`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>
A widget's region is now held in the coordinates of the slot it draws in
rather than the window's, and `Painter::place` is how a container asks for a
slot: it draws a child it decides the box of and may decide again. Everything
under that slot is a fraction of its box, so placing the child a second time
is one entry to write whether it moved or changed length. A child drawn any
other way has no slot and shares its nearest ancestor's.
That is what keeps the chain short. `chain_cost` measured depth as the cost
-- free to 8, +42.6% at 16 -- and a slot per widget put a transcript's glyphs
past that for nothing, since almost every slot was zero. `Span`, `Aligned`
and `Scroll` are the containers that re-place a child after drawing it, and
`tests/layout.rs` pins that four widgets between a span and a leaf leave the
leaf's chain one deep.
`UiRegion::stretch`, `UiRegion::stretchable` and `UiScalar::stretch` are
gone. Nothing is inverted any more: a box that changed length is written to
its slot, and the descendants recompose against it in the shader. That also
retires the case the guard existed for, where a fixed length has no fraction
to recover -- `tests/layout.rs` now stretches a 40-tall row on its other
axis, which `stretchable` refused outright.
What still walks the CPU is deciding who must draw again, which no chain can
answer: `mark_resized` descends from the widget whose box changed and marks
anything whose own box changed length and whose drawing reads it. A part of
a box with no relative extent on an axis is a fixed length, and composing
into it leaves none either, so the walk stops where a length did not change
-- an 80-wide child in a widened row is not redrawn though it says `Redraw`.
`Span`, `Pad`, `Stack`, `Offset`, `Aligned`, `SetSize` and `LayerOffset` say
`Scale`: each places in fractions and offsets of its own box and none reads
the box's pixel length. `Scroll` and `MaxSize` do read pixels and stay
`Redraw`.
45 tests pass, five of them new. Render verification comes after the CPU
side, per the owner.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A slot now holds the box its contents are placed within, in the coordinates
of the slot it names, and `prelude.wgsl` composes the chain with `within`
instead of adding a delta. A translation is the special case where the box
has its parent's relative extent, so every caller passes
`UiRegion::FULL.offset(delta)` and nothing changes on screen yet: 42 tests
pass and `tabs` at 1920x1200 is byte-identical.
`Moves::resolve` takes the region to compose rather than returning a sum, so
the CPU walk is the same operation the shader performs.
Measured against the translate slot on the same binary with
`tests/chain_cost.rs`, 200k instances: +0.6% at depth 1, +0.5% at 2, +0.8% at
4, then +9.6% at 8 and +32.2% at 64. Free at the depth opt-in slots produce,
which is the next commit; the per-level cost was always the dependent load
rather than the arithmetic.
The identity is `UiRegion::FULL` rather than zero, which `MoveOffset`'s
comment says beside the `Zeroable` that `Pod` requires: a zeroed entry is a
box of no extent and collapses its subtree to a point.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The plumbing for O(1) subtree movement (LAYOUT.md §2), with every slot
still at zero, so this changes no pixels and the next commit can change
behaviour against a known-good picture.
Every active widget owns a slot in `UiData::moves`: a translation in
physical pixels and the slot it is relative to. A primitive instance and
a mask each name one, and `prelude.wgsl` walks the chain and adds the
accumulated delta. A mask resolves its own chain rather than the drawn
primitive's, so a stationary viewport can clip content that moves inside
it. `CHAIN_LIMIT` is stated on both sides; it bounds a malformed cycle
rather than any real tree.
A slot outlives any one `ActiveData`, because a redraw replaces that
while the widget's children go on pointing at the slot, so it lives in
`UiRenderState::moves` keyed by widget and is retired when the widget
stops being drawn. `MoveIdx` is its own type rather than another
`Id<u32>`: it sits beside `MaskIdx` in an instance and the two must not
be swappable.
`Vec2` is now `repr(align(8))`, which is WGSL's alignment for a
`vec2<f32>`, so a GPU struct holding one is laid out the way its shader
reads it without saying so itself -- `GlyphPrimitive` no longer states
its own alignment, and `MoveOffset` never has to. Both keep a manual
`unsafe impl Pod`, since the trailing padding that alignment introduces
is what `derive(Pod)` refuses. `WindowUniform` holds the `Vec2` its
shader has always called `dim` rather than two loose floats, which was
the last place the two sides described the same bytes differently.
Checked: fmt, clippy and 40 tests. `tabs` (with the image replay),
`view` and `minimal` render byte-identical to `upstream/main`, and
`text` is unchanged.
Replaces the bindless `binding_array<texture_2d<f32>>` the renderer bound every texture through. That array needs `VK_EXT_descriptor_indexing`, which a real share of Android GPUs lack, so the old shape did not run there at all.
The two things being bound want opposite treatment, so they are now split:
- **Glyph atlas pages become layers of one `texture_2d_array`.** A glyph primitive carries a `layer` instead of a view/sampler index pair. A layer index is an ordinary sampling operand, so this needs nothing beyond plain Vulkan 1.0 / GLES. Growing the atlas recreates the array with headroom and `copy_texture_to_texture`s the old layers across, no readback.
- **A standalone image gets its own texture and its own bind group,** and draws in its own call. It no longer needs a per-instance entry in `PrimitiveData`: the bind group has already picked the texture.
`Primitives` keeps images in a list of their own as a result, with `PrimitiveChange::is_image` naming which list a renumbering belongs to -- the two have independent index spaces, so `(layer, inst_idx)` alone would collide between them.
Two notes on judgement calls, since this slice was rebuilt on top of `main` rather than transplanted:
- The source version renamed `GlyphEntry::is_colored` to `is_color` and added a second `IS_COLOR` flag constant beside the existing `GlyphEntry::IS_COLORED`. Both dropped: #10's naming and its `flags()` are kept, and UVs stay `Vec2` rather than going back to `[f32; 2]`.
- `ImageGpu` no longer holds the `Texture` behind its view, which removes an `#[allow(dead_code)]`. A `TextureView` keeps its own reference to the texture, checked by rendering rather than assumed -- see below.
### Verification
```
cargo fmt --all --check
cargo clippy --workspace --all-targets --locked -- -D warnings
cargo test --workspace --locked
```
All clean; the 4 text-edit tests pass. The only clippy output is the pre-existing future-incompatibility notice about `naga`/`wgpu`/`winit`.
Because this is a rendering change, it was also run for real rather than only compiled. The `tabs` example was rendered on this machine's GPU -- Venus onto an RX 7900 XT, confirmed from the loaded ICD (`libvulkan_virtio.so` on `/dev/dri/renderD128`) rather than assumed, since a failed Vulkan init here silently falls back to llvmpipe and would make the screenshots meaningless.
Screenshots before and after the change are **byte-identical** (same md5) in two scenes: the default tab, which exercises text (the atlas path) and rects, and the image tab with a standalone image pushed at startup, which exercises the per-image bind group. The image-tab scene needed a temporary local edit to the example to push the image without a click; that edit is not part of this branch. The same comparison, re-run after dropping the `Texture` field, is still byte-identical -- which is the check that the view alone keeps it alive.
---------
Co-authored-by: iris <2+iris@noreply.localhost>
Reviewed-on: iris/iris#11
Reviewed-by: iris <2+iris@noreply.localhost>
Co-authored-by: AIris <4+iris-ai@noreply.localhost>
iris-aiandClaude Opus 5
