Struct VelocityTracker 

pub struct VelocityTracker { /* private fields */ }

The speed and direction of a pointer, measured over a short trailing window.

The window rather than the last two events is the whole point. Platforms deliver moves at whatever rate they please, so the last pair can be a millisecond apart and report an impossible speed, and — more importantly — a gesture that stopped before release still has old fast samples behind it. Samples older than the window are discarded, so a drag the user parked reports a stop rather than the speed it had before the pause. A tracker that reported one would fling away the thing the user deliberately put down.

Implementations

impl VelocityTracker

pub fn new() -> Self

pub fn with_window(window: Duration) -> Self

pub fn sample(&mut self, position: Point<Pixels>, at: Instant)

Records where the pointer was at at.

A sample older than one already recorded is ignored: the tracker measures a gesture forward in time, and reordering events would let a late delivery invent a direction.

pub fn velocity_at(&self, now: Instant) -> Velocity

The speed the pointer is moving at as of now.

now rather than the last sample, because a pointer that has stopped sends nothing at all: the pause is visible only against a clock.

pub fn clear(&mut self)

Forgets the gesture, for a drag that was cancelled rather than dropped.

Trait Implementations

impl Clone for VelocityTracker

fn clone(&self) -> VelocityTracker

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for VelocityTracker

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

Formats the value using the given formatter.

impl Default for VelocityTracker

fn default() -> Self

Returns the “default value” for a type.