path: root/Master/texmf-dist/tex/context/third/letter/interface/default.nli

%D \module
%D   [       file=default,
%D        version=2009.07.22,
%D          title=\CONTEXT\ Letter Interface,
%D       subtitle=Default Interface,
%D         author=Wolfgang Schuster,
%D           date=\currentdate,
%D      copyright=Wolfgang Schuster,
%D          email=schuster.wolfgang@googlemail.com,
%D        license=Public Domain]

\unprotect

%D \subject{Reference line}
%D 
%D Dimen value to save the height of the reference line.

\newdimen\letter!height!reference

%D We come now to the new macros defined in this file, they are meant to place the
%D information about date, phone number and more information. You could select on of
%D the alternatives with \type{\setupletter[alternative=...]}.
%D 
%D I define here only what I need myself but you're free to define your own
%D alternatives but try to avoid to use the same names as I do. You could also send
%D me your alternatives and I will include them.
%D 
%D This is the first alternative a, it use the values from the style file without any
%D change, this is the normal layout for a DIN letter.

\long\def\doformatreferencelista#1%
  {\def\\{\egroup\hbox\bgroup}%
   \setupinterlinespace\hbox\bgroup#1\egroup\par}

\long\def\formatreferencelista#1%
  {\bgroup
   \convertargument#1\to\ascii
   \vbox
     {\vbox{\doattributes{\????ld\ascii}\c!titlestyle\c!titlecolor
        {\doformatreferencelista{\labeltext{\v!letter:\ascii}}}}
      \vtop{\doattributes{\????ld\ascii}\c!textstyle\c!textcolor
        {\doformatreferencelista{\lettervalue\ascii}}}}%
   \egroup
   \hfill}

% \defineletterelement[\v!reference][\v!a]
%   {\setbox\scratchbox\hbox\!!to\hsize
%      {\getcommacommandsize[\@@@@lsreferencelist]% \@@@@ldreference?
%       \ifnum\commalistsize<\plustwo\hfill\fi
%       \processcommacommand[\@@@@lsreferencelist]\formatreferencelista\unskip}%
%    \global\letter!height!reference\htdp\scratchbox
%    \box\scratchbox}

\defineletterelement[\v!reference][\v!a]
  {\setbox\scratchbox\hbox\!!to\hsize
     {\getcommacommandsize[\csname\????ls\currentcorrespondenceelement\c!list\endcsname]%
      \ifnum\commalistsize<\plustwo\hfill\fi
      \processcommacommand[\csname\????ls\currentcorrespondenceelement\c!list\endcsname]\formatreferencelista\unskip}%
   \ifx\currentcorrespondenceelement\v!reference\global\letter!height!reference\htdp\scratchbox\fi
   \box\scratchbox}

\startsetups[\v!letter:\v!reference:\v!a]

\setupletterstyle
  [\v!reference]
  [\c!hoffset=\backspace,
   \c!voffset=\dimexpr\letterstylevalue{\v!address\v!layer}\c!voffset+\letterstylevalue{\v!address\v!frame}\c!height+\plusthree\c!mm\relax,
   \c!width=\textwidth]

\setupletterstyle
  [\v!firstpage]
  [\c!topspace=\dimexpr\letterstylevalue{\v!reference\v!layer}\c!voffset+\letterstylevalue\v!reference\c!spaceafter+\letter!height!reference\relax]

\stopsetups

%D This is the alternative b, you could use it if you want to place the information
%D in a infoblock not just a simple line, it is also better suited if you want to
%D place more infomration.

