bug#33688: UTF symbols in 25.2.2 under Ubuntu

[Sergei Meshveliani <mechvel@botik.ru>]

On Sun, 2018-12-09 at 20:05 +0200, Eli Zaretskii wrote:
> > From: Sergei Meshveliani <mechvel@botik.ru>
> > Date: Sun, 09 Dec 2018 19:19:11 +0300
> > 
> > This is on  GNU Emacs 25.2.2  installed on Ubuntu Linux 18.04 LTS.
> > It draws wrongly some UTF symbols.
> > 
> > I see this when writing programs in Agda.
> > Agda is a programming language that uses some UTF symbols in the source
> > code. It has a certain Agda input method for UTF symbols.
> > For example, in
> >                     A\rB          (1)
> > 
> > \r is an UTF symbol \rightarrow in Agda programs.
> > (1) needs to be drawn somewht similar to
> >                                          A->B
> > 
> > But emacs draws the part `>' of the arrow inside B, so that the string
> > looks like
> >                     A-B
> > 
> > , and with with a certain garbage inside B. 
> 
> If you go to that character between A and B, and type "C-u C-x =",
> what does Emacs display in the *Help* buffer?  Please post the entire
> contents of the *Help* buffer you get.
> 


I print below what is shown in Debian + GNU Emacs 23.2.1
and
                            in Ubuntu 18.04 + GNU Emacs 25.2. 



**********************************************************************
In  Debian,  GNU Emacs 23.2.1   everything is drawn correct.

\r    Example:  A\rB   to be drawn close to   A->B
The codes are
        character: → (8594, #o20622, #x2192)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x2192
           syntax: w    which means: word
       category: .:Base, c:Chinese, h:Korean, j:Japanese
       to input: type
       "\r-" or "\rightarrow" or "\r" or "\longrightarrow" or "\to" or
"\->"
                   with Agda
      buffer code: #xE2 #x86 #x92
        file code: #xE2 #x86 #x92 (encoded by coding system utf-8-unix)
          display: terminal code #xE2 #x86 #x92

Character code properties: customize what to show
  name: RIGHTWARDS ARROW
  old-name: RIGHT ARROW
  general-category: Sm (Symbol, Math)

------------------------------------------------------------
\-->    Example:  Preserves_\-->_   to be drowun close to  Preserves_->_
 
The codes are

        character: ⟶ (10230, #o23766, #x27f6)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x27F6
           syntax: w    which means: word
         category: .:Base
         to input: type "\r--" or "\r" or "\-->" with Agda
      buffer code: #xE2 #x9F #xB6
        file code: #xE2 #x9F #xB6 (encoded by coding system utf-8-unix)
          display: terminal code #xE2 #x9F #xB6

Character code properties: customize what to show
  name: LONG RIGHTWARDS ARROW
  general-category: Sm (Symbol, Math)



************************************************************************
In Ubuntu 18.04,  Gnu Emacs 25.2 :

\r   is wrongly drawn in  A\rB

The codes are 
    character: → (displayed as →) (codepoint 8594, #o20622, #x2192)
    preferred charset: unicode (Unicode (ISO10646))
code point in charset: 0x2192
               script: symbol
               syntax: w        which means: word
    category: .:Base, c:Chinese, h:Korean, j:Japanese
    to input: type "\r-" or "\rightarrow" or "\r" or "\longrightarrow"\
 or "\to" or "\->" with Agda input method
          buffer code: #xE2 #x86 #x92
    file code: #xE2 #x86 #x92 (encoded by coding system utf-8-unix)
              display: terminal code #xE2 #x86 #x92

Character code properties: customize what to show
  name: RIGHTWARDS ARROW
  old-name: RIGHT ARROW
  general-category: Sm (Symbol, Math)
  decomposition: (8594) ('→')

---------------------------------------------------------------
\-->   is very wrongly drawn in  Preserves_\-->_

The codes are
    character: ⟶ (displayed as ⟶) (codepoint 10230, #o23766, #x27f6)
    preferred charset: unicode (Unicode (ISO10646))
code point in charset: 0x27F6
               script: symbol
               syntax: w        which means: word
             category: .:Base
       to input: type "\r--" or "\r" or "\-->" with Agda input method
       buffer code: #xE2 #x9F #xB6
       file code: #xE2 #x9F #xB6 (encoded by coding system utf-8-unix)
              display: terminal code #xE2 #x9F #xB6

Character code properties: customize what to show
  name: LONG RIGHTWARDS ARROW
  general-category: Sm (Symbol, Math)
  decomposition: (10230) ('⟶')