% Created 2024-10-23 Wed 10:12
% Intended LaTeX compiler: lualatex
\documentclass{letgut}
                                \setmainfont{KpRoman}
\setsansfont{KpSans}
\setmonofont[Scale = MatchLowercase]{RobotoMono}
\letgutsetup{editorial=false}
\input{listings-conf}
\author{Association GUTenberg}
\date{\today}
\title{Support for the banner of the newsletter "La Lettre de GUTenberg"}
\begin{document}


\section{Readme file}
\label{Readmefile-dlkgxqt0fck0}
\begin{lstlisting}
-------:| ---------------------------------------------------
 letgut:| Package for the banner of the newsletter
        | "La Lettre de GUTenberg"
 Author:| Association GUTenberg
 E-mail:| secretariat@gutenberg-asso.fr
License:| Released under the LaTeX Project Public License
        |  v1.3c or later
    See:| http://www.latex-project.org/lppl.txt

Copyright (C) 1994-2024 by Association GUTenberg
                  <secretariat@gutenberg-asso.fr>

This work may be distributed and/or modified under the
conditions of the LaTeX Project Public License (LPPL), either
version 1.3c of this license or (at your option) any later
version.  The latest version of this license is in the file:

http://www.latex-project.org/lppl.txt

This work is "maintained" (as per LPPL maintenance status)
by Association GUTenberg.
\end{lstlisting}

\section{Implementation}
\label{Implementation-ckogxqt0fck0}
\subsection{Identification}
\label{ImplementationIdentification-gwqgxqt0fck0}
\begin{lstlisting}
This is file `letgut-banner.sty,
generated with the Emacs Org-babel utility.

The original source file is letgut-banner.org
%% 
\end{lstlisting}

These document classes can only be used with \LaTeXe, so we make
sure that an appropriate message is displayed when another \TeX{}
format is used.

\begin{lstlisting}
\NeedsTeXFormat{LaTeX2e}[2020-10-01]
\end{lstlisting}

Now, we can announce the package name and its version:

\begin{lstlisting}
\ProvidesExplPackage{letgut-banner}
{2024-10-07}
{0.10}
{
  Package for the banner of the newsletter "La Lettre de GUTenberg"
}
\end{lstlisting}

\subsection{Packages loaded}
\label{ImplementationPackagesloaded-etvgxqt0fck0}
Till the Lua-based color will be  added to the core \package{l3color} approach,
we have to rely on \package{xcolor}

\begin{lstlisting}
\RequirePackage{xcolor}
\end{lstlisting}

We want the material added to the first page to be not selectable in order to let the
reader who wants to copy the interesting text be able to select it (see below).

\begin{lstlisting}
\RequirePackage{accsupp}
\end{lstlisting}

\begin{lstlisting}
\cs_generate_variant:Nn \color_fill:nn { nV }
\end{lstlisting}

\subsection{Declarations}
\label{ImplementationDeclarations-u0ygxqt0fck0}
\subsubsection{Dimensions}
\label{ImplementationDeclarationsDimensions-9t0hxqt0fck0}
\begin{lstlisting}
\dim_new:N \g__letgutbanner_area_height_dim
\dim_new:N \g__letgutbanner_La_height_dim
\dim_new:N \g__letgutbanner_La_depth_dim
\dim_new:N \g__letgutbanner_La_yoffset_dim
\dim_new:N \g__letgutbanner_banner_vertical_contents_width_dim
\dim_new:N \g__letgutbanner_largest_LETR_box_height_dim
\dim_new:N \g__letgutbanner_between_letters_yoffset_dim
\dim_new:N \g__letgutbanner_between_letters_vertical_space_dim
\dim_new:N \g__letgutbanner_banner_padding_dim
\dim_if_exist:NF \g__letgutbanner_first_page_shrink_dim {
  \dim_new:N \g__letgutbanner_first_page_shrink_dim
}
\dim_new:N \g__letgutbanner_textwidth_dim
\end{lstlisting}