\long\def\formatreferencelistb#1%
  {\bgroup
   \doifelse{#1}\v!line
     {\blank[\v!line]}
     {\hbox
        {\doattributes{\????ld#1}\c!titlestyle\c!titlecolor
           {\labeltext{\v!letter:#1}\lettervalue{#1\c!separator}}%
         \doattributes{\????ld#1}\c!textstyle\c!textcolor
           {\lettervalue{#1}}}}%
   \egroup}

% \defineletterelement[\v!reference][\v!b]
%   {\vtop % why not \vbox?
%      {\processcommacommand[\@@@@lsreferencelist]\formatreferencelistb}}

\defineletterelement[\v!reference][\v!b]
  {\vtop{\processcommacommand[\csname\????ls\currentcorrespondenceelement\c!list\endcsname]\formatreferencelistb}}

\startsetups[\v!letter:\v!reference:\v!b]

\setupletterstyle
  [\v!reference]
  [\v!layer]
  [\c!hoffset=125.7mm,
   \c!voffset=\letterstylevalue{\v!address\v!layer}\c!voffset]

\setupletterstyle
  [\v!reference]
  [\v!frame]
  [\c!width=\dimexpr\paperwidth-\letterstylevalue{\v!reference\v!layer}\c!hoffset-\cutspace\relax,
   \c!height=\v!fit]

\stopsetups

%D The third alternative c could used, if you want to place just a single line
%D with text and nothing more, like your place and the date. You need only the
%D following two lines in your document.
%D 
%D \starttyping
%D \setupletter[alternative=c,list=reference]
%D \setupletter[reference=\rightaligned{Place, \currentdate}]
%D \stoptyping

\long\def\formatreferencelistc#1%
  {\bgroup
   \convertargument#1\to\ascii
   \doattributes{\????ld\ascii}\c!textstyle\c!textcolor
     {\lettervalue\ascii}%
   \egroup}

% \defineletterelement[\v!reference][\v!c]
%   {\hbox\!!to\hsize
%      {\processcommacommand[\@@@@lsreferencelist]\formatreferencelistc}}

\defineletterelement[\v!reference][\v!c]
  {\hbox\!!to\hsize
     {\processcommacommand[\csname\????ls\currentcorrespondenceelement\c!list\endcsname]\formatreferencelistc}}

\startsetups[\v!letter:\v!reference:\v!c]

\setups[\v!letter:\v!reference:\v!a]

\stopsetups

%D Alternative d, text is placed in a block like alternative bit the text
%D is put in a table.

\long\def\doformatreferencelistd#1%
  {\doifelse{#1}\v!line
     {\NC\NC\NC\NR} % why did \TB not work?
     {\NC \doattributes{\????ld#1}\c!titlestyle\c!titlecolor
            {\labeltext{\v!letter:#1}\lettervalue{#1\c!separator}}%
      \NC\doattributes{\????ld#1}\c!textstyle\c!textcolor{\lettervalue{#1}}
      \NC\NR}}

\def\formatreferencelistd#1%
  {\appendtoks\doformatreferencelistd{#1}\to\scratchtoks}

% \defineletterelement[\v!reference][\v!d]
%   {\vtop % why not \vbox?
%      {\scratchtoks\emptytoks
%       \processcommacommand[\@@@@lsreferencelist]\formatreferencelistd
%       \setuptabulate[\c!before=,\c!after=]%
%       \starttabulate[|l|l|]
%       \the\scratchtoks
%       \stoptabulate}}

\defineletterelement[\v!reference][\v!d]
  {\vtop
     {\scratchtoks\emptytoks
      \processcommacommand[\csname\????ls\currentcorrespondenceelement\c!list\endcsname]\formatreferencelistd
      \setuptabulate[\c!before=,\c!after=]%
      \starttabulate[|l|l|]
      \the\scratchtoks
      \stoptabulate}}

\startsetups[\v!letter:\v!reference:\v!d]

\setupletterstyle
  [\v!reference]
  [\v!layer]
  [\c!hoffset=125.7mm,
   \c!voffset=\letterstylevalue{\v!address\v!layer}\c!voffset]

\setupletterstyle
  [\v!reference]
  [\v!frame]
  [\c!width=\dimexpr\paperwidth-\letterstylevalue{\v!reference\v!layer}\c!hoffset-\cutspace\relax,
   \c!height=\v!fit]

\stopsetups

%D Alternative e, nearly the same as a but you could control the width of the
%D fields with the width key for \tex{setupletter}.

