[XeTeX] combining characters in isolation

[Mike Maxwell]

David Perry wrote:
> I just downloaded a font called bangla.ttf from 
> http://www.omicronlab.com/bangla-fonts.html (lots of free/open source 
> Bengali fonts there; not sure if this is the Bangla that you have).  I 
> looked at the font in FontLab Studio and it does have all the Unicode 
> characters, and the following lines were successful:
> 
> {\fontspec{Bangla} \char"09C2  \qquad +/=  \qquad  \char"09C4}

OK, that allowed me to track down the problem.  If I do
    \newfontfamily\bengalifont[]{Bangla}
it works fine; I don't get the dashed circle.  In fact the space 
character doesn't even have to be inside the scope of the script.

But if I do
    \newfontfamily\bengalifont[Script=Bengali]{Bangla}
I get the dashed circle.  So apparently setting the script makes it pay 
attention to whether there is a Bengali base character for the combining 
character to combine with.  But not specifying the script causes other 
problems, namely the combining characters don't combine correctly with a 
Bengali base character when there is one (which of course is most of the 
time).

Guess I could fix my original problem without breaking the output and 
without making the XML non-portable by modifying our code that tags 
Bengali text during the conversion from XML to XeLaTeX...

Thanks for all the pointers!
-- 
    Mike Maxwell
    What good is a universe without somebody around to look at it?
    --Robert Dicke, Princeton physicist