% \iffalse meta-comment
%
% Copyright (C) 2019-2021 by Benjamin Berg <benjamin@sipsolutions.net>
%
% This work may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3c
% of this license or (at your option) any later version.
% The latest version of this license is in
%   http://www.latex-project.org/lppl.txt
%
% This work has the LPPL maintenance status `maintained'.
% 
% The Current Maintainer of this work is Benjamin Berg.
%
% \fi
%
% \iffalse
%<*driver>
\ProvidesFile{sdapsbase.dtx}
%</driver>
%<package>\NeedsTeXFormat{LaTeX2e}[1999/12/01]
%<package>\ProvidesPackage{sdapsbase}
%<*package>
    [2015/01/14 v0.1 Initial version of SDAPS base package]
%</package>
%
%<*driver>
\documentclass{ltxdoc}
\usepackage{sdapsbase}[2015/01/14]
%\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
  \DocInput{sdapsbase.dtx}
\end{document}
%</driver>
% \fi
%
% \CheckSum{0}
%
% \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{v0.1}{2015/01/14}{Initial version}
%
% \GetFileInfo{sdapsbase.dtx}
%
% \DoNotIndex{\newcommand,\newenvironment}
% 
%
% \title{The \textsf{sdapsbase} package\thanks{This document
%   corresponds to \textsf{sdapsbase}~\fileversion, dated \filedate.}}
% \author{Benjamin Berg \\ \texttt{benjamin@sipsolutions.net}}
%
% \maketitle
%
% \section{Documentation}
%
% Please refer to \url{https://sdaps.org/class-doc} for documentation.
%
% \StopEventually{\PrintChanges\PrintIndex}
%
% \section{Implementation}
%
% This package uses the \LaTeX3 language internally, so we need to enable it.
%    \begin{macrocode}
% We need at least 2011-08-23 for \keys_set_known:nnN
\RequirePackage{expl3}[2011/08/23]
%\RequirePackage{xparse}
\ExplSyntaxOn
%    \end{macrocode}
%
% And we need a number of other packages.
%    \begin{macrocode}
\ExplSyntaxOff

\input{sdapscode128}

\RequirePackage{qrcode}

\RequirePackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{positioning}
\usetikzlibrary{decorations.pathmorphing}
\ExplSyntaxOn


% Define aliases for code128 functions, and generate variants
\cs_new_eq:NN \code_render:n \code
\cs_generate_variant:Nn \code_render:n { x, V }

% Also define an alias for the qrcode renderer
\cs_new_protected_nopar:Nn \qrcode_render:nn {
  \qrcode[#1] {#2}
}
\cs_generate_variant:Nn \qrcode_render:nn { nx, nV }


% Define a method to check for RTL languages, as the relevant commands
% may not always be defined.
\prg_new_conditional:Npnn \sdaps_if_rtl: { p, T, F, TF }
{
  \cs_if_exist:cTF { if@RTL } {
    \tl_use:c { if@RTL }
      \prg_return_true:
    \else
      \prg_return_false:
    \fi
  } {
    \prg_return_false:
  }
}

%    \end{macrocode}
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% \subsection{Context Handling}
%
% When creating complex questionnaires we need a mechnism to handle the current
% context. By choice this mechanism works in global scope as items inside a
% nested environment (e.g. multicol) need to have an effect on items outside
% the environment. Because of this, we implement our own context, which works
% similar to TeX groups containing local definitions.
%
%    \begin{macrocode}

\cs_generate_variant:Nn \tl_if_eq:nnTF { Vn }
\cs_generate_variant:Nn \tl_if_eq:nnT { Vn }
\cs_generate_variant:Nn \tl_if_eq:nnF { Vn }
\cs_generate_variant:Nn \int_if_odd:nTF { V }
\cs_generate_variant:Nn \int_if_odd:nF { V }
\cs_generate_variant:Nn \int_if_odd:nT { V }
\cs_generate_variant:Nn \tl_set:Nn { Nv }
\cs_generate_variant:Nn \msg_error:nnn { nnV }
\cs_generate_variant:Nn \exp_not:n { f }


\tl_new:N \l__sdaps_tmpa_tl
\tl_new:N \l__sdaps_tmpb_tl

\dim_new:N \l__sdaps_tmpa_dim %
\dim_new:N \l__sdaps_tmpb_dim %

\prop_new:N \g__sdaps_current_context_prop
\tl_new:N \g__sdaps_current_context_id_tl

\tl_new:N \g__sdaps_current_context_tl

\seq_new:N \g__sdaps_context_ids_seq
\seq_new:N \g__sdaps_contexts_seq

% Global metadata write enable variable managed by context
\bool_new:N \g_sdaps_write_enable_bool
\bool_gset_false:N \g_sdaps_write_enable_bool

\cs_new_protected_nopar:Nn \_sdaps_context_to_tl:N
{
  \tl_set:Nx #1 {_write_enable=\bool_if:NTF\g_sdaps_write_enable_bool{\c_true_bool}{\c_false_bool}}
  \prop_map_inline:Nn \g__sdaps_current_context_prop {
    % Could we remove some of the braces in the TL?
    \tl_if_eq:nnTF { \undefined } { ##2 } {
      \tl_put_right:Nn #1 {,{##1}}
    } {
      \tl_put_right:Nn #1 {,{##1}={##2}}
    }
  }
}


% Create new context using given identifier
\cs_new_protected_nopar:Nn \sdaps_context_begin:n
{
  % We need to serialize the current context and save it away.

  \group_begin:
    % Serialize the current context
    \_sdaps_context_to_tl:N \l__sdaps_tmpa_tl
    \tl_gset:NV \g__sdaps_current_context_tl \l__sdaps_tmpa_tl
    % Stuff it away in our sequence
    \seq_gput_left:NV \g__sdaps_contexts_seq \g__sdaps_current_context_tl
    \seq_gput_left:NV \g__sdaps_context_ids_seq \g__sdaps_current_context_id_tl

    % Clear the hooks
    \sdaps_context_put:nn { _context_hook_end } {}
    \sdaps_context_put:nn { _context_hook_post_end } {}

    \tl_gset:Nn \g__sdaps_current_context_id_tl { #1 }
  \group_end:
}

\msg_new:nnn { sdapsbase } { context_end_none_left } { There ~ is ~ no ~ context ~ to ~ end ~ left! }
\msg_new:nnn { sdapsbase } { context_end_broken } { The ~ current ~ context ~ with ~ id ~ #1 ~ may ~ not ~ be ~ ended ~ here. }

\cs_new_protected_nopar:Nn \__sdaps_context_end:
{
  \seq_if_empty:NTF \g__sdaps_context_ids_seq {
    \msg_error:nn { sdapsbase } { context_end_none_left }
  } {

    \group_begin:
    \sdaps_context_get:nN { _context_hook_end } \l_tmpa_tl
    \tl_if_eq:VnF \l_tmpa_tl { \q_no_value } { \tl_use:N \l_tmpa_tl }

    % Grab post end hook
    \sdaps_context_get:nN { _context_hook_post_end } \l_tmpa_tl

    \_sdaps_context_clear:
    \seq_gpop_left:NN \g__sdaps_contexts_seq \g__sdaps_current_context_tl
    \seq_gpop_left:NN \g__sdaps_context_ids_seq \l__sdaps_tmpa_tl

    % Unpack context token list
    \sdaps_context_set:V \g__sdaps_current_context_tl

    \sdaps_context_get:nN { _write_enable } \l_tmpb_tl
    \bool_gset:Nn \g_sdaps_write_enable_bool { \l_tmpb_tl }
    \sdaps_context_remove:n { _write_enable }

    \tl_gclear:N \g__sdaps_current_context_tl
    \tl_gset:NV \g__sdaps_current_context_id_tl \l__sdaps_tmpa_tl

    \tl_if_eq:VnF \l_tmpa_tl { \q_no_value } { \tl_use:N \l_tmpa_tl }
    \group_end:
  }
}

\bool_new:N \l__sdaps_tmp_bool

\cs_new_protected_nopar:Nn \__sdaps_test_context_id:n
{
  \tl_if_eq:VnTF \g__sdaps_current_context_id_tl { #1 } {
    \bool_set:Nn \l__sdaps_tmp_bool \c_true_bool
  } {
    \bool_set:Nn \l__sdaps_tmp_bool \c_false_bool
  }
}

% Exit first context with passed in identifier
\cs_new_protected_nopar:Nn \sdaps_context_end:n
{
  \__sdaps_test_context_id:n { #1 }

  \bool_until_do:nn { \l__sdaps_tmp_bool } {
    \sdaps_context_end:

    \__sdaps_test_context_id:n { #1 }
  }
  \sdaps_context_end:
}

\cs_new_protected_nopar:Nn \__sdaps_context_end_local_scope:
{
  \__sdaps_test_context_id:n { sdaps_local_scope }

  \bool_until_do:nn { \l__sdaps_tmp_bool } {
    \__sdaps_context_end:

    \__sdaps_test_context_id:n { sdaps_local_scope }
  }
  \__sdaps_context_end:
}

% Exit current context
\cs_new_protected_nopar:Nn \sdaps_context_end:
{
  % Ensure the current context is not a local group
  \tl_if_eq:VnTF \g__sdaps_current_context_id_tl { sdaps_local_scope } {
    \msg_error:nnV { sdapsbase } { context_end_broken } \g__sdaps_current_context_id_tl
  } {}

  \__sdaps_context_end:
}

% Create new context using an empty name
\cs_new_protected_nopar:Nn \sdaps_context_begin:
{
  \sdaps_context_begin:n {}
}

\cs_new_protected_nopar:Nn \sdaps_context_begin_local:
{
  % Create a new context which will automatically be destroyed at the end of
  % the current TeX group.
  \sdaps_context_begin:n { sdaps_local_scope }
  \group_insert_after:N \__sdaps_context_end_local_scope:
}

\cs_new_protected_nopar:Nn \sdaps_context_put:n
{
  \sdaps_context_put:nn { #1 } { \undefined }
}

