Struct FadeTrack 

pub struct FadeTrack { /* private fields */ }

Injected-clock fade tracker keyed by a small u64 id — the per-element hover / selection progress the immediate-mode form facets were missing. Each key holds a factor in [0,1] that eases toward 1 while the key is “lit” this frame (hovered / selected) and toward 0 once it isn’t; keys that settle back at 0 are dropped, so the map only ever holds the handful of elements that are currently mid-fade.

The per-frame protocol is three calls: begin (mark all keys un-lit), lit for each element that should glow this frame, then advance with your own dt once the frame is laid out. Read the eased value with factor when you paint each element.

Determinism (FC-7): no egui state, no wall-clock — the factors live in the caller’s component struct and advance by the dt you own (pass ui.input(|i| i.stable_dt)), so snapshots reproduce. duration <= 0 snaps instantly (honours Motion::duration == 0, the reduced-motion / Device setting).

Implementations

impl FadeTrack

pub fn begin(&mut self)

Start a frame: mark every tracked key as not lit. Re-light the ones that should glow with lit before advance.

pub fn lit(&mut self, key: u64)

Mark key lit this frame (hovered / selected). Creates it at factor 0 (so it fades in) if it wasn’t tracked yet.

pub fn factor(&self, key: u64) -> f32

The current eased factor ∈[0,1] for key (0 if untracked) — multiply your highlight alpha by this when painting the element.

pub fn active(&self) -> usize

How many keys are currently tracked (lit or still fading out) — a host-readable “is motion live right now” signal for state_json proofs.

pub fn is_animating(&self) -> bool

Whether any tracked key is mid-fade (factor strictly between fully-off and fully-on) — i.e. a cross-fade is visibly animating this frame.

pub fn advance(&mut self, dt: f32, duration: f32) -> bool

Advance every key toward its target (lit → 1, else → 0) over duration seconds, dropping keys that have faded fully back to 0. Returns whether any key is still mid-fade (the caller requests a repaint while so). duration <= 0 snaps. Deterministic given the same factors + dt.

pub fn key(id: impl Hash) -> u64

Hash any Hash id (a row &str, a row index, a repo name) into the u64 key space — the convenience bridge for facets whose element ids aren’t already u64. Stable within a run (uses the std hasher).

Trait Implementations

impl Clone for FadeTrack

fn clone(&self) -> FadeTrack

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FadeTrack

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

Formats the value using the given formatter.

impl Default for FadeTrack

fn default() -> FadeTrack

Returns the “default value” for a type.