Add switch "NotifyUIAProviderTheText" to control screen Reader to announce the content of RichTextBox

[LeafShi1]

Fixes #12772

Proposed changes

• Add switch System.Windows.Forms.RichTextBox.NotifyUIAProviderTheText to control screen Reader to announce the content of RichTextBox

Customer Impact

• RichTextBox sends the currently focused line instead of its entire contents as an accessibility event on focus.

Regression?

• Yes

Risk

• Minimal

Screenshots

Before

When NVDA get focus, the entire content gets read, not just the currently focused line

After

When the switch is on, Narrator, JAWS and NVDA will read the full contents of the RichTextBox.
When the switch is off, JAWS and NVDA will only read the contents of the currently focused line, while Narrator will not read the contents of the RichTextBox.

Test methodology

• Manually

Test environment(s)

• .net 10.0.0-preview.2.25112.7

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.93695%. Comparing base (4de9ca9) to head (0902800).
Report is 291 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #12986         +/-   ##
===================================================
- Coverage   96.95378%   96.93695%   -0.01683%     
===================================================
  Files           1218        1220          +2     
  Lines         356671      356867        +196     
  Branches        5524        5529          +5     
===================================================
+ Hits          345806      345936        +130     
- Misses         10026       10090         +64     
- Partials         839         841          +2     

Flag	Coverage Δ
Debug	96.93695% <100.00000%> (-0.01683%)	⬇️
test	96.93695% <100.00000%> (-0.01683%)	⬇️

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[ricardobossan]

All LGTM!