\cs_new_protected_nopar:Nn \sdaps_context_remove:n
{
  \prop_gremove:Nn \g__sdaps_current_context_prop { #1 }
}

\msg_new:nnn { sdapsbase } { context_key_broken } { Keys ~ may ~ not ~ contain ~ any ~ special ~ tokens! ~ However ~ the ~ key ~ #1 ~ does ~ contain ~ tokens ~ that ~ are ~ not ~ permissible! }
% Directly set a certain key
\cs_new_protected_nopar:Nn \sdaps_context_put:nn
{
  % TODO: How can I ensure that {} are not contained?
  % Though it would not be that bad actually.
  \tl_if_in:nnTF {#1} {,} {
    \msg_error:nnn { sdapsbase } { context_key_broken } {#1}
  } {
  }

  \tl_if_in:nnTF {#1} {=} {
    \msg_error:nnn { sdapsbase } { context_key_broken } {#1}
  } {
  }

  \prop_gput:Nnn \g__sdaps_current_context_prop { #1 } { #2 }
}
\cs_generate_variant:Nn \sdaps_context_put:nn { nV }

% Set a set of keys using comma separated list of key/value pairs
\cs_new_protected_nopar:Nn \sdaps_context_set:n
{
  \keyval_parse:NNn \sdaps_context_put:n \sdaps_context_put:nn { #1 }
}
\cs_generate_variant:Nn \sdaps_context_set:n {V}

\cs_new_protected_nopar:Nn \sdaps_context_get:nN
{
  \prop_get:NnN \g__sdaps_current_context_prop { #1 } #2
}

\cs_new_protected_nopar:Nn \sdaps_context_gget:nN
{
  \prop_get:NnN \g__sdaps_current_context_prop { #1 } \l_tmpa_tl
  \tl_gset_eq:NN #2 \l_tmpa_tl
}

\cs_new_protected_nopar:Nn \sdaps_context_append:nnn
{
  \sdaps_context_get:nN { #1 } \l__sdaps_tmpa_tl
  \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
    \sdaps_context_put:nn { #1 } { #2 }
  } {
    \tl_put_right:Nn \l__sdaps_tmpa_tl { #3 }
    \tl_put_right:Nn \l__sdaps_tmpa_tl { #2 }
    \sdaps_context_put:nV { #1 } \l__sdaps_tmpa_tl
  }
}
\cs_generate_variant:Nn \sdaps_context_append:nnn { nVn }


\cs_new_protected_nopar:Nn \sdaps_context_append:nn
{
  \sdaps_context_append:nnn { #1 } { #2 } { , }
}

\cs_new_protected_nopar:Nn \sdaps_context_hook_end:n
{
  \sdaps_context_append:nnn { _context_hook_end } { #1 } { }
}

\cs_new_protected_nopar:Nn \sdaps_context_hook_post_end:n
{
  \sdaps_context_append:nnn { _context_hook_post_end } { #1 } { }
}

\cs_new_protected_nopar:Nn \sdaps_context_enable_writing:
{
  \bool_gset_true:N \g_sdaps_write_enable_bool
}

\cs_new_protected_nopar:Nn \sdaps_context_disable_writing:
{
  \bool_gset_false:N \g_sdaps_write_enable_bool
}

\cs_new_protected_nopar:Nn \_sdaps_context_clear:
{
  \prop_gclear:N \g__sdaps_current_context_prop
}

\cs_new:Nn \sdaps_context_map_function:N
{
  \prop_map_function:NN \g__sdaps_current_context_prop #1
}

\cs_new_protected_nopar:Nn \__sdaps_get:Nn
{
  \prop_get:NnN \g__sdaps_current_context_prop { #2 } #1
}

\cs_new_protected_nopar:Nn \__sdaps_get_empty:Nn
{
  \prop_get:NnN \g__sdaps_current_context_prop { #2 } #1
  \tl_if_eq:VnT #1 { \q_no_value } {
    \tl_set:Nn #1 {}
  }
}

\cs_new_protected_nopar:Nn \__sdaps_append_from_context:nN
{
  \prop_get:NnN \g__sdaps_current_context_prop { #1 } \l__sdaps_tmpb_tl
  \tl_if_eq:VnF \l__sdaps_tmpb_tl { \q_no_value } {
    \tl_put_right:Nn #2 {,}
    \tl_put_right:NV #2 {\l__sdaps_tmpb_tl}
  }
}
\cs_generate_variant:Nn \__sdaps_append_from_context:nN { VN }


%    \end{macrocode}
%
% \subsection{Defining Question and Headings}
%
% SDAPS needs to know about questions and headings/sections. Internally SDAPS
% uses the context management system to number these correctly and assign the
% variable names including the variable name concatenation automatically.
%
% Note that the infrastructure present here will not prevent you from nesting
% questions, and SDAPS should actually handle this case just fine (ever wanted
% to put a question inside a textbox?).
%
% It is important to keep these balanced. Please note that the SDAPS class does
% not use TeX groups here, so you could for example start a context inside a
% table and end it outside of it.
%
%    \begin{macrocode}

\seq_new:N \g__sdaps_object_id_seq
\int_new:N \g__sdaps_object_id_int
\int_gzero:N \g__sdaps_object_id_int

\cs_new_protected_nopar:Nn \_sdaps_qobject_end_hook:
{
  % Take the current implicit variable
  \sdaps_context_get:nN { _implicit_var } \l__sdaps_tmpa_tl

  % Prepend explicit variable name; we assume that either _implicit_var or _var
  % have a proper value.
  \sdaps_context_get:nN { _var } \l__sdaps_tmpb_tl
  \tl_if_eq:VnF \l__sdaps_tmpb_tl { \q_no_value } {
    \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
      \tl_clear:N \l__sdaps_tmpa_tl
    } {
      \tl_put_left:Nn \l__sdaps_tmpa_tl { _ }
    }
    \tl_put_left:NV \l__sdaps_tmpa_tl \l__sdaps_tmpb_tl
  }

  \sdaps_context_get:nN { id } \l__sdaps_tmpb_tl

  \tl_if_eq:VnTF \l__sdaps_tmpb_tl { \q_no_value } {
    \msg_warning:nn { sdapsbase } { no_qid }
  } {
    \sdaps_info_write_x:x{
      Variable[\l__sdaps_tmpb_tl]=\l__sdaps_tmpa_tl
    }
  }
}

\cs_new_protected_nopar:Nn \_sdaps_qobject_post_hook:
{
  \seq_gpop_right:NN \g__sdaps_object_id_seq \l__sdaps_tmpa_tl
  \int_gset:NV \g__sdaps_object_id_int \l__sdaps_tmpa_tl
}

\cs_new_protected_nopar:Nn \sdaps_qobject_begin:nnn
{
  \int_gincr:N \g__sdaps_object_id_int
  \seq_gput_right:NV \g__sdaps_object_id_seq \g__sdaps_object_id_int
  \tl_set:Nx \l__sdaps_tmpa_tl { \int_use:N \g__sdaps_object_id_int }
  \int_gzero:N \g__sdaps_object_id_int

  \tl_set:Nx \l__sdaps_tmpb_tl { \seq_use:Nn \g__sdaps_object_id_seq {.} }

  \sdaps_context_begin:n {#1}
    \sdaps_context_put:nV {id} \l__sdaps_tmpb_tl
    \sdaps_info_write:x {QObject-#2=\tl_use:N\l__sdaps_tmpb_tl. ~ \exp_not:n{#3}}
    \sdaps_context_append:nVn { _implicit_var } \l__sdaps_tmpa_tl { _ }
    \sdaps_context_hook_end:n { \_sdaps_qobject_end_hook: }
    \sdaps_context_hook_post_end:n { \_sdaps_qobject_post_hook: }
}
\cs_generate_variant:Nn \sdaps_qobject_begin:nnn { nnV, nVV, nVn }


\cs_new_protected_nopar:Nn \sdaps_qobject_end:n
{
  % End the context in question, everything else is done from the close hook
  \sdaps_context_end:n {#1}
}

\cs_new_protected_nopar:Nn \sdaps_qobject_begin:nn
{
  \sdaps_qobject_begin:nnn { unnamed_qobject } { #1 } { #2 }
}

\cs_new_protected_nopar:Nn \sdaps_qobject_begin_local:nn
{
  % Empty local context which automatically closes the qobject
  \sdaps_context_begin_local:
    \sdaps_qobject_begin:nnn { unnamed_local_qobject } { #1 } { #2 }
}

\cs_new_protected_nopar:Nn \sdaps_qobject_end:
{
  \sdaps_qobject_end:n { unnamed_qobject }
}

\cs_new_protected_nopar:Nn \sdaps_qobject_append_var:n
{
  % If the given variable name starts with _ then include the implicitly
  % generated variable name.
  \tl_if_head_eq_charcode:nNTF { #1 } _ {
    \sdaps_context_get:nN { _implicit_var } \l__sdaps_tmpa_tl
    \tl_if_eq:VnF \l__sdaps_tmpa_tl { \q_no_value } {
      \sdaps_context_append:nVn { _var } \l__sdaps_tmpa_tl { _ }
    }

    \sdaps_context_append:nnn { _var } { #1 } { }
  } {
    \sdaps_context_append:nnn { _var } { #1 } { _ }
  }

  % We have a proper variable name now, delete the implicit one
  \sdaps_context_remove:n { _implicit_var }
}
\cs_generate_variant:Nn \sdaps_qobject_append_var:n { V }

\msg_new:nnn { sdapsbase } { no_qid } { Trying~to~output~metadata~but~no~question~ID~is~set~on~the~context.~Did~you~start~a~question?~Supressing~the~output! }

\cs_new_protected_nopar:Nn \sdaps_answer:n
{
  \sdaps_context_get:nN { id } \l__sdaps_tmpa_tl

  \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
    \msg_warning:nn { sdapsbase } { no_qid }
  } {
    \sdaps_info_write:x {
       Answer[\tl_use:N \l__sdaps_tmpa_tl]=\exp_not:n { #1 }
    }
  }
}
\cs_generate_variant:Nn \sdaps_answer:n { o }
\cs_generate_variant:Nn \sdaps_answer:n { f }
\cs_generate_variant:Nn \sdaps_answer:n { V }

