Struct LayoutCache 

pub struct LayoutCache { /* private fields */ }

Cache for layout computation results.

Stores Vec<Rect> results keyed by LayoutCacheKey to avoid redundant constraint solving during rendering.

Capacity

The cache has a fixed maximum capacity. When full, the least recently used entries are evicted to make room for new ones.

Generation-Based Invalidation

Each entry is tagged with a generation number. Calling invalidate_all() bumps the generation, making all existing entries stale.

Implementations

impl LayoutCache

pub fn new(max_entries: usize) -> Self

Create a new cache with the specified maximum capacity.

Arguments

• max_entries - Maximum number of entries before LRU eviction occurs. A typical value is 64-256 for most UIs.

Example

use ftui_layout::LayoutCache;
let cache = LayoutCache::new(64);

pub fn get_or_compute<F>( &mut self, key: LayoutCacheKey, compute: F, ) -> Vec<Rect>

where F: FnOnce() -> Vec<Rect>,

Get cached layout or compute and cache a new one.

If a valid (same generation) cache entry exists for the given key, returns a clone of it. Otherwise, calls the compute closure, caches the result, and returns it.

Arguments

• key - The cache key identifying this layout computation
• compute - Closure to compute the layout if not cached

Example

let key = LayoutCacheKey::new(area, &constraints, Direction::Horizontal, None);
let rects = cache.get_or_compute(key, || flex.split(area));

pub fn invalidate_all(&mut self)

Invalidate all entries by bumping the generation.

Existing entries become stale and will be recomputed on next access. This is an O(1) operation - entries are not immediately removed.

When to Call

Call this after any state change that affects layout:

• Model data changes that affect widget content
• Theme/font changes that affect sizing

Note

Resize events don’t require invalidation because the area is part of the cache key.

pub fn stats(&self) -> LayoutCacheStats

Get current cache statistics.

Returns hit/miss counts and the current hit rate.

pub fn reset_stats(&mut self)

Reset statistics counters to zero.

Useful for measuring hit rate over a specific period (e.g., per frame).

pub fn clear(&mut self)

Clear all entries from the cache.

Unlike invalidate_all(), this immediately frees memory.

pub fn len(&self) -> usize

Returns the current number of entries in the cache.

pub fn is_empty(&self) -> bool

Returns true if the cache is empty.

pub fn capacity(&self) -> usize

Returns the maximum capacity of the cache.

Trait Implementations

impl Debug for LayoutCache

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

Formats the value using the given formatter.

impl Default for LayoutCache

fn default() -> Self

Creates a cache with default capacity of 64 entries.