% \iffalse
% This is textpos.dtx, which allows you to place text (and graphics)
% anywhere on the LaTeX page.  It's useful for posters.
%
%% This software is copyright, 1999, 2001, 2002, Norman Gray. 
%% 
%% This program is free software; you can redistribute it and/or
%% modify it under the terms of the GNU General Public License
%% as published by the Free Software Foundation; either version 2
%% of the License, or (at your option) any later version.
%% 
%% This program is distributed in the hope that it will be useful,
%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%% GNU General Public License for more details.
%% 
%% You should have received a copy of the GNU General Public License
%% along with this program; if not, write to the Free Software
%% Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
%% 
%% Author: Norman Gray, norman@astro.gla.ac.uk.
%% Department of Physics and Astronomy, University of Glasgow, UK
%%
%% See the file LICENCE for a copy of the GPL.
%% You can also find an online copy at http://www.gnu.org/copyleft/gpl.html .
%
%<+package|driver|example>
%%% Source: $Id: textpos.dtx,v 1.8 2002/07/01 09:55:19 norman Exp $
\def\ParseRCSDate$#1: #2 #3 ${\def\TP@Date{#2}}
\ParseRCSDate$Date: 2002/07/01 09:55:19 $
\def\filename{textpos}
\def\fileversion{1.2b}  %%VERSION%%
\def\filedate{\TP@Date}
\def\docdate{\TP@Date}
%<+package>\NeedsTeXFormat{LaTeX2e}
%<+package>\ProvidesPackage{textpos}[\filedate\space v\fileversion]
%<+package>\typeout{Package: `textpos' \fileversion\space<\filedate>}
%
%<*driver>
\documentclass{ltxdoc}
\title{Textpos: absolute positioning of text on the page%
  \thanks{This file has version number \fileversion, last revised
  \filedate}}
\author{Norman Gray\\(\texttt{norman@astro.gla.ac.uk})}
\date{Version \fileversion, \filedate}
\newcommand\Lopt[1]{\textsf {#1}}
\newcommand\file[1]{\texttt {#1}}
\newcommand\Lcount[1]{\textsl {\small#1}}
\newcommand\pstyle[1]{\textsl {#1}}
% Make command strings easier to write
{\catcode`\<=\active \gdef<#1>{\meta{#1}}}
\def\cmd{\begingroup
  \catcode`\\=12 \catcode`\{=12 \catcode`\}=12 
  \catcode`\<=\active \catcode`\|=12
  \docmd}
\def\docmd|#1|{\texttt{#1}\endgroup}
%% \url macro (url.sty does this better)
\def\setpathdots{\discretionary{.}{}{.}}
\def\setpathslash{\discretionary{/}{}{/}}
{\catcode`\.=\active 
 \catcode`\/=\active 
  \gdef\pathcats{%
    \catcode`\%=12      \catcode`\~=12 
    \catcode`\.=\active  \let.\setpathdots
    \catcode`\/=\active \let/\setpathslash
    \catcode`\#=12      \catcode`\_=12}%
    }
\def\setpath#1{\ttfamily <\nobreak #1\nobreak>\endgroup}
\def\url{\begingroup\pathcats\setpath}
%\RecordChanges
\OnlyDescription
\begin{document}
\maketitle
\DocInput{textpos.dtx}
\end{document}
%</driver>
%
% \fi
%
%
%
% \CheckSum{381}
%% \CharacterTable
%%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
%%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
%%   Digits        \0\1\2\3\4\5\6\7\8\9
%%   Exclamation   \!     Double quote  \"     Hash (number) \#
%%   Dollar        \$     Percent       \%     Ampersand     \&
%%   Acute accent  \'     Left paren    \(     Right paren   \)
%%   Asterisk      \*     Plus          \+     Comma         \,
%%   Minus         \-     Point         \.     Solidus       \/
%%   Colon         \:     Semicolon     \;     Less than     \<
%%   Equals        \=     Greater than  \>     Question mark \?
%%   Commercial at \@     Left bracket  \[     Backslash     \\
%%   Right bracket \]     Circumflex    \^     Underscore    \_
%%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%%   Right brace   \}     Tilde         \~}
%
% \changes{v1.0a}{1998/04/29}{Robin Fairbairns pointed out and adjusted errors in the documentation}
% \changes{v1.0b}{1998/04/30}{Reorganised documentation -- properly this time}
% \changes{v1.1b}{1999/03/05}{Added note to the effect that everyshi can be found at CTAN}
% \changes{v1.1c}{1999/03/09}{Corrected checksum (again!)}
% \changes{v1.1d}{1999/06/06}{Clarified copyright and licence status}
%
%
% This package facilitates placing boxes at absolute positions on the
% \LaTeX\ page.  There are several reasons why this might be useful, but
% the main one (or at least my motivating one) is to help produce a
% large-format conference poster.  
