bug#5667: 23.1.93; cursor movement in Korean text is slow with xfonts-baekmuk

[Jae-hyeon Park]

I am sorry if you are seeing this report more than once as I have
already posted about this problem to emacs-devel (which I suppose was
not the right list for a bug report).

I use the baekmuk bitmap font (available as the xfonts-baekmuk package
in debian for instance) to display Korean characters in emacs.  When
there are many Korean characters in a buffer, moving the cursor among
the Korean characters takes a long time (like a few seconds on my laptop
which is a fairly new hardware).  It is weird that this symptom occurs
only if I use this particular font.  However, the same font causes no
trouble when I am using emacs 22.

How to reproduce:

1) Start emacs with

    $ emacs -Q -xrm 'Emacs.FontBackend: x' &

2) In the scratch buffer, evaluate the following code

    (create-fontset-from-fontset-spec
     "-misc-fixed-medium-r-normal--15-140-75-75-c-90-fontset-baekmuk,
      ascii:-misc-fixed-medium-r-normal--15-140-75-75-c-90-iso8859-1")
    (set-fontset-font "fontset-baekmuk" 'korean-ksc5601
     "-baekmuk-gulim-medium-r-normal--18-180-75-75-m-180-ksc5601.1987-0")
    (set-frame-font "fontset-baekmuk")

3) In the same frame, fill a whole emacs window with Korean characters.
   For instance, open the sample Korean text file that can be downloaded
   from https://bugs.launchpad.net/bugs/471597.

4) Try to move the cursor downwards by pressing C-n several times


In GNU Emacs 23.1.93.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.18.3)
 of 2010-03-01 on aida
Windowing system distributor `The X.Org Foundation', version 11.0.10604000
configured using `configure  '--enable-profiling' '--with-xpm=no' 
'--with-gif=no' '--with-tiff=no''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=uim
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<down-mouse-2> <mouse-2> <backspace> C-j M-x s e t 
- v a <tab> <return> m a i l - s p e <tab> <return> 
t <return> <down-mouse-1> <mouse-1> C-h v m e s s a 
g e <tab> C-g C-h v m a i l - s p e <tab> <return> 
<help-echo> <help-echo> <down-mouse-1> <mouse-1> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <menu-bar> <help-menu> <se
nd-emacs-bug-report>

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