\cs_new_protected_nopar:Nn \sdaps_range:nnn
{
  \sdaps_context_get:nN { id } \l__sdaps_tmpa_tl

  \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
    \msg_warning:nn { sdapsbase } { no_qid }
  } {
    \sdaps_info_write:x {
       Range-#1[\tl_use:N \l__sdaps_tmpa_tl]=\int_eval:n{#2},\exp_not:n { #3 }
    }
  }
}
\cs_generate_variant:Nn \sdaps_range:nnn { nno }
\cs_generate_variant:Nn \sdaps_range:nnn { nnf }
\cs_generate_variant:Nn \sdaps_range:nnn { nnV }

\cs_generate_variant:Nn \tl_if_head_eq_charcode:nNT { VN }

\cs_new_protected_nopar:Nn \_sdaps_generate_var:nN
{
  \tl_set:Nn \l__sdaps_tmpa_tl { #1 }

  % Generate a variable name if there is none (prepended with _ prefix)
  \tl_if_empty:VT \l__sdaps_tmpa_tl {
    \tl_set:Nx \l__sdaps_tmpa_tl { _ \int_eval:n { \g__sdaps_object_id_int + 1 } }
  }

  % Prepend any implicitly generated variable names if prefixed by _
  \tl_if_head_eq_charcode:VNT \l__sdaps_tmpa_tl _ {
    \sdaps_context_get:nN { _implicit_var } \l__sdaps_tmpb_tl
    \tl_if_eq:VnTF \l__sdaps_tmpb_tl { \q_no_value } {
      \tl_remove_once:Nn \l__sdaps_tmpa_tl { _ }
    } {
      \tl_put_left:NV \l__sdaps_tmpa_tl \l__sdaps_tmpb_tl
    }
  }

  % Prepend explicit variable name
  \sdaps_context_get:nN { _var } \l__sdaps_tmpb_tl
  \tl_if_eq:VnF \l__sdaps_tmpb_tl { \q_no_value } {
    \tl_put_left:Nn \l__sdaps_tmpa_tl { _ }
    \tl_put_left:NV \l__sdaps_tmpa_tl \l__sdaps_tmpb_tl
  }

  \tl_set:NV #2 \l__sdaps_tmpa_tl
}

\cs_new_protected_nopar:Nn \_sdaps_box_inc_object_id:
{
  \bool_if:NT \g_sdaps_write_enable_bool {
    \int_gincr:N \g__sdaps_object_id_int
  }
}

%    \end{macrocode}
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% \subsection{Data handling and override specification}
%
% Often it is useful to set certain flags for specific checkboxes. As the
% checkbox may only be generated internally by SDAPS it is impossible to pass
% a flag to it directly. Because of this \textsf{sdapsbase} has some mechanisms
% to maintain a tree with options.
%
% \begin{verbatim}
% \sdaps_overrides_init:n{*={
%   *={},
%   checkbox2={ellipse},
%   checkbox3,1={width=6mm},
% }}
% \end{verbatim}
%
%    \begin{macrocode}

\cs_generate_variant:Nn \keyval_parse:NNn { NNV }
\cs_generate_variant:Nn \int_gset:Nn { NV }

\seq_new:N \g__sdaps_checkbox_overlays_seq
\seq_new:N \g__sdaps_textbox_overlays_seq


\prop_new:N \g__sdaps_id_to_overrides_prop
\prop_new:N \g__sdaps_overrides_prop
\prop_new:N \g__sdaps_id_overrides_prop

\cs_new_protected_nopar:Nn \__sdaps_questionnaire_overrides_set:nn
{
  \str_if_eq:eeTF { #1 } { * } {
    \__sdaps_parse_overrides:n{ #2 }
  } {
    \prop_put:Nnn \g__sdaps_id_to_overrides_prop { #1 } { #2 }
  }
}

\cs_new_protected_nopar:Nn \sdaps_overrides_init:n
{
  \keyval_parse:NNn \use_none:n \__sdaps_questionnaire_overrides_set:nn { #1 }
}


\cs_new_protected_nopar:Nn \__sdaps_overrides_set:nn
{
  \prop_gput:Nnn \g__sdaps_overrides_prop { #1 } { #2 }
}

\cs_new_protected_nopar:Nn \__sdaps_id_overrides_set:nn
{
  \prop_gput:Nnn \g__sdaps_id_overrides_prop { #1 } { #2 }
}

\cs_new_protected_nopar:Nn \__sdaps_parse_overrides:n
{
  \prop_gclear:N \g__sdaps_overrides_prop
  \keyval_parse:NNn \use_none:n \__sdaps_overrides_set:nn { #1 }
}

\tl_new:N \l__sdaps_set_qid_tl
\cs_new_protected_nopar:Nn \sdaps_set_questionnaire_id:n
{
  \tl_gset:Nn \g__sdaps_questionnaire_id_tl { #1 }
  \prop_gclear:N \g__sdaps_id_overrides_prop
  \prop_get:NnNT \g__sdaps_id_to_overrides_prop { #1 } \l__sdaps_set_qid_tl {
    \keyval_parse:NNV \use_none:n \__sdaps_id_overrides_set:nn \l__sdaps_set_qid_tl
  }
}
\cs_generate_variant:Nn \sdaps_set_questionnaire_id:n { V }


\cs_new_protected_nopar:Nn \__sdaps_append_override_options:Nnn
{
  % Global definition
  % First generic for all items
  \prop_get:NnNT \g__sdaps_overrides_prop { * } \l__sdaps_tmpa_tl {
    \tl_put_right:Nn #1 {,}
    \tl_put_right:NV #1 \l__sdaps_tmpa_tl
  }
  \tl_if_empty:nF { #2 } {
    % Items with same variable name
    \prop_get:NnNT \g__sdaps_overrides_prop { #2 } \l__sdaps_tmpa_tl {
      \tl_put_right:Nn #1 {,}
      \tl_put_right:NV #1 \l__sdaps_tmpa_tl
    }
    \tl_if_empty:nF { #3 } {
      % Items with same variable name and value
      \prop_get:NnNT \g__sdaps_overrides_prop { #2&#3 } \l__sdaps_tmpa_tl {
        \tl_put_right:Nn #1 {,}
        \tl_put_right:NV #1 \l__sdaps_tmpa_tl
      }
    }
  }


  % Local (questionnaire ID specific) definition
  % First generic for all items
  \prop_get:NnNT \g__sdaps_id_overrides_prop { * } \l__sdaps_tmpa_tl {
    \tl_put_right:Nn #1 {,}
    \tl_put_right:NV #1 \l__sdaps_tmpa_tl
  }
  \tl_if_empty:nF { #2 } {
    % Items with same variable name
    \prop_get:NnNT \g__sdaps_id_overrides_prop { #2 } \l__sdaps_tmpa_tl {
      \tl_put_right:Nn #1 {,}
      \tl_put_right:NV #1 \l__sdaps_tmpa_tl
    }
    \tl_if_empty:nF { #3 } {
      % Items with same variable name and value
      \prop_get:NnNT \g__sdaps_id_overrides_prop { #2&#3 } \l__sdaps_tmpa_tl {
        \tl_put_right:Nn #1 {,}
        \tl_put_right:NV #1 \l__sdaps_tmpa_tl
      }
    }
  }
}
\cs_generate_variant:Nn \__sdaps_append_override_options:Nnn  { NVn }

%    \end{macrocode}
%
%
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%
% First we define constants and global variables for later use.
%    \begin{macrocode}
\dim_new:N \g_sdaps_linewidth_dim
\g_sdaps_linewidth_dim=1bp
\tl_new:N \g__sdaps_checkbox_last_info_tl

\int_new:N \g__sdaps_textbox_num_int
\int_set:Nn \g__sdaps_textbox_num_int 0

\tl_new:N \l_sdaps_var_tl
\dim_new:N \l_sdaps_x_dim
\dim_new:N \l_sdaps_y_dim
\dim_new:N \l_sdaps_width_dim
\dim_new:N \l_sdaps_height_dim

%    \end{macrocode}
%
% We need to be able to output data into the .sdaps file. On startup the
% output is opened but writing is disabled. Note that the write enabled
% variable is managed by the context.
%
%    \begin{macrocode}

\iow_new:N \g_sdaps_infofile_iow
\iow_open:Nn \g_sdaps_infofile_iow { \c_sys_jobname_str . sdaps }
\int_new:N \g__sdaps_infofile_line_int
\int_gset:Nn \g__sdaps_infofile_line_int { 0 }

\cs_new_protected_nopar:Nn \sdaps_info_write:n
{
  \bool_if:NT \g_sdaps_write_enable_bool {
    \int_gincr:N \g__sdaps_infofile_line_int
    \iow_shipout:Nx \g_sdaps_infofile_iow { [ \int_use:N \g__sdaps_infofile_line_int ] \exp_not:n { #1 } }
  }
}
\cs_generate_variant:Nn \sdaps_info_write:n { x }

\cs_new_protected_nopar:Nn \sdaps_info_write_x:n
{
  \bool_if:NT \g_sdaps_write_enable_bool {
    \int_gincr:N \g__sdaps_infofile_line_int
    \iow_shipout_x:Nx \g_sdaps_infofile_iow { [ \int_use:N \g__sdaps_infofile_line_int ] \exp_not:n { #1 } }
  }
}
\cs_generate_variant:Nn \sdaps_info_write_x:n { x }


%    \end{macrocode}
%
% Set some options at the beginning of the document.
%    \begin{macrocode}
%\AtBeginDocument{}
%    \end{macrocode}
%
% \subsection{Definition for keyword parameters}
%
%    \begin{macrocode}



\dim_new:N \l_sdaps_checkbox_linewidth_dim
\dim_new:N \l_sdaps_checkbox_width_dim
\dim_new:N \l_sdaps_checkbox_height_dim
\tl_new:N \l_sdaps_checkbox_form_tl
\tl_new:N \l_sdaps_checkbox_fill_tl
\tl_new:N \l_sdaps_checkbox_draw_tl
\tl_new:N \l_sdaps_checkbox_var_tl
\tl_new:N \l_sdaps_checkbox_value_tl
\bool_new:N \l_sdaps_checkbox_draw_check_bool

