رد: رد: Wrong sequence for Arabic ligature marks(FC5E-FC62, FCF2-FCF4)

[Richard Wordingham]

On Sat, 19 Feb 2022 13:30:49 +0000
Saeed Hubaishan via Unicode <unicode at corp.unicode.org> wrote:

> See how some fonts in windows render FATHA + SHADDA in Pic

Well, the renderings are wrong.  Whether the problem is in the
application, the rendering engine or the font is less clear.  Peter
Constable recently opined that a font should work with all canonical
equivalents, which is a bit harsh given that OpenType lookups were
designed on the assumption that fonts would not have to reorder
characters.

Which application were you using, and what version of Windows?  What
fonts?  Were they designed for Uniscribe/DirectWrite, or were they
designed for HarfBuzz?  As HarfBuzz expressly aims to render canonical
equivalents the same, it is quite possible that the fonts used were
designed expecting the rendering engine to do the AMRTA processing that
Ken Whistler referred to earlier, and that they would work with the
HarfBuzz renderer, which on Windows is used in MS Edge, Chrome, Firefox
and LibreOffice.

Richard.