Struct ShadowCache 

pub struct ShadowCache { /* private fields */ }

Rendered shadows, most recently used last.

Implementations

impl ShadowCache

pub fn new(capacity: usize) -> Self

A cache holding capacity shadows.

Zero is treated as DEFAULT_CAPACITY: a cache that held nothing would re-blur every shadow every frame, which is the cost this type exists to remove.

pub fn len(&self) -> usize

How many shadows are cached.

pub fn is_empty(&self) -> bool

Whether nothing is cached.

pub const fn capacity(&self) -> usize

How many it will hold.

pub fn contains(&self, key: &ShadowKey) -> bool

Whether this shadow is already rendered.

pub fn clear(&mut self)

Forget everything.

For a theme change that invalidates every shadow at once, where evicting one at a time would blur each of them again on the way out.

pub fn blit_into( &mut self, key: ShadowKey, theme: &Theme, dst: &mut ShadowDest<'_>, ) -> bool

Composite this shadow onto dst, rendering it first if it is not cached.

Source-over, in premultiplied alpha, as the reference composites it: what is already in dst shows through where the shadow is not opaque. On a cleared buffer that is the same as a copy.

Returns false, writing nothing, for a zero-sized key or destination, and true otherwise — rather than failing: a window being resized passes through zero, and a decoration that errored on the way would flicker.

A destination smaller than the patch is clipped, not refused — the alternative is writing past the caller’s buffer. Rows that do not fit in pixels at stride are skipped too, and the call still returns true.

pub fn blit_cross_fade( &mut self, a: ShadowKey, b: ShadowKey, theme: &Theme, dst: &mut ShadowDest<'_>, t: f32, ) -> bool

Composite a blend of two shadows, t of the way from a to b, onto dst.

What a focus change animates through. Both patches are cached, so the transition costs a per-pixel lerp rather than a blur per frame — given a capacity of at least two. With a capacity of one, rendering b evicts a, and a mid-transition blend draws nothing and returns false. The blend is composited source-over, as blit_into is, and the endpoints are exactly blit_into of one patch.

t is clamped to 0..=1: an animation that overshoots is a caller bug, and extrapolating a color past its endpoints produces values that are not a shadow at all.

The two keys must be the same size, as the reference requires; keys that differ write nothing and return false. Otherwise the return is as for blit_into: false, writing nothing, for a zero-sized key or destination, and true once the blend is composited.

Trait Implementations

impl Debug for ShadowCache

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

Formats the value using the given formatter.

impl Default for ShadowCache

fn default() -> Self

Returns the “default value” for a type.