\long\def\doformatreferenceliste#1%
  {\def\\{\egroup\hbox\bgroup}%
   \setupinterlinespace\hbox\bgroup#1\egroup\par}

\long\def\formatreferenceliste#1%
  {\bgroup
   \convertargument#1\to\ascii
   \doifelselettervalue{\ascii\c!width}
     {\hbox\!!to\lettervalue{\ascii\c!width}}
     {\hbox}
     {\vbox
        {\vbox{\doattributes{\????ld\ascii}\c!titlestyle\c!titlecolor
           {\doformatreferenceliste{\labeltext{\v!letter:\ascii}}}}
         \vtop{\doattributes{\????ld\ascii}\c!textstyle\c!textcolor
           {\doformatreferenceliste{\lettervalue\ascii}}}}}%
   \egroup}

% \defineletterelement[\v!reference][\v!e]
%   {\hbox\!!to\hsize
%      {\processcommacommand[\@@@@lsreferencelist]\formatreferenceliste\hss}}

\defineletterelement[\v!reference][\v!e]
  {\hbox\!!to\hsize
     {\processcommacommand[\csname\????ls\currentcorrespondenceelement\c!list\endcsname]\formatreferenceliste\hss}}

\startsetups[\v!letter:\v!reference:\v!e]

\setups[\v!letter:\v!reference:\v!a]

\stopsetups

%D The alternative \mono{none} could be used to disable the reference.
%D 
%D The advantage is to change only the list alternative to nothing, another
%D method to get this result to use alternative c and remove all values from
%D the reference but the none key is better.

\resetletterelement[\v!reference][\v!none]

\startsetups[\v!letter:\v!reference:\v!none]

  % Use the topspace value from the style file

\stopsetups

%D \subject{Letter environment}
%D 
%D \macros
%D   {startletter}
%D 
%D The main macro in this file, it is used to write the letter content.
%D It is also possible to set the address and a few other values like
%D the opening and closing with the optional argument, the values are
%D local in this case and not global like the values you could set with
%D \tex{setupletter}.

\newtoks\letter!local!commands

\chardef\letterenvironmentmode\zerocount

\def\startletter
  {\begingroup
   \dodoubleempty\dostartletter}

\def\dostartletter[#1][#2]%
  {\ifcase\letterenvironmentmode\relax
     \@EA\dostartbufferletter
   \else
     \@EA\dostartcontentletter
   \fi[#1][#2]}

\long\def\dostartcontentletter[#1][#2]#3\stopletter
  {\ifsecondargument
     \getparameters[\????ld][#1]%
     \doifundefinedelse{\????ld\????ld#2}
       {\setvalue{\????ld\c!toaddress}{#2}}
       {\setvalue{\????ld\c!toaddress}{\getvalue{\????ld\????ld#2}}}%
   \else\iffirstargument
     \doifassignmentelse{#1}
       {\getparameters[\????ld][#1]}
       {\doifundefinedelse{\????ld\????ld#1}
          {\setvalue{\????ld\c!toaddress}{#1}}
          {\setvalue{\????ld\c!toaddress}{\getvalue{\????ld\????ld#1}}}}%
   \fi\fi
   \setbuffer[lettercontent]#3\endbuffer
   \processlettervalues
   \directsetup{\v!letter:\v!place}%
   \endgroup}

\def\dostartbufferletter[#1][#2]%
  {\def\stopletter
     {\processlettervalues
      \directsetup{\v!letter:\v!place}%
      \endgroup}
   \ifsecondargument
     \getparameters[\????ld][#1]%
     \doifundefinedelse{\????ld\????ld#2}
       {\setvalue{\????ld\c!toaddress}{#2}}
       {\setvalue{\????ld\c!toaddress}{\getvalue{\????ld\????ld#2}}}%
   \else\iffirstargument
     \doifassignmentelse{#1}
       {\getparameters[\????ld][#1]}
       {\doifundefinedelse{\????ld\????ld#1}
          {\setvalue{\????ld\c!toaddress}{#1}}
          {\setvalue{\????ld\c!toaddress}{\getvalue{\????ld\????ld#1}}}}%
   \fi\fi
   \dostartbuffer[lettercontent][startletter][stopletter]}

