add back in scrolling source tabs

index.html

@@ -62,9 +62,11 @@ <h1 id="title"></h1>
           <div class="sampleContainer"></div>
         </div>
         <nav id="code" class="sourceFileNav">
-          <div class="sourceFileScrollContainer">
+          <div class="sourceLR" id="sourceL">&lt;</div>
+          <div id="sourceTabs" class="sourceFileScrollContainer">
             <ul id="codeTabs"></ul>
           </div>
+          <div class="sourceLR" id="sourceR">&gt;</div>
         </nav>
         <div id="sources"></div>
       </main>

public/css/SampleLayout.css

@@ -47,12 +47,18 @@
   transform: translateY(0.25em);
 }
 
+nav.sourceFileNav {
+  display: flex;
+  align-items: center;
+}
+
 nav.sourceFileNav ul {
   box-sizing: border-box;
   list-style-type: none;
   padding: 0;
   margin: 0;
   margin-top: 15px;
+  position: relative;
 }
 
 nav.sourceFileNav li {
@@ -97,12 +103,59 @@ nav.sourceFileNav[data-right=true]::after {
   background: linear-gradient(270deg, rgba(0, 0, 0, 0.35), transparent);
 }
 
+.sourceLR {
+  display: none;
+  cursor: pointer;
+  width: 5em;
+  padding: 10px;
+  margin-top: 15px;
+  text-align: center;
+  color: var(--source-tab-color);
+  background-color: var(--source-tab-background);
+  border-left: 1px solid rgba(0, 0, 0, 0.5);
+  border-right: 1px solid rgba(0, 0, 0, 0.5);
+}
+.sourceLR:hover {
+  text-decoration: underline;
+}
+.sourceLRShow .sourceLR {
+  display: block;
+}
+
+nav.sourceFileNav div.sourceFileScrollContainer {
+  white-space: nowrap;
+  overflow-x: auto;
+  scrollbar-width: thin;
+}
+
+nav.sourceFileNav div.sourceFileScrollContainer::-webkit-scrollbar {
+  display: inline;
+  margin-top: 10px;
+  margin-bottom: 10px;
+  height: 11px;
+  width: 10px;
+}
+
+nav.sourceFileNav div.sourceFileScrollContainer::-webkit-scrollbar-thumb {
+  background: rgb(200, 200, 200);
+  height: 4px;
+  border-radius: 20px;
+  -webkit-box-shadow: inset 0px 0px 10px rgb(45, 33, 33);
+  border: 0.5px solid transparent;
+  background-clip: content-box;
+}
+
+nav.sourceFileNav div.sourceFileScrollContainer::-webkit-scrollbar-track {
+  background: rgba(0, 0, 0, 0);
+}
+
 nav.sourceFileNav li a {
   display: block;
   margin: 0;
   padding: 10px;
   color: var(--source-tab-color);
   background-color: var(--source-tab-background);
+  border-right: 1px solid rgba(0, 0, 0, 0.5);
 }
 
 nav.sourceFileNav li:hover {

src/main.ts

@@ -31,6 +31,10 @@ const sampleContainerElem = getElem('.sampleContainer', sampleElem);
 const titleElem = getElem('#title', sampleElem);
 const descriptionElem = getElem('#description', sampleElem);
 const menuToggleElem = getElem('#menuToggle') as HTMLInputElement;
+const codeElem = getElem('#code');
+const sourceTabsElem = getElem('#sourceTabs');
+const sourceLElem = getElem('#sourceL');
+const sourceRElem = getElem('#sourceR');
 
 // Get the parts of a string past the last `/`
 const basename = (name: string) => name.substring(name.lastIndexOf('/') + 1);
@@ -66,6 +70,35 @@ function setURL(url: string) {
 // Handle when the URL changes (browser back / forward)
 window.addEventListener('popstate', parseURL);
 
+/**
+ * Scrolls the current tab into view.
+ */
+function moveIntoView(parent: HTMLElement, element: HTMLElement) {
+  const parentLeft = parent.scrollLeft;
+  const parentRight = parentLeft + parent.clientWidth;
+
+  const elemLeft = element.offsetLeft;
+  const elemRight = elemLeft + element.clientWidth;
+
+  if (elemLeft < parentLeft) {
+    parent.scrollLeft -= parentLeft - elemLeft;
+  } else if (elemRight > parentRight) {
+    parent.scrollLeft += elemRight - parentRight;
+  }
+}
+
+/**
+ * Switches to a tab relative to the current tab
+ */
+function switchToRelativeTab(direction: number) {
+  const tabs = [...sourceTabsElem.querySelectorAll('a')];
+  const activeNdx = tabs.findIndex((tab) => tab.dataset.active === 'true');
+  const newNdx = (activeNdx + tabs.length + direction) % tabs.length;
+  const tab = tabs[newNdx];
+  moveIntoView(sourceTabsElem, tab.parentElement!);
+  tab.click();
+}
+
 /**
  * Show/hide source tabs
  */
@@ -75,6 +108,7 @@ function setSourceTab(sourceInfo: SourceInfo) {
     const elem = e as HTMLElement;
     elem.dataset.active = (elem.dataset.name === name).toString();
   });
+  switchToRelativeTab(0);
 }
 
 /**
@@ -241,6 +275,43 @@ for (const { title, description, samples } of pageCategories) {
   );
 }
 
+sourceLElem.addEventListener('click', () => switchToRelativeTab(-1));
+sourceRElem.addEventListener('click', () => switchToRelativeTab(1));
+
+function checkIfSourceTabsFit() {
+  const parentWidth = sourceTabsElem.clientWidth;
+  const childWidth = [...sourceTabsElem.querySelectorAll('li')].reduce(
+    (sum, elem) => sum + elem.clientWidth,
+    0
+  );
+  const showLR = childWidth > parentWidth;
+  codeElem.classList.toggle('sourceLRShow', showLR);
+}
+
+const registerResizeCallback = (() => {
+  const elemToResizeCallback = new Map<
+    Element,
+    (entry: ResizeObserverEntry) => void
+  >();
+  const observer = new ResizeObserver((entries) => {
+    for (const entry of entries) {
+      const cb = elemToResizeCallback.get(entry.target);
+      if (cb) {
+        cb(entry);
+      }
+    }
+  });
+  return function (
+    elem: Element,
+    callback: (entry: ResizeObserverEntry) => void
+  ) {
+    elemToResizeCallback.set(elem, callback);
+    observer.observe(elem);
+  };
+})();
+
+registerResizeCallback(sourceTabsElem, checkIfSourceTabsFit);
+
 /**
  * Parse the page's current URL and then set the iframe appropriately.
  */