%
% This package provides a single environment, which contains the text
% (or graphics, or table, or whatever) which is to be placed on the
% page, and which specifies where it is to be placed.
%
% The package tries not to get in the way.  That is, you should be
% able to use most of the apparatus of \LaTeX\ in your poster, such as
% section headings, citations, graphics inclusion, and so on.  Please
% let me know if you experience problems in this respect.
%
% This package requires the services of Martin Schr\"oder's package
% \texttt{everyshi}.  You will need to download this package from CTAN
% first.  See
% \url{http://www.tex.ac.uk/tex-archive/macros/latex/contrib/supported/ms/} 
% or one of the other CTAN hosts.
%
% This software is copyright, 1999, 2001, 2002, Norman Gray.  It is released under
% the terms of the GNU General Public Licence.  See the copyright
% declaration at the top of file \texttt{textpos.dtx}, and the file
% \texttt{LICENCE} for the licence conditions.  You can find an
% online copy of the GPL at \url{http://www.gnu.org/copyleft/gpl.html}.
%
% \section{Description}
%
% The environment is used as follows
% \DescribeEnv{textblock}
% \begin{quote}\begin{raggedright}
% \cmd|\begin{textblock}{<hsize>}(<hpos>,<vpos>)|\\
% text...\\
% |\end{textblock}|
% \end{raggedright}
% \end{quote}
% The \meta{hsize} and \meta{hpos} arguments are given in units of a
% module |\TPHorizModule|, and \meta{vpos} is given in units of a
% module |\TPVertModule|.  You set these using
% the command 
% \cmd|\setlength{\TPHorizModule}{<dimen>}|,
% and similarly for |\TPVertModule|.
% The arguments may be any dimension, and you may use the modules as
% units elsewhere in your document if you wish to, for example in
% \texttt{\bslash makebox[2\bslash TPHorizModule]\{gnus\}}.  The text in the
% environment will be set in a 
% box \textit{hsize} modules wide, and placed on the page with its
% upper left corner at the position (\textit{hpos,vpos})
%
% \DescribeMacro{\TPGrid}
% You will often wish to set up a grid on your page.  Rather than
% calculate and specify the two modules explicitly, you can set up the
% grid with a command
% \cmd|\TPGrid{<nhoriz>}{<nvert>}|, which sets
% |\TPHorizModule| to be \meta{paper
% width}/\meta{nhoriz}, and |\TPVertModule| to be
% \meta{paper height}/\meta{nvert}.  This takes an optional pair of
% arguments, which specify a coordinate, as follows.
% \begin{quote}\begin{raggedright}
%   \cmd|\TPGrid[<x>,<y>]{<nhoriz>}{<nvert>}|
% \end{raggedright}\end{quote}
% If these are present, then the modules are set
% up to leave a border of the given size around the grid.  That is, 
% |\TPHorizModule| is set to be (\meta{paper
% width}${}-{}2$\meta{x})/\meta{nhoriz}, and similarly for
% |\TPVertModule|.  Further, if the package was given
% the `absolute' option, then the text origin is set to be
% (\meta{x},\meta{y}) through a call to |\textblockorigin|
% (see below).
%
% You may give a optional argument to the \texttt{textblock}
% environment, specifying which point in the box
% is to be placed at the specified point:
% \begin{quote}
% \begin{raggedright}
% \cmd|\begin{textblock}{<hsize>}[<ho>,<vo>](<hpos>,<vpos>)|\\
% text...\\
% |\end{textblock}|
% \end{raggedright}
% \end{quote}
% The coordinates \meta{ho} and \meta{vo} are fractions of the
% width and height of the text box, respectively, and state that the
% box is to be placed so that the
% point (\meta{ho},\meta{vo}) within the box is to be placed at the point
% (\meta{hpos},\meta{vpos}) on the page.  The default specification is
% [0,0], the top left of the box: [0,1] would be the bottom left, and
% [0.5,0.5] the middle.
%
% \DescribeEnv{textblock*}
% There is an alternative, starred, form of the textblock
% environment.  In the argument to the |{textblock*}| environment, the 
% block width, and the block position (but \emph{not} the
% specification of the block reference point) are given as absolute
% dimensions, rather than as numbers in units of the horizontal and
% vertical modules.  Thus
% \begin{quote}
% \begin{raggedright}
% \cmd|\begin{textblock*}{<hsize>}[<ho>,<vo>](<hpos>,<vpos>)|\\
% text...\\
% \cmd|\end{textblock*}|
% \end{raggedright}
% \end{quote}
% produces a textblock of the given size, where this time \meta{hsize},
% \meta{hpos} and \meta{vpos} are absolute dimensions, but \meta{ho}
% and \meta{vo} are pure-number offsets (that is, fractions of the
% width and height of the textblock), as above.
