Struct ComputeCache 

pub struct ComputeCache { /* private fields */ }

An opt-in bounded cache for ComputedStyle results, keyed by an opaque signature that captures (node identity, ancestor-chain signature, media context, stylesheet generation).

See the module docs for the correctness invariants and the eviction policy. Two computes with the same signature yield the same ComputedStyle, so a hit short-circuits the cascade. The cache is an access-order LRU: both a get hit and an insert of an existing key promote that key to most-recently-used, and the least-recently-used entry is evicted when the cache is full.

get takes &mut self for two reasons: a stylesheet generation mismatch (detected on every access) clears the cache in place — see Self::check_generation — and a hit promotes the key to the back of the eviction order. Both get and insert are O(capacity) because promotion scans the order deque.

Implementations

impl ComputeCache

pub fn new(capacity: usize) -> Self

Build a cache with the given hard capacity. capacity == 0 disables storage: get always returns None and insert is a no-op.

pub fn get(&mut self, sig: u64, current_gen: u64) -> Option<ComputedStyle>

Look up a cached result by signature. Returns an owned ComputedStyle clone on a hit (cheap — a post-resolution ComputedStyle holds no heap Color::Var).

A hit promotes sig to the back of the eviction order (most-recently-used), so frequently accessed entries survive longer. This is the access-order LRU promotion. The scan over the order deque makes get O(capacity); acceptable for a small bounded cache. A miss does NOT mutate the order.

&mut self because check_generation may clear, and a hit promotes.

pub fn insert(&mut self, sig: u64, value: ComputedStyle, current_gen: u64)

Insert a computed result under sig. If the key already exists, update its value and move it to the back of the eviction order (most-recently-used) — an access-order LRU promotion. If at capacity and the key is new, evict the least-recently-used entry (front of the order). A no-op when capacity is 0. O(capacity) due to the promotion scan.

pub fn clear(&mut self)

Drop every entry. Keeps the capacity for reuse.

pub fn len(&self) -> usize

Number of entries currently cached.

pub fn is_empty(&self) -> bool

Whether the cache holds zero entries.

Trait Implementations

impl Default for ComputeCache

fn default() -> Self

Returns the “default value” for a type.