23.1.92: cursor movement in Korean text is slow with xfonts-baekmuk

[Jae-hyeon Park]

Hello,

I would like to draw your attention to a problem that I reported a few
months ago.  It can be found at https://bugs.launchpad.net/bugs/471597
The report is about emacs 23.1 but I still have the same problem with
the pretest version 23.1.92.  It is weird that this symptom occurs
only if I use the particular bitmap font, baekmuk.  However, this font
causes no trouble when I am using emacs 22.  For your convenience let
me copy the text below.  The attached file is available at the above
link.  Thank you.

Jae-hyeon Park


Binary package hint: emacs23

Source package: emacs23
Ubuntu release: 9.10 amd64
Package version: 23.1+1-4ubuntu3

I use the bitmap font xfonts-baekmuk 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).

How to reproduce:

1) Start emacs with

    $ emacs23 -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) Open the attached file in the same frame

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