\def\processlettervalues
  {\globalletempty\letter!list!descriptions
   \global\letter!local!commands\emptytoks
   \def\opening##1{\doglobal\appendtoks\setvalue{\????ld\c!opening   }{##1}\to\letter!local!commands}%
   \def\closing##1{\doglobal\appendtoks\setvalue{\????ld\c!closing   }{##1}\to\letter!local!commands}%
   \def\ps     ##1{\doglobal\appendtoks\setvalue{\????ld\c!postscript}{##1}\to\letter!local!commands\doglobal\appendtocommalist\c!postscript\letter!list!descriptions}%
   \def\cc     ##1{\doglobal\appendtoks\setvalue{\????ld\c!copy      }{##1}\to\letter!local!commands\doglobal\appendtocommalist\c!copy      \letter!list!descriptions}%
   \def\encl   ##1{\doglobal\appendtoks\setvalue{\????ld\c!enclosure }{##1}\to\letter!local!commands\doglobal\appendtocommalist\c!enclosure \letter!list!descriptions}%
   \setbox\scratchbox\hbox{\getbuffer[lettercontent]}%
   \flushtoks\letter!local!commands}

\def\gobblelettervalues
  {\def\dogobblelettervalues##1{\letcsnamecs\csname##1\endcsname\gobbleoneargument}%
   \processcommalist[\c!opening,\c!closing,\c!ps,\c!cc,\c!encl]\dogobblelettervalues}

%D \macros
%D   {startlettercontent}
%D 
%D The letter content is saved in the value content, although I could
%D place it in the corresponding I prefer this solution because you could
%D now use it in your own macros and redefine the content setups to your
%D own wishes.

\setupletter
  [\c!content={\getbuffer[lettercontent]}]

\def\startlettercontent
  {\dostartbuffer[lettercontent][startlettercontent][stoplettercontent]}

%D After the definition of all macros I could now put the content
%D in the corresponding setups, this is only important if you want
%D to define your own layout for header, address etc.

\defineletterelement[\v!head][\v!a]
  {\lettervalue\c!fromname
   \doiflettervalue\c!fromname\\
   \lettervalue\c!fromaddress}

\setvalue{@@head@@\c!rule\v!no    }{\!!doneafalse\!!donebfalse}
\setvalue{@@head@@\c!rule\v!none  }{\!!doneafalse\!!donebfalse}
\setvalue{@@head@@\c!rule\v!off   }{\!!doneafalse\!!donebfalse}
\setvalue{@@head@@\c!rule\v!top   }{\!!doneatrue              }
\setvalue{@@head@@\c!rule\v!before}{\!!doneatrue              }
\setvalue{@@head@@\c!rule\v!bottom}{\!!donebtrue              }
\setvalue{@@head@@\c!rule\v!after }{\!!donebtrue              }
\setvalue{@@head@@\c!rule\v!yes   }{\!!donebtrue              }
\setvalue{@@head@@\c!rule\v!on    }{\!!donebtrue              }

\def\doletterelementheadrule
  {\!!doneafalse
   \!!donebfalse
   \def\dodoletterelementheadrule##1{\csname @@head@@\c!rule##1\endcsname}%
   \processcommacommand[\letterstylevalue\v!head\c!fromrule]\dodoletterelementheadrule}

