Re: [NTG-context] horizontal position

5 Nov 2009

      Wolfgang Schuster wrote:
...
Hi,
whats the best method to determine the current horizontal position in 
the text because
I want to write a commands which behaves different whether it appears at 
the begin, end
or in the middle of the text.
pdfTeX’s savepos information are not the best method because it could 
take (in the worst
case) to many when i have many macros in a paragraph, display math mode 
can give me
the information i want (in combination with savepos information) but i 
wan't to know if
there a side effects.
Example:
\def\position
  {\bgroup
   \forgetdisplayskips
   \everymath{}%
   \everydisplay{}%
   $$\xdef\theposition{\the\predisplaysize}$$%
   \vskip-2\baselineskip
   \hskip\dimexpr\theposition-2em\relax
   \ifhmode\aftergroup\space\fi\aftergroup\theposition
   \egroup}
\starttext
text text \position{} text
text text text text text text \position{} text
\stoptext
you also need to compensate for usage like

\startnarrower
text text \position{} text

text text text text text text \position{} text
\stopnarrower

and other alignment cases; also, you values look wrong.

so, why not

\starttext

\xypos{first}x \hfill x\xypos{middle}x \hfill x\xypos{last}

\MPx{text:1}

\MPw{text:1}

\MPx{first}
\MPx{middle}
\MPx{last}

\stoptext

so, simple pos's (xy)

in mkiv the amount of them is no problem as they are stored at the lua end

test:

\def\position
   {\bgroup
    \forgetdisplayskips
    \everymath{}%
    \everydisplay{}%
    $$\xdef\theposition{\the\predisplaysize}$$%
    \vskip-2\baselineskip
    \hskip\dimexpr\theposition-2em\relax
    \ifhmode\aftergroup\space\fi\aftergroup\theposition
    \egroup}

\starttext

text text \position{} text

text text text text text text \position{} text

\newcount\MyPos

\def\position
   {\global\advance\MyPos\plusone
    \xypos{MyPos:\the\MyPos}%
    \the\dimexpr\MPx{MyPos:\the\MyPos}-\MPx{text:1}\relax}

text text \position{} text

text text text text text text \position{} text

\blackrule[width=48pt]

\blackrule[width=146pt]

Hans

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
      tel: 038 477 53 69 | fax: 038 477 53 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
-----------------------------------------------------------------