\begin{itemize}
\item Dimensions of the page. If the present package is used with the
\class*{letgut}, they are borrowed from it. Otherwise, they are set to default
values. For this, we first generate a variant of \lstinline+\dim_const:Nn+ (see
\url{https://github.com/latex3/latex3/issues/947\#issuecomment-860950569}).
\begin{lstlisting}
\cs_generate_variant:Nn \dim_const:Nn { NV }
\dim_if_exist:NTF \c__letgut_textheight_dim {
  \dim_const:NV \c__letgutbanner_textheight_dim
  \c__letgut_textheight_dim
}{
  \dim_const:Nn \c__letgutbanner_textheight_dim
  { 25cm }
}
\dim_if_exist:NTF \c__letgut_textwidth_dim {
  \dim_gset_eq:NN \g__letgutbanner_textwidth_dim \c__letgut_textwidth_dim
}{
  \dim_gset:Nn \g__letgutbanner_textwidth_dim { 14cm }
}
\dim_if_exist:NTF \c__letgut_lmargin_dim {
  \dim_const:NV \c__letgutbanner_lmargin_dim
    \c__letgut_lmargin_dim
}{
  \dim_const:Nn \c__letgutbanner_lmargin_dim
  { 5cm }
}
\dim_if_exist:NTF \c__letgut_tmargin_dim {
  \dim_const:NV \c__letgutbanner_tmargin_dim
    \c__letgut_tmargin_dim
}{
  \dim_const:Nn \c__letgutbanner_tmargin_dim
  { 2.92cm }
  % \dim_const:Nn \c__letgutbanner_tmargin_dim
  % { 3cm }
}
\dim_if_exist:NTF \c__letgut_head_dim {
  \dim_const:NV \c__letgutbanner_head_dim
    \c__letgut_head_dim
}{
  \dim_const:Nn \c__letgutbanner_head_dim
  { 0.6cm }
}
\dim_if_exist:NTF \c__letgut_headsep_dim {
  \dim_const:NV \c__letgutbanner_headsep_dim
    \c__letgut_headsep_dim
}{
  \dim_const:Nn \c__letgutbanner_headsep_dim
  { 0.82cm }
  % \dim_const:Nn \c__letgutbanner_headsep_dim
  % { 0.9cm }
}
\dim_if_exist:NTF \c__letgut_marginparwidth_dim {
  \dim_const:NV \c__letgutbanner_marginparwidth_dim
  \c__letgut_marginparwidth_dim
}{
  \dim_const:Nn \c__letgutbanner_marginparwidth_dim
  { 3.74cm }
}
\end{lstlisting}
\item Dimensions of the banner. If the present package is used with the
\class*{letgut}, they are borrowed from it. Otherwise, they are set to
default values.
\begin{itemize}
\item Thickness of the "L".
\begin{lstlisting}
\dim_if_exist:NTF \c__letgut_banner_thickness_dim {
  \dim_const:NV \c__letgutbanner_banner_thickness_dim
  \c__letgut_banner_thickness_dim
}{
  \dim_const:Nn \c__letgutbanner_banner_thickness_dim
  { 4cm }
}
\end{lstlisting}
\item Height of the "L" (that of the text area plus 3cm).
\begin{lstlisting}
\dim_if_exist:NTF \c__letgut_banner_height_dim {
  \dim_const:NV \c__letgutbanner_banner_height_dim
    \c__letgut_banner_height_dim
}{
  \dim_const:Nn \c__letgutbanner_banner_height_dim  {
    \c__letgutbanner_textheight_dim
    +
    3cm
  }
}
\end{lstlisting}
\item Initial padding of the text embedded in the vertical bar of the "L".
\begin{lstlisting}
\dim_const:Nn \c__letgutbanner_banner_padding_dim  { .25cm }
\end{lstlisting}
\item Width of the "L" (the width (\(w\)) of the text zone plus the width (\(l\)) of
the left margin minus half the difference between the width of the left
margin and the width (\(d\)) of the "L": \(=w+l-(l-d)/2=w+(l+d)/2\)).
\begin{lstlisting}
\dim_const:Nn \c__letgutbanner_banner_width_dim  {
  \g__letgutbanner_textwidth_dim
  +
  (
  \c__letgutbanner_banner_thickness_dim
  +
  \c__letgutbanner_lmargin_dim
  )/2
}
\end{lstlisting}
\item Initial width of the text embedded in the "L" vertical bar.
\begin{lstlisting}
\dim_const:Nn
\c__letgutbanner_banner_vertical_contents_width_dim {
  \c__letgutbanner_banner_thickness_dim
  -
  2\c__letgutbanner_banner_padding_dim
}
\end{lstlisting}
\item Width of the text embedded in the horizontal bar of the "L" (of the text
area plus half the difference between that of the left margin and that of
the thickness of the "L", minus the padding -- and not 2 times the
padding because this text will be stuck to its left "margin").
\begin{lstlisting}
\dim_const:Nn
\c__letgutbanner_banner_horizontal_contents_width_dim {
  \g__letgutbanner_textwidth_dim
  - (
  \c__letgutbanner_banner_thickness_dim
  -
  \c__letgutbanner_lmargin_dim
  )/2
  -
  \c__letgutbanner_banner_padding_dim
}
\end{lstlisting}
\end{itemize}
\end{itemize}

