Add a ToC that is always visible on desktop

config/_default/hugo.toml

@@ -40,6 +40,12 @@ page = ["HTML", "RSS"]
 [pagination]
 pagerSize = 12
 
+[markup]
+[markup.tableOfContents]
+endLevel = 4
+ordered = true
+startLevel = 2
+
 [params]
 dateform = "Jan 2, 2006"
 dateformShort = "Jan 2"

themes/maik-blog/assets/js/main.js

@@ -1,3 +1,14 @@
+const throttle = (func, timeFrame) => {
+    let lastTime = 0;
+    return () => {
+        let now = new Date();
+        if (now - lastTime >= timeFrame) {
+            func();
+            lastTime = now;
+        }
+    };
+};
+
 window.addEventListener("load", () => {
     // Enlarged floating figures
     for (let figure of document.getElementsByTagName("figure")) {
@@ -51,6 +62,50 @@ window.addEventListener("load", () => {
         }
     }
 
+    // set active toc heading
+    const toc = document.getElementById("toc");
+    const tocNav = toc.getElementsByTagName("nav")[0];
+    const headingsForToc = [
+        ...document.getElementsByTagName("article"),
+    ].flatMap((article) =>
+        [...article.querySelectorAll("h1, h2, h3, h4")]
+            .filter((heading) => heading.offsetParent.tagName === "MAIN")
+            .reverse()
+    );
+    const onTocScroll = () => {
+        for (const heading of headingsForToc) {
+            if (window.scrollY + window.innerHeight / 3 > heading.offsetTop) {
+                const headingAnchor = heading.getElementsByTagName("a")[0];
+
+                for (const tocAnchor of toc.getElementsByTagName("a")) {
+                    tocAnchor.classList.remove("current-toc");
+
+                    if (tocAnchor.href !== headingAnchor.href) continue;
+
+                    tocAnchor.classList.add("current-toc");
+
+                    // Scroll toc element into view
+                    const tocNavRect = tocNav.getBoundingClientRect();
+                    const tocAnchorRect = tocAnchor.getBoundingClientRect();
+
+                    const offset =
+                        tocAnchorRect.top -
+                        tocNavRect.top -
+                        tocNav.clientHeight / 2;
+
+                    const direction = offset / Math.abs(offset);
+                    const limit = (tocNav.clientHeight / 2) * 0.5;
+
+                    if (Math.abs(offset) > limit)
+                        tocNav.scrollTop += offset - direction * limit;
+                }
+                return;
+            }
+        }
+    };
+    window.addEventListener("scroll", throttle(onTocScroll, 50));
+    onTocScroll();
+
     // Code copy button
     for (let codeblock of document.querySelectorAll(".highlight pre")) {
         if (codeblock.querySelector(".lnt")) continue; // skip line numbers
@@ -70,6 +125,5 @@ window.addEventListener("load", () => {
 
             button.classList.add("current-code");
         });
-        console.log(codeblock);
     }
 });

themes/maik-blog/assets/scss/_main.scss

@@ -715,3 +715,132 @@ table {
         }
     }
 }
+
+#toc {
+    &.desktop-only {
+        display: none;
+    }
+
+    .toc-title {
+        display: flex;
+        align-items: center;
+        font-weight: bold;
+        font-size: 1.625rem;
+        line-height: 1.3;
+        margin: 0.83em 0;
+    }
+
+    ul,
+    ol {
+        li::marker {
+            content: "- ";
+        }
+    }
+
+    @media (min-width: 1840px) {
+        display: block !important;
+        position: absolute;
+        top: 100vh;
+        height: calc(100% - 100vh - 380px);
+
+        .toc-content {
+            position: sticky;
+            top: 10vh;
+            height: 70vh;
+            margin-bottom: -2em;
+            margin-left: calc(-300px - 100px);
+            display: flex !important;
+            flex-direction: column;
+            width: 300px;
+            right: calc(100% + 100px);
+
+            ::-webkit-scrollbar {
+                width: 6px;
+                height: 6px;
+                background: darken($light-background, 10%);
+                border-radius: 8px;
+            }
+
+            ::-webkit-scrollbar-thumb {
+                background: darken($light-background, 25%);
+                border-radius: 8px;
+
+                &:hover {
+                    background: darken($light-background, 40%);
+                }
+            }
+
+            .dark-theme & {
+                ::-webkit-scrollbar {
+                    background: lighten($dark-background, 10%);
+                }
+
+                ::-webkit-scrollbar-thumb {
+                    background: lighten($dark-background, 25%);
+
+                    &:hover {
+                        background: lighten($dark-background, 40%);
+                    }
+                }
+            }
+
+            .toc-title {
+                font-size: 1.375rem;
+                min-height: calc(1.625rem * 1.3);
+                margin: 0;
+            }
+
+            nav {
+                overflow-y: auto;
+                margin-top: 1em;
+            }
+
+            a {
+                display: block;
+                text-decoration: none;
+                padding: 5px;
+                border-radius: 8px;
+
+                &:hover {
+                    background: darken($light-background, 10%);
+
+                    .dark-theme & {
+                        background: lighten($dark-background, 10%);
+                    }
+                }
+
+                &.current-toc {
+                    background: darken($light-background, 10%);
+
+                    .dark-theme & {
+                        background: lighten($dark-background, 10%);
+                    }
+                }
+
+                &::before {
+                    content: "- ";
+                }
+            }
+
+            ul,
+            ol {
+                margin: 0;
+                padding: 0;
+
+                li::marker {
+                    content: "";
+                }
+
+                li a {
+                    padding-left: 20px;
+                }
+                li li a {
+                    padding-left: 40px;
+                }
+                li li li a {
+                    padding-left: 60px;
+                }
+            }
+        }
+    }
+}

themes/maik-blog/layouts/_default/single.html

@@ -38,14 +38,12 @@
     {{- partial "image.html" (dict "path" .Params.Cover "alt" (.Title | plainify) "class" "post-cover") }}
     {{- end }}
 
-    {{- if .Params.toc }}
+    <aside id="toc" class="{{- if not .Params.toc }}desktop-only{{- end }}">
-    <hr />
+      <div class="toc-content">
-    <aside id="toc">
         <div class="toc-title">{{ i18n "tableOfContents" }}</div>
         {{ .TableOfContents }}
+      </div>
     </aside>
-    <hr />
-    {{- end }}
 
     <div class="post-content">
       {{ .Content }}