Re: [Paps-discuss] Combining characters not rendered properly

[Jan W. S. <jst...@pl...>]

Arne G=C3=B6tje (=E9=AB=98=E7=9B=9B=E8=8F=AF) wrote:

> I highly doubt that the Arphic fonts can do combining accents.
> The accents are not present in those fonts. Which simply
> means, that your font rendering engine replaced the glyphs with
> some from other fonts.

Your explanation is enlightening. Thanks! I haven't yet found out
the exact mechanism by which some fonts which do not contain
combining accents, yet manage to display them. It must have
something to do with the order of preference in fontconfig's
config files.

>> But what are these bugs exactly?
>=20
> Both.
>=20
> The fonts need to contain a) the base glyphs b) the combining=20
> accents c) "anchors" in the GPOS table to tell the rendering=20
> engine where exactly to place the accents. In fontforge this is
> done easily. :)

I am sure I detect some irony here.. Anyway it is true that in all
cases when a), b), c) are fulfilled (but there are not many of
those), combining accents work (at least for *single* accents).
And they work (more or less by luck) also in some other cases.

I suppose for the Unicode "*multiple* combining accents" mechanism
to work, more complicated anchor classed ought to be defined
(allowing, e.g., "accent on top of accent"). But it seems no
actual font does this at the moment. In the case of the multiple
accents of Classical Greek, Openoffice seems to do OK. But I think
Openoffice uses another mechanism.

So the advice to users has to remain: use pre-combined accents
whenever possible. Don't count on the "combining accents"
mechanism to work. It won't, except from some lucky cases.

Thanks again for your explanation.

Regards, Jan