[Freedos-devel] DOS and Right-to-left support

[Henrique P. <hp...@te...>]

Hi all,

would anyone out there happen to know how did arabic DOS, on the old 
days, deal with:

1) The control characters needed to handle the script - ZWJ (Zero-width 
joiner), ZWNJ (zero-width non-joiner), RLM (right-to-left mark), LRM 
(left-to-right mark) and control characters needed to handle bilingual 
text (LTR and RTL) in a same sentence: RLE/LRE (right-to-left and 
left-to-right embedding), RLO/LRO (right-to-left and left-to-right 
override) and PDF (POP directional Formatting).

2) Codepage 720 and many others which only present the isolated shapes 
of the characters. DOS, seemingly, had somehow to rely on subfonts or 
any feature which would cause DOS to trade the characters' isolated 
shapes for their initial, medial or final shapes on-the-fly as the text 
was typed.

3) Combining chars. All arabic codepages, including cp864, include at 
least two codepoints which present them.

Hebrew DOS is a simpler case yet topic #3 also applies to the script 
and, with the exception of control characters ZWJ and ZWNJ, topic #1 
also does.

Thanks in advance,
Henrique