[XeTeX] Problem with Turkish dotted I (U+0130) in headers

[Khaled Hosny]

On Thu, May 30, 2013 at 02:45:26PM +0200, Alessandro Ceschini wrote:
> the problem is that "i" gets capitalized in Turkish
> as dotted I, that is: "İ" (U+0130) and this, XeLaTeX doesn't do. Is
> there a way to enjoin it to do so?

Changing \lccode and \uccode values might to the trick:

    \lccode`İ=`i
    \uccode`i=`İ
    \lccode`I=`ı
    \uccode`ı=`I

For testing:

    \uppercase{İiIı}
    \lowercase{İiIı}

But it might has other side effects I’m not aware about (hyphenation?),
and certainly should not be done globally for multilingual documents,
may be it is something for Polyglossia to do?

Regards,
Khaled