Add focused state for DropDownButton and reduces the icon width of the dropdown model button

[LeafShi1]

Fixes #13766, #13765

Proposed changes

• Added a Focused state to the property page's drop-down button.
• Reduces the icon width of the model button.

Customer Impact

• The drop-down button of the Property page can be focused under DarkMode

Regression?

• Yes

Risk

• Minimal

Screenshots

Before

Dropdown arrow and ellipse symbol in PropertyGrid appears larger in DarkMode and the focus indicator (e.g., dotted line or outline) is not visible when navigating to the DropDownButton or Ellipse Button controls by keyboard

Dark mode on 100% DPI:

Dark mode on 250% DPI:

After

The dropdown arrow appears normal and it can be focued

100% DPI:

250% DPI:

Test methodology

• manually

Test environment(s)

• .net 10.0.0-preview.7.25377.103

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull Request Overview

This PR fixes accessibility issues with the PropertyGrid's dropdown button by adding focused state support and correcting the dropdown chevron size in dark mode.

• Adds Focused state to ComboBoxState and ModernControlButtonState enums for proper focus indication
• Implements focus rectangle rendering for dropdown buttons to improve keyboard navigation accessibility
• Reduces dropdown chevron width from size + (size / 2) to just size to fix oversized appearance

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
ComboBoxState.cs	Adds Focused = 5 enum value for focus state support
ControlPaint_ModernControlButtonRenderer.cs	Implements focus rectangle drawing and fixes chevron width calculation
ControlPaint.ModernControlButtonState.cs	Adds Focused state to internal button state enum
DropDownButton.cs	Updates state logic to handle focused state and maps it to the renderer
PublicAPI.Unshipped.txt	Documents the new public API addition

[codecov]

Codecov Report

❌ Patch coverage is 21.05263% with 15 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@7c9d043). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13773   +/-   ##
==========================================
  Coverage        ?   77.08776%           
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  Files           ?        3271           
  Lines           ?      644363           
  Branches        ?       47660           
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  Hits            ?      496725           
  Misses          ?      143952           
  Partials        ?        3686           

Flag	Coverage Δ
Debug	77.08776% <21.05263%> (?)
integration	19.02731% <21.05263%> (?)
production	51.89803% <21.05263%> (?)
test	97.41609% <ø> (?)
unit	49.30118% <0.00000%> (?)

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