From d09d10f7742703800c0d0751bc9fb9c56b35d5ab Mon Sep 17 00:00:00 2001
From: Jens Reimann <ctron@dentrassi.de>
Date: Sun, 21 Apr 2024 13:13:52 +0200
Subject: [PATCH] docs: add a pagetoc to the theme

---
 guide/book.toml         |   4 +-
 guide/theme/pagetoc.css | 105 ++++++++++++++++++++++++++++++
 guide/theme/pagetoc.js  | 138 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 246 insertions(+), 1 deletion(-)
 create mode 100644 guide/theme/pagetoc.css
 create mode 100644 guide/theme/pagetoc.js

diff --git a/guide/book.toml b/guide/book.toml
index 80c22008..1f39cc63 100644
--- a/guide/book.toml
+++ b/guide/book.toml
@@ -1,5 +1,5 @@
 [book]
-title = "The `trunk` Guide"
+title = "The Trunk Guide"
 description = "Documention of Trunk, a web application bundler for Rust"
 src = "src"
 
@@ -21,7 +21,9 @@ assets_version = "3.0.2" # do not edit: managed by `mdbook-admonish install`
 [output.html]
 additional-css = [
     "./mdbook-admonish.css",
+    "theme/pagetoc.css"
 ]
 additional-js = [
+    "theme/pagetoc.js"
 ]
 
