The shared harness plus the two candidate binaries for Round 1 of the
toolkit spike. C1 tessellates each Bravura outline with lyon and draws it
through egui's own paint pipeline; C2 builds one kurbo BezPath and one
Scene::fill. Both classify their readback against the frozen oracle from
0a35697 and report per-point.
Three things this had to get right, none of which is the rendering:
A candidate must not be able to pass by drawing nothing. C1 initially
failed all fifteen ink points while passing all twelve background points,
which is the signature of a blank target, not of a fill bug: the mesh
named TextureId::default() and egui-wgpu silently skips primitives whose
texture id is unregistered. It now registers a 1x1 opaque-white texture.
The harness must not substitute for a broken readback. A short buffer
used to yield (0,0,0,0), whose luma is 0, so every ink point would pass.
Buffer length, coordinate range, and sample opacity are now hard errors
rather than clamps or defaults.
The oracle must not be editable into agreement. deny_unknown_fields
catches structural drift, but semantic drift is the dangerous kind, and
a validator that checks the oracle against its own other fields accepts
any self-consistent file. OracleFile::validate now checks against
literals restated in the harness: the exact five-glyph roster with its
requirement mapping, subpath counts and point counts, the 27-point
census, 1920x1080, the 8 px clearance floor and every sample's clearance,
and the requirement-specific status flags. Thirteen mutations were run
against it -- deleting a glyph, renaming one, duplicating one, dropping a
point, retargeting every glyph together, lowering the floor, relaxing
spacing -- and all thirteen are rejected.
AA is nominally 8x on both, as pin 4 requires, but the mechanisms differ:
C1 uses a hardware multisample attachment (which is why it must request
TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES, since 8x on Rgba8Unorm is off
the WebGPU baseline) while C2 uses vello's compute AA into a
sample_count:1 storage texture. The run report prints the mechanism beside
the number so no later round reads "8 == 8" as parity. Round 1 is
indifferent to the difference; Round 4's timings will not be.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RSX4zSLgKvtiXaPjnMqLGz
Levi Neuwirth
c20bc93247