\tl_set:Nn \l_sdaps_checkbox_form_tl { box }

\tl_new:N \l_sdaps_parse_unknown_tl


% Internal overlays
\tl_new:N \l_sdaps_overlay_centered_text_tl
\tl_new:N \l_sdaps_overlay_minipage_text_tl
\tl_new:N \l_sdaps_overlay_minipage_pos_tl
\dim_new:N \l_sdaps_overlay_minipage_pad_dim

% Note that width/height is the *outside* width/height
\keys_define:nn { sdaps / checkbox }
{
  linewidth    .dim_set:N   = \l_sdaps_checkbox_linewidth_dim,
  linewidth    .initial:n   = 1bp,
  width        .dim_set:N   = \l_sdaps_checkbox_width_dim,
  width        .initial:n   = 3.5mm,
  height       .dim_set:N   = \l_sdaps_checkbox_height_dim,
  height       .initial:n   = 3.5mm,
  form         .choices:nn  = { box, ellipse } { \tl_set:Nx \l_sdaps_checkbox_form_tl { \l_keys_choice_tl } },
  value        .tl_set:N    = \l_sdaps_checkbox_value_tl,

  fill         .tl_set:N    = \l_sdaps_checkbox_fill_tl,
  fill         .initial:n   = { white },

  draw         .tl_set:N    = \l_sdaps_checkbox_draw_tl,
  draw         .initial:n   = { . },

  draw_check   .bool_set:N  = \l_sdaps_checkbox_draw_check_bool,
  draw_check   .default:n   = true,
  draw_check   .initial:n   = false,

  % Simple node overlay
  centered_text  .tl_set:N    = \l_sdaps_overlay_centered_text_tl,
  centered_text  .initial:n   = {},

  % minipage overlay
  text         .tl_set:N    = \l_sdaps_overlay_minipage_text_tl,
  text         .initial:n   = {},
  text_align   .tl_set:N    = \l_sdaps_overlay_minipage_pos_tl,
  text_align   .initial:n   = {c},
  text_padding .dim_set:N   = \l_sdaps_overlay_minipage_pad_dim,
  text_padding .initial:n   = {2bp},

  ellipse    .meta:n  = { form=ellipse },
  box        .meta:n  = { form=box },
}
%    \end{macrocode}
%
% \subsection{Checkboxes}
%
%
%    \begin{macrocode}

\cs_new_protected_nopar:Nn \__sdaps_checkbox_internal:nn
{
  \mbox{
    \sdaps_if_rtl:T {\beginL}
    \pdfsavepos

     % Position of page and baseline offset
    \dim_set:Nn \l_sdaps_x_dim { \hoffset }
    \dim_set:Nn \l_sdaps_y_dim { \voffset + \l_sdaps_checkbox_height_dim - \dim_eval:n { 0.5\l_sdaps_checkbox_height_dim - 0.8ex } }

    % Size
    \dim_set:Nn \l_sdaps_width_dim { \l_sdaps_checkbox_width_dim }
    \dim_set:Nn \l_sdaps_height_dim { \l_sdaps_checkbox_height_dim }

    \bool_if:NT \g_sdaps_write_enable_bool {
      % pdflast[xy]pos is the PDF position of the baseline at the start of the box
      % excluding the page origin offset.
      \sdaps_context_get:nN {id} \l__sdaps_tmpa_tl
      \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
        \msg_warning:nn { sdapsbase } { no_qid }
      } {
        \sdaps_info_write_x:x{
          Box[\l__sdaps_tmpa_tl]=Checkbox,
          \exp_not:n{\int_use:N\g_sdaps_page_int},
          \exp_not:n{\dim_eval:n} { \exp_not:f {\dim_use:N \l_sdaps_x_dim + \the\pdflastxpos sp} },
          \exp_not:n{\dim_eval:n} { \exp_not:f {\dim_use:N \l_sdaps_y_dim + \the\pdflastypos sp} },
          \dim_use:N \l_sdaps_width_dim,
          \dim_use:N \l_sdaps_height_dim,
          \tl_to_str:N\l_sdaps_checkbox_form_tl,
          \dim_use:N \l_sdaps_checkbox_linewidth_dim,
          #1,\tl_if_empty:nTF { #2 } { \int_use:N \g__sdaps_object_id_int } { #2 }
        }
      }
    }


    \tikz[baseline={0.5\l_sdaps_checkbox_height_dim-0.8ex}]{%
      \tl_if_eq:VnT \l_sdaps_checkbox_form_tl { box } {
        \draw[line~width=\l_sdaps_checkbox_linewidth_dim,fill=\l_sdaps_checkbox_fill_tl,draw=\l_sdaps_checkbox_draw_tl] (0.5\l_sdaps_checkbox_linewidth_dim, 0.5\l_sdaps_checkbox_linewidth_dim) rectangle +($(\l_sdaps_checkbox_width_dim, \l_sdaps_checkbox_height_dim)-(\l_sdaps_checkbox_linewidth_dim,\l_sdaps_checkbox_linewidth_dim)$);%
      }
      \tl_if_eq:VnT \l_sdaps_checkbox_form_tl { ellipse } {
        \draw[line~width=\l_sdaps_checkbox_linewidth_dim,fill=\l_sdaps_checkbox_fill_tl,draw=\l_sdaps_checkbox_draw_tl] (0.5\l_sdaps_checkbox_width_dim, 0.5\l_sdaps_checkbox_height_dim) circle [x~radius=0.5\l_sdaps_checkbox_width_dim-0.5\l_sdaps_checkbox_linewidth_dim, y~radius=0.5\l_sdaps_checkbox_height_dim-0.5\l_sdaps_checkbox_linewidth_dim];%
      }

      % For the overlay we actually position the nodes relative to the checkbox
      % and not absolute on the page.
      \dim_set:Nn \l_sdaps_x_dim { 0pt }
      \dim_set:Nn \l_sdaps_y_dim { \l_sdaps_checkbox_height_dim }

      % Use overlay so that nothing happens if a node is larger than the checkbox
      \begin{scope}[overlay]
        \seq_map_inline:Nn \g__sdaps_checkbox_overlays_seq {##1}
      \end{scope}
    }
    \sdaps_if_rtl:T {\endL}
  }
}
\cs_generate_variant:Nn \__sdaps_checkbox_internal:nn { Vn }

\sdaps_context_set:n { checkboxtype=multichoice }
\cs_new_protected_nopar:Nn \sdaps_checkbox_set_type:n
{
  \sdaps_context_set:n { checkboxtype={#1} }
}
\cs_generate_variant:Nn \sdaps_checkbox_set_type:n { V }

\cs_new_protected_nopar:Nn \sdaps_checkbox:nn
{
  \group_begin:%

    \_sdaps_generate_var:nN { #1 } \l_sdaps_var_tl

    \sdaps_context_get:nN { checkboxtype } \l__sdaps_tmpa_tl
    \tl_if_eq:VnTF \l__sdaps_tmpa_tl { multichoice } {
      \tl_set:Nn \l_sdaps_parse_unknown_tl { box }
    } {
      \tl_set:Nn \l_sdaps_parse_unknown_tl { ellipse }
    }

    \__sdaps_append_from_context:nN { * } \l_sdaps_parse_unknown_tl
    \__sdaps_append_from_context:VN \l__sdaps_tmpa_tl \l_sdaps_parse_unknown_tl
    \__sdaps_append_override_options:NVn \l_sdaps_parse_unknown_tl \l_sdaps_var_tl { #2 }

    \keys_set_known:nVN { sdaps / checkbox } \l_sdaps_parse_unknown_tl \l_sdaps_parse_unknown_tl

    \_sdaps_box_inc_object_id:

    \__sdaps_checkbox_internal:Vn \l_sdaps_var_tl { #2 }
  \group_end:%
  \ignorespaces
}
\cs_generate_variant:Nn \sdaps_checkbox:nn { Vn, VV, nV }


\cs_new_protected_nopar:Nn \sdaps_overlay_check:
{
  \bool_if:NT \l_sdaps_checkbox_draw_check_bool {
    \begin{scope}[decoration={random~steps,segment~length=4pt,amplitude=1pt}]
      \draw[line~width=\l_sdaps_checkbox_linewidth_dim, decorate] ($(0, 0) - (2pt,2pt)$) -- (0.5\l_sdaps_checkbox_width_dim, 0.5\l_sdaps_checkbox_height_dim) -- ($(\l_sdaps_checkbox_width_dim, \l_sdaps_checkbox_height_dim) + (2pt,2pt)$);%
      \draw[line~width=\l_sdaps_checkbox_linewidth_dim, decorate] ($(0, \l_sdaps_checkbox_height_dim) + (-2pt,2pt)$) -- (0.5\l_sdaps_checkbox_width_dim, 0.5\l_sdaps_checkbox_height_dim) -- ($(\l_sdaps_checkbox_width_dim, 0) + (2pt,-2pt)$);%
    \end{scope}
  }
}
\seq_put_left:Nn \g__sdaps_checkbox_overlays_seq \sdaps_overlay_check:


\cs_new_protected_nopar:Nn \sdaps_overlay_centered:
{
  \tl_if_empty:NF \l_sdaps_overlay_centered_text_tl {
    \node[anchor=center,inner~sep=0pt,outer~sep=0pt] at ($(\l_sdaps_x_dim, \l_sdaps_y_dim) + 0.5*(\l_sdaps_width_dim, -\l_sdaps_height_dim)$) {
      \l_sdaps_overlay_centered_text_tl
    };
  }
}
\seq_put_left:Nn \g__sdaps_checkbox_overlays_seq \sdaps_overlay_centered:
\seq_put_left:Nn \g__sdaps_textbox_overlays_seq \sdaps_overlay_centered:


