Bug: progress-viewer-cancel-button

[drmoisan]

progress-viewer-cancel-button (Issue #339)

• Date captured: 2026-07-16
• Author: Dan Moisan
• Status: Promoted -> docs/features/active/2026-07-16-progress-viewer-cancel-button-339/ (Issue Bug: progress-viewer-cancel-button #339)

Automation note: Keep the section headings below unchanged; the promotion tooling maps each of them into the GitHub bug issue template.

• Issue: Bug: progress-viewer-cancel-button #339
• Issue URL: Bug: progress-viewer-cancel-button #339
• Last Updated: 2026-07-16
• Work Mode: minor-audit

Summary

ProgressViewer displays its Cancel button in a disabled state when a
ProgressTracker or ProgressTrackerAsync initializes the viewer for loading.
The configured CancellationTokenSource is stored, but the disabled control
prevents the user from requesting cooperative cancellation.

Environment

• OS/version: Windows desktop environment supported by TaskMaster
• Runtime: .NET Framework WinForms/VSTO solution
• Entry points: ProgressTracker.Initialize() and ProgressTrackerAsync.InitializeAsync()
• Data source or fixture: Any operation that displays ProgressViewer while loading

Steps to Reproduce

1. Create a ProgressTracker or ProgressTrackerAsync with a non-null
   CancellationTokenSource.
2. Initialize the tracker so that it constructs and displays ProgressViewer.
3. Observe the Cancel button while the operation is loading.

Expected Behavior

The Cancel button is enabled while loading. Selecting it calls Cancel() on
the configured CancellationTokenSource, allowing background work that observes
the token to stop cooperatively.

Actual Behavior

The Cancel button is disabled. The tracker assigns the token source through the
CancelSource property, whose setter stores the source without enabling the
button. Because the control cannot be selected, cancellation is not propagated
from this UI path.

Acceptance Criteria

• Assigning a non-null CancellationTokenSource through
  ProgressViewer.CancelSource enables the Cancel button immediately,
  including the initial loading state used by ProgressTracker and
  ProgressTrackerAsync.
• Selecting the enabled Cancel button requests cancellation on the same
  configured CancellationTokenSource so token-observing background work
  can stop cooperatively.
• A deterministic MSTest regression test fails against the current property
  setter, passes after the targeted fix, and the final C# toolchain completes
  in format, analyzer, nullable-analysis, and coverage-enabled test order
  without regression.

Logs / Screenshots

• Attached minimal logs or screenshot
• Snippet: No error is logged; the defect is the disabled control state.

Impact / Severity

• Blocker
• High
• Medium
• Low

Suspected Cause / Notes

ProgressViewer.SetCancellationTokenSource(...) enables the button after
storing the source, but ProgressTracker and ProgressTrackerAsync configure
the viewer through the CancelSource property. The property setter omits the
equivalent enabled-state update.

Proposed Fix / Validation Ideas

• Add a regression test that assigns CancelSource and verifies the Cancel
  control is enabled.
• Preserve the existing test that verifies selecting Cancel transitions the
  configured token to the cancellation-requested state.
• Run the repository C# format, analyzer, nullable-analysis, and
  coverage-enabled MSTest gates in the required order.

Next Step

• Promote to GitHub issue (bug-report template)
• Move to active fix folder / branch