bug#17739: 24.3; Dotted circle does not combine with Thai vowel markers

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 8 Jun 2014 16:37:55 -0500 (CDT)
> From: Brady Garvin <bgarvin@cse.unl.edu>
> 
> Thanks.  However, I see the same problem even putting both characters
> in the same font.  With S-mouse-1 "Change Buffer Font..." I select
> Norasi.  M-x describe-char then reports
> 
>          character: ◌ (9676, #o22714, #x25cc)
> preferred charset: unicode-bmp
>  		   (Unicode Basic Multilingual Plane (U+0000..U+FFFF))
>         code point: 0x25CC
>             syntax: w 	which means: word
>           category: .:Base
>        buffer code: #xE2 #x97 #x8C
>          file code: #xE2 #x97 #x8C (encoded by coding system utf-8-unix)
>            display: by this font (glyph code)
>      xft:-unknown-Norasi-normal-normal-normal-*-13-*-*-*-*-0-iso10646-1 (#x146)
> 
> and
> 
>          character: ึ (3638, #o7066, #xe36)
> preferred charset: unicode-bmp
>  		   (Unicode Basic Multilingual Plane (U+0000..U+FFFF))
>         code point: 0x0E36
>             syntax: w 	which means: word
>           category: 2:upper diacritic, t:Thai
>        buffer code: #xE0 #xB8 #xB6
>          file code: #xE0 #xB8 #xB6 (encoded by coding system utf-8-unix)
>            display: by this font (glyph code)
>      xft:-unknown-Norasi-normal-normal-normal-*-13-*-*-*-*-0-iso10646-1 (#x109)
> 
> The characters remain uncombined.

Check out the character composition rules in thai-util.el, perhaps
something is missing there.