Struct Length

pub struct Length {
    pub base: LengthBase,
    pub min_px: Option<f32>,
    pub max_px: Option<f32>,
}

A size or distance value that may be expressed in absolute pixels or relative to the rendering surface. Every widget API that used to take f32 for a size, padding, spacing or font height now takes impl Into<Length>, so existing call sites keep compiling unchanged while new code can switch to viewport-relative units for layouts that must scale across screen sizes (portrait phone, landscape tablet, 4K desktop) without per-target tweaks.

Resolution requires a viewport — passed in as (width, height) in logical pixels — and an em_base (the body-text font size that Em is a multiple of). All resolution funnels through Length::resolve, so widgets can stay backend-agnostic.

Construct directly via the LengthBase variants (Length::vmin( 18.0 ), Length::px( 24.0 ), …) or implicitly from f32/i32/u32 for the px case so legacy .size( 24.0 ) style keeps compiling unchanged. Optionally chain .clamp( min_px, max_px ) to bound a relative value into a safe range.

Fields

base: LengthBase

min_px: Option<f32>

Lower bound in absolute logical px. None means unbounded.

max_px: Option<f32>

Upper bound in absolute logical px. None means unbounded.

Implementations

impl Length

pub const EM_BASE_DEFAULT: f32 = 16f32

Default font-size that LengthBase::Em is a multiple of. Matches the typography::BODY constant of the default theme.

pub const fn from_base(base: LengthBase) -> Self

pub const fn px(v: f32) -> Self

Shorthand constructors. Length::vmin( 18.0 ) reads better than Length::from_base( LengthBase::Vmin( 18.0 ) ) at every call site and the brevity matters when these appear in tight view code.

pub const fn vw(v: f32) -> Self

pub const fn vh(v: f32) -> Self

pub const fn vmin(v: f32) -> Self

pub const fn vmax(v: f32) -> Self

pub const fn em(v: f32) -> Self

pub fn dp(px: f32) -> Self

“Design pixel”: px interpreted at the reference vmin set via set_design_reference (defaults to 412 px — the eydos mobile reference width). The result is a Vmin value clamped to [px * 0.7, px * 1.5], so the layout scales with the screen without collapsing on tiny surfaces or ballooning on 4K.

pub fn resolve(&self, viewport: (f32, f32), em_base: f32) -> f32

Resolve to a concrete logical-pixel value given a viewport and an em_base (the root font size that Em is a fraction of).

pub fn clamp(self, min_px: f32, max_px: f32) -> Length

Cap the resolved value to [min_px, max_px]. Bounds are absolute px because the typical use is “this Vmin should never shrink past readable nor balloon past comfortable”; bounding a relative value with another relative value is rare enough to not justify boxing the type. If you swap min/max the resolver tolerates it instead of panicking.

pub fn at_least(self, min_px: f32) -> Length

One-sided bound: never resolve below min_px. Named at_least (rather than min) to avoid clashing visually with f32::min, which has the opposite semantics (“return the smaller of two”).

pub fn at_most(self, max_px: f32) -> Length

One-sided bound: never resolve above max_px. Counterpart to Self::at_least.

Trait Implementations

impl Clone for Length

fn clone(&self) -> Length

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Length

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

Formats the value using the given formatter.

impl From<LengthBase> for Length

fn from(base: LengthBase) -> Self

Converts to this type from the input type.

impl From<f32> for Length

fn from(v: f32) -> Self

Converts to this type from the input type.

impl From<i32> for Length

fn from(v: i32) -> Self

Converts to this type from the input type.

impl From<u32> for Length

fn from(v: u32) -> Self

Converts to this type from the input type.

impl PartialEq for Length

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Length

impl StructuralPartialEq for Length