CNA-GAP-061: No renderer implements IResourcePreviewProvider, and the seam cannot cancel a preview ticket the agent abandons

CNA snapshot 009d40f5  ·  Known Issues › Functional gaps  ·  source links pinned to 009d40f5

Resource previews are unavailable in every real Inspector session because no CNA renderer installs a preview provider, and when a client disconnects the agent drops its pending tickets without telling the provider.

Identifier

CNA-GAP-061

Category

Functional gap

Subsystem

Diagnostics & Inspector

Status

Open

Verified against

CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

CNA::Inspector::IResourcePreviewProvider (RequestPreview, PollPreview) and AgentConfiguration::previewProvider

Expected behaviour

What the seam describes: explicit, bounded texture and render-target previews through renderer-local non-blocking readback, with outstanding work released when nobody will poll for it.

Actual behaviour at TARGET

IResourcePreviewProvider appears only in modules/inspector (Agent.hpp, its tests and its benchmark); no renderer or example installs one, so Capability::ResourcePreviews is never negotiated in a real session, a deferral docs/inspector.md records. The interface has no cancel method: Agent::Impl::Run clears pendingPreviews_ after each client disconnects without calling the provider, and a reconnecting client may start up to maximumPendingPreviews (default 4, at most 16) new tickets each time. Bounding outstanding readbacks is left to the provider, and the interface's documentation does not say so.

Source locations

• modules/inspector/include/CNA/Inspector/Agent.hpp — IResourcePreviewProvider; AgentConfiguration::previewProvider and maximumPendingPreviews
• modules/inspector/src/Agent.cpp — Agent::Impl::Run clears pendingPreviews_; HandlePreviewRequest, HandlePreviewPoll
• docs/inspector.md — Resource previews; deliberately deferred work

Evidence

Checked by searching modules and reading Agent.cpp and docs/inspector.md at 009d40f5. Not executed.

Focused reproduction

No focused reproduction is known. Nothing has been invented here; the evidence above is what exists.

Current tests

PreviewIsExplicitAsynchronousAndBounded, PendingPreviewCountIsBounded, PreviewPollHonorsTheOriginalRequestBounds and InvalidPreviewSourceCannotBreakTheConnection use fake providers; none disconnects with tickets pending.

Regression test

When a provider or a cancel call lands: disconnect with pending tickets and assert the provider is told (or that its documented expiry releases the work).

Blast radius

Inspector users (Preview is always unavailable) and future provider implementers.

Workaround

An application may install its own provider through AgentConfiguration::previewProvider and expire its own outstanding readbacks.