`MaxSize` on the app's pin narrows the box it asks its child in and cuts the
answer to the cap; nothing on this branch does either, so the capability is
missing rather than merely unported. This is that capability as a rule beside
the widget, the way `Exact` already is: `Min(Len)`, `Max(Len)` and
`Clamp { min, max }`, resolved against the rel base a declared length is a
fraction of, and never carrying `leftover` -- a cap containing a share admits
several self-sizing fixed points (`docs/LAYOUT.md`, failed hypotheses).
Where it stands: every hand-written test passes, including the capability the
app actually used -- `a_capped_scroll_takes_its_viewport_from_the_cap` puts
400 px of content under a 100 px cap and gets a 100 px viewport with 300 to
scroll, which is what `MaxSize` gave. The 400-seed depth-5 scan does not
pass, and the reason is a design question rather than a slip, so this sits on
its own branch instead of in #19.
What the scan finds: a bound is the first rule whose effect depends on the
box its parent gives it, and the retained machinery hands a widget a box by
paths that never ask it again -- `place_in` from a re-placing parent, and
`reposition` after a parent's box moved. A decision made when the box was one
length therefore survives into a box of another, so warm and cold disagree
about a tree they agree on structurally. Four readings were measured over 400
seeds at depth 5:
- deciding at every ask and keeping it: seeds 291, 1, 120, 178, 64 differ.
- the same, re-decided at `place_in` too: seeds 1, 362, 188, 254, 156 differ,
because that path's box is the one the answer chose rather than the one the
widget was asked in.
- skipping a place its parent decided outright, which is the rule the share
follows: worse -- the same widget then gets two decisions by two paths.
- the bound as an answer rule only, leaving the box alone: seeds 4 and 196,
and those are the closest to passing by a wide margin.
The share is the one existing rule of this kind and it is stable because
`place_at` re-asks a child whose rel base it narrows, and because its
decision is baked into the retained place as a `Sized` length. Neither
protection generalises: a bound that binds is a length of the rel base, and
`Sized` cannot say "this slot, narrowed" for a `Within` place.
Also here, because a bound needed them: `Len::longer_than` and
`Bound::outside` share one comparison with the span; a rule that is a
fraction now pins its rel base whether the fraction is a length or a bound,
which was a real gap for `Exact` too; `widget_trait!` passes attributes
through, so the methods it defines can carry doc comments (none could);
`From<N> for Len`, so a bound reads `max_width(300)`; and `random.rs` grows
all three variants, with `describe` printing them so a failure can be written
out by hand.
Format, clippy with and without layout-diagnostics, and the suite (142 + 19 +
13 + 4) are clean. The fast ten-seed oracle passes; the long scans do not.
Neutering the bounds in the generator while leaving its draws in place puts
the same shapes back to green, so the divergence is the bounds and not the
new trees.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A seventh sweep, over the parts no earlier round named: the tree generator
and the scenario harness, `Fixed`, the headless rig, and once more over the
commit the sixth sweep left, which was itself unreviewed.
`Scroll`'s content box is `answer_px.max(container_len)`, so a scroll whose
content fits has nothing to scroll through and `update_amt` has already put
`amt` at zero. The test choosing between the viewport and a scrolled span
asked `amt != ZERO || content_len != container_len`, where the first
disjunct can never decide it -- the same defect `b7b8d09` removed from the
line above, one operand over. A `debug_assert` of the implication held
across the whole suite, including every scrolling test.
`Fixed::to_scale` and its private `shift_round` arrived on this branch with
no caller and never got one; the only thing that called either was the test
written for them.
`Len::align` wrote `Len` arithmetic out a component at a time, around an
`at.px` that is always zero, where `Len::scale` and the `Add`/`Sub` beside
it say the whole rule in two lines. `LayoutLen::without_leftover` took
`self` where the `apply_leftover` its own doc calls the opposite reading of
the same value takes `&self`.
`run-headless.sh --resize` changed the output's mode but not `out_w`/`out_h`,
which is the extent `replay-touch` scales a recording against -- so
`--resize` with `--replay` put every sample of the gesture somewhere else
and still finished like a run that worked. Both come from one function now.
