Struct Bouncing 

pub struct Bouncing { /* private fields */ }

iOS’s scroll feel — Flutter’s BouncingScrollPhysics: a drag may pull the position past an edge against a friction factor that tightens with depth, nothing is ever boundary-rejected, and a release runs an exponential friction curve that hands over to a rubber-band spring at whichever edge it reaches.

See the module docs for the drag convention the surfaces hand this curve its depth through, and for the deviations from the Dart source.

Implementations

impl Bouncing

pub const MIN_FLING_VELOCITY: f64

Flutter’s BouncingScrollPhysics.minFlingVelocity: twice super::MIN_FLING_VELOCITY, because this physics’ ballistic curve decelerates more slowly than the clamping one, so a fling has to be a more deliberate flick to be worth starting.

pub fn new() -> Self

A standalone bouncing physics at DecelerationRate::Normal.

pub fn with_rate(rate: DecelerationRate) -> Self

A standalone bouncing physics at rate.

pub fn chain(self, parent: impl ScrollPhysics + 'static) -> Self

Chain parent behind this physics, the module-wide composition convention (ScrollPhysics’ Chaining).

pub fn friction_factor(&self, overscroll_fraction: f64) -> f64

The fraction of a past-edge pull that reaches the position at an overscroll of overscroll_fraction viewports — Flutter’s frictionFactor: 0.52·(1 − f)² at DecelerationRate::Normal, 0.26·(1 − f)² at DecelerationRate::Fast.

Trait Implementations

impl Debug for Bouncing

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

Formats the value using the given formatter.

impl Default for Bouncing

fn default() -> Self

Returns the “default value” for a type.

impl ScrollPhysics for Bouncing

fn apply_physics_to_user_offset( &self, metrics: &ScrollMetrics, offset: f64, ) -> f64

Travel inside the range passes through untouched, travel that deepens an overscroll is scaled by Self::friction_factor at the depth already held, and travel easing back toward the range passes through untouched too. That asymmetry is the signature of the feel: pulling further out gets progressively heavier, letting it back never fights the finger.

fn apply_boundary_conditions( &self, _metrics: &ScrollMetrics, _value: f64, ) -> f64

Nothing is ever rejected — holding an out-of-range position is the whole point of a bouncing surface, and the edge spring (not a boundary rule) is what returns it.

fn create_ballistic_simulation( &self, metrics: &ScrollMetrics, velocity: f64, ) -> Option<Box<dyn Simulation>>

An overscrolled surface always gets its spring back, in range a fling needs Self::MIN_FLING_VELOCITY, and anything else is no motion at all.

fn should_accept_user_offset(&self, _metrics: &ScrollMetrics) -> bool

Always true: an iOS surface whose content fits its viewport still scrolls — it just bounces straight back.

fn carried_momentum(&self, existing_velocity: f64) -> f64

Flutter’s fitted power curve, capped at MOMENTUM_CAP (40000 px/s) and signed like the motion it carries over.

fn parent(&self) -> Option<&dyn ScrollPhysics>

The chained parent physics, if this one was built via chain(...). None for a physics built standalone (the chain’s root).

fn min_fling_velocity(&self) -> f64

The minimum release speed that starts a fling.

fn spring(&self) -> SpringDescription

The spring a bounce-back/snap simulation is built from.

fn max_fling_velocity(&self) -> f64

The fastest fling speed this physics honors.

fn tolerance_for(&self, metrics: &ScrollMetrics) -> Tolerance

The velocity/distance tolerance a ballistic simulation settles within.