Two (or much more) cursors bug debugged (simple test case)

[Pavel Janík]

Hi,

today I've got a chance to debug the problem with two cursors in one
window. I wrote an e-mail in Gnus/message-mode with many modes turned
on. I got to the state where I could easily create at least one additional
cursor per line by simply inserting the same text as was on the previous
line and SPC which did not removed previous cursor. I have removed all
special modes I use in Gnus and end in fundamental mode with almost
nothing. Then I started emacs with -q and got this test case which is very
easy to repeat, please try it and tell me?

Run

LANG=cs_CZ emacs -q /tmp/this_file_does_not_exist -f toggle-input-method -f 
newline

it will toggle the default input method for Czech Language environment
(which is czech) and will insert new-line (do not ask me why this is
needed, but it is! ;-). Now, insert character ť (+t) and RET. When you
press SPC now, you will see what I have seen many times. Two black
cursors! ť is:

  character: ť (04473, 2363, 0x93b)
    charset: latin-iso8859-2 (Right-Hand Part of Latin Alphabet 2 (ISO/IEC 
8859-2): ISO-IR-101)
 code point: 59
     syntax: w  which means: word
   category: l:Latin  
buffer code: 0x82 0xBB
  file code: BB (encoded by coding system iso-8859-2)
       font: -Adobe-Courier-Medium-R-Normal--12-120-75-75-M-70-ISO8859-2

It is very suspicious, the same happens when you insert characters like ď,
É, É but it does not when you insert one of ěščřžýáíé. It is also font
dependent. When I'm using another font, nothing will happen (everything is
OK, only one cursor) :-(( So this can be connected to some bad default font
I use on my system. The font mentioned here comes from
/usr/X11R6/lib/X11/fonts/75dpi/courR12-ISO8859-2.pcf.gz. On the other hand,
it does not happen when I switch off the input method. I can reproduce that
on two systems. Mine is SuSE Linux 7.3, my friends' system is Red Hat Linux
7.2. I think it can be reproduced on other systems too. So, please, try it
on your system too.

BTW - would you like to see rainbow? No problem, C-u 20 RET up SPC up M-x
set-cursor-color red RET SPC up etc... :-))

I will happily provide any other needed details.
-- 
Pavel Janík

printk("Illegal format on cdrom.  Pester manufacturer.\n");
                  -- 2.2.16 fs/isofs/inode.c