zed/crates/theme
Finn Evers e63bd1ab32
language: Improve highlight map resolution (#52183)
This PR refactors the highlight map capture name resolution to be faster
and more predictable. Speficically,
- it changes the capture name matching to explicit prefix matching
(e.g., `function.call.whatever.jsx` will now be matched by only
`function`, `function.call`, `function.call.whatever` and
`function.call.whatever.jsx`). This matches the behavior VSCode has
- resolving highlights is now much more efficient, as we now look up
captures in a BTreeMap as opposed to searching in a Vector for these.

This substantially improves the performance for resolving capture names
against themes. With the benchmark added here for creating the
HighlightMap, we see quite some improvements:
```
Running benches/highlight_map.rs (target/release/deps/highlight_map-f99da68650aac85b)
HighlightMap::new/small_captures/small_theme
                        time:   [161.90 ns 162.70 ns 163.55 ns]
                        change: [-39.027% -38.352% -37.742%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 3 outliers among 100 measurements (3.00%)
  3 (3.00%) high mild
HighlightMap::new/small_captures/large_theme
                        time:   [231.37 ns 233.02 ns 234.70 ns]
                        change: [-91.570% -91.516% -91.464%] (p = 0.00 < 0.05)
                        Performance has improved.
HighlightMap::new/large_captures/small_theme
                        time:   [991.82 ns 994.94 ns 998.50 ns]
                        change: [-50.670% -50.443% -50.220%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 5 outliers among 100 measurements (5.00%)
  5 (5.00%) high mild
HighlightMap::new/large_captures/large_theme
                        time:   [1.6528 µs 1.6650 µs 1.6784 µs]
                        change: [-91.684% -91.637% -91.593%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
  1 (1.00%) low mild
```

For large themes and many capture names, the revised approach is much
faster.

With that in place, we can also add better fallbacks whenever we change
tokens, since e.g. a change from `@variable` to `@preproc` would
previously cause tokens to not be highlighted at all, whereas now we can
add fallbacks for such cases more efficiently. I'll add this later on to
this PR.


## Self-Review Checklist

<!-- Check before requesting review: -->
- [X] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [X] Tests cover the new/changed behavior
- [X] Performance impact has been considered and is acceptable

Release Notes:

- Improved resolution speed of theme highlight capture names. This might
change highlighting in some rare edge cases, but should overall make
highlighting more predicatable. Theme captures will now follow a strict
prefix matching, so e.g. function.call.decorator.jsx` will now be
matched by only `function`, `function.call`, `function.call.decorator`
and `function.call.decorator.jsx` with the most specific capture always
taking precedence.

---------

Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Co-authored-by: Gaauwe Rombouts <mail@grombouts.nl>
2026-03-25 17:01:17 +01:00
..
src language: Improve highlight map resolution (#52183) 2026-03-25 17:01:17 +01:00
Cargo.toml Remove workspace-hack (#40216) 2025-10-17 18:58:14 +00:00
LICENSE-GPL chore: Change AGPL-licensed crates to GPL (except for collab) (#4231) 2024-01-24 00:26:58 +01:00