From: Marco Cimarosti (marco.cimarosti@essetre.it)
Date: Thu Jan 30 2003 - 04:20:59 EST
Kent Karlsson wrote:
> Keyur Shroff wrote
> [...]
> > In Indic scripts any sign that appear in text not in
> > conjunction with a
> > valid consonant base may be rendered with dotted circle as fallback
> > mechanism (Section 5.14 "Rendering Nonspacing Marks"
> > http://www.unicode.org/uni2book/ch05.pdf).
>
> I don't know where you find support for that position in that text.
> Can you please quote? There are no "invalid base consonants" for
> any dependent vowel (for Indic scripts; similarly for any
> other script).
Actually, there is a mention of displaying combining marks on dotted
circles:
"Several methods are available to deal with an unknown composed
character sequence that is outside of a fixed, renderable set [...]. One
method (Show Hidden) indicates the inability to draw the sequence by drawing
the base character first and then rendering the nonspacing mark as an
individual unit - with the nonspacing mark positioned on a dotted circle."
(The Unicode Standard 3.0, page 120 - 5.14 Rendering Nonspacing Marks -
Fallback Rendering)
I add that this is a good way of displaying a combining mark that has no
base character, i.e. one occurring at the begin of a line or paragraph.
However, I totally agree with Kent that this funny rendering is *not* a
requirement of the Unicode standard, as Keyur Shroff seems to suggest. It is
just an example of many "several methods [that] are available to deal with"
strange sequences.
> > Any system implementing this as
> > default behaviour should not be considered buggy.
>
> Indeed they are. And it should certainly not be default behaviour.
In this case, I disagree with Kent: displaying these dotted circles is not
mandatory, but certainly not a bug.
> Any combining characters can be placed on any base characters without
> there being any dotted circles displayed.
True. But notice that Kent (against his own opinion) correctly wrote "can",
not "must".
> [...]
_ Marco
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