\defineletterelement[\v!head][\v!left]
  {\normalhbox
     {\framed[frame=off,location=bottom,align=right,width=\hsize]
        {\doletterelementheadrule
         \dostartattributes{\????ld\c!fromname}\c!style\c!color
         \lettervalue\c!fromname
         \if!!donea
           \doifelselettervalue\c!fromlogo
             {\setbox\scratchbox\hbox{\lettervalue\c!fromlogo}%
              \scratchdimen\dimexpr\letterstylevalue\v!head\c!rulewidth-\wd\scratchbox\relax}
             {\scratchdimen\letterstylevalue\v!head\c!rulewidth}%
           \vskip-.5\lineheight\blackrule
             [width=\scratchdimen,
              height=\letterstylevalue\v!head\c!rulethickness,
              color=\letterstylevalue\v!head\c!rulecolor]%
         \fi
         \dostopattributes
         \\
         \dostartattributes{\????ld\c!fromaddress}\c!style\c!color
         \lettervalue\c!fromaddress
         \doiflettervalue\c!fromphone{\\\lettervalue\c!fromphone}%
         \doiflettervalue\c!fromfax  {\\\lettervalue\c!fromfax  }%
         \doiflettervalue\c!frommail {\\\lettervalue\c!frommail }%
         \doiflettervalue\c!fromurl  {\\\lettervalue\c!fromurl  }%
         \if!!doneb
           \ifzeropt\letterstylevalue\v!head\c!rulewidth
             \scratchdimen\hsize
           \else
             \scratchdimen\letterstylevalue\v!head\c!rulewidth
           \fi
           \vskip-.5\lineheight\blackrule
             [width=\scratchdimen,
              height=\letterstylevalue\v!head\c!rulethickness,
              color=\letterstylevalue\v!head\c!rulecolor]%
         \fi
         \dostopattributes}%
      \doiflettervalue\c!fromlogo{\llap{\lettervalue\c!fromlogo}}}}%

\defineletterelement[\v!head][\v!middle]
  {\normalhbox
     {\framed[frame=off,location=bottom,align=middle,width=\hsize]
        {\doletterelementheadrule
         \dostartattributes{\????ld\c!fromname}\c!style\c!color
         \lettervalue\c!fromname
         \if!!donea
           \ifzeropt\letterstylevalue\v!head\c!rulewidth
             \scratchdimen\hsize
           \else
             \scratchdimen\letterstylevalue\v!head\c!rulewidth
           \fi
           \vskip-.5\lineheight\blackrule
             [width=\scratchdimen,
              height=\letterstylevalue\v!head\c!rulethickness,
              color=\letterstylevalue\v!head\c!rulecolor]%
         \fi
         \dostopattributes
         \\
         \dostartattributes{\????ld\c!fromaddress}\c!style\c!color
         \lettervalue\c!fromaddress
         \doiflettervalue\c!fromphone{\\\lettervalue\c!fromphone}%
         \doiflettervalue\c!fromfax  {\\\lettervalue\c!fromfax  }%
         \doiflettervalue\c!frommail {\\\lettervalue\c!frommail }%
         \doiflettervalue\c!fromurl  {\\\lettervalue\c!fromurl  }%
         \if!!doneb
           \ifzeropt\letterstylevalue\v!head\c!rulewidth
             \scratchdimen\hsize
           \else
             \scratchdimen\letterstylevalue\v!head\c!rulewidth
           \fi
           \vskip-.5\lineheight\blackrule
             [width=\scratchdimen,
              height=\letterstylevalue\v!head\c!rulethickness,
              color=\letterstylevalue\v!head\c!rulecolor]%
         \fi
         \dostopattributes}}}