The generator's plan/build split stranded a comment: "a row takes the height
it is given" describes the size rule `build` derives from `dir`, and it was
left above the `gap` draw, which is the one line it is not about and which
does consume randomness.
Format, clippy with and without layout-diagnostics, and the suite (131 + 19
+ 13 + 4) are clean. The cold dump over 400 depth-5 trees is byte-identical
to b7b8d09 across all 34,492 boxes, and all three seed scans pass: 400 at
depth 5 in 62.75s, 1,000 at depth 6 in 162.37s, 2,000 at depth 4 in 305.25s.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A method taking `self` can only be called on a value, so anywhere the caller
holds a reference it has to dereference to ask -- which costs the caller
whether or not the type is `Copy` (Bryan, 2026-09-20, correcting the opposite
change made in 7502176).
So every method that answers a question about a value takes `&self`:
`Holds`'s four, `AxisHolds` and `LayoutHolds`'s three each, `LayoutLen`'s
`is_px`, `is_only_leftover`, `declared` and `fills`, and `Size::within_box`.
The two callers passing `LayoutLen::declared` as a function value say the
closure instead.
Builders that return a changed copy, and methods on a handle that is meant to
be given up, still take `self`.
`declared_lens` filtered `leftover` out of both its sources and every
consumer then re-dropped it, so the rule lived in two filters and a comment.
A declaration is a `Len`: `LayoutLen::declared` states the rule once and both
sources go through it, and `Declared` replaces the bare two-element array on
`ActiveData` and in four signatures.
The two sources stay one value deliberately. A rule decides the child's box;
a hint only promises what it will report -- but `size_hint` is by contract an
exact answer with no painter context, and `hints_agree` fails a widget that
draws something else, so narrowing the box to a hint cannot change what is
drawn. Every consumer asks about the length, never which said it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Four rounds over the same idea: an expression that needed a comment to say
what it computed wanted to be a named operation.
The placement description is built by chaining off the value that says it.
`UiSpan::within_desc`/`shifted_desc` and `Len::as_desc` replace the
`PlaceDescAxis::` constructors, `PlaceDescAxis::axis` lifts one axis into a
pair with the whole box across it, and `PlaceDesc::per_axis` covers the case
where the two axes differ. `beside` is dropped: `from_axis` already said it.
Seven module-level functions become methods on the value each took first --
`Widgets::declared_lens`, `LayoutLen::fills`, `PlaceDesc::placement` and
`::rel_base_and_region`, `Size::within_box`, `UiRegion::at_origin` and
`::as_translation`.
`UiSpan::place` is the aligned-placement rule, which was written out three
times; `LayoutLen::without_leftover` is the sibling `apply_leftover` never
had, at six sites; `is_px` and `is_only_leftover` name field comparisons the
surrounding comments had to translate; `Holds::covers` was interval
containment spelled out by hand. A span's `shared` loses the two arguments
that did not vary across its loop.
`LayoutHolds` was four two-element arrays where every other pair here is a
struct of two per-axis values, so nothing it did could be written once.
It becomes `AxisHolds` on `x` and `y`, and `and`, `covers` and `contains`
lose their loops.
Every pair gets `Index<Axis>`/`IndexMut<Axis>` through one macro, and the
eighteen `axis`/`axis_mut` methods go. `const_index` keeps the accessors
usable in const context.
Cold layout is unchanged: `layout_dump` over 400 depth-5 trees is identical
to 58ce74d byte for byte, across all 34,492 boxes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A widget reports a fraction of the box it was given. Span added that
fraction straight into a cursor that counts fractions of the row, and Pad
summed its padding onto it, both right only while the offer had the
parent's whole extent -- which a span's does not after a relative child.
DrawResult::size and known_len now compose the answer through the offer's
length, so a container reads lengths of its own box.
That exposed placed_box scaling a fractional answer against a box the
parent had already chosen from it, halving a nested span twice. The
near-edge alignment override becomes per-axis `decided` flags: a box the
parent chose from the answer is the answer, and is not placed again.
Span decides the row axis; Scroll and Stack's sizing child decide both.
Alignment is always the widget's own property now.
