Struct LayoutCache 

pub struct LayoutCache {
    pub tree: Option<LayoutTree>,
    pub calculated_positions: PositionVec,
    pub viewport: Option<LogicalRect>,
    pub scroll_ids: BTreeMap<usize, u64>,
    pub scroll_id_to_node_id: BTreeMap<u64, NodeId>,
    pub counters: BTreeMap<(usize, String), i32>,
    pub float_cache: BTreeMap<usize, FloatingContext>,
    pub cache_map: LayoutCacheMap,
}

The persistent cache that holds the layout state between frames.

Fields

tree: Option<LayoutTree>

The fully laid-out tree from the previous frame. This is our primary cache.

calculated_positions: PositionVec

The final, absolute positions of all nodes from the previous frame.

viewport: Option<LogicalRect>

The viewport size from the last layout pass, used to detect resizes.

scroll_ids: BTreeMap<usize, u64>

Stable scroll IDs computed from node_data_hash (layout index -> scroll ID)

scroll_id_to_node_id: BTreeMap<u64, NodeId>

Mapping from scroll ID to DOM NodeId for hit testing

counters: BTreeMap<(usize, String), i32>

CSS counter values for each node and counter name. Key: (layout_index, counter_name), Value: counter value This stores the computed counter values after processing counter-reset and counter-increment.

float_cache: BTreeMap<usize, FloatingContext>

Cache of positioned floats for each BFC node (layout_index -> FloatingContext). This persists float positions across multiple layout passes, ensuring IFC children always have access to correct float exclusions even when layout is recalculated.

cache_map: LayoutCacheMap

Per-node multi-slot cache (inspired by Taffy’s 9+1 architecture). External to LayoutTree — indexed by node index for O(1) lookup. Persists across frames; resized after reconciliation.

Trait Implementations

impl Clone for LayoutCache

fn clone(&self) -> LayoutCache

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for LayoutCache

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

Formats the value using the given formatter.

impl Default for LayoutCache

fn default() -> LayoutCache

Returns the “default value” for a type.