fix(equalizer): redraw curve when <details> reopens (#747)

* fix(equalizer): redraw curve when surrounding <details> toggles open

ResizeObserver does not reliably fire for the `display:none → block`
transition that the SettingsSubSection `<details>` causes when the user
expands the Equalizer panel after collapsing it. drawCurve bails on a
zero-sized canvas (existing macOS-WebKit guard), and without a new
trigger the second open leaves the frequency-response canvas blank.
Add a `toggle` listener on the closest `<details>` ancestor; on open,
redraw after one rAF so the canvas has its laid-out size. Additive —
doesn't change the working ResizeObserver path.

* docs(changelog): note Equalizer canvas redraw fix (#747)

CHANGELOG.md

@@ -645,6 +645,12 @@ Foundational work: faster reviews, narrower diffs, and a safety net under the pa
 * Clicking the **artist** in the Favorites songs table opened the artist page _and_ started the song — the cell was missing the click guard the album cell already had. Now matches every other tracklist in the app.
 * Selecting a song no longer pushes the column header and every row down by one line. The "X selected / Add to playlist / Clear" cluster moved out of the full-width bar into the existing action-buttons row (right-aligned), matching the album toolbar, so the next item stays under the same cursor position.
 
+### Equalizer — frequency-response curve no longer disappears on re-expand
+
+**By [@Psychotoxical](https://github.com/Psychotoxical), thanks to zunoz for the report on the Psysonic Discord, PR [#747](https://github.com/Psychotoxical/psysonic/pull/747)**
+
+* Collapsing and re-expanding **Settings → Audio → Equalizer** sometimes left the curve area blank: `ResizeObserver` does not reliably fire for the `display: none → block` transition the surrounding `<details>` triggers, so the redraw that depends on it never ran on the second open. A `toggle` listener on the parent `<details>` now redraws explicitly on open.
+
 ## [1.45.0] - 2026-05-04
 
 ## Added

src/components/Equalizer.tsx

@@ -41,6 +41,20 @@ export default function Equalizer() {
     return () => ro.disconnect();
   }, [redraw]);
 
+  // ResizeObserver does not always fire for the `display: none → block`
+  // transition the surrounding <details> causes when toggled, leaving the
+  // canvas blank on the second open. Redraw explicitly when the parent
+  // <details> opens; rAF waits one frame for the canvas to take its size.
+  useEffect(() => {
+    const details = canvasRef.current?.closest('details');
+    if (!details) return;
+    const onToggle = () => {
+      if (details.open) requestAnimationFrame(redraw);
+    };
+    details.addEventListener('toggle', onToggle);
+    return () => details.removeEventListener('toggle', onToggle);
+  }, [redraw]);
+
   const isCustomSaved = activePreset && !BUILTIN_PRESETS.some(p => p.name === activePreset);
   const selectValue = activePreset ?? '__custom__';