Language subscripts not working properly for Khmer

[sharathkumar]

I am using Khmer language in my project. But when using a font in Prawn the subscripts are replacing with + symbol.
@prawnpdf

Actual Result :

Expected Result : សង្កាត់ ផ្សារដើមគរ, ខណ្ឌទួលគក, ភ្នំពេញ

[gettalong]

I'm not familiar with Khmer and how subscripts work there but this is most probably be a limitation of prawn/ttfunk since it doesn't support advanced glyph positioning via GSUB/GPOS font tables.

If you could provide a small sample script together with the appropriate font file, it might help to find the problem.

[pointlessone]

I'm closing this in favour of #1295.