A parent that sizes to a child offers it back the length it just reported,
so a wrapping text was re-broken at exactly its own longest line. That is a
knife edge: the length is composed back through the box chain, so it lands
an ulp either side of where it started, and which side decides whether the
longest line still fits. One side kept three lines at 167.41, the other
took four at 163.49 -- from the same text in the same box, differing only
in what the output size had been.
A greedy break does not need recomputing there. Breaking at one width gives
lines that each fit, none of which could have taken another word; at any
narrower width down to the longest of them, every line still fits and none
can take a word that did not fit in more room. So one break answers a whole
interval, and the cache now hits across it rather than on the exact width.
The tolerance is what makes it hold at the edge, which is the case that
matters: sub-pixel, so no break it admits is one anybody could see.
The generated sweep passes at depth 6, where it failed; the shrinking
fuzzer agrees over 800 trees at depth 7 on all three scenarios, where two
of them failed. `tests/unsettled.rs` is green, so the whole suite is.
Depth 7 of the generated sweep still fails.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
iris-aiandClaude Opus 5
99131940ab