The window is no longer a move entry. Chains bottom out in MoveIdx::NONE
and the window is applied where a fraction becomes pixels, in to_px on the
CPU and by the uniform in the shader, which now snaps the summed coordinate
since a floor does not distribute over a sum. A resize rewrites no entry.
Verified: view, minimal, random, tabs and text render byte-identical at
1920x1200 against 5f16617, a live resize to 1280x800 is identical to a
cold render, and the 100-seed oracle, all fifteen shrinker cases at 400
seeds of depth 5, and 1000 seeds of depth 6 pass.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
`UiScalar` was `Len` without the `leftover` weight, which is the separation
canonical `main` already had as `Len` beside `LayoutLen` and this branch
collapsed. It is needed back for the queued clamp: a cap may not contain a
share, because a cap has to read the report a rule otherwise makes moot, and
a share puts the container's division into the same equation -- two
self-consistent assignments, which is the multiple-fixed-point failure
generated seed 13 punished for orthogonal sizing. `min(report, cap)` is not
a `LayoutLen` either: it is a sum of parts, and the smaller of two of them
is not one.
So `UiScalar` is `Len`, what was `Len` is `LayoutLen`, and the two say in
their docs which is which: a `Len` is pixels plus a fraction of a box -- a
position being the length from the box's start, which is why a span is two
of them -- and a `LayoutLen` is a `Len` plus a claim only a container
dividing its room can answer. `From<Len> for LayoutLen` is the one-way step
between them.
Names only; the shader's `UiScalar` is renamed with them. Checked: fmt,
clippy, 105 tests, and `tabs`, `minimal`, `view`, `text` and `random`
byte-identical at 1920x1200.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
`Px` and `PxVec2` reach the last places a pixel was a float: the window, the
box a widget reads, the box it is compared against, and `PixelRegion`. A
pointer, a wheel notch and a shaped glyph advance still arrive as floats,
and each is put on the grid where it arrives.
`Holds` is an interval of `Px`. `HOLDS_EPSILON_PX` is gone with the
`exact`/tolerant split it existed for: `at` is the length a widget read, an
open end is the next step along, and `same_px` is equality. `Span`'s margin
from `5ed9e87` goes too -- the box a parent hands back and the sum of what
its children asked for are counts of the same step, so the boundary decides
the same way from either side.
Three things had to be true for that, and were not:
`Holds::through` inverts `px + rel * box`, which rounds -- so a part of a
given length came from a range of boxes, and inverting the length alone gave
a point that need not contain the box the part was drawn in. It now maps the
half step either side, and one more for a length composed down the chain
against the same length measured against the window.
`RegionRemap` translates when a box only moved, rather than dividing to find
each part's fraction and multiplying to place it again. Two roundings landed
a step from where growing the tree that way does; a move is exact on a grid,
which is the whole reason `tests/drift.rs` was written.
A pixel is `1/1024` rather than `1/64`. At `1/64` the residue of a length
reached two ways was one step, and one step was 0.016 px -- enough to move
a box. `PX_SHIFT` and `REL_SHIFT` are the only statement of the grid now,
and the shader's copy is prepended from them rather than written twice.
Checked: fmt, clippy, 102 tests, 100 generated seeds in 75 s, all five
shrinker cases at 300 seeds, and `tabs`, `view`, `minimal`, `text` and
`random` byte-identical at 1920x1200.
What the fuzzers ask for is now a step, not a twentieth of a pixel: the
shrinker's five cases agree within one (`resize` exactly), and the oracle's
two-operation cases within two. The residue is a single rounding either way
-- it scales with the grid rather than accumulating, which is why it is a
thousandth of a pixel now. Closing it means one way of asking how long a box
is, rather than a chain composed down and a length measured against the
window; that is a bigger change than this one.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
`Len` is `Px` beside `Rel` beside `Weight`, so the seam `4e28f10` left in
`Span` -- a float length added to a fixed-point cursor -- is gone, and the
sum a span compares against its box is exact.
