CacheMode

Item-coordinate paint caching.

When a SceneItem returns CacheMode::ItemCoordinate from SceneItem::cache_mode, the SceneView caches the item's paint output as a RenderFrame in local item coordinates. On subsequent paint passes the cached frame is replayed via Canvas::draw_render_frame instead of re-running item.paint. Cache validity is keyed by Scene::item_change_signal: a LocalBoundsChanged event for an id evicts that id's entry.

Items whose visual depends on signal state outside of their local_bounds (e.g. TextItem with with_signal_text) should NOT use ItemCoordinate — the cache won't see signal-driven repaint dirties. The default for every SceneItem is CacheMode::None.

Builder methods at a glance

get, insert, evict, clear, sync_glyph_epoch, len

API reference

📖 Full rustdoc API for this module

pub enum CacheMode

Per-item paint caching strategy.

#![allow(unused)]
fn main() {
pub enum CacheMode { /* variants */ }
}

Variants

• None — Re-run item.paint every frame. Default for every item.
• ItemCoordinate — Cache the paint output as a RenderFrame keyed by the item's local_bounds. Cheap when the item's geometry is stable and its content doesn't depend on external signal state. The cache is dropped on LocalBoundsChanged for the id.

pub struct ItemCoordinateCache

SceneView's per-item paint cache. Owned by the SceneView, shared via Rc<RefCell<>> so the paint walk and the item-change observer can both touch it.

#![allow(unused)]
fn main() {
pub struct ItemCoordinateCache { /* fields */ }
}

Methods

pub fn new() -> Self

An empty cache.

pub fn get(&self, id: ItemId, raster_scale: f32) -> Option<&RenderFrame>

Borrow the cached frame for id, if any — provided it was recorded at raster_scale. A scale mismatch reads as a miss: the caller re-records and insert replaces the stale entry.

pub fn insert(&mut self, id: ItemId, frame: RenderFrame, raster_scale: f32)

Insert (or replace) a cached frame for id, recorded at raster_scale.

pub fn evict(&mut self, id: ItemId)

Evict id's entry. Called on ItemChange::LocalBoundsChanged or any other invalidation.

pub fn clear(&mut self)

Drop every entry. Called when the glyph epoch moves (see sync_glyph_epoch).

pub fn sync_glyph_epoch(&mut self, current_epoch: u64) -> bool

Compare the text backend's current glyph epoch against the one recorded on the last paint pass; on a change, drop every cached frame (their baked atlas UVs may reference recycled slots) and record the new epoch. Returns true when the cache was cleared.

pub fn len(&self) -> usize

Number of cached entries (diagnostics / tests).