The root had a layout path of its own: `root_layout` read its declared
lengths against the window, while every other widget's box came of
`Painter::widget_at`, where a rule of the widget's own -- a share with pixels
or a fraction beside it -- is compared against the offer and can take the box
past it. So a share on the root was the window whatever it asked for, which
`docs/LAYOUT_LOG.md` recorded as a gap rather than fixing, and any later rule
that reads the offer would have had to be written twice.
There is one box nobody drew, and that is the whole of what the root is
asked in. `Placing::WINDOW` says it -- the full output, fractions of the full
output, no move entry and no mask -- and `Placing::ask` is then the one place
a box is decided, called by the painter, by a local redraw, and by the root's
first draw. The root's own path is what is left of it: a widget with no
parent keeps different bookkeeping, not a different layout.
Measured in a 400 px window, a probe under each of three parents, which now
agree on every row where two of them agreed before:
rule as root wrapped in a span
leftover(1) 400 400 400
px(50) + leftover(1) 400 400 400
px(500) + leftover(1) 500 500 500 (was 400 as root)
rel(0.5) + leftover(1) 400 400 400
rel(2.0) + leftover(1) 800 800 800 (was 400 as root)
px(500) 500 500 500
rel(0.5) 200 200 200
The comparison is kept on the widget asked about rather than on the asker,
which is what makes the root need nothing of its own: a window range means
the same thing at either end of an ask, `in_parent` passes one up unchanged,
and the asker ends up holding it through the child's drawing exactly as it
did when `longer_than` narrowed the asker directly. The root has no asker, so
its own record is the only place that range can live -- and `resize` already
checks that record, so a share crossing its length is caught with no new
code. `a_share_past_the_box_is_decided_again_on_either_side_of_the_crossing`
now runs at the root too: 500 at a 400 window, 900 at 900, 500 again at 400.
Two things this changes beyond the share. `DrawInfo::asked` is now the place
the parent offered rather than the place the ask came to, so a local redraw
re-decides the rule instead of re-reading the decision -- the two were the
same until a rule could move the box. And the root's `is_region_node` is
read, where the old path passed `false`: a region-node root now gets its
entry, whose translation is the identity, pinned by
`a_region_node_root_is_a_region_node`.
Format, clippy with and without layout-diagnostics, and the suite (136 + 19 +
13 + 4) are clean. The cold dump over 400 depth-5 trees is byte-identical to
`2dba90b` across all 34,571 boxes, and the three seed scans pass: 400 at
depth 5 (61s), 1,000 at depth 6 (155s), 2,000 at depth 4 (291s).
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
iris-aiandClaude Opus 5
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