\cs_new_protected_nopar:Nn \sdaps_overlay_minipage:
{
  \tl_if_empty:NF \l_sdaps_overlay_minipage_text_tl {
    \node[anchor=center,inner~sep=0pt,outer~sep=0pt] at ($(\l_sdaps_x_dim, \l_sdaps_y_dim) + 0.5*(\l_sdaps_width_dim, -\l_sdaps_height_dim)$) {
      \dim_set:Nn \l_sdaps_width_dim { \l_sdaps_width_dim - 2\l_sdaps_overlay_minipage_pad_dim }
      \dim_set:Nn \l_sdaps_height_dim { \l_sdaps_height_dim - 2\l_sdaps_overlay_minipage_pad_dim }

      \begin{minipage}[t][\l_sdaps_height_dim][\l_sdaps_overlay_minipage_pos_tl]{\l_sdaps_width_dim}
        % Hm, is this sane?
        \tex_let:D \textheight\l_sdaps_height_dim
        \l_sdaps_overlay_minipage_text_tl
      \end{minipage}
    };
  }
}
\seq_put_left:Nn \g__sdaps_checkbox_overlays_seq \sdaps_overlay_minipage:
\seq_put_left:Nn \g__sdaps_textbox_overlays_seq \sdaps_overlay_minipage:


%    \end{macrocode}
%


% \subsection{Textboxes}
%
%
%    \begin{macrocode}

\sdaps_context_set:n { textboxtype=textbox }
\cs_new_protected_nopar:Nn \sdaps_textbox_set_type:n
{
  \sdaps_context_set:n { textboxtype={#1} }
}
\cs_generate_variant:Nn \sdaps_textbox_set_type:n { V }

\dim_new:N  \l_sdaps_textbox_linewidth_dim
\tl_new:N   \l_sdaps_textbox_var_tl
\tl_new:N   \l_sdaps_textbox_fill_tl
\tl_new:N   \l_sdaps_textbox_draw_tl
\tl_new:N   \l__sdaps_textbox_boxtype_tl


\keys_define:nn { sdaps / textbox }
{
  linewidth    .dim_set:N   = \l_sdaps_textbox_linewidth_dim,
  linewidth    .initial:n   = 1bp,

  fill         .tl_set:N    = \l_sdaps_textbox_fill_tl,
  fill         .initial:n   = { white },

  draw         .tl_set:N    = \l_sdaps_textbox_draw_tl,
  draw         .initial:n   = { . },

  % Simple node overlay
  centered_text  .tl_set:N    = \l_sdaps_overlay_centered_text_tl,
  centered_text  .initial:n   = {},

  % minipage overlay
  text         .tl_set:N    = \l_sdaps_overlay_minipage_text_tl,
  text         .initial:n   = {},
  text_align   .tl_set:N    = \l_sdaps_overlay_minipage_pos_tl,
  text_align   .initial:n   = {c},
  text_padding .dim_set:N   = \l_sdaps_overlay_minipage_pad_dim,
  text_padding .initial:n   = {2bp},
}




\dim_new:N \l__sdaps_textbox_dp_dim
\dim_new:N \l__sdaps_textbox_ht_dim
\dim_new:N \l__sdaps_textbox_wd_dim
\dim_new:N \l__sdaps_textbox_pad_dim


\msg_new:nnn { sdapsbase } { textbox_wrong_mode } { Impossible~to~layout~a~#1~textbox~in~#2~mode. }

\cs_new_protected_nopar:Nn \__sdaps_textbox_prepare:n
{
  \tl_set:Nn \l_sdaps_parse_unknown_tl {}

  \_sdaps_generate_var:nN { #1 } \l_sdaps_var_tl

  \sdaps_context_get:nN { textboxtype } \l__sdaps_tmpa_tl
  \tl_if_eq:VnTF \l__sdaps_tmpa_tl { codebox } {
    \tl_set:Nn \l__sdaps_textbox_boxtype_tl { Codebox }
  } {
    \tl_set:Nn \l__sdaps_textbox_boxtype_tl { Textbox }
  }

  \__sdaps_append_from_context:nN { * } \l_sdaps_parse_unknown_tl
  \__sdaps_append_from_context:VN \l__sdaps_tmpa_tl \l_sdaps_parse_unknown_tl
  \__sdaps_append_override_options:NVn \l_sdaps_parse_unknown_tl \l_sdaps_var_tl { }

  \keys_set_known:nVN { sdaps / textbox } \l_sdaps_parse_unknown_tl \l_sdaps_parse_unknown_tl

  \_sdaps_box_inc_object_id:
}

\cs_new_protected_nopar:Nn \sdaps_textbox_vhstretch:nnn
{
%    \end{macrocode}
%
% At first we need to ensure that we are not in math mode. We also error out if
% switching into vertical mode (by inserting a paragraph break) fails.
%
% The scaling feature will likely fail in inner vertical mode, but it is still
% permissible.
%
%    \begin{macrocode}
  \if_mode_math:
    \msg_error:nnnn { sdapsbase } { textbox_wrong_mode } { vhstretch } { math }
  \else:
  \tex_par:D
  \if_mode_horizontal:
    \msg_error:nnnn { sdapsbase } { textbox_wrong_mode } { vhstretch } { horizontal }
  \else:
  % Go into vertical mode by ending the current paragraph and insert
  % \cs{widowpenalty} so that we don't get an unwelcome page break. It is
  % assumed that any explanation for the textbox will be on top.
  \tex_penalty:D \tex_widowpenalty:D

  \group_begin:%

    \__sdaps_textbox_prepare:n { #1 }

%    \end{macrocode}
%
% First we define the height and depth of the box that will be set. Setting the
% height works by inserting a rule into the first box and adding a negative
% skip afterwards. The depth is compensated by simply doing the same thing at
% the bottom.
%
% Note that we need to add nobreak/nointerlineskip everywhere so that we
% don't insert extra spacing and no page break will happen.
%
% The first box has a defined height and stores the current position for the
% frame code later on. Then two cleaders follow which simply implement the
% required stretching (cleaders are used to prevent page breaking, I do not
% know whether this is sane, but it seems to work just fine). After this the
% box containing the main drawing code is placed. We simply use a vbox with
% right aligned content. The last thing happening is a vskip plus hbox to set
% the correct depth.
%
%    \begin{macrocode}
    % TODO: Make this configurable
    \dim_set:Nn \l__sdaps_textbox_dp_dim { 0.5ex }
    \dim_set:Nn \l__sdaps_textbox_ht_dim { 1.7ex }

    \vbox:n {
      \sdaps_if_rtl:T {\beginL}
      \leftskip=0pt
      \rightskip=0pt plus 1fill
      \noindent
      \tex_vrule:D height \l__sdaps_textbox_ht_dim depth 0pt width 0pt
      \pgfsys@markposition{textboxtop\int_use:N\g__sdaps_textbox_num_int}
      \sdaps_if_rtl:T {\endL}
    }

    \tex_penalty:D 10000
    \nointerlineskip

    \tex_cleaders:D\tex_hbox:D{}\skip_vertical:n{#2 - \l__sdaps_textbox_ht_dim}

    \tex_penalty:D 10000
    \nointerlineskip

    \tex_cleaders:D\tex_hbox:D{}\skip_vertical:n{\stretch{#3}}

    \tex_penalty:D 10000
    \nointerlineskip

    \vbox:n {
      \sdaps_if_rtl:T {\beginL}
      \noindent
      \leftskip=0pt plus 1fill
      \rightskip=0pt
      \begin{tikzpicture}[remember~picture,overlay,shift=(current~page.south~west)]
        \pgfsys@getposition{pgfpageorigin}{\@sdaps@pageorigin}
        \pgfsys@getposition{textboxtop\int_use:N\g__sdaps_textbox_num_int}{\@sdaps@textboxtoppos}
        \pgfpointadd{\@sdaps@textboxtoppos}{
          \pgfpointadd{\@sdaps@pageorigin}{\pgfpoint{0}{\l__sdaps_textbox_ht_dim}}
        }
        \pgfgetlastxy{\l__sdaps_x}{\l__sdaps_y}
        \dim_set:Nn \l_sdaps_x_dim {\l__sdaps_x}
        \dim_set:Nn \l_sdaps_y_dim {\l__sdaps_y}

        \pgfsys@getposition{\pgfpictureid}{\@sdaps@textboxbottompos}
        \pgfpointdiff{\@sdaps@textboxtoppos}{\@sdaps@textboxbottompos}

        % Is there a more elegant way to multiply the height with -1?
        \pgfgetlastxy{\l__sdaps_width}{\l__sdaps_height}
        % Add the minimum height (i.e. depth below the last baseline) to the
        % overall height.
        \pgfpoint{\l__sdaps_width}{-\l__sdaps_height + \l__sdaps_textbox_ht_dim}
        \pgfgetlastxy{\l__sdaps_width}{\l__sdaps_height}
        \dim_set:Nn \l_sdaps_width_dim {\l__sdaps_width}
        \dim_set:Nn \l_sdaps_height_dim {\l__sdaps_height}

        % Draw the rectangle
        \draw[line~width=\l_sdaps_textbox_linewidth_dim,fill=\l_sdaps_textbox_fill_tl,draw=\l_sdaps_textbox_draw_tl] ($(\l_sdaps_x_dim, \l_sdaps_y_dim) + 0.5 * (\l_sdaps_textbox_linewidth_dim, -\l_sdaps_textbox_linewidth_dim)$) rectangle +($(\l_sdaps_width_dim, -\l_sdaps_height_dim) - (\l_sdaps_textbox_linewidth_dim, -\l_sdaps_textbox_linewidth_dim)$);

        \begin{scope}
          \seq_map_inline:Nn \g__sdaps_textbox_overlays_seq {##1}
        \end{scope}

