The queue was already deepest-first, but a widget that could not settle
where it was called `redraw` on its parent from inside itself. That drew a
shallow widget while dirty widgets deeper in other subtrees were still
pending, and a parent drawing over a subtree that has not settled reads
answers about to move: the one that settles does so inside the parent's
draw, where its mark comes off and nothing compares what it now answers.
Seed 564 was exactly that, and it is the second time this shape has been
found.
So a widget that cannot settle defers instead. It marks its parent, stays
marked itself, and waits in `deferred` until the walk down the depths
reaches the parent -- which cannot be before everything deeper has settled,
because the walk always takes the deepest widget that is not waiting. The
category stops being something to check for. (Bryan, 2026-09-17.)
`dirty_size_under` stays in `draw_inner` for now: `update` draws the root
for a resize before `redraw_updates` runs at all, so the ordering does not
cover that entry.
Green on the suite, the shrinker at 400 seeds of depth 5, the oracle at 1000
seeds of depth 6, and 2000 seeds at depth 4 over all fifteen cases. Drawn
widgets, widget draws and primitive writes are unchanged on every rig phase;
`many` pays 51 queue pops for 27 and 1059 depth reads for 410, which is the
deferring and nothing else.
iris-ai
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