Merge p10-w1-resolution-slider into dev (P10 W1: fix zoom slider stacking-context occlusion)

DeepDrftPublic/Interop/visualizer/MixVisualizer.ts

@@ -795,7 +795,12 @@ export function create(canvas: HTMLCanvasElement): MixVisualizerHandle {
         setZoom(seconds: number): void {
             // Clamp into the supported span so a stray value can't break the math.
             visibleSeconds = Math.min(MAX_VISIBLE_SECONDS, Math.max(MIN_VISIBLE_SECONDS, seconds));
-            if (!playback.isPlaying) redrawOnce();
+            // While playing, the running rAF loop uploads uVisibleSeconds next frame; while idle the
+            // loop is stopped (spec §E), so a zoom change must force one still frame here or the new
+            // span is uploaded only on the next unrelated redraw (theme/datum/resize) — i.e. never.
+            const idleRedraw = !playback.isPlaying;
+            debugLog(`setZoom — requested ${seconds.toFixed(3)}s, clamped ${visibleSeconds.toFixed(3)}s; idleRedraw=${idleRedraw} (isPlaying=${playback.isPlaying}).`);
+            if (idleRedraw) redrawOnce();
         },
 
         refreshTheme(): void {