# Handoff

Where the work in flight stands. The durable layout design and the
measurement method are in `docs/LAYOUT.md`; what the review of #19 found is
in `docs/LAYOUT_LOG.md`.

## The Iris layout repair is submitted

**Iris PR #19** (`layout/one-ask`) replaces closed #18. The tip is `5642f20`:
`add6774` fixes collapsed-share placement, retained mask ownership and a
redraw-on-reparent defect, `84dad21` removes repeated work in the test
harness, and `5642f20` is the naming sweep below. The core design remains
sound; round-to-nearest is still unchanged.

Two checkouts share one Git storage. `/home/bob/repos/iris` is the active
`layout/one-ask` worktree; `ai-app-2/iris` stays on `main` at the app's
`32f6ad8` pin, and is kept until the app's integration is ready.

Each round was checked with format, workspace clippy under `-D warnings`, the
workspace tests with and without `layout-diagnostics`, the release fast
oracle, and the three prescribed seed scans — 400 at depth 5, 1,000 at depth
6, 2,000 at depth 4. The cold dump covers 34,488 boxes: the fixes moved 650 of
them, all from the collapsed-share correction, and the naming sweep moved
none.

## The naming sweep is done

`5642f20` finished the rename decided on 2026-09-17, which `frame`'s return as
a length had left half-applied. The box a parent asks a widget in is the
**region**, and where its drawing ends up is its **placement**:

- `Painter::extent` → `region`, and its `extent_len()` → `region_len()`.
- `ActiveData::{part, extent}` → `{region, placement}`, and with them
  `DrawInfo::part` and `Placing::extent`.
- `LayoutHolds::{extent, extent_len}` → `{region, region_len}`, and
  `Counter::OutsideExtent` → `OutsideRegion`.
- `placed_extent` → `placement`, `frame_and_extent` → `frame_and_region`,
  `part_of` → `region_of`.
- `Painter`'s `window_own`, `extent_own`, `frame_own_len` and `extent_len`
  become the one `own: LayoutHolds` they were assembled into.

## What is next, in order

1. **Bryan's review of #19.** Fixes are themselves unreviewed code: repeat
   `pre-submit-review` over each round's changes, and re-run the three
   fuzzers and dump diff for edits to `Span`, `Painter`, or `render_state`.
   The ordinary oracle does not replace absolute geometry and
   retained-primitive expectations.
2. **Integrate the app's Iris capabilities before changing its pin.**
   `32f6ad8` has 45 commits not reachable from the review branch; shared UI
   ownership, richer masks, Android support, and app-side performance work
   must survive the integration. The app then absorbs the branch's
   vocabulary, all of it already upstream: `rest` → `leftover`, `SizeRule`
   beside widgets, alignment properties, the removal of `OrthoSize`, and the
   region/placement names above.
3. **Round-to-nearest**, CPU and shader together as one verified change.
   Bryan approved it on 2026-09-17 and neither half has landed; the
   derivation, the form to use and what to re-check are in `docs/LAYOUT.md`
   under "Rendering the grid (pending)".

## Smaller layout items, none urgent

- Nested spans pass `leftover` weight up, so three leftover children in one
  inner span beside one in another get three quarters to one quarter. No
  other layout system does that; confirm it is wanted.
- A span can overflow itself without bound, so boxes of negative length reach
  children and nothing states what a widget may assume about one.
- `Fixed::div` by zero answers `MIN`/`MAX` while `ratio` answers `ZERO`; both
  are caller bugs under `debug_assert`, but the fallbacks differ.
- The comment on the `local == UiRegion::FULL` shortcut in `widget_at` says
  composing through `FULL` "is not quite the identity in f32"; on the grid it
  is exact and the shortcut is performance only.
- `docs/LAYOUT.md` §4, §5 and the density section name `Painter::place`,
  `Painter::region()`, `SetSize`, `desired_width`, `apply_rest`, `Len::dp`,
  `Aligned` and `MaxSize`, none of which exist. Do not restore
  `OnResize::Translate` or `OrthoSize`.
- `LazySpan`, then `SizeRule::{Min, Max, Clamp}`. A cap may not contain
  `leftover`; whether `Max` narrows the child's drawing box is a product
  decision.
- `Scroll` taking a direction rather than one axis.

Other product work is in `docs/PLAN.md` and the focused documents it links.
Do not mix it into the Iris layout branch.