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

[Heiko Oberdiek]

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