Two things a grouped list has to keep in view while it scrolls, and neither one
was staying: the lane names that read every row, and the heading that says which
group a row belongs to.
The lanes come first. A column header means the same thing in every section, so
it is not a section landmark at all — it pins for the *whole* list, above any
heading, once it scrolls off (`Separator(pinned=True)`). It is drawn outside the
body slice, so it stays exactly one row: too wide for the terminal it ellipsizes
rather than wrapping and stealing a second reserved row from the content. And it
can now size itself — a Separator title may be a callable taking the render
width — so `column_header`/`Lane` lay each label over its own lane and hand back
the shorter form (DESCRIPTION → DESC) only for the lanes that actually overrun,
from the right, where the trailing lane is the only one with a cell to give.
`lane_header` is that header for `lane_row`'s lanes, shared by the two editors so
they head identical lanes identically.
The headings were the other half, and they were pinning the wrong row. Every
non-pinned separator was a candidate, and the rule takes the last one at or above
the scroll — so what pinned was whatever muted line sat lowest under the heading.
In the Trophy case that meant a discipline's *description* stuck to the top and
the heading itself never did; at the foot of any list, the blank spacer above
Back pinned a blank row. So heading-ness is explicit now (`Separator.heading`,
conferred by `section_heading`, which is why every hand-rolled `── … ──` in the
app — the main menu's categories, the chat picker's Channels/Direct, Trace path's
candidate and ranked lists — now goes through it, and why three lanes headers
that genuinely *are* their block's only landmark say so).
A landmark is also no longer one line but a block: a heading plus the separators
written immediately under it, before the section's first row. Prose written there
is the section's preamble — the Trophy case's "what this discipline scores" — and
it belongs overhead with the heading rather than scrolling away from the rows it
explains. The block hands its rows over one at a time as they leave, so the
heading pins while its description is still the top content row and the two pin
together once both are gone: what is overhead always continues seamlessly into
the body. It never takes more than half the viewport, giving rows up from the
end, so the row that says *which* section this is is the last one dropped.
The frame settles the scroll against however many rows come back rather than
assuming one, and re-asks after sliding the window at the bottom — a heading
among the dropped lines would otherwise vanish instead of pinning.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Jean-Pierre MartineauandClaude Opus 5
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