Struct MomentumScroller 

pub struct MomentumScroller {
    pub position: f32,
    pub scale: f32,
    pub velocity: f32,
    pub friction: f32,
    pub min_velocity: f32,
}

Scroll offset with velocity-based momentum and frame-rate-independent friction.

Fields

position: f32

Current scroll offset on this axis.

scale: f32

Multiplier applied to scroll deltas.

velocity: f32

Current scroll velocity in pixels per second.

friction: f32

Stored friction factor (1.0 − friction passed to new).

Momentum decay uses friction.powf(dt * 60.0) each frame.

min_velocity: f32

Velocity magnitudes below this threshold are zeroed out.

Implementations

impl MomentumScroller

pub fn new(scale: f32, friction: f32, min_velocity: f32) -> Self

Creates a momentum scroller at position zero.

• scale — multiplier for scroll deltas.
• friction — per-60-fps-step decay factor; must satisfy 0.0 < friction < 1.0. Stored internally as 1.0 - friction.
• min_velocity — stop threshold; must be positive.

Panics

Panics if friction is not in (0.0, 1.0) or if min_velocity <= 0.0.

pub fn direct_set_position(&mut self, position: f32)

Sets the scroll position and clears velocity.

pub fn update(&mut self, d_scroll: f32, dt: f32)

Advances scroll state for one frame.

When d_scroll != 0, applies the delta and sets velocity from d_scroll / dt. When d_scroll == 0, applies momentum with friction decay.

Examples

use cotis_interactivity::scroll::MomentumScroller;

let mut scroller = MomentumScroller::new(1.0, 0.1, 0.5);
scroller.update(10.0, 1.0 / 60.0);
assert!(scroller.get_position() > 0.0);

// Momentum continues when no new delta is applied
scroller.update(0.0, 1.0 / 60.0);
assert!(scroller.velocity.abs() > 0.0 || scroller.get_position() > 10.0);

pub fn get_position(&self) -> f32

Returns the current scroll offset.

Trait Implementations

impl Clone for MomentumScroller

fn clone(&self) -> MomentumScroller

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for MomentumScroller

impl Debug for MomentumScroller

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

Formats the value using the given formatter.