Update SetScreenCaptureModeInternal by reset WINDOW_DISPLAY_AFFINITY to NONE before setting new affinity

[LeafShi1]

Fixes #13680

Proposed changes

• Update SetScreenCaptureModeInternal by reset WINDOW_DISPLAY_AFFINITY to NONE before setting new affinity

Customer Impact

• FormScreenCaptureMode still works properly after multiple calls

Regression?

• Yes

Risk

• Minimal

Screenshots

Before

When the FormScreenCaptureMode property is set twice in succession, ScreenCaptureMode always retains the first setting.

FormScreenCaptureModeIssue.mp4

After

AfterChange.mp4

Test methodology

• Manually

Test environment(s)

• .net 10.0.0-preview.7.25320.118

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull Request Overview

This PR ensures that SetScreenCaptureModeInternal properly clears any existing WINDOW_DISPLAY_AFFINITY before applying a new screen-capture mode, fixing a regression when setting the property multiple times.

• Always reset window display affinity to WDA_NONE before computing the new affinity.
• Retains the existing switch logic to map ScreenCaptureMode to the correct WINDOW_DISPLAY_AFFINITY.

Comments suppressed due to low confidence (1)

src/System.Windows.Forms/System/Windows/Forms/Form.cs:1794

• Add automated tests that set FormScreenCaptureMode multiple times and verify the display affinity resets correctly, ensuring this change is covered by unit tests.

        PInvoke.SetWindowDisplayAffinity(HWND, WINDOW_DISPLAY_AFFINITY.WDA_NONE);

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.69345%. Comparing base (9856a7c) to head (19e74a5).
Report is 14 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13684         +/-   ##
===================================================
+ Coverage   76.60680%   76.69345%   +0.08664%     
===================================================
  Files           3253        3255          +2     
  Lines         641011      641605        +594     
  Branches       47442       47491         +49     
===================================================
+ Hits          491058      492069       +1011     
+ Misses        146303      145882        -421     
- Partials        3650        3654          +4     

Flag	Coverage Δ
Debug	76.69345% <0.00000%> (+0.08664%)	⬆️
integration	18.99518% <0.00000%> (+0.00762%)	⬆️
production	51.21181% <0.00000%> (+0.14732%)	⬆️
test	97.41503% <ø> (+0.00316%)	⬆️
unit	48.59080% <0.00000%> (+0.14113%)	⬆️

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[Epica3055]

looks good

[ricardobossan]

All LGTM!

[KlausLoeffelmann]

Thanks!