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List:       xfree-i18n
Subject:    Re: [I18n]Re: POSIX tty cooked mode editor and UTF-8
From:       numa () sysrap ! cs ! fujitsu ! co ! jp (NUMATA Toshinori)
Date:       2001-03-30 6:57:51
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Tomohiro KUBOTA <tkubota@riken.go.jp> wrote:
> # two <backspace>-<space>-<backspace>'s cannot erase one doublewidth
> # character - <backspace>-<backspace>-<space>-<space>-<backspace>-
> # <backspace> is needed.

Two <backspace>-<space>-<backspace> sequences work fine for the
terminals I know of.  Well, there may be others.  I don't know
which is common behavior.

> # However, this works on a line.  How about when the doublewidth character
> # was tried to be written at the last (for example, 79th) column?

If a two-column character is displayed when the cursor is at the end of
a line, most terminal implementations will display the two-column
character at the beginning of the next line and place the cursor next to
the character.  Erasing the character will place the cursor at the
beginning of the second line, not the end of the first line.

>  I
> # have never seen any systems which can handle such a situation -
> # including Microsoft products which are usually better than open
> # source softwares in handling of doublewidth characters.

MS-DOS Command Prompt of Microsoft Windows 98 will not move the cursor
beyond the beginning of the line when erasing characters.  However,
Command Prompt of Microsoft Windows NT 4.0 will place the cursor at the
end of the first line in the above situation.  Interestingly, executing
COMMAND.COM on Windows NT Command Prompt will emulate the Windows 98
behavior.

Anyway, erasing characters beyond a line boundary is a difficult job.
That's why the POSIX standard say "if possible" :-)

-- 
NUMATA Toshinori
Technology Development Dept., Strategic Planning Div.,
Software Group, FUJITSU LIMITED
Phone: +81-45-476-4586 (x4224)	Fax: +81-45-476-4749
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