Enum Gap 

pub enum Gap {
    Bound,
    Peer,
    Group,
    Section,
    Pane,
    Page,
}

A named separation between two things.

Pick by relationship. The size is a consequence of the name, not the other way round, and callers should never care what it is.

Variants

Bound

A control and the thing it belongs to: an edit field and its pop-up, a checkbox and its label, an icon and the text it labels. Reads as one object.

Peer

Items of the same kind in a list: stacked checkboxes, radio buttons, rows, chips in a row. Reads as a set.

Group

A container’s inner margin, and the distance between sibling groups side by side. Reads as “inside this box”.

Section

Separated groups, and rows of actions. The first gap that reads as a deliberate break rather than as breathing room.

Pane

Panel padding and content shells. Layout, not controls.

Page

The outermost shell margin. One per screen, usually.

Implementations

impl Gap

pub const fn step_at(self, density: Density) -> Step

The step this relationship resolves to at a given density, on a SizeClass::Medium or wider window.

Density::Pointer’s values are the HIG’s own. Density::Touch opens the three gaps that separate distinct tap targets and holds the rest, per the crate-level “Density presets” section.

Shells tighten on a compact window rather than at touch density. Use Self::step_at_size where the window width is known; this is the wider-window answer and the one every existing caller already meant.

pub const fn step_at_size(self, density: Density, size: SizeClass) -> Step

The step this relationship resolves to at a given density and window size class.

Only the two shells move, and only on SizeClass::Compact: pane 24 to 16, page 32 to 24, one step down each. The four gaps between controls do not, because how much room a window has says nothing about how far apart two tap targets should be.

Which axis owns this (Max, 2026-08-09). The Pointer preset was carrying a retune to pane 14 / page 16 on the strength of a specimen that wanted a tighter window edge. A tighter window edge is a claim about screen budget, and the 0.3.0 Touch re-derivation had already ruled that smuggling screen budget into the density axis was the whole bug the old Touch preset embodied — it just had nowhere else to put it, because SizeClass did not exist yet. It does now, so the claim goes where it belongs and the quoted Pointer values hold.

Two things fall out. There is no need for a Step at 7/8 = 14, which is off the eighths scale and would have wanted a public name; both compact values are already on it. And no consumer migrates, because no quoted value changed.

pub const fn step(self) -> Step

The step this relationship resolves to at the default density.

pub const fn px_at(self, density: Density) -> u16

Size in CSS pixels at the default base, at a given density.

pub const fn px_at_size(self, density: Density, size: SizeClass) -> u16

Size in CSS pixels at the default base, at a given density and window size class.

pub const fn px(self) -> u16

Size in CSS pixels at the default base and density.

pub const fn token(self) -> &'static str

The CSS custom-property name, without the leading --.

pub const fn all() -> [Self; 6]

Every relationship, tightest first.

Trait Implementations

impl Clone for Gap

fn clone(&self) -> Gap

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Gap

impl Debug for Gap

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

Formats the value using the given formatter.

impl Eq for Gap

impl Hash for Gap

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Gap

fn cmp(&self, other: &Gap) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Gap

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for Gap

fn partial_cmp(&self, other: &Gap) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralPartialEq for Gap