[boyan01]

Summary

MixinSelectionArea + MarkdownWidget never stopped scheduling frames, so pumpAndSettle timed out. Every registrar refresh rebuilt the document view, and the document view always asked for another refresh:

 MixinSelectionArea._refreshDocument
   ++documentVersion, setState
   MixinSelectionRegistrar.updateShouldNotify -> true
     MarkdownWidget (depends on registrar) rebuilds
       MarkdownDocumentView.didUpdateWidget
-        participantChanged(this)              // every time
+        if document is not identical:
+          participantChanged(this)
           _scheduleDocumentRefresh -> next frame -> _refreshDocument ...

The participant's blocks callback reads the current widget.document, so the registrar only needs to rebuild when the document changes. MixinSelectable already notifies only on real changes.

The MixinSelectionArea test in markdown_context_menu_test.dart (#551) worked around this with settle: false. It now uses pumpAndSettle, and the workaround parameter is gone.

Evidence

New test MixinSelectionArea with MarkdownWidget settles:

pump MixinSelectionArea(MarkdownWidget('Hello brave world', useColumn: true))
pumpAndSettle; expect no scheduled frame; selectAll == 'Hello brave world'
change data to 'Hello new world'
pumpAndSettle; expect no scheduled frame; selectAll == 'Hello new world'

• Before: pumpAndSettle timed out
  After: passes. The second half checks that real document changes still reach the registrar.

flutter test (281 passed) and flutter analyze (no issues) from packages/mixin_markdown_widget.

Merge Danger

Door: two-way

Blast Radius: small

Only MarkdownDocumentView inside a MixinSelectionArea is affected. A host that swaps MarkdownDocumentView arguments other than document (theme, selectable, controller) no longer triggers a registrar refresh by itself; registration and unregistration still go through _syncSelectionParticipant.