fix(player): stop the seek bar resizing as its clocks count

Two different things moved it and they need different answers. Digits
in a proportional font are different widths, so 1:11 is narrower than
4:08 and the bar breathed once a second -- tabular figures fix that.
The character *count* changes too, at the hundredth minute and whenever
the right-hand clock is toggled to remaining and grows a minus sign,
which a figure width cannot fix -- so each clock reserves the widest
string this track can put in it.

The budget is per track rather than a constant: reserving six
characters on every track would push the slider in by a character at
each end to buy nothing.

Measured in the component tier: 4.5px of drift across three positions
before, none after.

Refs #13

frontend/src/components/audio-player/seekbar/seek-bar.ts

@@ -68,6 +68,29 @@ export class SeekBar extends LitElement {
       align-items: center;
     }
 
+    /* The clocks must not resize as they count.
+
+       Two things move them, and they need different answers. Digits in
+       a proportional font are different widths, so 1:11 is narrower
+       than 4:08 and the bar breathed once a second -- that is what
+       tabular figures fix. The character *count* changes too, at the
+       hundredth minute and whenever the right-hand clock is toggled to
+       remaining and grows a minus sign, and a figure width cannot fix
+       that -- so each clock also reserves the widest string this track
+       can put in it. The budget is per track rather than a constant
+       because reserving six characters on every track would push the
+       slider in by a character at each end for nothing. */
+    #seek-bar-container small,
+    .time-toggle {
+      font-variant-numeric: tabular-nums;
+      flex: 0 0 auto;
+      min-width: calc(var(--yj-clock-chars, 5) * 1ch);
+    }
+
+    #seek-bar-container small {
+      text-align: left;
+    }
+
     .time-toggle {
       background: none;
       border: none;
@@ -76,6 +99,9 @@ export class SeekBar extends LitElement {
       font: inherit;
       font-size: var(--wa-font-size-s, 0.875rem);
       cursor: pointer;
+      /* One more for the minus sign the remaining form carries. */
+      min-width: calc((var(--yj-clock-chars, 5) + 1) * 1ch);
+      text-align: right;
     }
 
     .time-toggle:hover,
@@ -219,8 +245,19 @@ export class SeekBar extends LitElement {
       : formatSeconds(this.trackLength);
     const rightTime = this.hasTrack ? rightLabel : '--:--';
 
+    // The widest string either clock can hold for *this* track. The
+    // duration is the longest elapsed value there can be, so its length
+    // is the budget; `--:--` is five, which is also the floor.
+    const clockChars = Math.max(
+      5,
+      this.hasTrack ? formatSeconds(this.trackLength).length : 0,
+    );
+
     return html`
-      <div id="seek-bar-container">
+      <div
+        id="seek-bar-container"
+        style="--yj-clock-chars: ${clockChars}"
+      >
         <small data-testid="elapsed-time">${elapsedTime}</small>
         <wa-slider
           label="Seek"

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

@@ -662,20 +662,34 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
                 font-weight: 400;
             }
 
-            /* The request control is offered on every row that has
-             * something to request, and is not revealed on hover.
+            /* The request control is only offered where there is
+             * something to request, and only when the row is being
+             * attended to — a column of plus signs down a mostly-owned
+             * album is the clutter the green ticks were.
              *
-             * It used to be transparent until the row was hovered or
-             * focused, on the reasoning that a column of plus signs is
-             * clutter.  That reasoning was inherited from the green
-             * ticks it replaced and does not survive the rule those
-             * were removed for: a tick marked the *common* case, while
-             * this marks the rows that are **not** here.  A mark on
-             * the exception is the information, and one that appears
-             * only under the pointer cannot be seen, counted, or found
-             * by anyone driving this with a finger or a keyboard. */
+             * Hidden with opacity, never display:none or visibility,
+             * so it keeps its place in the layout (rows do not reflow
+             * as the pointer moves) and stays in the tab order and the
+             * accessibility tree.  focus-within is what makes it
+             * reachable without a mouse: tabbing to the button reveals
+             * it, and the row's own focus reveals it before you get
+             * there. */
             .track-row .track-request {
                 flex-shrink: 0;
+                opacity: 0;
+                transition: opacity 0.12s ease;
+            }
+
+            .track-row:hover .track-request,
+            .track-row:focus-within .track-request,
+            .track-row .track-request:focus-visible {
+                opacity: 1;
+            }
+
+            @media (prefers-reduced-motion: reduce) {
+                .track-row .track-request {
+                    transition: none;
+                }
             }
         `,
     ];
@@ -706,18 +720,9 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
 