\defineletterelement[\v!head][\v!right]
  {\normalhbox
     {\doiflettervalue\c!fromlogo{\rlap{\lettervalue\c!fromlogo}}%
      \framed[frame=off,location=bottom,align=left,width=\hsize]
        {\doletterelementheadrule
         \dostartattributes{\????ld\c!fromname}\c!style\c!color
         \lettervalue\c!fromname
         \if!!donea
           \ifzeropt\letterstylevalue\v!head\c!rulewidth
             \scratchdimen\hsize
           \else
             \doifelselettervalue\c!fromlogo
               {\setbox\scratchbox\hbox{\lettervalue\c!fromlogo}%
                \scratchdimen\dimexpr\letterstylevalue\v!head\c!rulewidth-\wd\scratchbox\relax}
               {\scratchdimen\letterstylevalue\v!head\c!rulewidth}%
           \fi
           \vskip-.5\lineheight\blackrule
             [width=\scratchdimen,
              height=\letterstylevalue\v!head\c!rulethickness,
              color=\letterstylevalue\v!head\c!rulecolor]%
         \fi
         \dostopattributes
         \\
         \dostartattributes{\????ld\c!fromaddress}\c!style\c!color
         \\\lettervalue\c!fromaddress
         \doiflettervalue\c!fromphone{\\\lettervalue\c!fromphone}%
         \doiflettervalue\c!fromfax  {\\\lettervalue\c!fromfax  }%
         \doiflettervalue\c!frommail {\\\lettervalue\c!frommail }%
         \doiflettervalue\c!fromurl  {\\\lettervalue\c!fromurl  }%
         \if!!doneb
           \ifzeropt\letterstylevalue\v!head\c!rulewidth
             \scratchdimen\hsize
           \else
             \scratchdimen\letterstylevalue\v!head\c!rulewidth
           \fi
           \vskip-.5\lineheight\blackrule
             [width=\scratchdimen,
              height=\letterstylevalue\v!head\c!rulethickness,
              color=\letterstylevalue\v!head\c!rulecolor]%
         \fi
         \dostopattributes}}}

\startsetups[\v!letter:\v!head]
\def\\{\letterstylevalue\v!head\c!separator}
\executeifdefined{\v!letter:\v!head:\@@@@lsheadalternative}{\letterelement[\v!head][\v!a]}
\stopsetups

\startsetups[\v!letter:\v!foot]
\executeifdefined{\v!letter:\v!foot:\@@@@lsfootalternative}\donothing
\stopsetups

\startsetups[\v!letter:\v!nexthead]
\executeifdefined{\v!letter:\v!nexthead:\@@@@lsnextheadalternative}\donothing
\stopsetups

\startsetups[\v!letter:\v!nextfoot]
\executeifdefined{\v!letter:\v!nextfoot:\@@@@lsnextfootalternative}\donothing
\stopsetups

\defineletterelement[\v!nexthead][\v!fullblock]
  {\hbox\!!to\hsize
     {\rlap{\lettervalue\c!toname}%
      \midaligned{\pagenumber}%
      \llap{\framed[\c!frame=\v!off,\c!location=\v!top,\c!align=\v!left]
        {\lettervalue\c!date   \\
         \lettervalue\c!reference}}}}

\defineletterelement[\v!nexthead][\v!hanging]
  {\hbox\!!to\hsize
     {\framed[\c!frame=\v!off,\c!location=\v!top,\c!align=v!right]
       {\lettervalue\c!toname    \\
        \lettervalue\c!date      \\
        \lettervalue\c!reference \\
        \labeltext\c!page\pagenumber}}\hss}

\defineletterelement[\v!nexthead][\v!semiblock]
  {\hbox\!!to\hsize
     {\rlap{\lettervalue\c!toname}%
      \midaligned{\pagenumber}%
      \llap{\lettervalue\c!date}}}

\copyletterelement[\v!nexthead][\v!simplified][\v!fullblock]
\copyletterelement[\v!nexthead][\v!modified  ][\v!hanging  ]

%D \subject{Addressee field}
%D 
%D The address field is separated into two different fields.
%D The upper field is meant for dispatch information, the official height
%D in germany is 3 lines but this would lead to different heights dependent
%D of the font size and the fonts own height. The lower field contains the
%D name and address of the receiver and has a height of 6 lines in germany.
%D This value will lead to the same problem as the upper field, because the
%D whole address field has a fixed height and both field should fit into
%D this space. I solved this problem by assinging the upper field 1/3 of the
%D address height and the lower field 2/3 of the address height.
%D 
%D If you hace problem to put all information in the limited space you could
%D try to reduce the font size or reduce the interlinespace in the field.