%
% Each textblock environment takes up zero space on the page (which
% means, by the way, that it cannot detect that it's overprinting or
% being overprinted), so you can (and typically will) use several of
% the environments in a row to scatter text all over the page.
%
% This package works in two modes, relative and absolute.  In the
% first one, the default, the block-positioning parameters in the
% \texttt{textblock} envirionment are taken to be relative to the
% current position on the page.  This will be appropriate if you are
% laying out text within a \texttt{figure} environment or the like.
% In this mode, you will typically give several \texttt{textblock}
% environments one after the other, so that they are all relative to
% the same point.
%
% If, however, your entire 
% document is to be laid out piece by piece (which is the case in the
% canonical use of the package, to lay out a poster), then you might
% want to be more sure of where the origin is.  In this case, you make
% the package work in its absolute mode, by invoking it with
% the `absolute' option: |\usepackage[absolute]{textpos}|.
% In this mode, all the block-positioning parameters are given
% relative to a single origin on the page.  By default, this is the
% top-left corner of the page, but you may change it with the 
% command \cmd|\textblockorigin{<hpos>}{<vpos>}|.
% Here \meta{hpos} and \meta{vpos} are dimensions such as `10mm',
% relative to the top-left corner of the paper.  You may use this
% command only if the package was invoked with the `absolute' option.
%
% The package is compatible with the \pstyle{calc} package, so that
% you may use calc-style expressions when specifying lengths.  Thus
% \begin{quote}
% \begin{raggedright}
% |\usepackage{calc}|\\
% |\textblockorigin{56.9055pt-10mm}{0pt+1cm}|\\
% |\begin{textblock*}{10mm+14cm}(0.3cm*5,10\TPVertModule+5mm)|\\
% text\dots\\
% |\end{textblock*}|\\
% \end{raggedright}
% \end{quote}
% Note that you can only use calc-style expressions where you would
% specify a length with units, such as the width and location
% arguments of |{textblock*}| or the arguments to |\textblockorigin|
% -- you can't use them when specifying a
% length in units of the horizontal and vertical modules, such as in
% the width and location arguments to the (unstarred) |{textblock}|
% environment.
%
% \subsection{Package options}
%
% There are several package options:
% \begin{description}
% \item[\Lopt{showboxes}]When you are laying things out, it can be
% useful to have the boxes drawn in for you.  This option draws a box
% fitting closely round the set text.
% \item[\Lopt{noshowtext}]This suppresses the display of the text in
% each block (so it's not really usable without the \Lopt{showboxes}
% option).  The resulting box will be the correct size, but empty,
% unless the |\textblocklabel| command has been given.  This
% can be useful when you are previewing a document.
% \item[\Lopt{absolute}]If this is present, then the positions on the
% \texttt{textblock} environment are taken to be absolute positions on
% the page.  See above.
% \item[\Lopt{overlay}]When using the absolute-position mode, the
% textblocks are placed under any other text on the page.  This is
% normally what you want, but if you have page contents, and they have
% something 
% which \emph{obscures} the textblocks (for example, a block of opaque
% colour), then the positioned textboxes disappear.  In this case,
% specify the option \Lopt{overlay}, to request that the positioned
% blocks of text overlay any other page contents, rather
% than being overlayed.
% \item[\Lopt{verbose}, \Lopt{quiet}]The package writes a few messages
% to the output, describing its calculations.  These are potentially
% irritating, so you can turn them off with the \Lopt{quiet} option or
% on with the \Lopt{verbose} option.  The default is currently
% \Lopt{verbose}, but this might change in future.
% \end{description}
%
% \subsection{Package parameters}
% \begin{raggedright}
% \begin{description}
% \item[\texttt{\bslash TPHorizModule}]
% \DescribeMacro{\TPHorizModule}
% The length unit which is used for the horizontal positioning and
% size parameters of the textblock environment.  Set it using
% the command \cmd|\setlength{\TPHorizModule}{<dimen>}| (or indeed
% |\addtolength|).
% The default is one sixteenth of the paper width.
% \item[\texttt{\bslash TPVertModule}]
% \DescribeMacro{\TPVertModule}
% The length unit which is used for the vertical positioning and
% size parameters of the textblock environment.  Set it using
% the command \cmd|\setlength{\TPVertModule}{<dimen>}| (or |\addtolength|). 
