[XeTeX] Position of kasra when used together with tashdid in Arabic

[Otto Maderdonner]

Hi Khaled,

I hope this message reaches you as I have found your address on a 7-year old XeTeX blog entry.

I am using a font called W_kelas aval, which is freely available for download, for a basic Farsi manuscript for German learners.

My problem is the KASRA (U+0650). In the original font, it is positioned so far below the descender that it looks a FATHA on the next line.

I nudged KASRA up using Font Lab, which solved my problem only partly. While it is now more pleasing with most characters, it collides with characters that extend below the base line, e.g. three dots in TCHEH or PEH.

I have seen in other fonts such as Geeza Pro on Mac that KASRA can move its position relative to the previous character, i.e. it is positioned close to the base line of a medial character such as HAH, but moves downwards so it never overlaps the dots of TCHEH.

Is there an option to make the W-kelas aval font behave in a similar fashion?
 
I would really appreciate your answer,

Otto