Fix issue 11939: [Dark Mode]HelpProvider text color is barely visible

[SimonZhao888]

Fixes #11939

Proposed changes

• Modify the clrForeground property of the HH_POPUP struct instance to ensure that the font color of the pop-up help bubble matches the WinForms theme font color.

Customer Impact

• HelpProvider text color is clearly visible.

Regression?

• Yes

Risk

• Min

Screenshots

Before

After

2026-03-02.095343.mp4

2026-03-02.095705.mp4

Test methodology

• Manually

Test environment(s)

• 11.0.100-preview.1.26104.118

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

This PR fixes issue #11939 where the HelpProvider popup text color was barely visible in WinForms dark mode. Previously, clrForeground in the HH_POPUP struct was set to 0xFFFFFFFF (commented as "Ignore" — a "use default" sentinel), which caused the HtmlHelp API to use a default foreground color that didn't adapt to the WinForms theme. The fix replaces this with SystemColors.WindowText, consistent with how clrBackground was already set using SystemColors.Window.

Changes:

• Replace the clrForeground "ignore" sentinel value in HH_POPUP with SystemColors.WindowText to ensure the popup text color matches the current WinForms theme (including dark mode).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.31714%. Comparing base (3d190f7) to head (7999788).
⚠️ Report is 55 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #14338         +/-   ##
===================================================
+ Coverage   77.25545%   77.31714%   +0.06168%     
===================================================
  Files           3280        3265         -15     
  Lines         645315      644447        -868     
  Branches       47780       47631        -149     
===================================================
- Hits          498541      498268        -273     
+ Misses        143088      142482        -606     
- Partials        3686        3697         +11     

Flag	Coverage Δ
Debug	77.31714% <100.00000%> (+0.06168%)	⬆️
integration	19.14767% <0.00000%> (+0.06367%)	⬆️
production	52.29198% <100.00000%> (+0.07361%)	⬆️
test	97.41580% <ø> (-0.00047%)	⬇️
unit	49.66242% <100.00000%> (+0.06036%)	⬆️

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