From: Keyur Shroff (keyur_shroff@yahoo.com)
Date: Wed Jan 29 2003 - 10:41:23 EST
--- Kent Karlsson <kentk@md.chalmers.se> wrote:
>
> A space followed by a dependent vowel sign should display just the
> dependent vowel sign, no dotted circle. Indeed, (except for a "show
> invisibles" mode, or a "character chart" display mode) no (Indic or
> other)
> text that does not contain the *character* DOTTED CIRCLE should ever
> display a dotted circle as part of the displayed text. Systems that
> do display a dotted circle (in normal display mode) where there is
> no such *character* in the displayed text are buggy!
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). Any system implementing this as
default behaviour should not be considered buggy. What should be the
default rendering behaviour (i.e., show hidden or not) may vary from one
script to another script and also depends on implementation policy.
For scripts other than Indic scripts, it may be useful to render the
nonspacing mark without dotted circle because even after rendering it as an
overlap glyph, the result is recognizable. However, for Indic scripts use
of dotted circle is very useful as default behaviour since it gives
immediate feedback to the user that there may be some defective combining
character in the text. Most of the time such errors are unintentional
rather than intentional.
Unicode has provision to remove this dotted circle. Space character is used
to give indication to fallback mechanism that no dotted circle should be
used while rendering this stand alone sign which is normally attached to
other characters. This is useful when sometimes user want to display the
sign without any circle. Also, with this scheme it is possible to show some
combining marks with dotted circle and some without dotted circle.
- Keyur
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