fix: Update capability checks and enhance search functionality in Semantic Search

[surajkumar-08]

Updates the WCRAPIs Application Content Search (ACS) sample to align with the latest AppContentIndexer IDL and apispec. Adds live text + image suggestions, renders region-of-interest overlays on image matches, fixes a mis-mapped capability check, and resolves several crash / NRE bugs surfaced during testing.

Changes

AIDevGallery/Samples/WCRAPIs/AppIndexCapability.xaml.cs (+2 / −2)

• Fixed swapped capability checks: the OCR row was reading IndexCapability.ImageSemantic and the Semantic-Image row was reading IndexCapability.ImageOcr. Now each row reflects its intended IndexCapability value.

AIDevGallery/Samples/WCRAPIs/SemanticSearch.xaml (+57 / −16)

• SearchBox: added TextChanged handler, TextMemberPath="QueryText", and an ItemTemplate that renders live suggestion text with wrapping.
• ImageResultsBox: new item template renders each result image at scaled display size with a caption and an accent-colored region-of-interest overlay (Canvas + Border) when RegionOfInterest is present.

AIDevGallery/Samples/WCRAPIs/SemanticSearch.xaml.cs (+654 / −107)

Live suggestions (text + image)

• New session fields: _suggestionTextQuerySession (AppIndexTextQuerySession) and _suggestionImageQuerySession (AppIndexImageQuerySession).
• Options-signature tracking (_suggestionTextQueryOptionsSignature, _suggestionImageQueryOptionsSignature, _currentSuggestionQueryText) so sessions are only restarted when the relevant options actually change.
• Per-stream result caches _lastTextSuggestionItems and _lastImageSuggestionItems, merged into the AutoSuggestBox via UpdateCombinedSuggestions.
• New SearchBox_TextChanged handler creates / updates both sessions via GetOrCreateSuggestionTextQuerySession and GetOrCreateSuggestionImageQuerySession, subscribing to ResultChanged for incremental updates.
• New session-lifecycle helpers: StopSuggestionTextQuerySession, StopSuggestionImageQuerySession, StopSuggestionQuerySession, plus GetTextMatchSuggestionItems, GetImageMatchSuggestionItems, GetTextQueryOptionsSignature,GetImageQueryOptionsSignature.

Image results with region-of-interest overlay

• New view-model ImageDisplayItem (ImageSource, Caption, DisplayWidth/Height, RegionLeft/Top/Width/Height, RegionVisibility).
• GetImageMatchDisplayItems consumes AppManagedImageQueryMatch.RegionOfInterest (IReference<Rect> ⇒ Rect?) and computes display-coordinate overlays scaled to a max width.
• _imageDimensions dictionary captures original PixelWidth/PixelHeight at index time inside IndexImageData, so overlays scale correctly regardless of display size.

Bug fixes

• Search crash on Enter ("Failed to search indexed content.") in SearchBox_QuerySubmitted:
  • Removed StopSuggestionQuerySession() before Task.Run — stopping the image session immediately before invoking indexer.CreateImageQuery(...) on the same indexer was the crash trigger. Sessions now stay alive and are recycledby the next TextChanged / CleanUp(), matching the apispec's interactive-search pattern (sessions only, no mixing one-shots on the same indexer mid-flight).
  • Materialized IVectorView<TextQueryMatch> / IVectorView<ImageQueryMatch> into List<T> inside Task.Run to avoid cross-apartment COM enumeration on the UI thread.
  • Catch block now calls ShowException(ex) (no optionalMessage) and writes ex.Message into ResultStatusTextBlock so the real failure surfaces instead of a generic message.
• NRE in indexing path: replaced await _indexer?.WaitForIndexingIdleAsync(...) (which becomes await null ⇒ NRE) with a local capture + null-check in TextData_TextChanged, ImageData_ImageOpened, and IndexAll.
• Misleading "No results found." dropdown: removed the SearchSuggestionItem.NoResults placeholder injection; QuerySubmitted now ignores IsPlaceholder chosen suggestions.

Cleanup

• CleanUp() now stops both suggestion sessions (text + image) and clears suggestion caches.

Validation

• ✅ dotnet build AIDevGallery -r win-x64 -f net9.0-windows10.0.26100.0 … → 0 errors.
• ✅ Self-contained MSIX rebuilt, signed, installed on a clean machine — search no longer crashes; image matches show ROI overlays; capability page correctly identifies OCR vs Semantic-Image availability.
• ✅ Verified text + image suggestions appear as the user types and that pressing Enter returns results (previously crashed).

References

• IDL: Microsoft.Windows.Search-Lib/AppContentIndex/AppContentIndexer.idl
  • CreateTextQuery / CreateImageQuery are synchronous, no cancellation (lines 218-235).
  • AppIndexImageQuerySession mirrors AppIndexTextQuerySession (lines 900-942).
  • IndexCapability enum (lines 1122-1142).
• API spec: ApplicationContentIndexer-apispec.md §1627-1690 — canonical interactive-search pattern (sessions only).