Spotlight's Liquid Glass Morph, Frame by Frame

A measured teardown of the macOS Tahoe Spotlight enter/exit animation, from a 57 fps screen recording — so we can clone it faithfully in Script Kit.

Method

Frame 1 contains no Spotlight — a clean background plate. Every other frame is background-subtracted against it, so the only differing pixels belong to Spotlight itself. Per frame, three measurements were extracted:

1. Edges — column/row intensity profiles of the diff, smoothed, with edges at threshold crossings (per-frame–relative for bright frames, absolute-from-steady for cross-checks). 2. Presence — mean diff intensity inside the fixed steady-state bar rectangle, normalized so steady = 1.0. This is an opacity proxy (during the exit it conflates fade with blur, both of which remove energy from the region — which is exactly what your eye sees). 3. Visual keyframes — cropped strips for qualitative confirmation.

The Enter: fade in wide → squish under → rebound out

Measured timeline (t=0 at first visible frame)

What the numbers say

It's released elastic, and the timing is asymmetric. The compression stroke (wide → max squish) takes ~140 ms; the rebound (squish → natural) takes ~140 ms more but travels only a quarter of the distance — so the rebound feels much slower and softer. The window is effectively at rest at max compression: velocity passes through zero there, which is what makes it read as physics instead of keyframes.

The fade and the compression are phase-locked. Opacity completes (≥0.99) at almost exactly the moment width bottoms out. The bar is never fully opaque while still larger than its natural size.

The morph is width-dominant. Height reaches its final value by ~120 ms and does not undershoot measurably (±0–2 px), while width undershoots by ~6 px. The "squish" your eye reads is horizontal.

The Exit: dematerialize — fade + blur + slight growth

Measured presence (opacity × blur energy)

The presence curve is a symmetric S (slow-fast-slow), and the visual signature is unmistakable: this is a dematerialize, not a shrink. The bar releases outward (the inverse of its entry direction — it entered by shrinking in, it leaves by relaxing back out), while a gaussian blur dissolves the edges and the whole thing fades. No bounce on the way out.

Porting this to Script Kit

Enter — current implementation vs. measured Spotlight

// Recommended knob changes (theme defaults)
GLASS_MORPH_DEFAULT_DURATION = 0.28   // was 0.26
GLASS_MORPH_DEFAULT_INSET    = 0.03   // was 0.02 (per side)
// phase split in animate_tahoe_glass_appearance:
phase1 = duration * 0.50              // was 0.62 — equal strokes,
                                      // rebound covers 1/4 the distance
                                      // so it reads twice as gentle

Exit — new design (we currently hard-cut)

Three simultaneous channels over ~120 ms, all ease-in-out:

// 1. alpha: 1 → 0            (window animator, 0.12 s)
// 2. frame: grow ~3% per side (the inverse release of the entry)
// 3. blur : CAFilter "gaussianBlur" on contentView.layer,
//           inputRadius 0 → ~8pt   ← same private-API pattern the
//           repo already uses for backdrop saturation
// then orderOut.

Appendix: full measurement dump

Width ratios are only reported where presence > 0.5 (below that, compression noise dominates the edges). Frames 20–29 are omitted — all identical to steady state within ±0.4%.

Measured with background subtraction + intensity-profile edge detection (numpy/PIL) from a 1588×1062 @ 57 fps CleanShot recording, 2026-07-20.