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Re: change proposal: nvi behavior for multi-width character

On 2017/11/07 3:41, Zhihao Yuan wrote:
    (1) cursor position (nvi-cursor.patch)

    This patch fixes cursor position when a multi-width character
    does not fit in a line, and is located on the next line.

Can you describe the problem?  Such as, is the cursor
currently misplaced (to the first line)?

When a double-width character does not fit in a line, and cursor
moves to that char by 'l' command, cursor is put on the 1st column
of that char, instead of the 2nd column. Then, if cursor moves
further from a double-width char in that line to a single-width one,
it is located on the 2nd column of the double-width char, instead of
the single-width char it moving toward.

Well, this is very complicated to explain in words. Can you please
test cursor motion with long lines which contain both single- and
double-width chars? Then, you will find something wrong. This problem
occurs not only with our nvi but also with your nvi2.

    Also, when cursor indicates a multi-width character, put it on
    the first column of the character, instead of the last column in
    the current implementation. Otherwise, some terminal emulators
    do not focus on the entire the character, the right-most column

As long as it doesn't break xterm.

Xterm focuses entire of a double-width char in both cases when cursor
is located on the left or right parts of that char.

    (2) join command (nvi-join.patch)

    This patch changes amount of white spaces inserted when lines
    ending or beginning with multi-width characters are joined:

      last char       first char      behavior
      ---             ---             ---
      multi-width     multi-width     nothing ins'ed
      multi-width     single-width    1 spc ins'ed
      single-width    multi-width     1 spc ins'ed
      single-width    single-width    original

    This is (basically) the same behavior to nvi-m17n. As a Japanese,
    I feel this is a quite reasonable choice, and I guess it may be
    for other non-European languages that leave no space between

It's true to CJK, but generally unsafe to make such
an assumption.  Unless nvi2 (
can recognize Unicode codepoints, unlikely I can
take this change.

Do you know specific languages for which this makes things
inconvenient? I've also found that vi shipped with Solaris 10
(Version SVR4.0, Solaris 2.5.0) works similarly.


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