Re: master bf0aeaa0d7a: Re-enable displaying `han' characters on Android

[Po Lu <luangruo@yahoo.com>]

pipcet@protonmail.com writes:

> Thanks again! I really appreciate that there's a second set of eyeballs
> going over these before pushing to master, let alone emacs-30 :-)
>
> The next issue on my LineageOS (an Android variant) phone is that the
> Noto CJK fonts have an "OTTO" header, not a "true"/00010000 one, so
> they're not enumerated at all. At first glance, this doesn't appear to
> be a LineageOS quirk; downloads available elsewhere also have the OTTO
> header.
>
> My understanding of the source code is we currently don't support OTTO
> fonts at all, and my experiment in forcing the header to be recognized
> seems to agree with me there: I get tofu even for ASCII characters,
> which FontForge indicates are present in the font.

Yes, because OTTO fonts are actually a completely distinct format from
TTF, with a unique bytecode language for constructing glyph outlines.
See:

  https://learn.microsoft.com/en-us/typography/opentype/spec/glyphformatcomparison

> I have (lossily!) converted Noto Sans CJK SC to TTF format (with a
> "glyf" table), and installed that in
> /data/data/org.gnu.emacs/files/fonts, customized the "region" face to
> use that font, and now I can see some Han characters when I select them,
> but they turn into tofu when using the default face. (It's possible this
> is due to the experiment I've described above and goes away when I
> revert it...)
>
> Of course, Noto CJK doesn't provide U+20000 (it does provide U+2000B),
> so all this is a bit off-topic.

That's quite a circutous means of obtaining a TTF version of the Noto
CJK fonts.  These fonts are compiled into both formats from a number of
common source files, and there is an index of the options available at:

  https://github.com/notofonts/noto-cjk/tree/main/Serif

an amalgamation of all CJK variants is:

  https://github.com/googlefonts/noto-cjk/raw/main/Serif/Variable/OTC/NotoSerifCJK-VF.ttf.ttc

but since it is enormous, I suggest installing only those regional
variants which cover the scripts you require.