bug#20793: 25.0.50; Some Unicode glyphs aren't monospaced

[Eli Zaretskii <eliz@gnu.org>]

> From: Oleh Krehel <ohwoeowho@gmail.com>
> Date: Fri, 12 Jun 2015 14:54:51 +0200
> 
> My preferred font is "DejaVu Sans Mono".  When using the Unicode
> character "✜", its width is more than the standard char width. This
> causes alignment problems for me.

Which alignment problems?  Can you describe them?

In general, Emacs cannot ensure all characters it displays will be of
the same pixel width, this is simply impossible, especially when some
characters require the use of non-default fonts.

> This issue doesn't occur in Emacs 24.5.2. There, the char has the same
> width as all others.
> 
> Details on the char in Emacs 25:
> 
>              position: 227 of 348 (65%), column: 35
>             character: ✜ (displayed as ✜) (codepoint 10012, #o23434, #x271c)
>     preferred charset: unicode (Unicode (ISO10646))
> code point in charset: 0x271C
>                script: symbol
>                syntax: w 	which means: word
>              category: .:Base
>              to input: type "C-x 8 RET 271c" or "C-x 8 RET HEAVY OPEN CENTRE CROSS"
>           buffer code: #xE2 #x9C #x9C
>             file code: #xE2 #x9C #x9C (encoded by coding system utf-8-emacs-unix)
>               display: by this font (glyph code)
>     xft:-unknown-Symbola-normal-normal-semicondensed-*-15-*-*-*-*-0-iso10646-1 (#x9F9)
> 
> Character code properties: customize what to show
>   name: HEAVY OPEN CENTRE CROSS
>   old-name: HEAVY OPEN CENTER CROSS
>   general-category: So (Symbol, Other)
>   decomposition: (10012) ('✜')
> 
> There are text properties here:
>   fontified            t
> 
> Details on the char in Emacs 24.5.2:
> 
>              position: 1819 of 2174 (84%), column: 5
>             character: ✜ (displayed as ✜) (codepoint 10012, #o23434, #x271c)
>     preferred charset: unicode (Unicode (ISO10646))
> code point in charset: 0x271C
>                script: symbol
>                syntax: w 	which means: word
>              category: .:Base
>              to input: type "C-x 8 RET HEX-CODEPOINT" or "C-x 8 RET NAME"
>           buffer code: #xE2 #x9C #x9C
>             file code: #xE2 #x9C #x9C (encoded by coding system utf-8-unix)
>               display: by this font (glyph code)
>     xft:-unknown-DejaVu Sans Mono-normal-normal-normal-*-15-*-*-*-m-0-iso10646-1 (#xAD1)

As you see, Emacs 25.0.50 used a different font for this character.
Why did you expect it to use DejaVu Sans Mono?  What is your frame's
default font?  Do you have any font-related customizations, and if so,
could you please show them?

Also, when was your Emacs 25 built?  There were changes lately in this
area, so it's important to know whether your binary is recent or not.
(The output of "M-x report-emacs-bug RET" will be appreciated.)