[OLPC India] Keyboard layout: Use of Circle to denote combining characters

[Sayamindu Dasgupta]

Hi,
While looking at http://wiki.laptop.org/go/Devanagari_Keyboard, I
noticed that the vowel signs (as well as the Virama/Halant) are preceded
by a circle.

Rendering engines use the circle (U+25CC DOTTED CIRCLE to be exact) to
do fallback rendering for invalid combining marks (ie, a standalone
vowel sign). This behaviour is documented in the Unicode standard 5.0
(section 5.13, Rendering Nonspacing Marks, pg 173):

        "One method 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."

I was wondering if this behaviour is required for the keyboard as well.
In all our textbooks (language primers), no such circle is used to
indicate vowel signs. This may create confusion among the children,
since such a circle does not exist in the Devanagari alphabet.

On the other hand, it might also serve as a good indication that the
characters with a circle before/under/after them in there are dependant
ones.

Regards,
Sayamindu



-- 
Sayamindu Dasgupta
http://sayamindu.randomink.org/ramblings