\presetlocalframed[\????ls\v!dispatch]
\presetlocalframed[\????ls\v!addressee]

\startsetups[\v!letter:\v!place:\v!dispatch]

  \localframed
    [\????ls\v!dispatch]
    {\doadaptleftskip {\letterstylevalue\v!dispatch\c!leftmargin}%
     \doadaptrightskip{\letterstylevalue\v!dispatch\c!rightmargin}%
     \doattributes{\????ls\v!dispatch}\c!style\c!color{\directsetup{\v!letter:\v!address:\v!dispatch}}}

\stopsetups

\startsetups[\v!letter:\v!place:\v!addressee]

  \localframed
    [\????ls\v!addressee]
    {\doadaptleftskip {\letterstylevalue\v!addressee\c!leftmargin}%
     \doadaptrightskip{\letterstylevalue\v!addressee\c!rightmargin}%
     \doattributes{\????ls\v!addressee}\c!style\c!color{\directsetup{\v!letter:\v!address:\v!content}}}

\stopsetups

\defineletterelement[\v!address][\v!a]
  {\doif\@@@@lsoptiondispatch \v!yes{\directsetup{\v!letter:\v!place:\v!dispatch }}%
   \doif\@@@@lsoptionaddressee\v!yes{\directsetup{\v!letter:\v!place:\v!addressee}}}

\startsetups[\v!letter:\v!address]
\offinterlineskip\endgraf
\executeifdefined{\v!letter:\v!address:\@@@@lsaddressalternative}{\letterelement[\v!address][\v!a]}%
\stopsetups

\startsetups[\v!letter:\v!address:\v!dispatch]
\lettervalue\c!dispatch
\stopsetups

\startsetups[\v!letter:\v!address:\v!content]
\def\\{\letterstylevalue\v!address\c!separator}%
\lettervalue\c!toname
\doiflettervalue\c!toname\\
\lettervalue\c!toaddress
\stopsetups

%D The following setups shouldn't be changed ar you will loose information
%D in the output.
%D 
%D The reference line is choosen with the alternative key or if you set
%D a not defined alternative the definition a is choosen.

\startsetups[\v!letter:\v!reference]
\executeifdefined{\v!letter:\v!reference:\@@@@lsreferencealternative}{\letterelement[\v!reference][\v!a]}
\stopsetups

\resetletterelement[\v!location][\v!a]

\setvalue{\v!letter:\v!location:\v!french}%
  {\lettervalue\c!place
   \doiflettervalue\c!place{\lettervalue{\c!place\c!separator}}%
   \lettervalue\c!date}

\startsetups[\v!letter:\v!location]
\executeifdefined{\v!letter:\v!location:\@@@@lslocationalternative}{\letterelement[\v!location][\v!a]}
\stopsetups

\startsetups[\v!letter:\v!title]
\doifelselettervalue\c!title
  {\lettervalue\c!title}
  {\doiflettervalue\c!attention
     {\labeltext{\v!letter:\c!attention}\lettervalue\c!attention}}
\stopsetups

\startsetups[\v!letter:\v!subject]
\def\\{\letterstylevalue\v!subject\c!separator}%
\labeltext{\v!letter:\c!subject}\lettervalue\c!subject
\stopsetups

\defineletterelement[\v!opening][\v!a]
  {\doifelselettervalue\c!opening
     {\lettervalue\c!opening}
     {\doiflettervalue\c!salutation
        {\lettervalue\c!salutation}}}

\defineletterelement[\v!opening][\v!french]
  {\ExpandSecondAfter\doifsomething{\letterstylevalue\v!option\c!indenting}
     {\setupindenting[\@@@@lsoptionindenting]}%
   \letterelement[\v!opening][\v!a]}

\startsetups[\v!letter:\v!opening]
\executeifdefined{\v!letter:\v!opening:\@@@@lsopeningalternative}{\letterelement[\v!opening][\v!a]}
\stopsetups

\startsetups[\v!letter:\v!content]
\gobblelettervalues\lettervalue\c!content
\stopsetups

%D \subject{Closing and appendices}
%D 
%D It is possible to attach a signature to the closing command, before the signature
%D a skip is inserted but only if the the signature key has a value. The height of the
%D closing environment itself has a height of 4 lines to provide a free space for your
%D own handwritten signature and to have a little bit space between the closing text
%D and the appendices.

