Question:
If we do Arabic presentation form rendering in a terminal emulator, how
much of the ligature support is essential? Unicode 3.0 says on page 194
(top): Certain types of ligatures are obligatory in arabic script,
regardless of font design. They refer to the LAM-ALEF ligatures:
FC43 ARABIC LIGATURE LAM WITH ALEF MAKSURA ISOLATED FORM
FC86 ARABIC LIGATURE LAM WITH ALEF MAKSURA FINAL FORM
FD82 ARABIC LIGATURE LAM WITH HAH WITH ALEF MAKSURA FINAL FORM
FEF5 ARABIC LIGATURE LAM WITH ALEF WITH MADDA ABOVE ISOLATED FORM
FEF6 ARABIC LIGATURE LAM WITH ALEF WITH MADDA ABOVE FINAL FORM
FEF7 ARABIC LIGATURE LAM WITH ALEF WITH HAMZA ABOVE ISOLATED FORM
FEF8 ARABIC LIGATURE LAM WITH ALEF WITH HAMZA ABOVE FINAL FORM
FEF9 ARABIC LIGATURE LAM WITH ALEF WITH HAMZA BELOW ISOLATED FORM
FEFA ARABIC LIGATURE LAM WITH ALEF WITH HAMZA BELOW FINAL FORM
FEFB ARABIC LIGATURE LAM WITH ALEF ISOLATED FORM
FEFC ARABIC LIGATURE LAM WITH ALEF FINAL FORM
If we really need to implement ligature substitution at least for these,
then would it make sense to take the ligatures out of the wide font
(like the CJK ideographs), such that the number of charcells occupied by
two characters remains constant, independent of whether ligature
substitution is done or not.
This approach limits the amount of headache for wcwidth() implementors
and users.
Comments?
Markus
--
Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org, WWW: <http://www.cl.cam.ac.uk/~mgk25/>
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Linux-UTF8: i18n of Linux on all levels
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