% The default is one sixteenth of the paper height.
% \item[\texttt{\bslash TPboxrulesize}]
% \DescribeMacro{\TPboxrulesize}
% When you use the \Lopt{showboxes} option,
% the lines drawn are of this width.  If this too small to show up
% when you are previewing your document, you may adjust the size using
% |\setlength| or |\addtolength|.  The default is 0.4pt. 
% \item[\texttt{\bslash textblocklabel}]
% \DescribeMacro{\textblocklabel}
% This may be used within any textblock
% environment.  It is ignored, unless the \Lopt{noshowtext} option has
% been specified, when it will be used to label the textblock it is
% inside.  Use: |\textblocklabel{Identifying text}|.
% \item[\texttt{\bslash showtextsize}]
% \DescribeMacro{\showtextsize}
% When |\textblocklabel| is being
% shown, the text appears in size |\showtextsize|, which is
% defined by default to be |\normalsize|.  If this is too
% small, you may adjust it using |\newcommand{\showtextsize}{\large}|, or
% whatever size you prefer.
% \item[\texttt{\bslash textblockorigin}]
% \DescribeMacro{\textblockorigin}
% Sets the position of the top-left of the
% printable area.  See above.
% \end{description}
% \end{raggedright}
%
% \subsection{Suggestions: Producing large-format posters}
% 
% If you are producing a large-format poster, such as A0 size, you
% might want to use Gerlinde Kettl and Matthias Weiser's a0poster
% class, which painlessly deals with the miscellaneous hassles of
% printing to a large-format postscript printer.
%
% I have a collection of suggestions for producing such posters at
% \url{http://www.astro.gla.ac.uk/users/norman/docs/posters/}.
%
% The text on a large poster will typically use a very large font.  It
% can be a hassle to create (or have dvips create) these fonts, and
% they take up a good deal of space on your disk.  You might want to
% investigate the BlueSky/AMS fonts (available at CTAN), which are
% postscript versions of the Computer Modern fonts, and which can
% therefore be scaled arbitrarily.
%
% \section{Credits}
%
% Olaf Maibaum, \texttt{Olaf.Maibaum@informatik.uni-oldenburg.de},
% made an elegant improvement to an earlier version of this package,
% by producing the code which I've incorporated here as the `absolute
% mode' (I'd had something like this before, but it was \emph{very}
% kludgy).
%
% Bjoern Pedersen, \texttt{bjoern@poseidon.org.chemie.tu-muenchen.de},
% made the excellent suggestion that the horizontal and vertical
% modules should be independent, and provided code to implement this.
%
% Rolf Niepraschk, \texttt{niepraschk@ptb.de}, provided the code changes
% which made textpos compatible with the \pstyle{calc} package.
%
% Wybo Dekker, \texttt{wybo@servalys.nl}, reported a problem when
% box~255 was (erroneously) not a vbox, and passed on a fix from Hans Hagen.
%
% \section{Example}
%
% Here is a short example file.
%    \begin{macrocode}
%<*example>
\documentclass{article}

\usepackage[absolute]{textpos}

\setlength{\TPHorizModule}{30mm}
\setlength{\TPVertModule}{\TPHorizModule}
\textblockorigin{10mm}{10mm} % start everything near the top-left corner

\begin{document}

\begin{textblock}{3}(0,0)
This block is 3 modules wide, and is placed with its top left corner
at the `origin' on the page.  Note that the length of the block is not
specified in the arguments -- the box will be as long as necessary to
accomodate the text inside it.  You need to examine the output of the
text to adjust the positioning of the blocks on the page.
\end{textblock}

\begin{textblock}{2}(2,1)
\textblocklabel{block two}
Here is another, slightly narrower, block, at position (2,1) on the page.
\end{textblock}

\begin{textblock}{3}[0.5,0.5](1,3)
This block is at position (1,3), but because the optional argument
[0.5,0.5] has been given, it is the centre of the block which is
located at that point, rather than the top-left corner.
\end{textblock}

\end{document}
%</example>
%    \end{macrocode}
%
% \StopEventually{}
%
% \section{Implementation}
%
%
% \subsection{Options}
%
% Allow the user to switch on display of boxes round the text.
%    \begin{macrocode}
%<*package>
\newif\ifTP@showboxes
\TP@showboxesfalse
\DeclareOption{showboxes}{\TP@showboxestrue}
%    \end{macrocode}
% \dots and switch off printing of text.
