Face issue -- possible bug

[Joost Kremers <joostkremers@fastmail.fm>]

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Hi all,

I'm running into an issue with a particular font. I'm not sure if 
this is a problem with Emacs or with the font, so before reporting 
an actual bug, I thought I'd ask here first.

The font I'm having trouble with is Linux Libertine O, which is a 
variable-width font, so it only shows when `variable-pitch-mode` 
is enabled.

The issue occurs with several diacritics of the International 
Phonetic Alphabet[1], which are combining characters. One 
character causing the issue is ̩ COMBINING VERTICAL LINE BELOW 
0x0329. When this character is combined with e.g., n, the result 
is displayed as a (small) capital n with the diacritic, not as an 
lower case n.

The screen show below shows the problem (it's the final letter in 
the word):


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This screen shot was taken with `emacs -Q` and executing 
`(set-face-attribute 'variable-pitch nil :height 1.4 :family 
"Linux Libertine O")` at an `IELM` prompt and `M-x 
variable-pitch-mode` in the buffer. To see what the word *should* 
look like, consider this screen shot:


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This is also `emacs -Q`, with `(set-face-attribute 'default nil 
:height 110 :foundry "unknown" :family "DejaVu Sans Mono")` and 
`variable-pitch-mode` disabled.

The fact that Emacs displays the word correctly with DejaVu Sans 
Mono seems to suggest that it's not an Emacs problem but rather a 
font problem, but note that the same diacritic with the same font 
displays correctly in a pdf:


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(That's a screen shot of the pdf resulting from the LaTeX file in 
the first two screen shots, created with xelatex).

So should this be reported as an Emacs bug, or should I contact 
the font creator?

TIA

Joost



[1] 
<https://en.wikipedia.org/wiki/International_Phonetic_Alphabet>

-- 
Joost Kremers
Life has its moments