Neon outlines

SWGlassLogo is a multi-layer composited showcase: it is not one monolithic shader but four cheap SwiftUI primitives stacked in a ZStack, producing an SF Symbol (default apple.logo) rendered as a sheet of frosted, refractive glass that glows on a near-black canvas with flowing colored light trapped inside it.

The four passes are:

1. Canvas — a near-black background (#0a0a0a).
2. Flowing light — a slowly rotating tri-color MeshGradient (cool-blue / orange / deep-blue) with a few faint diagonal stripes drifting across it. This is the light the glass refracts.
3. Glass logo — pass 2 masked to the silhouette of the SF Symbol, then run through the swGlassLogo Metal layerEffect. Because there is no analytic shape, the surface normal is recovered directly from the layer's alpha gradient across the antialiased silhouette: that drives a subtle refraction + a small golden-angle frosted disk + a luminosity-preserving tint + a cool Fresnel rim, all clipped to the symbol shape (transparent outside).
4. Bloom — two stacked .shadow halos (one tight, one wide soft) that breathe slowly on the flow's own clock, giving the logo an outer cool glow.

This is a first-pass approximation that leans on frost + a cool rim + a soft bloom over flowing color, and intentionally leaves thin-film iridescence, twirl distortion and exact SDF shaping for later refinement.

Requires iOS 18+ / macOS 15+ (SwiftUI ShaderLibrary / Shader / layerEffect, Metal stitchable, MeshGradient, TimelineView).