A Lightroom collection imported whole (11 113 presets, a 42 MB presets.json)
made every interaction take seconds:
- Session::persist ran after every command and serialized the whole preset
list to compare it with the last write: 609 ms per slider tick (release,
the real collection). Session::presets is now a PresetList whose generation
changes on mutable access; persist serializes only when it (or the profile
lists) changed, and skips the write when the bytes hash the same.
develop.set: 609 ms -> 2.3 ms; preset.apply: 598 ms -> 3.1 ms.
- The Presets panel deep-cloned every preset into a BTreeMap, built a row,
widget id and (with thumbnails) a variant render job for each of them every
frame. Grouping is cached per generation and only rows in view are laid
out: 5041 -> ~20 rows a frame, 2.3 ms with 5000 presets.
- The preset pickers (Import dialog, Settings > Import) build only the rows
in view.
- add_presets and opening a library compared every preset with every other
(quadratic); both use hash indexes now. Opening no longer serializes the
list once just to remember it.
Tests: develop commands don't re-serialize unchanged presets (and a change
is still saved), generation semantics, a 20 000-preset import, and the
panel building only visible rows (fails on the old code: 5041 rows).
An ignored bench (presets_scale_bench, LIGHTCRAFT_BENCH_PRESETS) times a
real presets.json.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
