% \iffalse
%%
%% File: textarea.dtx Copyright (C) 2005 by Alexander I. Rozhenko
%%
%<package>\NeedsTeXFormat{LaTeX2e}
%<package>\ProvidesPackage{textarea}
%<package>         [2005/12/26 v1.0 Text area control (NCC)]
%
% \changes{v1.0}{2005/12/26}{Initial version}
%
%<*driver>
\let\makeindex\relax
\documentclass{ltxdoc}
\usepackage{textarea}
\GetFileInfo{textarea.sty}
\begin{document}
\title{The \textsf{textarea} package\thanks{This file
        has version number \fileversion, last
        revised \filedate.}}
\author{Alexander I. Rozhenko\\rozhenko@oapmg.sscc.ru}
\date{\filedate}
\maketitle
\DocInput{textarea.dtx}
\end{document}
%</driver>
% \fi
%
% The package allows expand the text area of a document on other
% areas: footer, header, and margin. There are two ways for such
% expansion --- temporary expansion of a current page on the header using
% a special negative vertical skip, or global change of page layout
% parameters with possibility of later restoration them to the original
% values. All these actions should be applied at the beginning of page.
%
% \section{User Interface}
%
% \DescribeMacro\StartFromTextArea
% Applied at the beginning of page, it allows using the non-starred
% form of the |\vspace| command after it. The introduced command provides
% exact vertical skips at the beginning of page. Unlike it, the standard
% \LaTeX's |\vspace*| command skips more space at the beginning of page
% than it is required in its parameter. So, using the
% |\StartFromTextArea| command prevents
% incorrect spacing at the beginning of page.
%
% \DescribeMacro\StartFromHeaderArea
% Applied at the beginning of page, it adjusts the beginning of text area
% to the header area by inserting a negative vertical skip. The header
% of this page should be empty. Otherwise, the consequent text will
% overprint the header.
%
% \DescribeMacro{\ExpandTextArea\oarg{hfm}}
% Expands the text area on other areas of page by changing page layout
% parameters. It can be used in one-column mode only.
% The letters in optional argument mean the following: |h| (header),
% |f| (footer), and |m| (margins). If an optional argument is omitted
% or equals to |[*]|, the temporary expansion to the header is applied
% with the |\StartFromHeaderArea| command. Anyway, you can use the
% non-starred form of the |\vspace| command after expansion of the
% text area.
%
% When a text area is expanded (non-temporary), the repeated call of
% this command is disallowed.
%
% \DescribeMacro\RestoreTextArea
% Restores page layout parameters to their previous values. After that,
% the |\ExpandTextArea| command can be applied again.
%
% \DescribeMacro\NCC@restoretextarea
% This hook can be used to provide an automatic restoration of the text
% area. In \textbf{ncc} class, we use it as follows: set it empty at
% the beginning of |titlepage| environment and call this command at
% the end of |titlepage| environment. So, if the text area will be
% expanded within the |titlepage| environment, it will be automatically
% restored at the end of it.
%
% \StopEventually{}
%
% \section{The Implementation}
%
% \begin{macro}{\StartFromTextArea}
% \begin{macro}{\StartFromHeaderArea}
% Both these commands are defined in two packages: in this and in
% \textbf{nccsect}. To be sure that the commands are specified
% in these packages only, we mutually test packages to be loaded.
%    \begin{macrocode}
%<*package>
\@ifpackageloaded{nccsect}{}{%
  \newcommand\StartFromTextArea{\par
    {\parskip\z@ \strut\par}\vskip -\baselineskip
  }
  \newcommand\StartFromHeaderArea{%
    \StartFromTextArea
    \vskip -\headsep \vskip -\ht\strutbox
  }
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\RestoreTextArea}
% This command is usually empty. But it is globally redefined
% when the layout of page is modified by the |\ExpandTextArea|
% command.
%    \begin{macrocode}
\newcommand*\RestoreTextArea{}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ExpandTextArea}
% This command should be applied at the beginning of page
% in one-column mode only.
%    \begin{macrocode}
\newcommand*\ExpandTextArea[1][*]{%
  \if@twocolumn
    \PackageError{textarea}%
                 {The \string\ExpandTextArea\space command\MessageBreak
                  cannot work in two-column mode}{}%
%    \end{macrocode}
% Test for temporary expansion mode and do it.