\subsubsection{Boxes}
\label{ImplementationDeclarationsBoxes-s83hxqt0fck0}
New boxes, for each of the letters in the word "LETTRE" (!), and then for the
rest of the content listed in the banner.
\begin{lstlisting}
\box_new:N \g__letgutbanner_L_box
\box_new:N \g__letgutbanner_E_box
\box_new:N \g__letgutbanner_T_box
\box_new:N \g__letgutbanner_R_box
\box_new:N \g__letgutbanner_La_box
\box_new:N \g__letgutbanner_GUTenberg_box
\box_new:N \g__letgutbanner_largest_LETR_box
\box_new:N \g__letgutbanner_g_box
\end{lstlisting}

\subsubsection{Floating point numbers}
\label{ImplementationDeclarationsFloatingpointnumbers-e75hxqt0fck0}
\begin{itemize}
\item Minimum percentage of the common height of the letters of the word "LETTRE"
that their line spacing must represent.
\end{itemize}
\begin{lstlisting}
\fp_const:Nn \c__letgutbanner_leading_minimum_percent_fp { 0.15 }
\end{lstlisting}
\begin{itemize}
\item Factor applied to the line spacing between "La" and the 1st letter of
"LETTRE" compared to that between the letters of "LETTRE".
\end{itemize}
\begin{lstlisting}
\fp_const:Nn \c__letgutbanner_leading_La_factor_fp { 1.5 }
\end{lstlisting}

\subsection{Applying the page dimensions}
\label{ImplementationApplyingthepagedimensions-187hxqt0fck0}
\begin{lstlisting}
\geometry{
  asymmetric,
  textheight    = \c__letgutbanner_textheight_dim,
  textwidth     = \g__letgutbanner_textwidth_dim,
  lmargin       = \c__letgutbanner_lmargin_dim,
  tmargin       = \c__letgutbanner_tmargin_dim,
  head          = \c__letgutbanner_head_dim,
  headsep       = \c__letgutbanner_headsep_dim,
  marginparwidth= \c__letgutbanner_marginparwidth_dim,
  % showframe,
  % verbose,
}
\end{lstlisting}

\subsection{Filling of the boxes}
\label{ImplementationFillingoftheboxes-q49hxqt0fck0}
\begin{lstlisting}
\hbox_gset:Nn \g__letgutbanner_L_box { \textbf{L} }
\hbox_gset:Nn \g__letgutbanner_E_box { \textbf{E} }
\hbox_gset:Nn \g__letgutbanner_T_box { \textbf{T} }
\hbox_gset:Nn \g__letgutbanner_R_box { \textbf{R} }
\hbox_gset:Nn \g__letgutbanner_La_box { \textbf{\textit{La}} }
\hbox_gset:Nn \g__letgutbanner_GUTenberg_box {
  \textbf{\textit{GUTenberg}}
}
\hbox_gset:Nn \g__letgutbanner_g_box { \textbf{g} }
\end{lstlisting}

\subsection{Options of the package}
\label{ImplementationOptionsofthepackage-21ri36v0fck0}
We define:

\begin{itemize}
\item an option for the color of the text in the "L" (that has to be the same as the
page color of the document),
\item an option that let us choose another letter than “g” as the watermark letter.
\end{itemize}

\begin{lstlisting}
\keys_define:nn { letgut-banner }
{
  , pagecolor .clist_gset:N = \g__letgutbanner_pagecolor_clist
  , pagecolor .initial:n = { 1,1,1 }
  , watermark~ letter .code:n = {
    \hbox_gset:Nn \g__letgutbanner_g_box { \textbf{#1} }
  }
  , watermark~ scale .tl_gset:N = \g__letgutbanner_watermark_scale_tl
  , watermark~ scale .initial:n = 1
}
\ProcessKeyOptions [ letgut-banner ]
\end{lstlisting}

What follows has to be done at this end of the preamble, otherwise the font set
with \lstinline+\setmainfont+ in the preamble isn't taken in account in the banner.

