Adds the widget facade that B2 inspector widgets and Phase C event
handling will plug into. Logic-bearing widget code lives in
shell-core (per spec §1.4); shell-native + shell-web only own their
RenderBackend impls + DOM event mapping + accesskit DOM mirror.
What's added:
- `widgets::Widget` trait with `id` / `layout` / `paint(&self,...)` /
`access_node` methods. Phase B widgets are static — `paint` is
`&self`, mutable per-widget state lives in `*State` structs that
B2 lands. Phase C will extend the trait with a `&mut self` event
method for input handling.
- `widgets::WidgetId(pub u64)` plus a `pub const ROOT_WIDGET_ID =
WidgetId(0)` and a `WidgetId::new(id)` constructor with
`debug_assert!(id != 0)`. The tuple constructor stays public so
pattern matching + `const` contexts keep working; `::new` is the
conventional path that surfaces the root-id reservation in debug
builds. (Codex B1 R1 NIT-7 — make the convention compiler-visible
before Phase C tree routing lands.)
- `widgets::PaintCx<'a> { backend: &'a mut dyn RenderBackend }` and
`widgets::LayoutCx { available_width, dpi }` — frame-scoped paint
context + layout-time context. The `&mut dyn` indirection lets
shell-native + shell-web reuse the widget code without
monomorphising over the concrete backend.
- `widgets::LayoutBox { rect: Rect }` with `Debug + Clone + Copy +
PartialEq` derives.
- A `rect(x, y, w, h)` constructor convenience used by tests + B2.
Test harness (`tests/widgets_static.rs`):
- `RecordingBackend` impl `RenderBackend` counting each call.
- `paint_cx_dispatches_through_dyn_backend` — verifies fill_rect /
stroke_rect / save / translate / clip_rect / restore all dispatch
via `&mut dyn RenderBackend`.
- `widget_trait_dispatches_layout_and_paint` — minimal `StubWidget`
proves the trait shape compiles; asserts layout result, paint
dispatch count, `WidgetId::new(7)` round-trip, `ROOT_WIDGET_ID.0
== 0`, and `access_node().role() == Role::GenericContainer`. Real
semantic roles (TreeItem / EditableText / etc) land with B2.
Plumbing:
- `accesskit = "0.24"` added to shell-core deps to match shell-web's
pin (the version compatible with shell-native's accesskit_winit
Step 1a usage). Codex B1 R1 Q3 flagged that shell-native does not
yet pull accesskit; this is acknowledged as a Phase C tracked item
— verify the same version when DOM mirror / native a11y wires up.
- `Rect` now derives `PartialEq` so `LayoutBox` can use the same
derive. `Eq` is intentionally NOT derived (Vec2 carries floats);
comment in render_backend.rs explains.
Plan-vs-implementation deviations (deliberate, all kept narrow):
- Plan B1 step 2 declares `pub mod {dropdown, prop_row, text_input,
tree};` + re-exports inside widgets/mod.rs. Omitted here because
those modules don't exist until B2; declaring them now would
break the B1 standalone build. Top-block plan mini-patch
convention applies (override sketches in body).
- Plan didn't enumerate the accesskit dep + `Rect: PartialEq`
deltas — added with rationale comments.
Verification:
- `cargo test -p openpencil-shell-core` — green
- `cargo check -p openpencil-shell-core --target
wasm32-unknown-unknown` — green (shell-core stays wasm32-clean
per spec §1.2)
- `cargo check -p openpencil-shell-native` — green (no regression)
Codex iterate review: 4 rounds → GO. Round 1 CONCERN (3 items),
Round 2 CONCERN (1 stale comment), Round 3 CONCERN (comment vs
test body mismatch), Round 4 GO clean. Q3 (accesskit_winit
alignment) carries to Phase C as informational.
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