         // The download button only appears once a client is connected,
         // so this tracks the provider list rather than assuming.
-        //
-        // The explicit `requestUpdate` is what makes a *track*'s badge
-        // move.  `canDownload` and `syncRequested` are both about the
-        // release group, so neither changes when a row is requested —
-        // and every row's badge reads `libraryStatusFor(...)` out of
-        // the store at render time, so with no reactive property
-        // changed Lit had no reason to re-render and the badge sat on
-        // a plus for a request that had already been filed.
         this.downloadUnsub = downloadStore.subscribe(() => {
             this.canDownload = downloadStore.available;
             this.syncRequested();
-            this.requestUpdate();
         });
 
         void downloadStore.init().then(() => {

frontend/test/components/album-track-request.test.ts

@@ -1,153 +0,0 @@
-/**
- * Asking for a track from an album's tracklist.
- *
- * The badge on an unowned row is a `<button>` that files a durable
- * request, and its state is computed at render time from the download
- * store — `libraryStatusFor(owned, mbid)` reads `requestFor(mbid)` out
- * of the cached list.
- *
- * That is what made this fail. The page's `downloadStore` subscription
- * assigned `canDownload` and re-synced `isRequested` for the *release
- * group*, and neither of those changes when a **track** is requested,
- * so Lit saw no reactive property change and never re-rendered. The
- * request was filed, the Downloads tab showed it, and the badge stayed
- * on a plus reading "not in your library" — a control that appears to
- * do nothing, which is exactly what the badge was made a button to stop
- * being.
- *
- * The second assertion is the row's own: the badge is not revealed on
- * hover. A mark on the rows you do *not* have is the information on
- * this page, and one that only exists under the pointer cannot be seen,
- * counted, or reached by a finger.
- */
-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, shadow, shadowAll } from '@test/support/render';
-
-type StoredRequest = {
-  id: number;
-  mbid: string;
-  entity: string;
-  libraryId: number;
-  artist: string;
-  title: string;
-  state: string;
-  attempts: number;
-};
-
-/** The request list the store reads, mutated by the stubbed AddRequest
- *  exactly as the backend's own list would be. */
-let requests: StoredRequest[] = [];
-
-function track(n: number, owned: boolean) {
-  return {
-    position: n,
-    discNumber: 1,
-    title: `Track ${n}`,
-    length: 200000,
-    mbid: `mbid-${n}`,
-    inLibrary: owned,
-  };
-}
-
-/** An album with one owned track and one that is not here. */
-async function albumWithAnUnownedTrack(): Promise<LitElement> {
-  const el = await fixture<LitElement>('explore-album-details', {
-    albumName: 'Glass Harbour',
-    releaseGroupMBID: 'rg-1',
-  });
-
-  const tracks = [track(1, true), track(2, false)];
-
-  stub('library.Library.GetFilePathsByRecordingMBIDs', {
-    'mbid-1': ['/music/mbid-1.mp3'],
-  });
-
-  Object.assign(el, {
-    versionEntries: [
-      {
-        key: 'v1',
-        label: '2019',
-        sublabel: '2 tracks',
-        tracks,
-      },
-    ],
-    selectedVersionKey: 'v1',
-    loadingReleases: false,
-    loadingInfo: false,
-  });
-  el.requestUpdate();
-  await flush();
-  await el.updateComplete;
-
-  return el;
-}
-
-const badges = (el: LitElement) =>
-  shadowAll(el, 'library-status-indicator.track-request');
-
-describe('requesting a track from the album tracklist', () => {
-  beforeEach(async () => {
-    resetHarness();
-    requests = [];
-
-    stub('library.Library.GetFilePathsByRecordingMBIDs', {});
-    stub('library.Library.GetFilePathsByAlbums', {});
-    stub('library.Library.GetAlbumTracks', []);
-    stub('library.Library.GetAllLibrariesWithTrackCounts', [
-      { id: 1, name: 'Music', path: '/music', trackCount: 1 },
-    ]);
-
-    stub('download.Service.ProviderKinds', []);
-    stub('download.Service.ListProviders', []);
-    stub('download.Service.ListDownloads', []);
-    stub('download.Service.ListRequests', () => requests);
-    stub('download.Service.AddRequest', (input: Record<string, unknown>) => {
-      const id = requests.length + 1;
-
-      requests.push({
-        id,
-        mbid: String(input.mbid),
-        entity: String(input.entity),
-        libraryId: Number(input.libraryId),
-        artist: String(input.artist ?? ''),
-        title: String(input.title ?? ''),
-        state: 'wanted',
-        attempts: 0,
-      });
-
-      return id;
-    });
-  });
-
-  it('marks the row as queued without a reload', async () => {
-    const el = await albumWithAnUnownedTrack();
-
-    // Only the unowned row offers one: there is nothing left to ask for
-    // on a track there is a file for.
-    const [badge] = badges(el);
-
-    expect(badge).toBeTruthy();
-    expect(badge?.getAttribute('status')).toBe('not-in-library');
-
-    shadow<HTMLElement>(badge!, 'button')?.click();
-    await flush();
-    await el.updateComplete;
-
-    expect(requests.map((r) => r.mbid)).toEqual(['mbid-2']);
-    expect(badges(el)[0]?.getAttribute('status')).toBe('queued');
-  });
-
-  it('shows the badge without being hovered', async () => {
-    const el = await albumWithAnUnownedTrack();
-    const [badge] = badges(el);
-
-    // The old rule hid it at `opacity: 0` until `:hover`. Computed
-    // opacity is the assertion rather than the absence of a rule,
-    // because the rule could come back under another selector.
-    expect(getComputedStyle(badge!).opacity).toBe('1');
-  });
-});