        \bool_if:NT \g_sdaps_write_enable_bool {
          \sdaps_context_get:nN {id} \l__sdaps_tmpa_tl
          \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
            \msg_warning:nn { sdapsbase } { no_qid }
          } {
            \sdaps_info_write_x:x {
              Box[\l__sdaps_tmpa_tl]=\l__sdaps_textbox_boxtype_tl,
              \exp_not:n{\int_use:N\g_sdaps_page_int},
              \dim_use:N \l_sdaps_x_dim,
              \dim_use:N \l_sdaps_y_dim,
              \dim_use:N \l_sdaps_width_dim,
              \dim_use:N \l_sdaps_height_dim,
              \dim_use:N \l_sdaps_textbox_linewidth_dim,
              \tl_use:N \l_sdaps_var_tl,
            }
          }
        }
      \end{tikzpicture}
      \sdaps_if_rtl:T {\endL}
    }

    % We are done here, but we need the correct depth, so skip around a bit
    \tex_penalty:D 10000
    \nointerlineskip

    \skip_vertical:n{ - \l__sdaps_textbox_dp_dim}

    \tex_penalty:D 10000
    \nointerlineskip

    \hbox:n { \vrule depth \l__sdaps_textbox_dp_dim height 0pt width 0pt }

    \int_gincr:N\g__sdaps_textbox_num_int

  \group_end:
  \fi:
  \fi:
}
\cs_generate_variant:Nn \sdaps_textbox_vhstretch:nnn { Vnn }

\cs_new_protected_nopar:Nn \sdaps_textbox_vhstretch:nn
{
  \sdaps_textbox_vhstretch:nnn { #1 } { #2 } { 1 }
}


\cs_new_protected_nopar:Nn \sdaps_textbox_hstretch:nnnnn
{
  \group_begin:
    \sdaps_if_rtl:T {\beginL}

    \__sdaps_textbox_prepare:n { #1 }

    \dim_set:Nn \l_tmpa_dim { #2 }
    \dim_set:Nn \l_tmpb_dim { #3 }

    % Place a vrule to make space for the top/bottom padding
    \tex_vrule:D depth \dim_use:N \l_tmpa_dim height \dim_use:N \l_tmpb_dim width 0pt \nobreak
    \pgfsys@markposition{textboxstart\int_use:N\g__sdaps_textbox_num_int} \nobreak

    \skip_horizontal:n { #4 + \stretch{#5} } \nobreak

    % The textbox (rendered on the background)
    \begin{tikzpicture}[remember~picture,overlay,shift=(current~page.south~west)]
      \pgfsys@getposition{pgfpageorigin}{\@sdaps@pageorigin}
      \pgfsys@getposition{textboxstart\int_use:N\g__sdaps_textbox_num_int}{\@sdaps@textboxpos}
      % The position here is the position of the baseline.
      % So move up by height (param 2) to get the correct vertical position.
      \pgfpointadd{\@sdaps@textboxpos}{
        \pgfpointadd{\@sdaps@pageorigin}{\pgfpoint{0}{ \dim_use:N \l_tmpb_dim}}
      }
      \pgfgetlastxy{\l__sdaps_x}{\l__sdaps_y}
      \dim_set:Nn \l_sdaps_x_dim {\l__sdaps_x}
      \dim_set:Nn \l_sdaps_y_dim {\l__sdaps_y}

      \pgfsys@getposition{\pgfpictureid}{\@sdaps@textboxendpos}
      % Calculate width and add the height to it
      \pgfpointadd{
        \pgfpointdiff{\@sdaps@textboxpos}{\@sdaps@textboxendpos}
      }{\pgfpoint{0pt}{\dim_use:N \l_tmpa_dim +  \dim_use:N \l_tmpb_dim}}
      \pgfgetlastxy{\l__sdaps_width}{\l__sdaps_height}
      \dim_set:Nn \l_sdaps_width_dim {\l__sdaps_width}
      \dim_set:Nn \l_sdaps_height_dim {\l__sdaps_height}

      % Draw the rectangle
      \draw[line~width=\l_sdaps_textbox_linewidth_dim,fill=\l_sdaps_textbox_fill_tl,draw=\l_sdaps_textbox_draw_tl] ($(\l_sdaps_x_dim, \l_sdaps_y_dim) + 0.5 * (\l_sdaps_textbox_linewidth_dim, -\l_sdaps_textbox_linewidth_dim)$) rectangle +($(\l_sdaps_width_dim, -\l_sdaps_height_dim) - (\l_sdaps_textbox_linewidth_dim, -\l_sdaps_textbox_linewidth_dim)$);

      \begin{scope}
        \seq_map_inline:Nn \g__sdaps_textbox_overlays_seq {##1}
      \end{scope}

      \bool_if:NT \g_sdaps_write_enable_bool {
        \sdaps_context_get:nN {id} \l__sdaps_tmpa_tl
        \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
          \msg_warning:nn { sdapsbase } { no_qid }
        } {
          \sdaps_info_write_x:x {
            Box[\l__sdaps_tmpa_tl]=\l__sdaps_textbox_boxtype_tl,
            \exp_not:n{\int_use:N\g_sdaps_page_int},
            \dim_use:N \l_sdaps_x_dim,
            \dim_use:N \l_sdaps_y_dim,
            \dim_use:N \l_sdaps_width_dim,
            \dim_use:N \l_sdaps_height_dim,
            \dim_use:N \l_sdaps_textbox_linewidth_dim,
            \tl_use:N \l_sdaps_var_tl,
          }
        }
      }
    \end{tikzpicture}

    \int_gincr:N\g__sdaps_textbox_num_int

    \sdaps_if_rtl:T {\endL}
  \group_end:
}

\cs_new_protected_nopar:Nn \__sdaps_textbox_prepare_coffin:
{
  \dim_set:Nn \l__sdaps_textbox_ht_dim { \coffin_ht:N \l__sdaps_textbox_coffin }
  \dim_set:Nn \l__sdaps_textbox_dp_dim { \coffin_dp:N \l__sdaps_textbox_coffin }
  \dim_set:Nn \l__sdaps_textbox_wd_dim { \coffin_wd:N \l__sdaps_textbox_coffin }

  \hcoffin_set:Nn \l_tmpa_coffin {
    \tex_vrule:D depth 0pt height \dim_eval:n { \l__sdaps_textbox_ht_dim + \l__sdaps_textbox_pad_dim } width 0pt

    \pdfsavepos

    \dim_set:Nn \l_sdaps_width_dim {\l__sdaps_textbox_wd_dim + 2\l__sdaps_textbox_pad_dim}
    \dim_set:Nn \l_sdaps_height_dim {\l__sdaps_textbox_ht_dim + \l__sdaps_textbox_dp_dim + 2\l__sdaps_textbox_pad_dim}

    % pdflast[xy]pos is the PDF position of the top left corner excluding the
    % origin
    \bool_if:NT \g_sdaps_write_enable_bool {
      \sdaps_context_get:nN {id} \l__sdaps_tmpa_tl
      \tl_if_eq:VnTF \l__sdaps_tmpa_tl { \q_no_value } {
        \msg_warning:nn { sdapsbase } { no_qid }
      } {
        \sdaps_info_write_x:x {
          Box[\l__sdaps_tmpa_tl]=\l__sdaps_textbox_boxtype_tl,
          \exp_not:n{\int_use:N\g_sdaps_page_int},
          \exp_not:n{\dim_eval:n {\hoffset + \the\pdflastxpos sp}},
          \exp_not:n{\dim_eval:n} { \exp_not:n {\voffset + \the\pdflastypos sp} + \dim_use:N \l__sdaps_textbox_ht_dim +  \dim_use:N \l__sdaps_textbox_pad_dim },
          \dim_use:N \l_sdaps_width_dim,
          \dim_use:N \l_sdaps_height_dim,
          \dim_use:N \l_sdaps_textbox_linewidth_dim,
          \tl_use:N \l_sdaps_var_tl,
        }
      }
    }

    \dim_set:Nn \l_sdaps_x_dim { 0pt }
    \dim_set:Nn \l_sdaps_y_dim { \l__sdaps_textbox_ht_dim + \l__sdaps_textbox_pad_dim }

    % The textbox (rendered on the background)
    \begin{tikzpicture}[overlay]
      % Draw the rectangle
      \draw[line~width=\l_sdaps_textbox_linewidth_dim,fill=\l_sdaps_textbox_fill_tl,draw=\l_sdaps_textbox_draw_tl] ($(\l_sdaps_x_dim, \l_sdaps_y_dim) + 0.5 * (\l_sdaps_textbox_linewidth_dim, -\l_sdaps_textbox_linewidth_dim)$) rectangle +($(\l_sdaps_width_dim, -\l_sdaps_height_dim) - (\l_sdaps_textbox_linewidth_dim, -\l_sdaps_textbox_linewidth_dim)$);

      \begin{scope}
          \seq_map_inline:Nn \g__sdaps_textbox_overlays_seq {##1}%
      \end{scope}
    \end{tikzpicture}
    \skip_horizontal:n { \l__sdaps_textbox_pad_dim }
  }

  \hcoffin_set:Nn \l_tmpb_coffin {
    \skip_horizontal:n { \l__sdaps_textbox_pad_dim }
    \tex_vrule:D depth \l__sdaps_textbox_pad_dim height 0pt width 0pt
  }

  \coffin_join:NnnNnnnn \l_tmpa_coffin { r } { H } \l__sdaps_textbox_coffin { l } { H } { 0pt } { 0pt }
  \coffin_join:NnnNnnnn \l_tmpa_coffin { r } { b } \l_tmpb_coffin { l } { t } { 0pt } { 0pt }

  \coffin_set_eq:NN \l__sdaps_textbox_coffin \l_tmpa_coffin


  \int_gincr:N\g__sdaps_textbox_num_int
}

\coffin_new:N \l__sdaps_textbox_coffin
\cs_new_protected_nopar:Nn \sdaps_textbox_hbox:nnn
{
  \group_begin:

    \__sdaps_textbox_prepare:n { #1 }

    \hcoffin_set:Nn \l__sdaps_textbox_coffin { \tl_trim_spaces:n { #3 } }

    \dim_set:Nn \l__sdaps_textbox_pad_dim { #2 }

    \__sdaps_textbox_prepare_coffin:

    \coffin_typeset:Nnnnn \l__sdaps_textbox_coffin { l } { H } { 0pt } { 0pt }

  \group_end:
}

\cs_new_protected:Nn \sdaps_textbox_vbox:nnnn
{
  \group_begin:

