For SetDarkThemeEnabled, I propose something like:

void SetDarkThemeEnabled(darkSkin = Ctrl::AutodetectDarkSkin);

with

Ctrl::AutodetectDarkSkin autodetecting and behaving like old SetDarkThemeEnabled(true)
Ctrl::DarkSkin always dark, with SetDarkThemeEnabled(true) and sEmulateDarkTheme always true
Ctrl::WhiteSkin always light, with SetDarkThemeEnabled(false) and sEmulateDarkTheme always false

And bool IsSystemThemeDark() made public.