[XeTeX] Incorrect rendering of Vedic Sanskrit accents

[BPJ]

Den 2015-05-22 21:14, David M. Jones skrev:
> Arguably, it never is -- if you want a dotted circle, you can add it
> yourself, whereas it's not at all unusual to want to show combining
> marks in isolation in, say, textbooks.

Showing it with a dotted circle as stand in for a base character, 
whether automatically inserted (which I wouldn't like) or with an 
explicit U+25CC is the correct way to show a combining character 
in such a case, since it shows clearly where the combining mark 
would be in relation to the base character. You can always add a 
footnote to the effect that ◌ is conventionally used in place of a 
base character when discussing a combining mark without reference 
to a base character.

Even if you want the mark to 'hang in the air' a combining mark
needs something with width to 'hang' it on even in that case, and
a nonbreaking space would seem to be the natural choice. If you
(likely) need finer control over spacing one or more of the
characters in the U+2000...U+200A range may serve, but remember 
that the visual effect may be font dependent.

FWIW I checked some lead-printed Sanskrit grammars and 
dictionaries and they all use some base character (क or त in all 
cases) when discussing combining marks; there simply weren't any 
type for marks without a base character.  Compared to that the 
dotted circle is a huge advance! Especially in a table it makes 
the difference between superscript, subscript and superimposed 
marks immediately clear.

Alas U+25CC seldom is equipped with the anchors necessary to 
display marks correctly in relation to it, if there is a glyph for 
it at all.  Often you need to use another font and adjust the size 
of the dotted circle itself.