Module width_cache 

LRU width cache for efficient text measurement.

Text width calculation is a hot path (called every render frame). This cache stores computed widths to avoid redundant Unicode width calculations for repeated strings.

VS16 Policy and Caching

Cache keys are the grapheme string itself. The VS16 width policy (controlled by FTUI_EMOJI_VS16_WIDTH) is global and read once at startup via OnceLock in ftui_core::text_width. Changing the env var mid-process has no effect on cached or future lookups.

Example

use ftui_text::WidthCache;

let mut cache = WidthCache::new(1000);

// First call computes width
let width = cache.get_or_compute("Hello, world!");
assert_eq!(width, 13);

// Second call hits cache
let width2 = cache.get_or_compute("Hello, world!");
assert_eq!(width2, 13);

// Check stats
let stats = cache.stats();
assert_eq!(stats.hits, 1);
assert_eq!(stats.misses, 1);

Structs

CacheStats

Statistics about cache performance.

CountMinSketch

Count-Min Sketch for approximate frequency estimation.

Doorkeeper

1-bit Bloom filter used as a doorkeeper to filter one-hit wonders.

S3FifoWidthCache

Width cache backed by S3-FIFO eviction (bd-l6yba.2).

TinyLfuWidthCache

Width cache using W-TinyLFU admission policy.

WidthCache

LRU cache for text width measurements.

Constants

DEFAULT_CACHE_CAPACITY

Default cache capacity.

Functions

fingerprint_hash

Compute a secondary fingerprint hash for collision guard.

tinylfu_admit

Evaluate the TinyLFU admission rule.