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1//! Glyph bitmap cache: avoids re-rasterizing the same glyphs at the same size.
2
3use std::collections::HashMap;
4
5use crate::font::rasterizer::GlyphBitmap;
6
7/// Cache key: (glyph_id, size_px quantized to integer pixels).
8type CacheKey = (u16, u16);
9
10/// A per-font cache of rasterized glyph bitmaps.
11///
12/// Keys are `(glyph_id, size_px)` where size_px is rounded to the nearest
13/// integer pixel to bound cache size. No eviction policy — Phase 12 will
14/// add a texture atlas with LRU.
15#[derive(Debug)]
16pub struct GlyphCache {
17 entries: HashMap<CacheKey, GlyphBitmap>,
18}
19
20impl GlyphCache {
21 /// Create an empty glyph cache.
22 pub fn new() -> Self {
23 Self {
24 entries: HashMap::new(),
25 }
26 }
27
28 /// Quantize a floating-point pixel size to an integer key.
29 pub fn quantize_size(size_px: f32) -> u16 {
30 size_px.round().max(1.0) as u16
31 }
32
33 /// Look up a cached bitmap. Returns `None` on cache miss.
34 pub fn get(&self, glyph_id: u16, size_key: u16) -> Option<&GlyphBitmap> {
35 self.entries.get(&(glyph_id, size_key))
36 }
37
38 /// Insert a rasterized bitmap into the cache.
39 pub fn insert(&mut self, glyph_id: u16, size_key: u16, bitmap: GlyphBitmap) {
40 self.entries.insert((glyph_id, size_key), bitmap);
41 }
42
43 /// Number of cached entries.
44 pub fn len(&self) -> usize {
45 self.entries.len()
46 }
47
48 /// Returns true if the cache is empty.
49 pub fn is_empty(&self) -> bool {
50 self.entries.is_empty()
51 }
52}
53
54impl Default for GlyphCache {
55 fn default() -> Self {
56 Self::new()
57 }
58}