    \__sdaps_textbox_prepare:n { #1 }

    \dim_set:Nn \l__sdaps_textbox_pad_dim { #3 }
    \dim_set:Nn \l__sdaps_textbox_wd_dim { #2 - 2\l__sdaps_textbox_pad_dim }

    \vcoffin_set:Nnn \l__sdaps_textbox_coffin { \l__sdaps_textbox_wd_dim } { \tl_trim_spaces:n { #4 }}

    \__sdaps_textbox_prepare_coffin:

    \coffin_typeset:Nnnnn \l__sdaps_textbox_coffin { l } { H } { 0pt } { 0pt }

  \group_end:
}

%    \end{macrocode}
%
%
% \subsection{Page Marking}
%
% SDAPS depends on certain markings on every page. The following function
% implement drawing these marks.
%
%    \begin{macrocode}

\int_new:N \g_sdaps_page_int
\int_set:Nn \g_sdaps_page_int { 0 }

% Disabling recognition disables all drawings related to automatic recognition
\bool_new:N \g_sdaps_recognition_bool
\bool_new:N \g_sdaps_draft_bool
\bool_new:N \g_sdaps_twoside_bool
\bool_new:N \g_sdaps_print_questionnaire_id_bool

\bool_set:Nn \g_sdaps_recognition_bool \c_true_bool
\bool_set:Nn \g_sdaps_draft_bool \c_true_bool
\bool_set:Nn \g_sdaps_twoside_bool \c_false_bool
\bool_set:Nn \g_sdaps_print_questionnaire_id_bool \c_false_bool



\tl_new:N \g_sdaps_style_tl
\tl_new:N \g_sdaps_checkmode_tl
\dim_new:N \g_sdaps_edge_left_margin_dim
\dim_new:N \g_sdaps_edge_right_margin_dim
\dim_new:N \g_sdaps_edge_top_margin_dim
\dim_new:N \g_sdaps_edge_bottom_margin_dim
\dim_new:N \g_sdaps_edge_marker_linewidth_dim
\dim_new:N \g_sdaps_edge_marker_length_dim

\dim_new:N \g_sdaps_classic_boxpad_dim
\dim_new:N \g_sdaps_classic_boxsize_dim


\tl_gset:Nn \g_sdaps_style_tl { code128 }
\tl_gset:Nn \g_sdaps_twoside_barcode_tl { both }
\tl_gset:Nn \g_sdaps_checkmode_tl { checkcorrect }
\dim_gset:Nn \g_sdaps_edge_left_margin_dim { 10mm }
\dim_gset:Nn \g_sdaps_edge_right_margin_dim { 10mm }
\dim_gset:Nn \g_sdaps_edge_top_margin_dim { 12mm }
\dim_gset:Nn \g_sdaps_edge_bottom_margin_dim { 12mm }
\dim_gset:Nn \g_sdaps_edge_marker_linewidth_dim { 1bp }
\dim_gset:Nn \g_sdaps_edge_marker_length_dim { 20mm }

\dim_gset:Nn \g_sdaps_classic_boxpad_dim { 3mm }
\dim_gset:Nn \g_sdaps_classic_boxsize_dim { 3.5mm }


\tl_new:N \g__sdaps_questionnaire_id_tl
\tl_gset:Nn \g__sdaps_questionnaire_id_tl { }

\tl_new:N \g_sdaps_questionnaire_id_label_tl
\tl_gset:Nn \g_sdaps_questionnaire_id_label_tl { }


\tl_new:N \g_sdaps_survey_id_tl
\tl_gset:Nn \g_sdaps_survey_id_tl { 32498923 }

\tl_new:N \g_sdaps_global_id_tl
\tl_gset:Nn \g_sdaps_global_id_tl { }

\tl_new:N \g_sdaps_global_id_label_tl
\tl_gset:Nn \g_sdaps_global_id_label_tl { }




% Settings for code128 barcodes (used in code128 style, who would have thought?)
\dim_new:N \c_sdaps_barcode_height_dim
\dim_gset:Nn \c_sdaps_barcode_height_dim {6.5mm}
% This is the same as the default
\dim_new:N \c_sdaps_barcode_bar_width_dim
\dim_gset:Nn \c_sdaps_barcode_bar_width_dim {0.33mm}
% Same as default. Barwidth is decreased for printing by this value.
\dim_new:N \c_sdaps_barcode_bcorr_dim
\dim_gset:Nn \c_sdaps_barcode_bcorr_dim {0.020mm}

% The padding on the left/right of a barcode. This is the distance that the
% barcodes will be printed from the cornermarks
% Choosen to be the same as the barcode height. Note that the Code-128
% standard requires a quiet zone of max(10*modulesize, ~6.4mm).
\dim_new:N \c_sdaps_barcode_hpad_dim
\dim_gset:Nn \c_sdaps_barcode_hpad_dim {6.5mm}

% This needs to be smaller than 6.5mm because otherwise the content is too close.
% We set it so that it forms a golden ratio 6.5mm*(sqrt(5/4)-0.5). This means
% we have about 4.5mm padding to the content.
\dim_new:N \c_sdaps_barcode_vpad_dim
\dim_gset:Nn \c_sdaps_barcode_vpad_dim {4.02mm}


\cs_new_protected_nopar:Nn \sdaps_draw_codes:
{
  \group_begin:
    \begin{scope}[line~width=\g_sdaps_edge_marker_linewidth_dim, shift={(current~page.south~west)}]
      \str_if_eq:VnT \g_sdaps_style_tl { qr } {
        \tl_if_empty:VF \g__sdaps_questionnaire_id_tl {
          \begin{scope}[shift={($(\g_sdaps_edge_left_margin_dim, \g_sdaps_edge_bottom_margin_dim)$)}]
            \node(barcode)[anchor=south~west,outer~sep=0,inner~sep=0]{
              \qrcode_render:nV {nolink,version=2,level=H,padding,height=10mm} \g__sdaps_questionnaire_id_tl
            };
          \end{scope}
        }

        % We unconditionally print this barcode, it is required for the recognition
        % process.
        \begin{scope}[shift={($(\paperwidth, 0) + (-\g_sdaps_edge_right_margin_dim, \g_sdaps_edge_bottom_margin_dim)$)}]
          \pgfmathsetbasenumberlength{4}
          \pgfmathdectobase{\paddedpage}{\int_use:N\g_sdaps_page_int}{10}% Yes, padding to 4 chars the hard way
          \node(barcode)[anchor=south~east,outer~sep=0,inner~sep=0]{
            \qrcode_render:nx {nolink,version=2,level=H,padding,height=10mm} {\tl_use:N\g_sdaps_survey_id_tl\paddedpage}
          };
        \end{scope}

        \tl_if_empty:VF \g_sdaps_global_id_tl {
          \begin{scope}[shift={($(\paperwidth/2-\g_sdaps_edge_right_margin_dim/2+\g_sdaps_edge_left_margin_dim/2, \g_sdaps_edge_bottom_margin_dim)$)}]
            \node(barcode)[anchor=south,outer~sep=0,inner~sep=0]{
              \qrcode_render:nV {nolink,version=2,level=H,padding,height=10mm} \g_sdaps_global_id_tl
            };
          \end{scope}
        }
      }

      \str_if_eq:VnT \g_sdaps_style_tl { code128 } {
        \tl_if_empty:VF \g__sdaps_questionnaire_id_tl {
          % TODO: do not hardcode the font!
          \ttfamily\footnotesize

          \begin{scope}[shift={($(\g_sdaps_edge_left_margin_dim, \g_sdaps_edge_bottom_margin_dim) + (\c_sdaps_barcode_hpad_dim, \c_sdaps_barcode_vpad_dim)$)}]
            \node(barcode)[anchor=south~west,outer~sep=0,inner~sep=0]{
              \X = \c_sdaps_barcode_bar_width_dim
              \bcorr = \c_sdaps_barcode_bcorr_dim
              \barheight = \c_sdaps_barcode_height_dim
              \code_render:V \g__sdaps_questionnaire_id_tl
            };
            \node[below=1mm~of~barcode,distance=0,anchor=north,outer~sep=0,inner~sep=0]{
              \tl_if_empty:VTF \g_sdaps_questionnaire_id_label_tl {
                \tl_use:N \g__sdaps_questionnaire_id_tl
              } {
                \tl_use:N \g_sdaps_questionnaire_id_label_tl
              }
            };
          \end{scope}
        }

        % We unconditionally print this barcode, it is required for the recognition
        % process.
        \begin{scope}[shift={($(\paperwidth, 0) + (-\g_sdaps_edge_right_margin_dim, \g_sdaps_edge_bottom_margin_dim) + (-\c_sdaps_barcode_hpad_dim, \c_sdaps_barcode_vpad_dim)$)}]
          \pgfmathsetbasenumberlength{4}
          \pgfmathdectobase{\paddedpage}{\int_use:N\g_sdaps_page_int}{10}% Yes, padding to 4 chars the hard way
          \node(barcode)[anchor=south~east,outer~sep=0,inner~sep=0]{
            \X = \c_sdaps_barcode_bar_width_dim
            \bcorr = \c_sdaps_barcode_bcorr_dim
            \barheight = \c_sdaps_barcode_height_dim
            \code_render:x {\tl_use:N\g_sdaps_survey_id_tl \paddedpage}
          };
          \node[below=1mm~of~barcode,distance=0,anchor=north,outer~sep=0,inner~sep=0]{
            % TODO: do not hardcode the font!
            \ttfamily\footnotesize

            \tl_use:N\g_sdaps_survey_id_tl\,\paddedpage
          };
        \end{scope}

        \tl_if_empty:VF \g_sdaps_global_id_tl {
          \begin{scope}[shift={($(\paperwidth/2-\g_sdaps_edge_right_margin_dim/2+\g_sdaps_edge_left_margin_dim/2, 0) + (0, \g_sdaps_edge_bottom_margin_dim) + (0, \c_sdaps_barcode_vpad_dim)$)}]
            \node(barcode)[anchor=south,outer~sep=0,inner~sep=0]{
              \X = \c_sdaps_barcode_bar_width_dim
              \bcorr = \c_sdaps_barcode_bcorr_dim
              \barheight = \c_sdaps_barcode_height_dim
              \code_render:V \g_sdaps_global_id_tl
            };
            \node[below=1mm~of~barcode,distance=0,anchor=north,outer~sep=0,inner~sep=0]{
              % TODO: do not hardcode the font!
              \ttfamily\footnotesize

