Struct ScrollLink 

pub struct ScrollLink { /* private fields */ }

Scroll offsets mapped onto progress from 0 to 1.

Reduced motion

A link makes no decision of its own, and that is deliberate rather than lazy. A header that collapses as the content scrolls under it, or a shadow that appears once there is something above the fold, is not gratuitous motion: it is a direct, one-to-one response to a movement the user is making with their own hand, and suppressing it would remove information rather than calm. A decorative parallax — a background drifting at a different rate to say nothing at all — is the opposite, and under reduced motion it should not drift.

Only the caller knows which of those it is building, so the caller says so with ScrollLink::decorative. A decorative link marked under reduced motion reports 0 at every offset, which is the resting end of the effect: the parallax layer simply sits where it belongs.

Implementations

impl ScrollLink

pub fn new(start: Pixels, end: Pixels) -> Self

Over the offsets start..end, measured the way a reader thinks about scrolling: 0 is the top of the content and the number grows as the content moves up.

A range with no length is a threshold rather than a ramp: progress is 0 below it and 1 from it on.

pub fn over(distance: Pixels) -> Self

Over the first distance of scrolling.

pub fn decorative(self, reduce_motion: bool) -> Self

Marks the effect decorative, and suppresses it when the user has asked for less motion.

Pass reduce_motion. A link left unmarked always reports the offset, because a response to the user’s own scrolling is not the motion the preference is about.

pub fn progress(self, offset: Pixels) -> f32

Where offset sits in the range: 0 before it, 1 after it, and monotonically between.

pub fn sample<T: Interpolate>(self, offset: Pixels, from: T, to: T) -> T

Anything interpolable, read off the offset.

Anything that takes a progress can be driven from here, including Keyframes::sample for a value that passes through stops on the way.

Trait Implementations

impl Clone for ScrollLink

fn clone(&self) -> ScrollLink

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ScrollLink

impl Debug for ScrollLink

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

Formats the value using the given formatter.

impl PartialEq for ScrollLink

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for ScrollLink