render: placed glyph slots are bounded only by the atlas filling #451

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opened 2026-09-25 13:37:11 +09:00 by natsukium · 0 comments

natsukium commented

2026-09-25 13:37:11 +09:00

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GlyphIndex::slots (crates/felis-render-wgpu/src/glyphs.rs) keeps one entry per placed glyph key, and that map is emptied only when the atlas recycles. PR #450 (#406) capped the blank entries, which take no atlas space. Placed entries are still bounded only by how many glyphs fit in an atlas sheet before it fills.

Failure scenario. A producer can emit OSC 66 runs at many tiny fractional scales, so each char × sizing × style key rasterizes to a 1–2 px glyph. A 2048² sheet then holds a few million placed entries before a recycle frees them. The slot map and the matching ShapeCache entries grow to that size from PTY output alone. The ShapeCache side is already bounded by the byte cap after #450.

Done when:

the slot map has a bound on the entry count that does not depend on glyph size, for example by recycling the atlas, or evicting, once placed entries pass a cap;
the hit path stays as it is;
a test drives distinct tiny placed glyphs past the cap and shows the map stays under it;
docs/explanation/security-model.md "Resource exhaustion" and the atlas section of docs/explanation/rendering/pipeline.md state the bound.

Refs #406, #450.

`GlyphIndex::slots` (`crates/felis-render-wgpu/src/glyphs.rs`) keeps one entry per placed glyph key, and that map is emptied only when the atlas recycles. PR #450 (#406) capped the blank entries, which take no atlas space. Placed entries are still bounded only by how many glyphs fit in an atlas sheet before it fills. **Failure scenario.** A producer can emit OSC 66 runs at many tiny fractional scales, so each char × sizing × style key rasterizes to a 1–2 px glyph. A 2048² sheet then holds a few million placed entries before a recycle frees them. The slot map and the matching `ShapeCache` entries grow to that size from PTY output alone. The `ShapeCache` side is already bounded by the byte cap after #450. **Done when:** - the slot map has a bound on the entry count that does not depend on glyph size, for example by recycling the atlas, or evicting, once placed entries pass a cap; - the hit path stays as it is; - a test drives distinct tiny placed glyphs past the cap and shows the map stays under it; - `docs/explanation/security-model.md` "Resource exhaustion" and the atlas section of `docs/explanation/rendering/pipeline.md` state the bound. Refs #406, #450.

natsukium referenced this issue from a pull request that will close it,

2026-09-25 18:48:46 +09:00

render: recycle the glyph atlas at a placed-slot count #459

natsukium closed this issue

2026-09-25 18:53:34 +09:00

natsukium referenced this issue from a commit

2026-09-25 18:53:35 +09:00

render: recycle the glyph atlas at a placed-slot count (#459)

natsukium referenced this issue

2026-09-25 19:00:17 +09:00

bench: follow up the 9d1d842f cross-terminal run #405

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