%    \begin{macrocode}
\newif\ifTP@showtext
\TP@showtexttrue
\DeclareOption{noshowtext}{\TP@showtextfalse}
%    \end{macrocode}
%
% User may declare that the positions given to the |\textblock|
% environment are to be absolute on the page, rather than relative to
% the current position.
%    \begin{macrocode}
\newif\ifTP@abspos
\TP@absposfalse
\DeclareOption{absolute}{\TP@abspostrue}
%    \end{macrocode}
%
% When using the absolute-position mode, the holdbox is placed into
% box~255 in front of the previous contents of box~255.  This is
% normally what you want, but if the page contents have something
% which \emph{obscures} the hold box (for example, a block of opaque
% colour), then the positioned textboxes disappear.  In this case,
% allow the user to specify that the holdbox is to be placed
% \emph{after} the contents of box~255, so that it overlays it rather
% than being overlayed.
% \changes{v1.1c}{1999/03/22}{Added overlay option}
%    \begin{macrocode}
\newif\ifTP@overlay
\TP@overlayfalse
\DeclareOption{overlay}{\TP@overlaytrue}
%    \end{macrocode}
%
% The package can produce some messages reporting on its progress.
% Allow these to be turned off and on explicitly.  The default is
% (currently) on.
% \changes{v1.2}{2002/04/21}{Added verbose and quiet options}
%    \begin{macrocode}
\newif\ifTP@chatter
\TP@chattertrue
\DeclareOption{quiet}{\TP@chatterfalse}
\DeclareOption{verbose}{\TP@chattertrue}
%    \end{macrocode}
%
% That's it.  Now process the options and get on with it.
%    \begin{macrocode}
\ProcessOptions
%    \end{macrocode}
%
% \subsection{Required Packages}
%
% To manipulate |\box255|, this package needs the package
% \texttt{everyshi}, which provides the command |\EveryShipout|.
%    \begin{macrocode}
\ifTP@abspos
  \RequirePackage{everyshi}
\fi
%    \end{macrocode}
%
% \subsection{The Details}
% The box we construct will be put into the box |\TP@textbox|.
%    \begin{macrocode}
\newbox\TP@textbox
%    \end{macrocode}
% When the package is invoked in `absolute' mode, the contents of
% |\TP@textbox| are not shipped out immediately, but instead put into the box
% |\TP@holdbox|, which holds the boxes until the page as a whole is
% shipped out (these additions contributed by Olaf Maibaum).
% \changes{v1.1}{1999/02/22}{Introduce holdbox, and absolute/relative modes}
%   \begin{macrocode}
\ifTP@abspos
  \newbox\TP@holdbox
  \setbox\TP@holdbox\vbox to 0mm{}
\fi
%    \end{macrocode}
% All the dimensions (except the optional argument of the textblock
% environment) are in terms of the modules |\TPHorizModule| and
% |\TPVertModule|.
% \changes{v1.1}{1999/02/22}{Distinguish horizontal and vertical modules}
%    \begin{macrocode}
\newdimen\TPHorizModule
\newdimen\TPVertModule
%    \end{macrocode}
%
% \begin{macro}{\TPGrid}
% Rather than declare the modules to be specific sizes, they can be
% declared to be proportions of the paper size.  The command
% |\TPGrid{16}{10}| would declare the horizontal module to be a
% sixteenth of the paper size, and the vertical one to be a tenth of
% the paper height.  Set the textblockorigin if the optional arguments
% were provided.
% \changes{v1.1c}{1999/03/09}{Add optional argument to TPGrid}
%    \begin{macrocode}
\def\TPGrid{%
  \@ifnextchar[{\@tempswatrue\TP@Grid}{\@tempswafalse\TP@Grid[0pt,0pt]}}
\def\TP@Grid[#1,#2]#3#4{
  \setlength{\@tempdima}{#1}
  \multiply\@tempdima by 2
  \TPHorizModule=\paperwidth
  \advance\TPHorizModule by -\@tempdima
  \divide\TPHorizModule by #3
  \setlength{\@tempdima}{#2}
  \multiply\@tempdima by 2
  \TPVertModule=\paperheight
  \advance\TPVertModule by -\@tempdima
  \divide\TPVertModule by #4
  \ifTP@chatter
    \typeout{Grid set #3 x #4 = \the\TPHorizModule\space x \the\TPVertModule}%
  \fi
  \ifTP@abspos\if@tempswa \textblockorigin{#1}{#2}\fi\fi
}
%    \end{macrocode}
% \end{macro}
% And use this to initialise initialise the modules to a suitable
% default -- one sixteenth of the paper width and height.
%    \begin{macrocode}
\TPGrid{16}{16}
%    \end{macrocode}
%
% The rules round the boxes are of width |\TPboxrulesize|, and the
% label text within them is |\normalsize|.
