[luatex] Why does LuaTeX show the middle dot instead of ano teleia?

[Heiko Oberdiek]

Hello,

On 2023-08-29 20:29, Joseph Wright wrote:
> On 29/08/2023 19:27, Heiko Oberdiek via luatex wrote:
>>
>> using LuaTeX to review the glyphs of a font, I discovered an oddity 
>> about U+0387 ANO TELEIA. LuaTeX shows U+00B7 MIDDLE DOT instead.

>>          \symbol{"00B7}% MIDDLE DOT
>>          \symbol{"0387}% ANO TELEIA

>  From UnicodeData.txt:
> 
>      0387;GREEK ANO TELEIA;Po;0;ON;00B7;;;;N;;;;;
> 
> so it looks like it's a simple normalisation.

Start of the UnicodeData.txt format description 
(https://www.unicode.org/reports/tr44/#UnicodeData.txt):
   [0] Code value
   [1] Character name
   [2] General category
   [3] Canonical combining classes
   [4] Bidirectional category
   [5] Character decomposition
   ...

In the LuaTeX manual, I found:

| Normalization of the Unicode input is on purpose not built-in and
| can be handled by a macro package during callback processing.
| We have made some practical choices and the user has to
| live with those.

The TeX input above, however, is plain ASCII. Therefore, any 
normalization of the file contents should not matter.

Of course, I do not want to have any decomposition that replaces
the glyph with a different character. That would make reviewing
the original glyph impossible.

Yours sincerely
   Heiko