%    \begin{macrocode}
  \else
   \def\@tempa{*}\edef\@tempb{#1}%
   \ifx\@tempa\@tempb
     \StartFromHeaderArea
%    \end{macrocode}
% Otherwise, apply the permanent expansion but in the only case if
% it was not already applied.
%    \begin{macrocode}
   \else
    \ifx\RestoreTextArea\@empty
%    \end{macrocode}
% |\NCC@|\meta{x} hooks will be applied right here to modify the layout and
% |\NCC@resore@|\meta{x} hooks will applied later when the original layout
% will be restored.
%    \begin{macrocode}
     \let\NCC@h\@empty \global\let\NCC@restore@h\@empty
     \let\NCC@f\@empty \global\let\NCC@restore@f\@empty
     \let\NCC@m\@empty \global\let\NCC@restore@m\@empty
%    \end{macrocode}
% Analyze letters in the optional parameter and prepare the respective hooks.
% The first parameter in all adjustment commands is a sign of adjustment:
% the empty value means adjust and the minus sign means restore.
%    \begin{macrocode}
     \expandafter\@tfor\expandafter\@tempa\expandafter:\expandafter=#1\do{%
       \if h\@tempa
        \def\NCC@h{\NCC@adjusttoheader{}}%
        \gdef\NCC@restore@h{\NCC@adjusttoheader-}%
       \else
        \if f\@tempa
         \def\NCC@f{\NCC@adjusttofooter{}}%
         \gdef\NCC@restore@f{\NCC@adjusttofooter-}%
        \else
         \if m\@tempa
          \if@reversemargin \@tempcnta\@ne \else \@tempcnta\tw@ \fi
          \edef\NCC@m{\noexpand\NCC@adjusttomargin{}{\the\@tempcnta}}%
          \xdef\NCC@restore@m{\noexpand\NCC@adjusttomargin-{\the\@tempcnta}}%
         \fi
        \fi
       \fi
     }%
%    \end{macrocode}
% Modify the layout, apply the |\StartFromTextArea| command, and prepare
% the |\RestoreTextArea| command and the auto-restoration hook.
%    \begin{macrocode}
     \NCC@h\NCC@f\NCC@m
     \StartFromTextArea
     \gdef\RestoreTextArea{%
       \NCC@restore@h\NCC@restore@f\NCC@restore@m
       \global\let\RestoreTextArea\@empty
     }%
     \def\NCC@restoretextarea{\RestoreTextArea}%
    \fi
   \fi
  \fi
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\NCC@adjusttoheader}
% Adjust text height parameters and |\topmargin|.
%    \begin{macrocode}
\def\NCC@adjusttoheader#1{%
  \@tempdima #1\headheight
  \advance\@tempdima #1\headsep
  \global\advance\textheight\@tempdima
  \global\advance\topmargin-\@tempdima
  \global\@colht\textheight
  \global\@colroom\textheight
  \global\vsize\textheight
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\NCC@adjusttofooter}
% Adjust text height parameters.
%    \begin{macrocode}
\def\NCC@adjusttofooter#1{%
  \global\advance\textheight#1\footskip
  \global\@colht\textheight
  \global\@colroom\textheight
  \global\vsize\textheight
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\NCC@adjusttomargin}
% Adjust text width parameters, |\oddsidemargin| or
% |\evensidemargin|. The second parameter specifies
% the mode of marginal notes: reverse (1) or normal (2) margins.
%    \begin{macrocode}
\def\NCC@adjusttomargin#1#2{%
  \@tempdima #1\marginparwidth
  \advance\@tempdima #1\marginparsep
  \@tempcnta#2%
  \ifodd\@tempcnta
    \global\advance\oddsidemargin -\@tempdima
  \else
    \global\advance\evensidemargin -\@tempdima
  \fi
  \global\advance\textwidth\@tempdima
  \global\columnwidth\textwidth
  \global\linewidth\textwidth
  \global\hsize\textwidth
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\NCC@restoretextarea}
% Text area auto-restoration hook.
%    \begin{macrocode}
\let\NCC@restoretextarea\@empty
%</package>
%    \end{macrocode}
% \end{macro}
\endinput