%    \begin{macrocode}
\newdimen\TPboxrulesize
\setlength{\TPboxrulesize}{0.4pt}
\def\showtextsize{\normalsize}
%    \end{macrocode}
%
% \begin{macro}{\textblockorigin}
% If we're producing a single page of text, it can be convenient to
% set an origin.  This command may only be used in absolute mode.
%
% First, we need two dimensions, to hold the position of the origin.
% These are relative to the top-left corner of the page, so we need to
% shift them by (1in,1in) to make them relative to the \TeX\ origin.
%    \begin{macrocode}
\ifTP@abspos
  \newdimen\TP@ox
  \newdimen\TP@oy
\fi
%    \end{macrocode}
% The |\textblockorigin| command sets the origin of the page.  It may
% only be called if the package was loaded with the \Lopt{absolute}
% option, so output an error message if that's not the case.
%    \begin{macrocode}
\def\textblockorigin#1#2{%
\ifTP@abspos
  \TP@ox=-1in    \addtolength\TP@ox{#1}%\advance\TP@ox by #1
  \TP@oy=-1in    \addtolength\TP@oy{#2}%\advance\TP@oy by #2
  \ifTP@chatter\typeout{TextBlockOrigin set to #1 x #2}\fi
\else
  \PackageError{textpos}
    {The \protect\textblockorigin\space command\MessageBreak
     may only be used if the package was given\MessageBreak
     the`absolute' option when it was invoked}
    {If you want to use the \protect\textblockorigin\space command, then
       \MessageBreak
     invoke the package with the syntax\MessageBreak
     \protect\usepackage[absolute]{textpos}}
\fi
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\textblocklabel}
% When we're only displaying rules boxes, instead of the text contents
% of the blocks, it's useful to be able to identify which block is
% which.  The contents of |\textblocklabel| are ignored except when
% the \Lopt{noshowtext} option has been used.
%    \begin{macrocode}
\def\textblocklabel#1{\gdef\TP@textblocklabel{#1}}
% (should I use \@bsphack...\@esphack for this?)
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\textblock}
% Now define the start of the textblock environment.  Read the first
% argument, and save it for the moment as |\@tempdima|, then check
% that we're in vertical mode (positionings will probably  go
% skee-whiff otherwise), and warn if we're not.  Then call
% |\TP@textblock| to read the remaining arguments and start off the
% |\vbox| the body text will be set in.
% \changes{v1.1}{1999/02/22}{Add par here, to put us back into vertical mode}
%    \begin{macrocode}
\def\textblock#1{%
  \@tempdima=#1\TPHorizModule
  \ifvmode\else    
    \PackageWarning{textpos}{environment textblock not in vertical mode.
      \MessageBreak
      Environment textblock should not have any text\MessageBreak
      or printable material appearing before it.\MessageBreak 
      Alignment may work out wrongly.}%
    \par % force us back into vertical mode
  \fi
  \@ifnextchar[{\TP@textblock}{\TP@textblock[0,0]}%] bracematch
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\textblock*}
% |\begin{textblock*}| is a variant of |\begin{textblock}| which takes 
% absolute values for its arguments.  It uses |\setlength| throughout, 
% and is therefore compatible with the \pstyle{calc} package.
% \changes{1.2a}{2002/04/28}{Added textblock* env}
%    \begin{macrocode}
\def\TP@textblockstar#1{%
  \setlength{\@tempdima}{#1}
  \ifvmode\else    
    \PackageWarning{textpos}{environment textblock* not in vertical mode.
      \MessageBreak
      Environment textblock* should not have any text\MessageBreak
      or printable material appearing before it.\MessageBreak 
      Alignment may work out wrongly.}%
    \par % force us back into vertical mode
  \fi
  \@ifnextchar[{\TP@textblock}{\TP@textblock[0,0]}%] bracematch
}
\expandafter\let\csname textblock*\endcsname\TP@textblockstar
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP@textblock}
% Command |\TP@textblock| saves all its arguments in a token list, for
% use in |\TP@endtextblock| later, then it starts a vbox.
%    \begin{macrocode}
\newtoks\TP@tbargs
\def\TP@textblock[#1,#2](#3,#4){%
  \TP@tbargs={{#1}{#2}{#3}{#4}}%
  \setbox\TP@textbox=\vbox\bgroup
%    \end{macrocode}
% If we're showing boxes, then draw a rule here
%    \begin{macrocode}
    \ifTP@showboxes
      \hrule height0pt depth \TPboxrulesize 
      \vskip-\TPboxrulesize
    \fi
%    \end{macrocode}
% Set the |\hsize| to the temporary dimension set in |\textblock|
% above, and set the other \LaTeX{} parameters to match.
