Layout reaches one place by more than one route -- a box composed down the
chain, and the same box summed from what its children asked for -- and the
two land a few bits apart in floats. Where that decides something structural
rather than something positional, a warm tree disagrees with a cold one:
`5ed9e87` is the instance, and its margin is a patch over the representation
rather than a fix to it.
`Fixed<SHIFT>` is a count of `1 / 2^SHIFT`s in an `i32`. Adding and
subtracting are exact, a multiply rounds once back onto the same steps, and
two routes that come within half a step land on the same number -- so the
comparisons downstream can ask for equality rather than for nearness.
`Px = Fixed<6>` and `Rel = Fixed<24>`: a sixty-fourth of a pixel is finer
than a display and still exact in `f32` up to 262,144 px, and twenty-four
bits of fraction matches `f32` at a half, beats it above one where anchors
sit, and leaves +/-128 of range to sum relative children in.
Nothing uses it yet. The arithmetic saturates rather than wrapping, because
a clamped coordinate keeps the ordering a wrapped one inverts, and the ends
are what an unbounded interval will be written with.
Checked: fmt, clippy, 99 tests including ten for this type -- the round trip
through `f32`, halves rounding away from zero either side, saturation at both
ends, and 20,000 additions landing exactly where the count says.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Replace the cosmic-text path with Parley layout and Swash rasterization, backed by shared glyph-atlas pages. Shaping, editing, rasterization, and glyph rendering move together because they share the text buffer and rendered-glyph types; splitting them further would require a temporary renderer that is immediately removed.
This is reconstructed rather than replayed from the extraction history. It also fixes issues found during review:
- texture binding changes remain set when an atlas patch follows a new page
- pressing an empty field places a caret and accepts input
- selection motion delegates collapse behavior to Parley
- character deletion follows logical clusters rather than visual neighbors
- the unused root-level Swash dependency is omitted
Four public-behavior integration tests live in `tests/text_edit.rs`: empty-field input, multibyte IME preedit replacement, UTF-8-safe backspace, and selection replacement. The old twelve-test inline block and implementation-restating cases are omitted.
Every added source comment was manually reviewed. Comments that narrated implementation or history were removed; retained comments document cache/rasterization keys, GPU upload constraints, focus representation, bidi geometry, or IME semantics.
Known limitation: atlas pages currently grow without eviction. Each page is 4 MiB on CPU and GPU. An arbitrary cap would leave cached rendered-text UVs pointing at reused glyph slots, so bounding this safely needs a later generation/invalidation change.
This changes public text types and signatures. GPU glyph rendering is covered by compilation rather than a live-surface test.
Verified with:
- `cargo fmt --all --check`
- `cargo clippy --workspace --all-targets -- -D warnings`
- `cargo test --workspace` (four integration tests pass)
Cargo still reports inherited future-incompatibility notices for existing wgpu/winit dependencies; there are no current clippy warnings.
---------
Co-authored-by: iris <2+iris@noreply.localhost>
Reviewed-on: iris/iris#10
Reviewed-by: iris <2+iris@noreply.localhost>
Co-authored-by: AIris <4+iris-ai@noreply.localhost>
iris-aiandClaude Opus 5