diff --git a/guide/theme/pagetoc.css b/guide/theme/pagetoc.css
new file mode 100644
index 00000000..1cc776b5
--- /dev/null
+++ b/guide/theme/pagetoc.css
@@ -0,0 +1,105 @@
+:root {
+    --toc-width: 270px;
+    --center-content-toc-shift: calc(-1 * var(--toc-width) / 2);
+}
+
+.nav-chapters {
+    /* adjust width of buttons that bring to the previous or the next page */
+    min-width: 50px;
+}
+
+.previous {
+    /*
+    adjust the space between the left sidebar or the left side of the screen
+    and the button that leads to the previous page
+    */
+    margin-left: var(--page-padding);
+}
+
+@media only screen {
+    main {
+        display: flex;
+    }
+
+    @media (max-width: 1179px) {
+        .sidebar-hidden .sidetoc {
+            display: none;
+        }
+    }
+
+    @media (max-width: 1439px) {
+        .sidebar-visible .sidetoc {
+            display: none;
+        }
+    }
+
+    @media (1180px <= width <= 1439px) {
+        .sidebar-hidden main {
+            position: relative;
+            left: var(--center-content-toc-shift);
+        }
+    }
+
+    @media (1440px <= width <= 1700px) {
+        .sidebar-visible main {
+            position: relative;
+            left: var(--center-content-toc-shift);
+        }
+    }
+
+    .content-wrap {
+        overflow-y: auto;
+        width: 100%;
+    }
+
+    .sidetoc {
+        margin-top: 20px;
+        margin-left: 10px;
+        margin-right: auto;
+    }
+    .pagetoc {
+        position: fixed;
+        /* adjust TOC width */
+        width: var(--toc-width);
+        height: calc(100vh - var(--menu-bar-height) - 0.67em * 4);
+        overflow: auto;
+    }
+    .pagetoc a {
+        border-left: 1px solid var(--sidebar-bg);
+        color: var(--fg) !important;
+        display: block;
+        padding-bottom: 5px;
+        padding-top: 5px;
+        padding-left: 10px;
+        text-align: left;
+        text-decoration: none;
+    }
+    .pagetoc a:hover,
+    .pagetoc a.active {
+        background: var(--sidebar-bg);
+        color: var(--sidebar-fg) !important;
+    }
+    .pagetoc .active {
+        background: var(--sidebar-bg);
+        color: var(--sidebar-fg);
+        font-weight: bold;
+    }
+    .pagetoc .pagetoc-H2 {
+        padding-left: 20px;
+        font-size: 90%;
+    }
+    .pagetoc .pagetoc-H3 {
+        padding-left: 40px;
+        font-size: 90%;
+    }
+    .pagetoc .pagetoc-H4 {
+        padding-left: 60px;
+        font-size: 90%;
+    }
+}
+
+@media print {
+    .sidetoc {
+        display: none;
+    }
+}
diff --git a/guide/theme/pagetoc.js b/guide/theme/pagetoc.js
new file mode 100644
index 00000000..2e09e770
--- /dev/null
+++ b/guide/theme/pagetoc.js
@@ -0,0 +1,138 @@
+function forEach(elems, fun) {
+  Array.prototype.forEach.call(elems, fun);
+}
+
+function getPagetoc(){
+  const pagetoc = document.getElementsByClassName("pagetoc")[0];
+
+  if (pagetoc) {
+    return pagetoc;
+  }
+
+  return autoCreatePagetoc();
+}
+
+function autoCreatePagetoc() {
+  const main = document.querySelector("#content > main");
+
+  const content = document.createElement("div");
+  content.classList.add("content-wrap");
+  content.append(...main.childNodes);
+
+  main.appendChild(content);
+
+  main.insertAdjacentHTML("beforeend", `
+    <div class="sidetoc">
+      <nav class="pagetoc"></nav>
+    </div>
+  `);
+
+  return document.getElementsByClassName("pagetoc")[0]
+}
+
+function getPagetocElems() {
+  return getPagetoc().children;
+}
+
+function getHeaders(){
+  return document.getElementsByClassName("header")
+}
+
+// Un-active everything when you click it
+function forPagetocElem(fun) {
+  forEach(getPagetocElems(), fun);
+}
+
+function getRect(element) {
+  return element.getBoundingClientRect();
+}
+
+function overflowTop(container, element) {
+  return getRect(container).top - getRect(element).top;
+}
+
+function overflowBottom(container, element) {
+  return getRect(container).bottom - getRect(element).bottom;
+}
+
+var activeHref = location.href;
+
+var updateFunction = function (elem = undefined) {
+  var id = elem;
+
+  if (!id && location.href != activeHref) {
+    activeHref = location.href;
+    forPagetocElem(function (el) {
+      if (el.href === activeHref) {
+        id = el;
+      }
+    });
+  }
+
+  if (!id) {
+    var elements = getHeaders();
+    let margin = window.innerHeight / 3;
+
+    forEach(elements, function (el, i, arr) {
+      if (!id && getRect(el).top >= 0) {
+        if (getRect(el).top < margin) {
+          id = el;
+        } else {
+          id = arr[Math.max(0, i - 1)];
+        }
+      }
+      // a very long last section
+      // its heading is over the screen
+      if (!id && i == arr.length - 1) {
+        id = el
+      }
+    });
+  }
+
+  forPagetocElem(function (el) {
+    el.classList.remove("active");
+  });
+
+  if (!id) return;
+
+  forPagetocElem(function (el) {
+    if (id.href.localeCompare(el.href) == 0) {
+      el.classList.add("active");
+      let pagetoc = getPagetoc();
+      if (overflowTop(pagetoc, el) > 0) {
+        pagetoc.scrollTop = el.offsetTop;
+      }
+      if (overflowBottom(pagetoc, el) < 0) {
+        pagetoc.scrollTop -= overflowBottom(pagetoc, el);
+      }
+    }
+  });
+};
+
+let elements = getHeaders();
+
+if (elements.length > 1) {
+  // Populate sidebar on load
+  window.addEventListener("load", function () {
+    var pagetoc = getPagetoc();
+    var elements = getHeaders();
+    forEach(elements, function (el) {
+      var link = document.createElement("a");
+      link.appendChild(document.createTextNode(el.text));
+      link.href = el.hash;
+      link.classList.add("pagetoc-" + el.parentElement.tagName);
+      pagetoc.appendChild(link);
+      link.onclick = function () {
+        updateFunction(link);
+      };
+    });
+    updateFunction();
+  });
+
+  // Handle active elements on scroll
+  window.addEventListener("scroll", function () {
+    updateFunction();
+  });
+} else {
+  document.getElementsByClassName("sidetoc")[0].remove();
+}