bug#3325: 23.0.93; Unexpected font for composed character

[Alan Third]

Kenichi Handa <handa@m17n.org> writes:

> In article <m2skj2s2w7.fsf@gmx.at>, Markus Triska <markus.triska@gmx.at> 
> writes:
>
>> I have a file ~/Downloads/Büroanwendungen.zip. When I visit ~/Downloads/
>> in dired (C-x d ~/Downloads/ RET) and press C-u x = on the "ü", I get:
>
>>            character: u (117, #o165, #x75)
>>    preferred charset: ascii (ASCII (ISO646 IRV))
>>           code point: 0x75
>>               syntax: w      which means: word
>>             category: .:Base, a:ASCII, l:Latin, r:Roman
>>          buffer code: #x75
>>            file code: #x75 (encoded by coding system utf-8-unix)
>>              display: composed to form "ü" (see below)
>
>>    Composed with the following character(s) "̈" using this font:
>>      xft:-itc-American 
>> Typewriter-normal-normal-normal-*-20-*-*-*-*-0-iso10646-1
> [...]
>> This font differs unexpectedly (for me) from the one used for the "r":
> [...]
>>        xft:-bitstream-Bitstream Vera Sans 
>> Mono-normal-normal-normal-*-20-*-*-*-m-0-iso10646-1 (#x55)
>
> In your file, `ü" is acually not a signle character but two
> characters `u' and U+308 (COMBINING DIAERESIS), and it seems
> that the above bitstream font doesn't contain a glyph of
> U+308.  So, Emacs searches for a font that has that glyph.
> The found font in your case was "American Typewriter".

This still happens in Emacs 25, but from the above description it
doesn't really sound like a bug. It's Emacs working around the fact that
the font doesn't have the glyph.

> It may be good that Emacs knows that `u'+U+308 = `ü', but
> that kind of normalization is not yet supported.

I'm changing this bug report to wishlist.
-- 
Alan Third