fix #12663 [Accessibility][High Contrast] ToolStrip grip icon colour contrast is less than 4.5:1 in Normal Mode and HC Desert mode

[Epica3055]

Fixes #12663

root cause

dot color is not contrasting enough compared to the background color.

Proposed changes

• Change the color to a more contrasting color compared to the background color.

Regression?

• No

Risk

• low

Screenshots

Before

HC Aquatic

HC Desert

HC Dusk

HC Night Sky

After

win11

win10

Test methodology

• manual,

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.03546%. Comparing base (58d5c74) to head (174a974).
Report is 19 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #12682         +/-   ##
===================================================
+ Coverage   76.03484%   76.03546%   +0.00061%     
===================================================
  Files           3180        3181          +1     
  Lines         639637      639670         +33     
  Branches       47213       47215          +2     
===================================================
+ Hits          486347      486376         +29     
- Misses        149773      149781          +8     
+ Partials        3517        3513          -4     

Flag	Coverage Δ
Debug	76.03546% <66.66667%> (+0.00061%)	⬆️
integration	18.17487% <0.00000%> (+0.00967%)	⬆️
production	49.83006% <66.66667%> (+0.00387%)	⬆️
test	97.02915% <ø> (-0.00209%)	⬇️
unit	47.05204% <66.66667%> (+0.00365%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[ricardobossan]

All LGTM!

None

Night Sky

Aquatic

Desert

Dusk

[LeafShi1]

It seems that the ToolStripProfessionalRenderer has been changed. Can you confirm whether this problem also exists in other rendering modes?

[Tanya-Solyanik]

Please get this fix tested on Win10 themes.

[Epica3055]

@LeafShi1

This is the code how the Grip is painted, I don't think we can control the color 🤔

winforms/src/System.Windows.Forms/src/System/Windows/Forms/VisualStyles/VisualStyleRenderer.cs

Lines 219 to 235 in 0ce1218

	internal unsafe void DrawBackground(HDC dc, Rectangle bounds, HWND hwnd = default)
	{
	if (bounds.Width < 0 || bounds.Height < 0)
	{
	return;
	}
	if (!hwnd.IsNull)
	{
	using var htheme = OpenThemeData(hwnd, Class);
	_lastHResult = PInvoke.DrawThemeBackground(htheme, dc, Part, State, bounds, null);
	}
	else
	{
	_lastHResult = PInvoke.DrawThemeBackground(HTHEME, dc, Part, State, bounds, null);
	}
	}

[Epica3055]

@Tanya-Solyanik I have updated the description.