DP44/enriched-qwen3-coder-next/Common/DTS.Common/Events/RegionOfInterest.md

source_files, generated_at, model, schema_version, sha256

source_files	generated_at	model	schema_version	sha256
Common/DTS.Common/Events/RegionOfInterest/RegionOfInterestChangedEvent.cs	2026-04-16T03:24:29.831249+00:00	Qwen/Qwen3-Coder-Next-FP8	1	b57954f8953ae512

RegionOfInterest

1. Purpose

This module defines a Prism-based event (RegionOfInterestChangedEvent) used to publish notifications when the current region of interest (ROI) changes in the application. It serves as a decoupling mechanism in the MVVM pattern, allowing view models or services to subscribe to ROI changes without direct references, enabling reactive UI updates or downstream processing (e.g., image analysis, rendering, or logging) in response to ROI modifications.

2. Public Interface

• RegionOfInterestChangedEvent
  • Type: class (inherits from Prism.Events.PubSubEvent<IRegionOfInterest>)
  • Behavior: A Prism PubSubEvent that carries an IRegionOfInterest payload. When published (via Publish), all subscribers receive the new ROI instance. This event is not thread-safe by default (Prism’s PubSubEvent uses the synchronization context of the publisher unless configured otherwise).

3. Invariants

• The event payload is always of type IRegionOfInterest (from DTS.Common.Interface.RegionOfInterest).
• The event is publish-only in this file—no custom logic is defined for subscription, filtering, or persistence.
• No validation or normalization of the IRegionOfInterest instance is performed by this class; validity of the payload is assumed to be enforced by publishers.

4. Dependencies

• External:
  • Prism.Events (specifically PubSubEvent<TPayload>)
  • DTS.Common.Interface.RegionOfInterest (for the IRegionOfInterest interface)
• Internal:
  • Consumers: Any module/service/view model that needs to react to ROI changes (e.g., via IEventAggregator.GetEvent<RegionOfInterestChangedEvent>().Subscribe(...)).
  • Producers: Code that calls eventAggregator.GetEvent<RegionOfInterestChangedEvent>().Publish(roi), where roi implements IRegionOfInterest.

5. Gotchas

• No default thread-safety: Subscribers may execute on the publisher’s thread context; if the publisher is on a background thread, subscribers must handle cross-thread access (e.g., via Subscribe(..., ThreadOption.PublisherThread) or UI dispatcher invocation).
• Lifetime management: Subscribers must manually unsubscribe (e.g., in Dispose or view model cleanup) to avoid memory leaks, as Prism’s PubSubEvent holds strong references by default.
• No null-safety guarantee: The event does not enforce non-null payloads; publishers must ensure IRegionOfInterest instances are valid (though null may be used intentionally to signal "clear ROI" if documented elsewhere).
• Interface dependency: Behavior relies entirely on the contract of IRegionOfInterest; changes to that interface may silently break subscribers.
• None identified from source alone regarding ordering guarantees, deduplication, or historical quirks—these would require inspection of publishers/subscribers.