Detect if any right-to-left language is installed

Question

What is the easiest way to detect whether any right-to-left language is installed on the host Windows OS?

(I need this in order to know if LTR marks will be displayed as

Answer 1

Probably unmanaged API like IsValidLanguageGroup, IsValidLocaleName (or IsValidLocale) or IsValidCodePage is what you are looking for

For example the code

if (IsValidLanguageGroup (LGRPID_ARABIC, LGRPID_INSTALLED) ||
    IsValidLanguageGroup (LGRPID_TURKIC, LGRPID_INSTALLED) || 
    IsValidLanguageGroup (LGRPID_HEBREW, LGRPID_INSTALLED)) {
    // RTL is supported 
}

can be used to test whether you have at least one from two most known right-to-left (RTL) languages installed on the windows computer. I don't know the corresponding .NET API, but probably CultureInfo.GetCultures could be used in your case.

UPDATED: I included Thai language group in the list of language groups for testing, but I am not sure, that any of this languages you really need. Typically you application supports only selected languages.