\defineletterelement[\v!closing][\v!a]
  {\lettervalue\c!closing
   \doiflettervalue\c!signature{\letterstylevalue\v!closing\c!inbetween}%
   \lettervalue\c!signature}

\defineletterelement[\v!closing][\v!french]
  {\ExpandSecondAfter\doifsomething{\letterstylevalue\v!option\c!indenting}
     {\setupindenting[\@@@@lsoptionindenting,\v!first]}%
   \lettervalue\c!closing
   \doiflettervalue\c!signature{\letterstylevalue\v!closing\c!inbetween}%
   \raggedcenter\doadaptleftskip{.5\textwidth}% quick and dirty
   \lettervalue\c!signature\endgraf}

\defineletterelement[\v!closing][\v!simplified]
  {\doiflettervalue\c!signature{\letterstylevalue\v!closing\c!inbetween}%
   \lettervalue\c!signature}

\startsetups[\v!letter:\v!closing]
\def\\{\letterstylevalue\v!closing\c!separator}
\executeifdefined{\v!letter:\v!closing:\@@@@lsclosingalternative}{\letterelement[\v!closing][\v!a]}
\stopsetups

\startsetups[\v!letter:\v!appendices]
\let\\\crlf
\doflushletterdescription
\stopsetups

\dodefineletterdescription[\v!enclosure]

\startsetups[\v!letter:\v!enclosure]
\lettervalue\c!enclosure
\stopsetups

\dodefineletterdescription[\v!copy]

\startsetups[\v!letter:\v!copy]
\lettervalue\c!copy
\stopsetups

\dodefineletterdescription[\v!postscript]

\startsetups[\v!letter:\v!postscript]
\lettervalue\c!postscript
\stopsetups

\defineletterelement[\v!backaddress][\v!yes]
  {\lettervalue\c!fromname
   \doiflettervalue\c!fromaddress\\
   \lettervalue\c!fromaddress}

\resetletterelement[\v!backaddress][\v!no]

\defineletterelement[\v!backaddress][\v!auto]
  {\doifelselettervalue\c!backaddress
     {\lettervalue\c!backaddress}
     {\lettervalue\c!fromname
      \doiflettervalue\c!fromaddress\\
      \lettervalue\c!fromaddress}}

\startsetups[\v!letter:\v!backaddress]
\def\\{\letterstylevalue\c!backaddress\c!separator}
\executeifdefined{\v!letter:\v!backaddress:\@@@@lsbackaddressalternative}{\letterelement[\v!backaddress][\v!no]}
\stopsetups

%D To prevent a pagebreak between the last line of the text and
%D the siganture a nonbreakable vertical space is necessary.
%D The vertical space is inserted in the style file with the normal
%D before and after commands where we control the distance between
%D the elements.

\defineblankmethod [\v!nobreak] {\penalty\plustenthousand}
\defineblankmethod [\v!endgraf] {\endgraf                }

%D \subject{Additional settings}
%D 
%D I set alternative a as default value for alternative, the only content
%D is the date with a label. f you dont want a label choose alternative c
%D or change the label.

\startsetups[\v!letter:\v!optimize]

  \startnointerference % trial typesetting to get the heigth of the reference line
    \dontcomplain
    \let\currentcorrespondenceelement\v!reference
    \executeifdefined{\v!letter:\v!reference:\@@@@lsreferencealternative}\donothing
  \stopnointerference

  \setups[\v!letter:\v!reference:\@@@@lsreferencealternative]

\stopsetups

%D We have at the moment only the values from the core module, I use the settings
%D from the dinb file as default settings, you could replace them in your own
%D document but I won't change the default style.
%D 
%D The labels are stored in a common file, you could use them in your own interface
%D but you have to live with my names.

\useletterstyle    [dinb]      % layout
\useletterextension[label]     % labels
\useletterextension[addrentry] % database

\protect \endinput