better velocity on now playing swipedown

src/components/player/nowPlayingDismiss.ts

@@ -0,0 +1,45 @@
+const ADAPTIVE_VELOCITY_ONSET = 1000;
+const ADAPTIVE_VELOCITY_RANGE = 4000;
+const BASE_STIFFNESS = 240;
+const MAX_STIFFNESS = 480;
+const BASE_DAMPING = 28;
+const MAX_DAMPING = 60;
+const MIN_REMAINING_DISTANCE = 120;
+const VELOCITY_TRAVEL_DAMPING = 1.35;
+
+interface NowPlayingDismissSpring {
+  velocity: number;
+  stiffness: number;
+  damping: number;
+}
+
+/**
+ * Preserve the exact release velocity, then make the spring progressively
+ * stronger and more damped for hard flicks so it sheds speed after handoff.
+ */
+export function resolveNowPlayingDismissSpring(
+  velocityY: number,
+  remainingDistance: number
+): NowPlayingDismissSpring {
+  'worklet';
+
+  const velocity = Number.isFinite(velocityY) && velocityY > 0 ? velocityY : 0;
+  const excessVelocity = Math.max(0, velocity - ADAPTIVE_VELOCITY_ONSET);
+  const adaptiveProgress = 1 - Math.exp(-excessVelocity / ADAPTIVE_VELOCITY_RANGE);
+  const safeRemainingDistance = Number.isFinite(remainingDistance)
+    ? Math.max(MIN_REMAINING_DISTANCE, remainingDistance)
+    : MIN_REMAINING_DISTANCE;
+  const adaptiveDamping =
+    BASE_DAMPING + (MAX_DAMPING - BASE_DAMPING) * adaptiveProgress;
+  // Extreme gesture velocities can otherwise cross the remaining screen travel
+  // in a single frame and trip overshootClamping. Scale damping only above that
+  // risk boundary so the already-good ordinary flick path remains unchanged.
+  const travelDamping =
+    velocity > 0 ? (velocity / safeRemainingDistance) * VELOCITY_TRAVEL_DAMPING : 0;
+
+  return {
+    velocity,
+    stiffness: BASE_STIFFNESS + (MAX_STIFFNESS - BASE_STIFFNESS) * adaptiveProgress,
+    damping: Math.max(adaptiveDamping, travelDamping),
+  };
+}