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

[Joseph Wright]

On 29/08/2023 19:27, Heiko Oberdiek via luatex wrote:
> Hello,
> 
> 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.
> Minimal example (the font does not matter, if it contains both glyphs
> that are different in some way, e.g. shape or position):
> 
>      \documentclass{standalone}
>      \usepackage{fontspec}
>      \newfontface\TestFont{FreeSans.ttf}
>      \begin{document}
>          \TestFont
>          \symbol{"00B7}% MIDDLE DOT
>          \symbol{"0387}% ANO TELEIA
>      \end{document}
> 
> The bounding boxes of the glyphs can be retrieved with FontForge:
> 
>      #!/usr/bin/env fontforge
> 
>      import fontforge
> 
>      font = fontforge.open('FreeSans.ttf')
>      print(f'U+00B7: {font[0x00B7].boundingBox()}')
>      print(f'U+0387: {font[0x0387].boundingBox()}')
> 
> The result:
> 
>      U+00B7: (87.0, 227.0, 191.0, 331.0)
>      U+0387: (86.0, 420.0, 190.0, 524.0)
> 
> The vertical positions of the dots are quite different with
> U+0387 at a higher position.
> 
> * But LuaTeX  1.16.0 (TeX Live 2023/Cygwin) with
>    development id 7567 shows the middle dot in both cases.
> * XeTeX 3.141592653-2.6-0.999995 (TeX Live 2023/Cygwin)
>    shows the expected result where U+0387 is shown at a
>    higher vertical position.
> 
> Yours sincerely
>    Heiko

 From UnicodeData.txt:

     0387;GREEK ANO TELEIA;Po;0;ON;00B7;;;;N;;;;;

so it looks like it's a simple normalisation.

Joseph