Line break immediately after a ideographic space (zenkaku space)

[minamotorin]

In LuaLaTeX, a line break immediately after ideographic space (zenkaku space) is converted to a word space. This behavior is different from (u)pLaTeX.

The cause is that ideographic space (　) is active and line end is not commented out. One solution is to add to callback to process_input_buffer like LuaTeX-ja as followings.

% The parts of this program other than Lua code are public domain.
\documentclass{jlreq}
\begin{document}

□□□□　□□□□　□□□□　□□□□　□□□□　□□□□　□□□□　□□□□　

□□□□　
□□□□　
□□□□　
□□□□　
□□□□　
□□□□　
□□□□　
□□□□　

\ifx\directlua\undefined
  \end{document}
\fi

\directlua{
  % This Lua code is based on ltj-inputbuf.lua of The LuaTeX-ja project.
  % Rights is waived for changes from the original code by The LuaTeX-ja project.
  % The original copyright notice (Modified BSD License) is as follows.
  %
  % > Copyright (c) 2011--2016 The LuaTeX-ja project, All rights reserved.
  % >
  % > Redistribution and use in source and binary forms, with or without
  % > modification, are permitted provided that the following conditions are met:
  % >     * Redistributions of source code must retain the above copyright
  % >       notice, this list of conditions and the following disclaimer.
  % >     * Redistributions in binary form must reproduce the above copyright
  % >       notice, this list of conditions and the following disclaimer in the
  % >       documentation and/or other materials provided with the distribution.
  % >     * Neither the name of the LuaTeX-ja project nor the
  % >       names of its contributors may be used to endorse or promote products
  % >       derived from this software without specific prior written permission.
  % >
  % > THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  % > ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  % > WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  % > DISCLAIMED. IN NO EVENT SHALL THE LUATEX-JA PROJECT OR CONTRIBUTORS BE LIABLE
  % > FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  % > (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  % > LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  % > ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  % > (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  % > SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  local function add_comment(buffer)
    local getcatcode = tex.getcatcode
    local getcount = tex.getcount
    local i = utf.len(buffer)
    local c = utf.byte(buffer, i)
    while (i>0) and (getcatcode(c)==1 or getcatcode(c)==2) do
      i = i - 1
      if (i>0) then
        c = utf.byte(buffer, i)
      end
    end
    local te = tex.endlinechar
    local lec = getcount 'ltjlineendcomment'
    if (i>0) and (te \string~= -1) and (getcatcode(te)==5) and (getcatcode(lec)==14) then
      if (c==utf.byte('　')) and (getcatcode(c)==13) then
        return buffer .. utf.char(lec)
      end
    end
    return buffer
  end
  luatexbase.add_to_callback('process_input_buffer', add_comment, 'my.zenkaku_space')
}

□□□□　□□□□　□□□□　□□□□　□□□□　□□□□　□□□□　□□□□　

□□□□　
□□□□　
□□□□　
□□□□　
□□□□　
□□□□　
□□□□　
□□□□　

\end{document}

• pLaTeX

• LuaLaTeX

Certainly it is better to take measures, but I think it's a rare case and it's okay if you don't take measures.

Thanks.

[abenori]

Thank you. I think just adding \ignorespaces solve the problem.

% line 1150
\expandafter\long\expandafter\def\expandafter\jlreq@zenkakuspace@main\expandafter{\@tempa
    \hskip 1\jlreq@zw\hbox{}%
    \jlreq@lastnodechar=`　
    \expandafter\jlreq@fixjfm
  \else\expandafter　\fi
  \ignorespaces % added
}

[minamotorin]

Thanks for your reply.

\ignorespaces causes the following problem in really rare case.

% This program is in the public domain.
\documentclass{jlreq}% Added \ignorespaces
\begin{document}
\catcode`\@=\active
\let@　% For readability

@ @ □□□□

□□□□

@@□□□□

\end{document}

• LuaLaTeX

• pLaTeX

I think the importance of this problem is as low as the first problem.

[abenori]

Thank you again.

The current 　 is just an alias of \　 and I think it's better to keep this to make understanding the correct behavior easier. Perhaps, make 　 non-active may be a possibility. I thought users do not use 　 because this is not compatible with JLReq. This was a reason why I make 　 an alias of \　.

[minamotorin]

I understand, thanks.