Struct AppBarCollapse 

pub struct AppBarCollapse { /* private fields */ }

The collapse geometry of one sliver_app_bar configuration: the pure mapping between an app’s scroll offset, the bar’s collapse fraction, and the band it occupies.

Every method is clamp-disciplined and NaN-safe — a non-finite input resolves to the resting (expanded) end rather than propagating.

use frust_material::{AppBarCollapse, AppBarDensity, AppBarVariant};

let geometry = AppBarCollapse::new(AppBarVariant::Large, AppBarDensity::Regular, true);
assert_eq!(geometry.expanded_height(), 152.0);
assert_eq!(geometry.collapsed_height(), 64.0);

// A pinned bar bottoms out at its collapsed band, 88px of scroll later.
assert_eq!(geometry.travel(), 88.0);
assert_eq!(geometry.height(0.0), 152.0);
assert_eq!(geometry.height(1.0), 64.0);
assert_eq!(geometry.fraction_for_offset(44.0), 0.5);

// Past the end, and off the map, both clamp.
assert_eq!(geometry.fraction_for_offset(1_000.0), 1.0);
assert_eq!(geometry.fraction_for_offset(f64::NAN), 0.0);

Implementations

impl AppBarCollapse

pub const fn new( variant: AppBarVariant, density: AppBarDensity, pinned: bool, ) -> Self

The geometry of a variant bar at density, bottoming out at its collapsed band when pinned and at zero height otherwise.

pub const fn expanded_height(&self) -> f64

The band at collapse 0.0, in logical px.

pub const fn collapsed_height(&self) -> f64

The collapsed band — the top row’s own height, in logical px. A pinned bar bottoms out here; an unpinned one keeps shrinking past it.

pub const fn min_height(&self) -> f64

The band at collapse 1.0, in logical px: the collapsed band when pinned, 0.0 otherwise.

pub fn travel(&self) -> f64

The scroll distance, in logical px, that carries this bar from fully expanded to fully collapsed — never negative.

pub fn fraction_for_offset(&self, offset: f64) -> f64

The collapse fraction a scroll offset (a ScrollInfo’s own clamped offset) maps to, in [0, 1].

A bar with no travel at all (AppBarVariant::Small, pinned) reports 1.0 for any positive offset and 0.0 at rest — it has no expanded state to leave, so the answer is only ever cosmetic.

pub fn height(&self, collapse: f64) -> f64

The band this bar occupies at collapse fraction collapse, in logical px — linear between Self::expanded_height and Self::min_height.

pub fn headline(&self, collapse: f64) -> f64

How far the headline has collapsed at collapse fraction collapse, in [0, 1]: 0.0 is the expanded headline (bottom-anchored, headlineSmall), 1.0 the collapsed one (in the top row, titleLarge).

This is not Self::height’s own fraction: an unpinned bar keeps shrinking after the headline has fully collapsed, so the headline saturates first.

Trait Implementations

impl Clone for AppBarCollapse

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for AppBarCollapse

impl Debug for AppBarCollapse

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for AppBarCollapse

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for AppBarCollapse