Struct LayoutCache 

pub struct LayoutCache {
    pub safe_area: SafeArea,
    pub delta_time: f32,
    pub scale_factor: f32,
    pub viewport: Option<Rect>,
    pub layout_time_budget: Duration,
    pub layout_start_time: Option<Instant>,
    pub parent_map: HashMap<u64, u64>,
    pub engine: Option<Box<dyn Any + Send + Sync>>,
    pub animators: Option<Box<dyn Any + Send + Sync>>,
    pub previous_rects: HashMap<u64, Rect>,
    pub eviction_generation: u64,
    pub previous_rects_generation: HashMap<u64, u64>,
    /* private fields */
}

Fields

safe_area: SafeArea

delta_time: f32

scale_factor: f32

Device scale factor for HiDPI / retina snapping. Defaults to 1.0.

viewport: Option<Rect>

The visible viewport bounds in logical pixels. If Some, layout execution can cull offscreen subtrees.

layout_time_budget: Duration

Time budget for the layout pass. Defaults to 4.0ms.

layout_start_time: Option<Instant>

Start of the layout pass, captured at the beginning of the frame/layout run.

parent_map: HashMap<u64, u64>

Map tracking child-to-parent view hash relationships for bottom-up invalidation.

engine: Option<Box<dyn Any + Send + Sync>>

Opaque pointer to the active layout engine (e.g. Taffy)

animators: Option<Box<dyn Any + Send + Sync>>

Opaque pointer to the active animation orchestrator

previous_rects: HashMap<u64, Rect>

Cached previous rects for view transitions

eviction_generation: u64

Generation counter for cache eviction. Incremented each frame; entries not touched for N frames are evicted.

previous_rects_generation: HashMap<u64, u64>

Tracks which generation each previous_rects entry was last touched in.

Implementations

impl LayoutCache

pub fn new() -> Self

pub fn generation(&self) -> u64

Returns the current generation counter.

pub fn evict_stale_entries(&mut self)

Evict entries from previous_rects that haven’t been touched for N generations.

pub fn is_over_budget(&self) -> bool

Checks if the layout pass is currently running over its allocated time budget.

pub fn set_layout_budget_deadline(deadline: Option<Instant>)

Set a process-local deadline for layout cache consumers. When this deadline is exceeded, caches should reuse previous rects instead of recomputing expensive layout work.

pub fn clear_layout_budget_deadline()

Clear any process-local layout budget deadline.

pub fn invalidate(&mut self)

Bump the generation counter, logically invalidating all cached entries without eagerly clearing them. Subsequent lookups with the old generation will miss until re-populated.

pub fn is_valid(&self, key: LayoutKey, current_gen: u64) -> bool

Check whether a cached entry for the given key is still valid against the current generation.

pub fn clear(&mut self)

pub fn get_size(&self, view_hash: u64, proposal: SizeProposal) -> Option<Size>

pub fn set_size(&mut self, view_hash: u64, proposal: SizeProposal, size: Size)

pub fn register_parent(&mut self, child_hash: u64, parent_hash: u64)

Register a child-to-parent layout relationship for bottom-up invalidation propagation.

pub fn invalidate_view(&mut self, view_hash: u64)

Remove all cached size entries for a specific view hash and propagate the invalidation bottom-up to all its layout ancestors to ensure consistent layout updates.

Trait Implementations

impl Default for LayoutCache

fn default() -> Self

Returns the “default value” for a type.