%    \begin{macrocode}
    \hsize=\@tempdima
    \textwidth\hsize \columnwidth\hsize \linewidth\hsize
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\endtextblock}
% \begin{macro}{\endtextblock*} 
% We have two slight variants of the end-block code, depending on
% whether we're in a |{textblock}| or a |{textblock*}| environment.
% The |\if@tempswa| set here is tested below, in |\TP@endtextblock|.
% \changes{1.2a}{2002/04/28}{Added commonendtextblock, and starred variant}
%    \begin{macrocode}
\def\endtextblock{\global\@tempswatrue\TP@commonendtextblock}
\@namedef{endtextblock*}{\global\@tempswafalse\TP@commonendtextblock}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\TP@commonendtextblock}
% At the end of the environment, draw the matching horizontal rule
% (if we're showing boxes),
% and finish off the vbox begun in |\TP@textblock|.  Then call
% |\TP@endtextblock| with the arguments we saved in the token register
% in |\TP@tbargs|.
%    \begin{macrocode}
\def\TP@commonendtextblock{%
  \ifTP@showboxes 
    \vskip-\TPboxrulesize
    \hrule depth 0pt height \TPboxrulesize
  \fi
  \egroup
%    \end{macrocode}
%
% \TeX\ does not call the output routine if there is nothing on the
% page.  To deal with this situation, put a zero-size box on the page
% just here, at the end of the \texttt{textblock} environment: the
% page is no longer empty, so the output routine must be called at
% some point.
%
% An alternative approach to this is to set a switch true
% whenever anything is put into the holdbox, and clear it when that
% box is shipped out.  I could add a test for this at the end of the document,
% using |\AtEndDocument|, and if the switch is true, shipout the
% holdbox.  This solution is attractive because it deals more-or-less
% directly with the problem.  However, messing with |\AtEndDocument|
% brings us too close for comfort to the swamp of \LaTeX's internals,
% and means we'd have to worry about side-effects, interactions with
% other packages, timings, and we'd sink.  This solution is hacky but,
% paradoxically, more robust than the `correct' solution
% (thanks to Bjoern Pedersen for diagnosing this).
% \changes{v1.1a}{1999/03/05}{Added the vbox to ensure some output on page}
% \changes{v1.1c}{1999/03/22}{Added a nointerlineskip to avoid spacing bug}
%
% The order is important here, as we need to avoid causing the
% insertion of more space in the case where this \texttt{textblock} is
% between paragraphs of text.  Save the |\prevdepth|, then set it to
% $-1000pt$, suppressing interline glue; then add the zero-size vbox;
% then restore |\prevdepth| to what it was before.  See the discussion
% of interline glue (ie, |\baselineskip| and |\prevdepth|) in
% Chapter~12 (p.~80) of the \TeX book (thanks to Peter M\"unster
% \texttt{<peter@univ-rennes1.fr>} for spotting that I'd got this
% wrong in the previous version).
% \changes{v1.1e}{2001/04/29}{Replace randomly-placed nointerline skip with prevdepth acrobatics, to avoid spacing misfeatures}
%    \begin{macrocode}
  \@tempdimb=\prevdepth
  \prevdepth=-1000pt  % \nointerlineskip
  \vbox to 0pt{\hbox to 0pt{}}%
  \prevdepth=\@tempdimb
%    \end{macrocode}
% Finally, call |\TP@endtextblock| to do the work of putting the text
% on the page, directly or indirectly.
%    \begin{macrocode}
  \expandafter\TP@endtextblock\the\TP@tbargs
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP@endtextblock}
% This is where most of the calculations are. Set temporary dimensions
% a and b to be the coordinates (again, in units of the modules), and
% then adjust them by subtracting the position of the `reference point'
% given by parameters~1 and~2.  These dimensions are pure numbers,
% fractions of the width and height, respectively, of the text block.
% Parameters~3 and~4 indicate where the reference point will be
% positioned.  In the unstarred case (|\if@tempswa| true), these are
% pure numbers, indicating dimensions in units of the |\TPHorizModule| 
% and |\TPVertModule| respectively; in the starred case (|\if@tempswa| 
% false), they're dimensions.
%
% That is, position the box |\TP@textbox|, which was build up between
% |\TP@textblock| and |\endtextblock|, at (x,y)=|(#3,#4)|.  
% The point that is so positioned is at |(#1\wd,#2\ht)| of
% |\TP@textbox|, so that |(#1,#2)| =(0,0) means top left.
