Cache and Invalidation

LayoutCache reduces repeated layout work.

What It Stores

• intrinsic sizes per entity
• dirty flags
• per-depth entity lists

When A Node Becomes Dirty

Whenever one of these changes:

• UNode
• ULayout
• USelf
• hierarchy structure

Important exception:

• if the only change is IntrinsicSize on a node with children, the cache may ignore it to reduce noise

Lifecycle

• track_layout_changes marks dirty nodes
• update_depth_cache rebuilds the depth map on structural changes
• upward_measure_pass_cached reads the cache and clears dirty flags afterward

Performance Diagnostics

• watch dirty_count and dirty_ratio
• enable the profiler overlay when needed