Struct ExtractContextCache 

pub struct ExtractContextCache { /* private fields */ }

Per-extract-phase memo of the parent-derived maps that every extract fn recomputes identically within a single frame.

The default extract pass runs six extract fns back-to-back (extract_shadows, extract_rects, extract_borders, extract_text, extract_clips, extract_scrollbars) - plus the image/SVG extractors registered by lumen-assets - and each one independently rebuilds the same hierarchy-derived structures via build_parent_map, hidden_entities, parent_scroll_offsets, parent_opacities, and parent_scroll_clip_rects. Those depend only on the main-world hierarchy / ScrollOffset / Opacity / Visible / clip components, none of which mutate between extractors of the same phase (extract fns only read the main world and write the render world). Recomputing them six times is pure redundant traversal + allocation on every dirty frame - the steady-state cost of any animation, scroll, or state change.

crate::app::App::tick wraps the extract-fn loop with Self::begin_phase / Self::end_phase. The first extractor of a phase computes each map and stores a copy here; the rest clone it back (an O(n) memcpy instead of the query + DFS + sort rebuild). Reuse is gated on Self::active, so Systems-stage callers that share these helpers - hit-testing hover, which runs before the <if> / <for> reconcilers have finalised the tree - never observe a cached, stale hierarchy: with active == false they always recompute. begin_phase clears every slot, so no data survives across phases either.

Mirrors the “compute the frame’s scene-graph context once” pattern in retained-scene toolkits (Qt Quick’s QSGRenderContext, GTK4’s snapshot pass): shared per-frame derivations are built once and threaded through the emitters, not rederived per draw-list.

Implementations

impl ExtractContextCache

pub fn begin_phase(&mut self)

Open the extract phase: enable reuse and drop any slots left from a prior phase so the first extractor recomputes against the current (post-reconcile, post-layout) hierarchy.

pub fn end_phase(&mut self)

Close the extract phase: disable reuse and release the memoised maps so they cannot be observed by out-of-phase callers or pin memory between frames.

Trait Implementations

impl Component for ExtractContextCache

where Self: Send + Sync + 'static,

const STORAGE_TYPE: StorageType = bevy_ecs::component::StorageType::SparseSet

A constant indicating the storage type used for this component.

type Mutability = Mutable

A marker type to assist Bevy with determining if this component is mutable, or immutable. Mutable components will have Component<Mutability = Mutable>, while immutable components will instead have Component<Mutability = Immutable>.

fn register_required_components( _requiree: ComponentId, required_components: &mut RequiredComponentsRegistrator<'_, '_>, )

Registers required components.

fn clone_behavior() -> ComponentCloneBehavior

Called when registering this component, allowing to override clone function (or disable cloning altogether) for this component.

fn relationship_accessor() -> Option<ComponentRelationshipAccessor<Self>>

Returns [ComponentRelationshipAccessor] required for working with relationships in dynamic contexts.

fn on_add() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_add [ComponentHook] for this Component if one is defined.

fn on_insert() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_insert [ComponentHook] for this Component if one is defined.

fn on_discard() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_discard [ComponentHook] for this Component if one is defined.

fn on_remove() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_remove [ComponentHook] for this Component if one is defined.

fn on_despawn() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_despawn [ComponentHook] for this Component if one is defined.

fn map_entities<E>(_this: &mut Self, _mapper: &mut E)

where E: EntityMapper,

Maps the entities on this component using the given EntityMapper. This is used to remap entities in contexts like scenes and entity cloning. When deriving Component, this is populated by annotating fields containing entities with #[entities]

impl Default for ExtractContextCache

fn default() -> ExtractContextCache

Returns the “default value” for a type.

impl Resource for ExtractContextCache

where Self: Send + Sync + 'static,