Struct PaneAffordanceMotion 

pub struct PaneAffordanceMotion {
    pub reduced_motion: bool,
    pub fade_in_frames: u16,
    pub pulse_period_frames: u16,
    pub pulse_floor_bps: u16,
}

Deterministic micro-animation policy for pane affordances (bd-18yus).

Pane affordances (splitter handles, focus emphasis, snap previews) gain a subtle emphasis ramp when they activate — a hover fade-in, a slow active pulse — so a state change reads as motion rather than a hard cut. The policy is host-agnostic and reports only a bounded emphasis weight in basis points ([0, 10_000]); hosts map that to blend weight / brightness themselves.

Design properties:

• Deterministic. Emphasis is a pure function of an integer phase tick supplied by the caller (a frame counter / animation clock), never a wall clock, and uses integer-only math — so replays and snapshots are byte-stable across platforms with no floating-point drift.
• Reduced-motion safe. When reduced_motion is set, every ramp collapses to a step function: emphasis jumps to its terminal value on the first frame. No semantic cue is lost — the affordance still changes state — only the in-between motion is removed, satisfying the reduced-motion behavior-parity requirement.
• Bounded & cheap. Each query is constant-time, allocation-free integer arithmetic (a couple of multiplies and a divide), so per-affordance, per-frame overhead is negligible even with many splitters on screen.

Fields

reduced_motion: bool

When set, all ramps collapse to instantaneous steps (no in-between frames), preserving the state change without motion.

fade_in_frames: u16

Frames over which a hover emphasis fades in (≈100 ms at 60 fps by default). Zero means “instant”.

pulse_period_frames: u16

Period of the active-state pulse in frames (≈0.8 s at 60 fps by default). Zero disables the pulse (steady full emphasis).

pulse_floor_bps: u16

Low point of the active pulse in basis points; the pulse oscillates between this floor and full emphasis.

Implementations

impl PaneAffordanceMotion

pub fn reduced() -> Self

The reduced-motion preset: identical timing fields, but every ramp is stepped. Use this when the host reports a reduced-motion preference.

pub fn with_reduced_motion(self, reduced_motion: bool) -> Self

Apply a reduced-motion preference to this policy, returning the adjusted copy. Lets a host derive the effective policy from a preference flag.

pub fn hover_emphasis_bps(&self, elapsed_frames: u16) -> u16

Hover emphasis ramp in basis points.

elapsed_frames counts frames since the affordance entered the hovered state. The ramp is a quadratic ease-out from 0 to full over fade_in_frames. Under reduced motion (or a zero fade) it returns full emphasis immediately.

pub fn active_pulse_bps(&self, phase_frames: u64) -> u16

Active (dragging) emphasis pulse in basis points.

phase_frames is a free-running frame counter; the pulse smoothly ping-pongs between pulse_floor_bps and full emphasis over pulse_period_frames. Under reduced motion (or a zero period) it returns steady full emphasis.

Trait Implementations

impl Clone for PaneAffordanceMotion

fn clone(&self) -> PaneAffordanceMotion

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for PaneAffordanceMotion

impl Debug for PaneAffordanceMotion

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

Formats the value using the given formatter.

impl Default for PaneAffordanceMotion

fn default() -> Self

Returns the “default value” for a type.

impl Eq for PaneAffordanceMotion

impl PartialEq for PaneAffordanceMotion

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for PaneAffordanceMotion