Fix semantics of expandable sections (explorer, toc).

This adds the appropriate aria attributes for the [disclosure pattern](https://www.w3.org/WAI/ARIA/apg/patterns/disclosure/examples/disclosure-image-description/#javascriptandcsssourcecode) and uses `visibility: hidden` to remove the hidden elements from the focus order without disrupting the animations. Further work is needed on the tree view nodes.

quartz/components/Explorer.tsx

@@ -91,6 +91,8 @@ export default ((userOpts?: Partial<Options>) => {
           data-collapsed={opts.folderDefaultState}
           data-savestate={opts.useSavedState}
           data-tree={jsonTree}
+          aria-controls="explorer-content"
+          aria-expanded={opts.folderDefaultState === "open"}
         >
           <h2>{opts.title ?? i18n(cfg.locale).components.explorer.title}</h2>
           <svg

quartz/components/TableOfContents.tsx

@@ -26,7 +26,13 @@ const TableOfContents: QuartzComponent = ({
 
   return (
     <div class={classNames(displayClass, "toc")}>
-      <button type="button" id="toc" class={fileData.collapseToc ? "collapsed" : ""}>
+      <button
+        type="button"
+        id="toc"
+        class={fileData.collapseToc ? "collapsed" : ""}
+        aria-controls="toc-content"
+        aria-expanded={!fileData.collapseToc}
+      >
         <h3>{i18n(cfg.locale).components.tableOfContents.title}</h3>
         <svg
           xmlns="http://www.w3.org/2000/svg"

quartz/components/scripts/explorer.inline.ts

@@ -17,6 +17,10 @@ const observer = new IntersectionObserver((entries) => {
 
 function toggleExplorer(this: HTMLElement) {
   this.classList.toggle("collapsed")
+  this.setAttribute(
+    "aria-expanded",
+    this.getAttribute("aria-expanded") === "true" ? "false" : "true",
+  )
   const content = this.nextElementSibling as MaybeHTMLElement
   if (!content) return
 

quartz/components/scripts/toc.inline.ts

@@ -16,6 +16,10 @@ const observer = new IntersectionObserver((entries) => {
 
 function toggleToc(this: HTMLElement) {
   this.classList.toggle("collapsed")
+  this.setAttribute(
+    "aria-expanded",
+    this.getAttribute("aria-expanded") === "true" ? "false" : "true",
+  )
   const content = this.nextElementSibling as HTMLElement | undefined
   if (!content) return
   content.classList.toggle("collapsed")

quartz/components/styles/explorer.scss

@@ -45,8 +45,14 @@ button#explorer {
   list-style: none;
   overflow: hidden;
   max-height: none;
-  transition: max-height 0.35s ease;
+  transition: max-height 0.35s ease, visibility 0s linear 0s;
   margin-top: 0.5rem;
+  visibility: visible;
+
+  &.collapsed {
+    transition: max-height 0.35s ease, visibility 0s linear 0.35s;
+    visibility: hidden;
+  }
 
   &.collapsed > .overflow::after {
     opacity: 0;

quartz/components/styles/toc.scss

@@ -29,8 +29,14 @@ button#toc {
   list-style: none;
   overflow: hidden;
   max-height: none;
-  transition: max-height 0.5s ease;
+  transition: max-height 0.5s ease, visibility 0s linear 0s;
   position: relative;
+  visibility: visible;
+
+  &.collapsed {
+    transition: max-height 0.5s ease, visibility 0s linear 0.5s;
+    visibility: hidden;
+  }
 
   &.collapsed > .overflow::after {
     opacity: 0;