%
% If we're in the absolute-position mode, then we need to make further
% adjustments to these dimensions.
%    \begin{macrocode}
\def\TP@endtextblock#1#2#3#4{%
  \if@tempswa % modular/unstarred endtextblock
    \@tempdima=#3\TPHorizModule
    \@tempdimb=#4\TPVertModule  
  \else % absolute/starred endtextblock
    \setlength{\@tempdima}{#3}
    \setlength{\@tempdimb}{#4}
  \fi
  \@tempdimc=-#1\wd\TP@textbox
  \advance\@tempdima\@tempdimc
  \@tempdimc=-#2\ht\TP@textbox
  \advance\@tempdimb\@tempdimc
  \ifTP@abspos
    \advance\@tempdima by \TP@ox
    \advance\@tempdimb by \TP@oy
  \fi
%    \end{macrocode}
% Then create an hbox inside a vbox, both of size 0pt, in each case
% with the contents prefixed by a skip of the appropriate size, and
% suffixed by |\hss| or |\vss| respectively.  Put the result into the
% temporary box~0
%    \begin{macrocode}
  \setbox0=\vbox to 0pt{\vskip\@tempdimb
    \hbox to 0pt{\hskip\@tempdima
    \ifTP@showboxes \vrule width \TPboxrulesize \hskip -\TPboxrulesize \fi
    \ifTP@showtext
      \box\TP@textbox
    \else
      \vbox to\ht\TP@textbox{%
        \ifTP@showboxes 
          \hrule depth 0pt height \TPboxrulesize \vskip-\TPboxrulesize
        \fi
        \vskip\smallskipamount
        \hbox to\wd\TP@textbox{%
          \ifx\TP@textblocklabel\undefined
            \hbox{}%
          \else
            \hskip\smallskipamount
            \fbox{\showtextsize \TP@textblocklabel}%
            \global\let\TP@textblocklabel\undefined
          \fi
          \hss
        }%
        \vss
        \ifTP@showboxes 
          \vskip -\TPboxrulesize
          \hrule depth 0pt height \TPboxrulesize
        \fi
      }%
    \fi
    \ifTP@showboxes \hskip -\TPboxrulesize \vrule width \TPboxrulesize \fi
    \hss}%
  \vss
  }%  end of box0
%    \end{macrocode}
% Now switch behaviour depending on whether or not we're in the
% absolute-position mode.  If we are, then add the newly-constructed
% box 0 to (the beginning of) the holdbox.
%    \begin{macrocode}
  \ifTP@abspos
    \global\setbox\TP@holdbox\vbox{%
      \box0
      \unvbox\TP@holdbox
    }%
%    \end{macrocode}
% Else, place the box on the page immediately, adding
% |\nointerlineskip| to suppress interbox space, so that we can 
% list several textblock environments one after another, and have them
% all offset from the same point
%    \begin{macrocode}
  \else
    \box0
    \nointerlineskip
  \fi
  }%
%    \end{macrocode}
% \end{macro}
%
% Finally, and only if we are in the absolute-position mode, set up
% the output routine with |\EveryShipout|, and set the textblockorigin
% to the (default) upper-left corner of the paper.  Respect the
% \Lopt{overlay} option by putting the |\TP@holdbox| contents
% \emph{after} the |\@cclv| contents, putting the latter into a size-0
% box (could this cause a problem with spacing?  I don't think so, at
% this stage).
%
% Box 255 should be either a vbox or void (see \TeX Book pp.~125
% or~253), but if it is an hbox, because some package has misbehaved,
% then we ought to try not to simply collapse.  Work round this by
% testing explicitly whether box~255 is a vbox or not.
% \changes{v1.2b}{2002/07/01}{Defend against box 255 not being a vbox}
%    \begin{macrocode}
\ifTP@abspos
  \ifTP@overlay
    \EveryShipout{%
      \global\setbox\@cclv\vbox{%
        \vbox to 0pt{\ifvbox\@cclv \unvbox\@cclv \else \box\@cclv \fi \vss}%
        \unvbox\TP@holdbox
      }%
      \global\setbox\TP@holdbox\vbox to 0mm{}%
    }%
  \else
    \EveryShipout{%
      \global\setbox\@cclv\vbox{%
        \unvbox\TP@holdbox
        \ifvbox\@cclv \unvbox\@cclv \else \box\@cclv \fi
      }%
      \global\setbox\TP@holdbox\vbox to 0mm{}%
    }%
  \fi
  \textblockorigin{0pt}{0pt}%
\fi
%    \end{macrocode}
% Done!
%    \begin{macrocode}
%</package>
%    \end{macrocode}
%
% \Finale
%
\endinput