`Weight` is its own scale, `Fixed<16>`, because a share of what is left over
is not a fraction of anything: a list divides its room by the total of them,
so the range has to hold a whole list's worth while the precision only has to
tell two weights apart. `Rel::ratio` turns two weights into a share on the
finer grid, which is what a span needs and what dividing them on their own
grid would round away.
`AxisAlign` holds a `Rel` rather than a float, which is what the layout was
reading out of it anyway. `Padding` and `Span::gap` hold `Px`, converted
where they are built instead of on every frame. `RegionAlign::rel` is gone;
its one caller wanted a position, and now builds one.
`Fixed` gains `from_num` for a number as it is written in source, `mul_int`
for a length repeated a whole number of times, and `ratio`.
Checked: fmt, clippy, 101 tests, 100 generated seeds in 86 s, all five
shrinker cases at 300 seeds, and all five examples byte-identical at
1920x1200 against `4e28f10`.
With the fuzzer comparing for equality rather than within 0.05 px, four of
the five cases now pass 100 seeds -- `resize-repaint` joins the other three.
`reorder` still fails one seed by one step, so the last of it is in what a
box is measured *in*: `px_len` and the window are still floats.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
`UiScalar` is `Rel` beside `Px` rather than two floats, so composing a
position down a chain of boxes adds exactly and rounds only at the two
multiplies `within` makes. `UiSpan`, `UiRegion` and `UiVec2` follow it, the
hand-written `Hash` goes away with the bits it hashed, and `impl_op!` grows a
`same` form for a type whose fields are not the same kind of number.
`Len` is still floats, so the seam converts: `Px::from_f32` where a span adds
a child's length to its cursor, and `to_f32` where something outside layout
wants pixels. Those go when `Len` follows.
The GPU reads what the CPU wrote: the instance attributes are `Sint32x2` and
the shader decodes by `1/64` and `1/2^24`, both exact in `f32`, then composes
the move chain in floats as before. It has to agree with itself frame to
frame rather than with the CPU to the last bit.
Two things fell out of making the numbers exact.
`floor` at the rasteriser was picking the pixel below wherever a fraction
divided a window exactly. A fifth of 1920 is 383.99998 through a rounded
`Rel` -- and was 384.0 through an `f32` that happened to round up -- so five
tabs each lost their last column. `snap_floor` takes a coordinate within half
a step of a boundary to be on it, which is the same rule as everywhere else
here: decide where values do not land.
A widget measured on one layer and drawn again on another kept the first
layer, because `try_reuse` compared everything about a retained drawing
except which list it sits in. `Stack` does exactly that for its background,
so every panel's text went under its own background. It only worked before
because the two asks differed by a rounding and forced a redraw;
`tests/retained.rs` pins it now, and `ReuseOutcome` can say `WrongLayer`.
Checked: fmt, clippy, 100 tests, 100 generated seeds in 70 s, all five
shrinker cases at 300 seeds. `tabs`, `view` and `minimal` render
byte-identical at 1920x1200; `random` differs in 36 pixels by one level;
`text` differs where glyph origins moved onto the grid -- same positions,
same spacing, different subpixel coverage, checked at 6x against the old
render.
Measured on the way: with the fuzzer comparing for *equality* rather than
within 0.05 px, `resize`, `repaint` and `size-change` already pass 100 seeds.
`reorder` fails one seed by exactly one step, which is the `Len` seam above.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The length kind that asks for a part of what is left once the fixed
lengths are taken is called leftover: Len::leftover(2), Len::LEFTOVER,
Size::LEFTOVER, Len::leftover the field, and apply_leftover. It says
what it is where "rest" reads as "the remainder of the list" as often as
"the remaining space", and every agent who has touched this has reached
for a third word for it.
Locals called rest that meant a region or a widget are renamed with it,
since the word now names something else.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
`dp` is coming, and then `abs` says which of the two it is not. The
component has always been a pixel count, so the name that admits it is
the one that leaves room for a second unit beside it.
Mechanical: the field on `Len` and `UiScalar`, their constructors,
`to_abs`/`get_abs`, the matching WGSL struct member and the locals
composing it. Field order and types are unchanged, so the `Pod` layout
the shader reads is the same bytes. `f32::abs` is untouched.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
iris-aiandClaude Opus 5
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