Struct DensityProjection 

pub struct DensityProjection(pub fn(&Theme, TargetDensity) -> Theme);

How a theme re-derives itself for another TargetDensity, registered as a ThemeExtensions entry.

Absent — the default, and what every raw-token theme gets — means Theme::with_density swaps Theme::input and changes nothing else. That is right for a theme whose style_slots are all None, because each widget then builds its own Recipe*Style from ctx.theme().input at its next build.

A preset that installs Tier-3 slots of its own (Fluent, macOS, Material 3) needs more: its slots are Some(..), so they would ride across a density switch still carrying the dimensions they were built with, and a Fluent button would stay 32 dp tall under Touch. Such a preset registers this — a function taking the current theme, so it can recover the palette it was built from (theme.extension::<FluentPalette>()) and rebuild only the slots it owns, leaving colours, id, other extensions and any slot the app installed itself alone.

It lives in the extension registry rather than as a Theme field for the reason the registry exists: it is optional, typed, non-serializable state that only some themes carry.

Tuple Fields

0: fn(&Theme, TargetDensity) -> Theme

Trait Implementations

impl Clone for DensityProjection

fn clone(&self) -> DensityProjection

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for DensityProjection

impl Debug for DensityProjection

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

Formats the value using the given formatter.