FontStyle will affect all subsequent non-English text globally

[DearVa]

Describe the bug

Once FontStyle (Italic or Oblique) is applied to any text, all subsequent non-English text will be affected across the entire Avalonia application. This issue appeared in version 11.3.5. I haven't thoroughly examined Avalonia's source code, but I suspect it might be related to some global state or the rendering stack?

To Reproduce

<Window
  x:Class="LiveMarkdown.Avalonia.Demo.MainWindow" xmlns="https://github.com/avaloniaui"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" d:DesignHeight="450"
  d:DesignWidth="800" Title="LiveMarkdown.Avalonia.Demo"
  mc:Ignorable="d">
  <StackPanel>
    <TextBlock
      FontStyle="Italic" Text="叮咚鸡 Italic"/>
    <TextBlock Text="大狗叫"/>
    <TextBlock
      FontStyle="Italic" Text="Test Italic"/>
    <TextBlock Text="Test"/>
    <TextBlock
      FontStyle="Italic" Text="こんにちは Italic"/>
    <TextBlock Text="こんにちは"/>
  </StackPanel>
</Window>

Expected behavior

FontStyle of "大狗叫" and "こんにちは" should be normal.

Avalonia version

11.3.5 and above

OS

No response

Additional context

No response

[DearVa]

After a quick review of the commit in 11.3.5, I suspect this issue relates to the caching of FontFamily. Text with the same FontFamily is influenced by the first text, causing English text explicitly assigned a FontFamily to also become Italic. The reason English text remains unaffected by default is likely because its default FontFamily is not cached.

Possible related code:
https://github.com/AvaloniaUI/Avalonia/blob/00138379c8c09986cb50f063c8e0f52f04fcf10b/src/Avalonia.Base/Media/FontManager.cs#L91C5-L91C114