rimShade property

Strength of the hairline outline on the very edge of the glass, 0 to 1.

iOS 27 glass is bounded by a half-point line that is the backdrop at its own position, untinted and unblurred, darkened by a fixed step: about 31% across the light axis and a fifth of that at its ends, where the rim light sits (rimShadeEnds). Together with rimLight this is what reads as the "bubble" edge of a native control. 1.0 matches both native materials, the dark one's taken below a bodyShade.

Unlike edgeAbsorption, which darkens the whole bevel, this touches only the outermost pixels. The line is subtracted from the colour beneath it rather than blended, so it stays the same step below any backdrop.

Above zero (or under a frost) the glass's edge is also drawn as the native one is: its anti-aliasing narrows to half a logical pixel, so the outline lands on an opaque pixel, and the silhouette grows by a physical pixel at 3x, where the native outline sits outside the frame.

Only affects the Premium (Impeller) path. Defaults to 0.0, off.