62 lines
3.1 KiB
Markdown
62 lines
3.1 KiB
Markdown
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# Browser displays
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This package owns ordinary graph transactions for browser enrollment, assignment
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and reported mount state. Studio supplies the host adapter; the package contains
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no browser heartbeat, DOM code or private storage API.
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A workspace entry conforms to `WebStudioDisplayDirectory`. Its conformance owns
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an enrollment edge, and `enroll({nonce,label})` returns the same target for that
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nonce. Each directory currently permits 128 targets and rejects further enrollment
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explicitly. This is a bounded prototype, not an automatic device inventory GC.
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`WebStudioDisplayTarget.assign` accepts an optional subject/presentation pair.
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The subject conforms to `WebStudioPresentable`, whose `canPresent` validates the
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selected registered presentation. This role does not require Canvas or placements;
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the example workspace adapters forward their existing presentation check. Named
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presentations have checked subject-only module contracts; callbacks cannot be
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stored in assignments. The target's subject is a graph edge, not a string ID in
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JSON. Changing the edge and desired generation is one transaction.
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Assignments and observed outcomes are durable. `acknowledge` accepts a generation,
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monotonic report sequence, status (`mounted`, `failed`, `empty`) and bounded error.
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Old generations and reordered reports return false without modifying state.
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Reported success describes a client mount; it is not a claim of trusted execution.
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The browser adapter uses a per-tab nonce and Web Lock. Duplicated tabs get distinct
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nonces; reloading resumes enrollment. Enrollment is a host startup/user action,
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never business-object creation from a component render. Multiple displays may
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mount the same subject. Losing the connection does not clear its desired state.
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Studio's authenticated presence adapter validates target references against Camino
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before issuing an opaque connection lease. Leases expire after 45 seconds; recent
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connection observations remain for at most ten minutes, with a 256-record cap.
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A target ID is not a credential. There is no persistent heartbeat history.
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## Headless calls
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A headless session uses the same generated descriptors and public operations as
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Studio. The caller supplies normal workspace authorization when opening its
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session; graph references alone grant no access.
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```ts
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const directory = await session.acquire(
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{ enroll: interfaces.WebStudioDisplayDirectory.enroll },
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session.bootstrap.entry,
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);
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const enrollment = await directory.enroll.call({
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nonce: savedClientNonce,
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label: "Preview display",
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}).settled;
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if (enrollment.status !== "accepted") throw Error(enrollment.status);
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const target = await session.acquire(interfaces.WebStudioDisplayTarget, enrollment.value);
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const result = await target.assign.call({
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subject: presentableSubject,
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presentation: "presentation:studio:canvas",
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}).settled;
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```
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`tools/local-first/studio-session.test.mjs` is the executable example, including
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reference rejection and stale-report tests. `package.nix` selects the server-only
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TypeScript artifact. Native fields and relationships remain queryable in browser
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replicas without bundling mutation implementations there.
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