fix(explore): stop labelling the album tracklist "TRACKLIST"

A list of numbered titles with durations, under the album's cover, was
the one thing on the page carrying a word above it saying what it is.

What goes is the ink and not the element: the section is a landmark and
the page's heading structure runs through it, so the h3 stays and is
clipped the way sr-only clips -- never display:none, which would take
it out of the accessibility tree along with the layout.

Refs #9

frontend/src/components/explore-album-details/explore-album-details.ts

@@ -2,6 +2,7 @@ import { LitElement, html, css, nothing } from 'lit';
 import { customElement, property, state, query } from 'lit/decorators.js';
 import { classMap } from 'lit/directives/class-map.js';
 import { designTokens } from '../../styles/tokens.css';
+import { srOnly } from '../../styles/sr-only.css';
 import {
     LookupReleaseGroup,
     BrowseReleases,
@@ -289,6 +290,7 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
         designTokens,
         exploreLinkStyles,
         contextMenuStyles,
+        srOnly,
         css`
             :host {
                 display: flex;
@@ -3033,11 +3035,21 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
 
     /* ── Tracklist ── */
 
+    /**
+     * The heading is there and is not drawn.
+     *
+     * A list of numbered titles with durations under an album's cover
+     * does not need a word above it saying what it is — it was the
+     * only thing on this page labelling something already obvious. But
+     * the section is a landmark and the page's heading structure runs
+     * through it, so what goes is the *ink*, not the element: a reader
+     * jumping by heading still finds the tracklist.
+     */
     private renderTracklist() {
         if (this.loadingReleases) {
             return html`
                 <section>
-                    <h3 class="section-header">Tracklist</h3>
+                    <h3 class="sr-only">Tracklist</h3>
                     <div class="section-loading">Loading tracks\u2026</div>
                 </section>
             `;
@@ -3050,7 +3062,7 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
         if (!current) {
             return html`
                 <section>
-                    <h3 class="section-header">Tracklist</h3>
+                    <h3 class="sr-only">Tracklist</h3>
                     <div class="section-error">
                         <wa-icon name="triangle-exclamation"></wa-icon>
                         No release data available.
@@ -3063,7 +3075,7 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
         if (tracks.length === 0) {
             return html`
                 <section>
-                    <h3 class="section-header">Tracklist</h3>
+                    <h3 class="sr-only">Tracklist</h3>
                     <div
                         style="color: var(--yj-text-tertiary, #888); font-size: var(--yj-text-md)"
                     >
@@ -3079,7 +3091,7 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
 
         return html`
             <section>
-                <h3 class="section-header">Tracklist</h3>
+                <h3 class="sr-only">Tracklist</h3>
                 <div class="tracklist">
                     ${discNumbers.map((discNum) => {
                         const discTracks = discMap.get(discNum) ?? [];

frontend/test/components/album-tracklist-heading.test.ts

@@ -0,0 +1,89 @@
+/**
+ * The tracklist's own heading.
+ *
+ * A list of numbered titles with durations, under the album's cover, is
+ * the one thing on this page that did not need a word above it saying
+ * what it was — "TRACKLIST" labelled the only thing already obvious.
+ *
+ * What goes is the *ink*, not the element. The section is a landmark
+ * and the page's heading structure runs through it, so a reader moving
+ * by heading still has to be able to find it, and it is hidden the way
+ * `sr-only` hides things: `clip-path`, never `display: none`, which
+ * would take it out of the accessibility tree along with the layout.
+ */
+import { describe, expect, it, beforeEach } from 'vitest';
+import type { LitElement } from 'lit';
+
+import '@components/explore-album-details/explore-album-details';
+import { stub, flush, resetHarness } from '@test/support/harness';
+import { fixture, shadowAll } from '@test/support/render';
+
+function track(n: number) {
+  return {
+    position: n,
+    discNumber: 1,
+    title: `Track ${n}`,
+    length: 200000,
+    mbid: `mbid-${n}`,
+    inLibrary: true,
+  };
+}
+
+async function albumPage(): Promise<LitElement> {
+  const el = await fixture<LitElement>('explore-album-details', {
+    albumName: 'Glass Harbour',
+    releaseGroupMBID: 'rg-1',
+  });
+
+  Object.assign(el, {
+    versionEntries: [
+      {
+        key: 'v1',
+        label: '2019',
+        sublabel: '2 tracks',
+        tracks: [track(1), track(2)],
+      },
+    ],
+    selectedVersionKey: 'v1',
+    loadingReleases: false,
+    loadingInfo: false,
+  });
+  el.requestUpdate();
+  await flush();
+  await el.updateComplete;
+
+  return el;
+}
+
+const tracklistHeading = (el: LitElement) =>
+  shadowAll(el, 'h3').find((h) => h.textContent?.trim() === 'Tracklist');
+
+describe('the album tracklist heading', () => {
+  beforeEach(() => {
+    resetHarness();
+    stub('library.Library.GetFilePathsByRecordingMBIDs', {});
+    stub('library.Library.GetFilePathsByAlbums', {});
+    stub('library.Library.GetAlbumTracks', []);
+    stub('library.Library.GetAllLibrariesWithTrackCounts', []);
+    stub('download.Service.ProviderKinds', []);
+    stub('download.Service.ListProviders', []);
+    stub('download.Service.ListDownloads', []);
+    stub('download.Service.ListRequests', []);
+  });
+
+  it('is still in the tree', async () => {
+    expect(tracklistHeading(await albumPage())).toBeTruthy();
+  });
+
+  it('takes up no room on the page', async () => {
+    const heading = tracklistHeading(await albumPage())!;
+    const box = heading.getBoundingClientRect();
+
+    expect(box.width).toBeLessThanOrEqual(1);
+    expect(box.height).toBeLessThanOrEqual(1);
+    // Hidden by clipping, not by removal: display:none and
+    // visibility:hidden both take it out of the accessibility tree.
+    expect(getComputedStyle(heading).display).not.toBe('none');
+    expect(getComputedStyle(heading).visibility).not.toBe('hidden');
+  });
+});