Add InternalRaiseAutomationNotification in WmDateChanged of the MonthCalendar

[LeafShi1]

Fixes #13657

Proposed changes

• Send MSAA focus notification in WmDateChanged of the MonthCalendar so that the MonthCalendar remains in the Focused state when switching dates with the keyboard

Customer Impact

• NVDA can announce the correct information for the calendar date on which keyboard focus is shifting

Regression?

• No

Risk

• Minimal

Screenshots

Before

NVDA cannot announce the correct information for the calendar date

Bug_13657_A11y_WinForms.NETRuntime_CommonControl2_InfoAndRelationships.mp4

After

The calendar date can be announced and the MonthCalendar can be focused with NVDA

NVDA-2024.4.2.mp4

Test methodology

• Manually

Test environment(s)

• .net 10.0.0-preview.7.25365.101

Microsoft Reviewers: Open in CodeFlow

[LeafShi1]

Draft the PR because Narrator will announce the calendar date 2 times after the changes

[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.14924%. Comparing base (118a672) to head (fb866e2).
⚠️ Report is 148 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13707         +/-   ##
===================================================
+ Coverage   76.82947%   77.14924%   +0.31977%     
===================================================
  Files           3257        3276         +19     
  Lines         642592      645134       +2542     
  Branches       47565       47706        +141     
===================================================
+ Hits          493700      497716       +4016     
+ Misses        145232      143733       -1499     
- Partials        3660        3685         +25     

Flag	Coverage Δ
Debug	77.14924% <62.50000%> (+0.31977%)	⬆️
integration	18.99657% <62.50000%> (+0.00638%)	⬆️
production	52.01139% <62.50000%> (+0.56972%)	⬆️
test	97.40947% <ø> (-0.00876%)	⬇️
unit	49.45886% <56.25000%> (+0.63815%)	⬆️

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[Copilot]

Pull Request Overview

This PR enhances accessibility support for the MonthCalendar control by adding automation notifications when the selected date changes. The change ensures that screen readers like NVDA can properly announce date changes when users navigate the calendar with keyboard inputs.

Key changes:

• Adds automation notification calls in the WmDateChanged method to notify accessibility tools when calendar focus/selection changes
• Introduces a new app context switch to control this behavior
• Uses both legacy MSAA events and modern UIA notifications for broader compatibility

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
MonthCalendar.cs	Adds automation notification logic in WmDateChanged method with app context switch guard
LocalAppContextSwitches.cs	Defines new app context switch for enabling MonthCalendar automation notifications

Comments suppressed due to low confidence (1)

src/System.Windows.Forms.Primitives/src/System/LocalAppContextSwitches/LocalAppContextSwitches.cs:29

• The switch name contains 'RichTextBox' but should reference 'MonthCalendar' since this switch is for MonthCalendar automation notifications. It should be 'System.Windows.Forms.MonthCalendar.EnableMonthCalendarAutomationNotification'.

    internal const string EnableMonthCalendarAutomationNotificationSwitchName = "System.Windows.Forms.RichTextBox.EnableMonthCalendarAutomationNotification";

[LeafShi1]

@merriemcgaw Regarding this PR, I need to correct a mistake

Turning on the existing switch AppContextSwitches.NoClientNotifications will turn on MSAA notifications, and NVDA can read calendar date information, but it will also disable UIA notifications, causing Narrator to not focus on MonthCalendar.

I updated the PR, adding MSAA events to MonthCalendar while retaining the original UIA events, so that both tools can read cell content normally, please review again

[LeafShi1]

@merriemcgaw please review this PR again.
After testing, the current fix does not affect the behavior of tools like Narrator and Jaws, and NVDA responds normally to keyboard events.

The only issue currently is that the MonthCalendar control triggers two screen reader announcements when a mouse click occurs: one from the control itself, and one from the manual NotifyWinEvent(AccessibleEvents.Focus) call in WmDateChanged. However, this Focus event cannot be disabled because it is necessary for keyboard navigation and causes NVDA's Focus box to appear.

I can disable NotifyWinEvent(AccessibleEvents.Focus) when executing mouse events, which prevents NVDA from repeating announcements during mouse operations. However, this prevents NVDA's Focus box from appearing.

So, can the mouse issue here be ignored?

[merriemcgaw]

@KlausLoeffelmann getting this one on your radar for review.

[KlausLoeffelmann]

Just one little thing, OK otherwise!
Thanks!