`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>
`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 shader used mix() where UiScalar::within writes from + (to - from) *
t, so the two associate the arithmetic differently and can put an edge on
either side of an integer. Writing it out matches them, and is a
multiplication cheaper. The five reference renders and the resize render
are byte-identical either way.
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>
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
