GlassAppearance class

How a glass tab bar adapts to what is behind it, as UIKit's does (iOS 26.5 simulator, measured from its layers over stepped backdrops).

UIKit reads the backdrop's mean luma (Rec. 709 on its colors) around the bar, about every frame, and keeps a light or a dark appearance with hysteresis. The glass's color inputs follow the luma and the appearance on a critically damped 0.5s spring; the resting selection's on a 0.24s one; the symbols and labels switch at once.

Constructors

GlassAppearance({Brightness system = Brightness.light})

Properties

adaptive ← bool: Whether the appearance follows the backdrop. When false, it keeps the system's, and only the glass's colors follow the backdrop's luma.
no getter
chroma → double: The face's chroma gain: 1, but less with contrast or reduceTransparency.
no setter
contrast ← bool: Increase Contrast, as UIKit's glass honors it (iOS 26.5, from its filters' inputs): the light glass is filled 80% white over its face, its face keeps 0.8 / 1.1 of the chroma it would, and its shadow's fill is 0.12.
no getter
face → (double, double, double, double): The platter's face: luma black and white points, fill alpha and gray.
no setter
hashCode → int: The hash code for this object.
no setterinherited
isDark → bool: Whether the glass is in its dark appearance.
no setter
lensRim → (double, double, double): no setter
luma → double: The backdrop's luma, as last sampled.
no setter
pill → (double, double, double): The resting selection's matrix.
no setter
platterRim → (double, double, double): The platter's and the lens's rim matrices.
no setter
reduceTransparency ← bool: Reduce Transparency, the same way: on top of contrast's fill and shadow, the light glass maps every luma to 0.9, keeps 0.9 / 1.1 of the chroma, and does not refract; the bar blurs what is below it heavily (see GlassTabBar).
no getter
refraction → double: How much the glass refracts: none with reduceTransparency.
no setter
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
shadow → double: The platter shadow's strength.
no setter
symbol → (double, double): Normal symbols' luma weight and lift.
no setter
system ← Brightness: The system's appearance: the bar's own until the backdrop says otherwise.
no getter

Methods

noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
sample(double luma) → void: A new reading of the backdrop's luma under the bar. The first one takes effect at once; later ones after a moment, and animate.
tick(double now) → bool: Advances the springs to now (seconds). Returns whether anything is still moving.
toString() → String: A string representation of this object.
inherited
wouldKeep(double luma) → bool: Whether a reading of luma would change nothing: it is the luma in effect, and no other reading is still waiting to take effect.

Operators

operator ==(Object other) → bool: The equality operator.
inherited

Static Properties

debugOnChange ↔ void Function(GlassAppearance appearance, String event)?: Called after every tick and sample, for logging.
getter/setter pair

Static Methods

sampleArea(Rect bar) → Rect: Where UIKit reads the backdrop: its mean luma over the bar's container (the screen's width, from the bar's top to the screen's bottom) grown by the glass's 12.4pt margin. For a bar laid out 21pt from the screen's sides and bottom, that is the bar grown by 21pt to the sides and below and 12.4pt above.