Add first try at scrollspy (broken right now)

.gitignore

@@ -1,3 +1,4 @@
 public
 resources
 assets/jsconfig.json
+.hugo_build.lock

assets/jsconfig.json

@@ -1,10 +1,10 @@
 {
-    "compilerOptions": {
-        "baseUrl": ".",
-        "paths": {
-            "*": [
-                "*"
-            ]
-        },
-    }
+ "compilerOptions": {
+  "baseUrl": ".",
+  "paths": {
+   "*": [
+    "*"
+   ]
+  }
+ }
 }

assets/scss/partials/base.scss

@@ -1,7 +1,6 @@
 html {
     font-size: 62.5%;
     overflow-y: scroll;
-    scroll-behavior: smooth;
 }
 
 * {

assets/scss/partials/layout/article.scss

@@ -122,7 +122,6 @@
 }
 
 .article-page.has-toc {
-    scroll-behavior: smooth;
 
     .left-sidebar {
         display: none;
@@ -193,6 +192,10 @@
     color: var(--card-text-color-main);
     overflow: hidden;
 
+    ::-webkit-scrollbar-thumb {
+        background-color: var(--card-separator-color);
+    }
+
     #TableOfContents {
         overflow-x: auto;
         max-height: 75vh;
@@ -220,7 +223,7 @@
         }
 
         li {
-            margin: 15px 20px;
+            margin: 15px 0 15px 20px;
             padding: 5px;
 
             & > ol,
@@ -234,6 +237,25 @@
                 }
             }
         }
+        li.active-class > a {
+            border-left: var(--heading-border-size) solid var(--accent-color);
+            font-weight: bold;
+            display: block;
+        }
+        & > ul > li.active-class > a {
+            margin-left: calc(-25px - 1em);
+            padding-left: calc(25px + 1em - var(--heading-border-size));
+        }
+
+        & > ul > li > ul > li.active-class > a {
+            margin-left: calc(-60px - 1em);
+            padding-left: calc(60px + 1em - var(--heading-border-size));
+        }
+
+        & > ul > li > ul > li > ul > li.active-class > a {
+            margin-left: calc(-95px - 1em);
+            padding-left: calc(95px + 1em - var(--heading-border-size));
+        }
     }
 }
 

assets/ts/main.ts

@@ -10,6 +10,7 @@ import { getColor } from 'ts/color';
 import menu from 'ts/menu';
 import createElement from 'ts/createElement';
 import StackColorScheme from 'ts/colorScheme';
+import { setupScrollspy } from 'ts/scrollspy';
 
 let Stack = {
     init: () => {
@@ -21,6 +22,7 @@ let Stack = {
         const articleContent = document.querySelector('.article-content') as HTMLElement;
         if (articleContent) {
             new StackGallery(articleContent);
+            setupScrollspy(".article-content h1[id], .article-content h2[id], .article-content h3[id], .article-content h4[id], .article-content h5[id], .article-content h6[id]", "#TableOfContents", "#TableOfContents li", "active-class")
         }
 
         /**

assets/ts/scrollspy.ts

@@ -0,0 +1,99 @@
+// While solutions for debouncing like the ones in https://gomakethings.com/debouncing-your-javascript-events/ could work,
+// we do need an actual debouncing of scroll events in order to only capture the "end" of the scroll.
+function debounced(func: Function) {
+    let timeout;
+    return (e: Event) => {
+        /*
+        if (timeout) {
+            clearTimeout(timeout);
+        }
+        timeout = window.requestAnimationFrame(func);
+        */
+        if (timeout) {
+            window.cancelAnimationFrame(timeout);
+        }
+
+        timeout = window.requestAnimationFrame(() => func(e));
+    }
+}
+
+function setupScrollspy(headersQuery: string, tocQuery: string, navigationQuery: string, activeClass: string) {
+    let headers = document.querySelectorAll(headersQuery);
+    if (!headers) {
+        console.warn("No header matched query", headers);
+        return;
+    }
+
+    let scrollableNavigation = document.querySelector(tocQuery);
+    if (!scrollableNavigation) {
+        console.warn("No toc matched query", tocQuery);
+        return;
+    }
+
+    let navigation = document.querySelectorAll(navigationQuery);
+    if (!navigation) {
+        console.warn("No navigation matched query", navigationQuery);
+        return;
+    }
+
+    let sectionsOffsets = [];
+
+    headers.forEach((header: HTMLElement) => { sectionsOffsets.push({ id: header.id, offset: header.offsetTop }) });
+    sectionsOffsets.sort((a, b) => a.offset - b.offset);
+
+    let activeSectionLink: Element;
+    let tocHovered: boolean = false;
+
+    function hoverHandler(isHovered: boolean) {
+        tocHovered = isHovered;
+    }
+
+    function scrollHandler(e: Event) {
+        let scrollPosition = document.documentElement.scrollTop || document.body.scrollTop;
+
+        let newActiveSection: HTMLElement;
+
+        sectionsOffsets.forEach((section) => {
+            if (scrollPosition >= section.offset - 20) {
+                newActiveSection = document.getElementById(section.id);
+            }
+        });
+
+        let newActiveSectionLink: HTMLElement;
+        if (newActiveSection) {
+            for (let i = 0; i < navigation.length; i++) {
+                let link = navigation[i].querySelector("a");
+                if (link.getAttribute("href") === "#" + newActiveSection.id) {
+                    newActiveSectionLink = navigation[i] as HTMLElement;
+                    break;
+                }
+            }
+        }
+
+        if (newActiveSection && !newActiveSectionLink) {
+            console.warn("No link found for section", newActiveSection);
+        } else if (newActiveSectionLink !== activeSectionLink) {
+            if (activeSectionLink)
+                activeSectionLink.classList.remove(activeClass);
+            if (newActiveSectionLink) {
+                newActiveSectionLink.classList.add(activeClass);
+                if (!tocHovered) {
+                    // Scroll so that newActiveSectionLink is in the middle of scrollableNavigation, except when it's from a manual click (hence the tocHovered check)
+                    let textHeight = newActiveSectionLink.querySelector("a").offsetHeight;
+                    let scrollTop = newActiveSectionLink.offsetTop - scrollableNavigation.offsetHeight / 2 + textHeight / 2 - scrollableNavigation.offsetTop;
+                    if (scrollTop < 0) {
+                        scrollTop = 0;
+                    }
+                    scrollableNavigation.scrollTo({ top: scrollTop, behavior: "auto" });
+                }
+            }
+            activeSectionLink = newActiveSectionLink;
+        }
+    }
+
+    window.addEventListener("scroll", debounced(scrollHandler));
+    scrollableNavigation.addEventListener("mouseenter", debounced(() => hoverHandler(true)));
+    scrollableNavigation.addEventListener("mouseleave", debounced(() => hoverHandler(false)));
+}
+
+export { setupScrollspy };