From: Kent Karlsson (kentk@md.chalmers.se)
Date: Mon Feb 03 2003 - 12:12:14 EST
> --- Kent Karlsson <kentk@md.chalmers.se> wrote:
> > >
> > > No fallback rendering is coming into picture with your explanation.
> >
> > Yes, there is. A character sequence <FULL STOP, VOWEL SIGN E> (say)
> > is very unlikely to have a ligature, specially adapted (and fitting)
> > adjustment points, or similar. The rendering would in that sense
> > need to use a fallback mechanism that renders an "approximation"
> > for this rare combination.
>
> Do you mean to say that an application has to take care of combination of
s/has to/should, also in display,/
> all other Unicode characters with each combining marks in the fallback
Including multiple combining marks on one base character.
> mechanism for such approximation? Can you count the number of combinations
> which may result in millions!?
Many, many more. Which is why you need a fallback mechanism (rather
than ligatures, adjustment points, etc. which cannot handle that many
combinations).
In the case of Indic postfix and prefix matras, the general handling is
in principle simple: for the postfix ones, nothing special need be done,
for the prefix ones (i.e. the reordrant ones) do the reordering (before
the preceding base character at least, for certain Indic combinations,
move it even earlier). Then the you have the "visual order". I'm
ignoring ligature formation here, but that has to be done as well. For
the superscript, subscript, and split matras (and other combining
marks) the general approach is a bit more complicated. See
http://www.unicode.org/notes/tn2/ for hints.
/Kent K
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