Fix Button click after Dark to Light color mode switch

[abineshPalanisamy]

Fixes #13636

Proposed changes

• Handle WM_SETTINGCHANGE with ImmersiveColorSet in Control.WndProc.
• Raise OnSystemColorsChanged when the application color mode is set and the OS dark/light mode changes.
• Update ButtonBase.OnSystemColorsChanged to refresh the owner-draw state.
• Ensure Button, CheckBox, and RadioButton update their dark-mode rendering path after OS color mode changes.

Root cause

• When the application starts in Dark mode, button-based controls initialize their rendering path based on the current dark-mode state.
• When the OS color mode changes from Dark to Light while the application is running, WinForms receives WM_SETTINGCHANGE with ImmersiveColorSet.
• This message was not updating the ButtonBase owner-draw state.
• As a result, ButtonBase-derived controls could remain in an outdated rendering state after the OS color mode changed.
• This caused Button.Click to stop firing in the Dark-to-Light transition scenario.

Customer Impact

• Fixes an issue where Button.Click stops working after switching the Windows OS color mode from Dark to Light.
• Ensures ButtonBase-derived controls correctly refresh their rendering state when the OS color mode changes.
• Improves dark-mode transition behavior for Button, CheckBox, and RadioButton.
• Preserves existing behavior for unrelated system setting changes.

Regression?

• No

Risk

• Low.
• The change is limited to handling ImmersiveColorSet system setting changes and refreshing ButtonBase owner-draw state.
• Existing WM_SETTINGCHANGE behavior is preserved for unrelated settings.
• The fix uses the existing OnSystemColorsChanged flow instead of adding separate Button-specific system message handling.
• The update applies only when application color mode has been configured.

Screenshots

Before

ButtonClick_Before_fix.mp4

After

ButtonClick_After_fix.mp4

Test methodology

• Reproduced the issue with Application.SetColorMode(SystemColorMode.System).
• Verified the issue occurs when:
  • Windows starts in Dark mode.
  • The application starts in Dark mode.
  • Windows color mode is switched from Dark to Light.
  • Button click stops working before the fix.
• Verified that after the fix, Button click continues to work after the Dark-to-Light transition.
• Verified Light-to-Dark transition continues to work.
• Verified the fix across ButtonBase-derived controls:
  • Button
  • CheckBox
  • RadioButton
• Verified multiple FlatStyle values:
  • Standard
  • System
  • Flat
  • Popup
• Verified owner-draw and non-owner-draw paths.
• Added unit test coverage for WM_SETTINGCHANGE with ImmersiveColorSet.
• Added unit test coverage to ensure ButtonBase refreshes owner-draw state on system color changes.
• Ran related WinForms unit tests to ensure no regressions were introduced.

Accessibility testing

Test environment(s)

• 11.0.100-preview.5.26302.115

Microsoft Reviewers: Open in CodeFlow