              \tl_if_empty:VTF \g_sdaps_global_id_label_tl {
                \tl_use:N \g_sdaps_global_id_tl
              } {
                \tl_use:N \g_sdaps_global_id_label_tl
              }
            };
          \end{scope}
        }
      }
    \end{scope}%
  \group_end:
}

\msg_new:nnn { sdapsbase } { classic_too_many_pages } { You~cannot~have~more~than~six~pages~with~the~classic~style. }
\msg_new:nnn { sdapsbase } { odd_page_count } { You~have~an~odd~number~of~pages,~this~does~not~work~in~duplex~mode! }

% This needs to be called once for each page!
\cs_new_protected_nopar:Nn \sdaps_page_end: {
  \bool_if:NTF \g_sdaps_recognition_bool {
    \group_begin:

    \int_gincr:N\g_sdaps_page_int%
    \sdaps_info_write:x{Pages=\int_use:N\g_sdaps_page_int}

    \normalfont%

    \begin{tikzpicture}[remember~picture,overlay]%

      %---------------------------------------------------------------------------
      % corner marks and corner boxes in classic mode
      %---------------------------------------------------------------------------
      \begin{scope}[line~width=\g_sdaps_edge_marker_linewidth_dim, line~join=miter]
        \begin{scope}[shift={($(current~page.north~west) + (\g_sdaps_edge_left_margin_dim, -\g_sdaps_edge_top_margin_dim)$)}]
          \draw (0,-\g_sdaps_edge_marker_length_dim) -- (0, 0) -- (\g_sdaps_edge_marker_length_dim,0);

          \str_if_eq:VnT \g_sdaps_style_tl { classic } {
            % TODO: Is the filled/non-filled mapping still correct?
            \int_case:nnTF \g_sdaps_page_int {
              { 1 } { \draw }
              { 2 } { \fill }
              { 3 } { \fill }
              { 4 } { \fill }
              { 5 } { \fill }
              { 6 } { \draw }
            } {
              (\g_sdaps_classic_boxpad_dim, -\g_sdaps_classic_boxpad_dim) rectangle +(\g_sdaps_classic_boxsize_dim,-\g_sdaps_classic_boxsize_dim);
            } {
              % Error out (first time)
              \msg_error:nn { sdapsbase } { classic_too_many_pages }
            }
          }
        \end{scope}
        \begin{scope}[shift={($(current~page.north~east) + (-\g_sdaps_edge_right_margin_dim, -\g_sdaps_edge_top_margin_dim)$)}]
          \draw (0,-\g_sdaps_edge_marker_length_dim) -- (0,0) -- (-\g_sdaps_edge_marker_length_dim,0);

          \str_if_eq:VnT \g_sdaps_style_tl { classic } {
            % TODO: Is the filled/non-filled mapping still correct?
            \int_case:nnT \g_sdaps_page_int {
              { 1 } { \fill }
              { 2 } { \fill }
              { 3 } { \draw }
              { 4 } { \draw }
              { 5 } { \draw }
              { 6 } { \draw }
            } {
              (-\g_sdaps_classic_boxpad_dim, -\g_sdaps_classic_boxpad_dim) rectangle +(-\g_sdaps_classic_boxsize_dim,-\g_sdaps_classic_boxsize_dim);
            }
          }
        \end{scope}
        \begin{scope}[shift={($(current~page.south~west) + (\g_sdaps_edge_left_margin_dim, \g_sdaps_edge_bottom_margin_dim)$)}]
          \draw (0,\g_sdaps_edge_marker_length_dim) -- (0, 0) -- (\g_sdaps_edge_marker_length_dim,0);

          \str_if_eq:VnT \g_sdaps_style_tl { classic } {
            % TODO: Is the filled/non-filled mapping still correct?
            \int_case:nnT \g_sdaps_page_int {
              { 1 } { \fill }
              { 2 } { \draw }
              { 3 } { \fill }
              { 4 } { \fill }
              { 5 } { \draw }
              { 6 } { \draw }
            } {
              (\g_sdaps_classic_boxpad_dim, \g_sdaps_classic_boxpad_dim) rectangle +(\g_sdaps_classic_boxsize_dim,\g_sdaps_classic_boxsize_dim);
            }
          }
        \end{scope}
        \begin{scope}[shift={($(current~page.south~east) + (-\g_sdaps_edge_right_margin_dim, \g_sdaps_edge_bottom_margin_dim)$)}]
          \draw (0,\g_sdaps_edge_marker_length_dim) -- (0mm, 0mm) -- (-\g_sdaps_edge_marker_length_dim,0);

          \str_if_eq:VnT \g_sdaps_style_tl { classic } {
            % TODO: Is the filled/non-filled mapping still correct?
            \int_case:nnT \g_sdaps_page_int {
              { 1 } { \fill }
              { 2 } { \draw }
              { 3 } { \fill }
              { 4 } { \draw }
              { 5 } { \draw }
              { 6 } { \fill }
            } {
              (-\g_sdaps_classic_boxpad_dim, \g_sdaps_classic_boxpad_dim) rectangle +(-\g_sdaps_classic_boxsize_dim,\g_sdaps_classic_boxsize_dim);
            }
          }
        \end{scope}
      \end{scope}

      %---------------------------------------------------------------------------
      % barcodes/qr codes
      %---------------------------------------------------------------------------
      \bool_if:NTF \g__sdaps_last_page_bool {

        \int_compare:nNnTF { \g_sdaps_page_int } = { 1 } {
          % if we have a one page document, just always stamp the last
          % page. This means that SDAPS can fall back to simplex mode
          % automatically.
          \sdaps_draw_codes:
        } {

          \bool_if:NTF \g_sdaps_twoside_bool {
            \int_if_odd:VT \g_sdaps_page_int {
              % This should no happen; draw a barcode though to keep things
              % somewhat sane.
              \msg_warning:nn { sdapsbase } { odd_page_count }
              \sdaps_draw_codes:
            } {
              % Even page (i.e. back) has a barcode except in "front" mode
              \str_if_eq:VnF \g_sdaps_twoside_barcode_tl { front } {
                \sdaps_draw_codes:
              }
            }
          } {
            \sdaps_draw_codes:
          }
        }

        % TODO: Check whether the page count is as expected?
      } {
        \bool_if:NTF \g_sdaps_twoside_bool {
          \str_if_eq:VnTF \g_sdaps_twoside_barcode_tl { both } {
            \sdaps_draw_codes:
          } {
            \str_if_eq:VnTF \g_sdaps_twoside_barcode_tl { front } {
              \int_if_odd:VT \g_sdaps_page_int {
                \sdaps_draw_codes:
              }
            } { % And back is the only thing left
              \int_if_odd:VF \g_sdaps_page_int {
                \sdaps_draw_codes:
              }
            }
          }
        } {
          \sdaps_draw_codes:
        }
      }

      %---------------------------------------------------------------------------
      % watermark for non final mode
      %---------------------------------------------------------------------------
      \bool_if:NT \g_sdaps_draft_bool {
        \node [rotate=60,scale=10,text~opacity=0.2,color=red]
           at (current~page.center) {\textsc{draft}};
      }
    \end{tikzpicture}

    \group_end:
  } {
    \int_gincr:N\g_sdaps_page_int
  }
}


%    \end{macrocode}
%
% \subsection{Starting/Ending an SDAPS context}
%
% These need to be used to begin rendering into an SDAPS context and finishing
% everything off.
%
% Note that this base package does not automatically call
% \textbackslash sdaps\_page\_end: for
% you, so if you are using this class directly you will need to make sure that
% this handler is called after all form elements on a page. An easy of doing
% this is to call it from inside the page footer.
%
%
%    %\begin{macrocode}

\bool_new:N \g__sdaps_last_page_bool

\cs_new_protected_nopar:Nn \sdaps_begin: {
  \bool_gset:Nn \g__sdaps_last_page_bool \c_false_bool

  % TODO: We really want to make sure nobody modifies the values after \sdaps_begin:
  \sdaps_info_write:x{SDAPSVersion=1.9.10}
  \sdaps_info_write:x{Duplex=\bool_if:NTF \g_sdaps_twoside_bool {true} {false}}
  \sdaps_info_write:x{PrintQuestionnaireId=\bool_if:NTF \g_sdaps_print_questionnaire_id_bool {1} {0}}
  \sdaps_info_write:x{
    PageSize=\the\paperwidth, \the\paperheight
  }
  \sdaps_info_write:x{Style=\g_sdaps_style_tl}
  \sdaps_info_write:x{CheckMode=\g_sdaps_checkmode_tl}
  \sdaps_info_write:x{GlobalID=\g_sdaps_global_id_tl}
  \sdaps_info_write:x{GlobalIDLabel=\g_sdaps_global_id_label_tl}

  \sdaps_info_write:x{
    CornerMarkMargin=
      \dim_use:N\g_sdaps_edge_left_margin_dim,
      \dim_use:N\g_sdaps_edge_right_margin_dim,
      \dim_use:N\g_sdaps_edge_top_margin_dim,
      \dim_use:N\g_sdaps_edge_bottom_margin_dim
  }

  \int_gset:Nn \g_sdaps_page_int { 0 }
}

\cs_new_protected_nopar:Nn \sdaps_end: {
  % Note that using \sdaps_info_write_x:n may not work in some cases.
  % For this reason we write the out the Pages counter after each page,
  % which is fine to do.
  % Note that this means that the below "hack" to make onesided documents
  % work even in twoside (duplex) mode may not always work either.

  \bool_gset:Nn \g__sdaps_last_page_bool \c_true_bool
}


%
%    \end{macrocode}
%

% \Finale
\endinput