocElement) > 0) { |
| 64 | + pagetoc.scrollTop = pageTocElement.offsetTop; |
| 65 | + } |
| 66 | + if (overflowBottom(pagetoc, pageTocElement) < 0) { |
| 67 | + pagetoc.scrollTop -= overflowBottom(pagetoc, pageTocElement); |
| 68 | + } |
| 69 | + } |
| 70 | + } |
| 71 | + } |
| 72 | +} |
| 73 | + |
| 74 | +if (document.getElementById("sidetoc") === null && |
| 75 | + document.getElementsByClassName("header").length > 0) { |
| 76 | + // The sidetoc element doesn't exist yet, let's create it |
| 77 | + |
| 78 | + // Create the empty sidetoc and pagetoc elements |
| 79 | + const sidetoc = document.createElement("div"); |
| 80 | + const pagetoc = document.createElement("div"); |
| 81 | + sidetoc.id = "sidetoc"; |
| 82 | + pagetoc.id = "pagetoc"; |
| 83 | + sidetoc.appendChild(pagetoc); |
| 84 | + |
| 85 | + // And append them to the current DOM |
| 86 | + const main = document.querySelector('main'); |
| 87 | + main.insertBefore(sidetoc, main.firstChild); |
| 88 | + |
| 89 | + // Populate sidebar on load |
| 90 | + window.addEventListener("load", () => { |
| 91 | + for (const header of document.getElementsByClassName("header")) { |
| 92 | + const link = document.createElement("a"); |
| 93 | + link.innerHTML = header.innerHTML; |
| 94 | + link.href = header.hash; |
| 95 | + link.classList.add("pagetoc-" + header.parentElement.tagName); |
| 96 | + document.getElementById("pagetoc").appendChild(link); |
| 97 | + link.onclick = () => updatePageToc(link); |
| 98 | + } |
| 99 | + updatePageToc(); |
| 100 | + }); |
| 101 | + |
| 102 | + // Update page table of contents selected heading on scroll |
| 103 | + window.addEventListener("scroll", () => updatePageToc()); |
| 104 | +} |
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