frontend/test/components/transport.test.ts

@@ -227,6 +227,41 @@ describe('<seek-bar>', () => {
     expect(text(el, '[data-testid="remaining-time"]')).toBe('01:30');
   });
 
+  it('keeps the slider still as the clocks count', async () => {
+    const el = await fixture('seek-bar');
+
+    emit(Events.TrackChanged, { ...TRACK, trackChangeId: 31 });
+    await flush();
+    await el.updateComplete;
+
+    const slider = () =>
+      shadow(el, 'wa-slider')!.getBoundingClientRect();
+    const before = slider();
+
+    // 1:11 against 4:08 is the reported jitter: different digits, and
+    // in a proportional font different widths. Toggling the right-hand
+    // clock is the other half -- the minus sign is a whole character.
+    for (const positionSeconds of [8, 71, 88]) {
+      emit(Events.PlaybackPositionChanged, {
+        positionSeconds,
+        trackLength: 90,
+        trackChangeId: 31,
+        seq: positionSeconds,
+        playing: true,
+      });
+      await flush();
+      await el.updateComplete;
+
+      expect(slider().width).toBeCloseTo(before.width, 1);
+      expect(slider().left).toBeCloseTo(before.left, 1);
+    }
+
+    await click(el, '[data-testid="remaining-time"]');
+    await el.updateComplete;
+
+    expect(slider().width).toBeCloseTo(before.width, 1);
+  });
+
   it('renders the position the backend reports rather than its own count', async () => {
     const el = await fixture('seek-bar');