Case 3 of the characterization suite (a sync use_state write from a backend-fired handler
re-renders) is true of the ENGINE and was taken as license to de-hoist event-driven page
state — and the live app immediately disproved it: with settings componentized and its
scope local, a real ComboBox pick changed nothing on screen (UIA-verified, no repaint).
The real WinUI backend's handler wiring still never pumps the pass the harness pumps.
The de-hoist is reverted one commit back; this one makes the record honest. The module
discipline note now separates the three tiers of evidence — engine rules (harness-pinned),
real-backend behaviour (live-verified, hoisting stays), and the tween-keyed corollary —
and case 3's comment warns it must not be read as de-hoist permission without a live UIA
check. The upstream gap worth reporting grows to two: the AsyncSetState HostId registry
miss, and the backend event wiring that bypasses the render pump.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Adopts windows-reactor's own headless harness (the `test` feature + the upstream repo's
`test_reactor`/RecordingBackend crate, same pinned rev) and pins the three semantics this
client's state placement depends on, in tests/reactor_semantics.rs:
* A child's sync `use_state` re-renders it through element-equal wrappers — the pre-bump
reconciler pruned at the wrapper; fixed upstream (`nested_state_rerender.rs`).
* A sync write from a backend-fired event handler re-renders — the "MenuFlyout handlers
bypass the flush" claim does not hold at the engine level on this rev.
* A child-owned `AsyncSetState` write still does NOT re-render its owner — newly diagnosed:
every component RenderCx draws a fresh HostId but rerender callbacks are registered only
for the root, so the child's request is a registry miss, silently dropped; the value
surfaces on the next unrelated pass. The test asserts the broken behaviour on purpose, so
the bump that fixes it upstream turns the test red and the discipline can be relaxed.
(Upstream's own async test installs the guard for the very cx it tests and cannot see
this; worth reporting with this repro.)
The stale discipline note in app/mod.rs — written against the June rev — is replaced by the
measured rules, each citing its test. Net: per-screen EVENT-driven UI state may live in the
screen's own component; THREAD-driven state stays hoisted at root, now for a proven reason.
Riding along (field report from the live review): the scope switcher no longer clips when
the NavigationView collapses. WinUI's Auto mode shrinks the pane below 1008 epx and CLIPS
pane-footer content to the rail; reactor exposes no pane-opened event, so root now reads
the window size and the switcher follows the same threshold — expanded pane → pane footer,
collapsed → a slim row leading the content column (an Auto/Star grid row, not a vstack,
so the scroll viewport survives).
Test builds use their own CARGO_TARGET_DIR by convention: windows-reactor-setup stages
resources.pri next to the test binary and a RUNNING dev client holds that file mapped.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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