Font style does not work in Application.SetDefaultFont() when the text scale value is bigger than 100% in OS

[John-Qiao]

• .NET Core Version:

  .NET SDK 6.0.100-preview.5.21275.4

• Have you experienced this same bug with .NET Framework?:

  No

More Info:

This issue occurs in other System.Drawing.FontStyle enum values too, like Bold, Strikeout and Underline...

Problem description:

The font style is not Italic for controls in form.

Expected behavior:

The font style should be Italic in form, like it works when text scale is 100%.

Minimal repro:

1. Open the attached TestApp.zip project in VS, run it and check the font style of buttons. -- Font style is Italic in this time.
2. Stop the project, and open the Display setting in OS, then change the text scale(Make text bigger) to 150% and click Apply option.
3. Run project again and observe the font style in controls.

[Olina-Zhang]

This issue was found after the PR: #4911 merged.

[kirsan31]

The problem is here:

winforms/src/System.Windows.Forms/src/System/Windows/Forms/Application.cs

Line 1243 in f577471

s_defaultFontScaled = new Font(s_defaultFont.FontFamily, s_defaultFont.Size * textScaleValue);

We need to set FontStyle too:

s_defaultFontScaled = new Font(s_defaultFont.FontFamily, s_defaultFont.Size * textScaleValue, s_defaultFont.Style);

Miss it too during review :(

[RussKie]

🤦‍♂️

[John-Qiao]

Verified with .NET 6.0.100-preview.6.21315.23 + private binaries build from main branch in dotnet/winforms repo, this issue has been fixed that font style works when the text scale value is bigger than 100% in OS.

[John-Qiao]

Verified with .NET 6.0.100-preview.7.21320.2 from main branch, this issue has been fixed that font style works as above when the text scale value is bigger than 100% in OS.

[John-Qiao]

Verified the issue with .NET 6.0 6.0.100-preview.6.21323.1, it is fixed as above result too.