\begin{lstlisting}
\AddToHook{begindocument}{
\end{lstlisting}


\subsection{Computations}
\label{ImplementationComputations-r7bhxqt0fck0}
Determination of the widths of each of the letter boxes of the word "LETTRE".
\begin{lstlisting}
\dim_const:Nn \c__letgutbanner_L_width_dim {
  \box_wd:N \g__letgutbanner_L_box
}
\dim_const:Nn \c__letgutbanner_E_width_dim {
  \box_wd:N \g__letgutbanner_E_box
}
\dim_const:Nn \c__letgutbanner_T_width_dim {
  \box_wd:N \g__letgutbanner_T_box
}
\dim_const:Nn \c__letgutbanner_R_width_dim {
  \box_wd:N \g__letgutbanner_R_box
}
\end{lstlisting}
Determination of the largest of these widths, stored in the scratch dimension
\lstinline+\g_tmpa_dim+.
\begin{lstlisting}
\dim_gset:Nn \g_tmpa_dim {
  \fp_eval:n {
    max (
    \c__letgutbanner_L_width_dim,
    \c__letgutbanner_E_width_dim,
    \c__letgutbanner_T_width_dim,
    \c__letgutbanner_R_width_dim,
    )
  }pt
}
\end{lstlisting}
Determination of the (1st) box whose width is the largest of all (\lstinline+argmax+, as
it were).
\begin{lstlisting}
\box_gset_eq:NN \g__letgutbanner_largest_LETR_box \dim_case:nnF
{ \g_tmpa_dim }
{
  { \c__letgutbanner_L_width_dim } { \g__letgutbanner_L_box }
  { \c__letgutbanner_E_width_dim } { \g__letgutbanner_E_box }
  { \c__letgutbanner_T_width_dim } { \g__letgutbanner_T_box }
  { \c__letgutbanner_R_width_dim } { \g__letgutbanner_R_box }
}
{ No~ idea! }
\end{lstlisting}
Resize the box containing "GUTenberg" to the width of the text embedded in the
horizontal bar of the "L".
\begin{lstlisting}
\box_gresize_to_wd:Nn \g__letgutbanner_GUTenberg_box {
  \c__letgutbanner_banner_horizontal_contents_width_dim
}
\end{lstlisting}
Determination of the height and depth of the box containing "GUTenberg" resized.
\begin{lstlisting}
\dim_const:Nn \c__letgutbanner_GUTenberg_height_dim {
  \box_ht:N \g__letgutbanner_GUTenberg_box
}
\dim_const:Nn \c__letgutbanner_GUTenberg_depth_dim  {
  \box_dp:N \g__letgutbanner_GUTenberg_box
}
\end{lstlisting}
Determining the size of the vertical offset of the box containing the resized
"GUTenberg", so that it is vertically centered in the horizontal bar of the "L":
the box positioned in \(0\) would be at the very bottom of the box containing the
banner so with base line at the bottom the horizontal bar of the "L" so we raise
it first by its depth (\(d\)) and then by half the difference between the heights
(\(H\)) of the horizontal bar of the "L" and (\(h+d\)) total of the box containing
"GUTenberg" resized (\(=d+H/2-(h+d)/2=(H-h+d)/2\)).
\begin{lstlisting}
\dim_const:Nn \c__letgutbanner_GUTenberg_yoffset_dim {
  (
  \c__letgutbanner_banner_thickness_dim
  -
  \c__letgutbanner_GUTenberg_height_dim
  +
  \c__letgutbanner_GUTenberg_depth_dim
  )/2
}
\end{lstlisting}
Once the height of the zone devoted to "La LETTRE" in the vertical bar of the
"L" has been fixed, the line spacing between the letters of the word "LETTRE"
depends in fact only on the width occupied by the widest of them, by definition
equal to the width allocated to the text embedded in the vertical bar of the
"L". The latter, stored in \lstinline+\g__letgutbanner_banner_vertical_contents_width_dim+, is
initially fixed:
\begin{lstlisting}
\dim_gset:Nn
\g__letgutbanner_banner_vertical_contents_width_dim
\c__letgutbanner_banner_vertical_contents_width_dim
\end{lstlisting}
but, to avoid this line spacing being too small (or even negative), we test that
it is greater than a certain threshold, equal to a certain minimum percentage of
the height common to the letters of the word "LETTRE", stored in:

\lstinline+\c__letgutbanner_leading_minimum_percent_fp+

and fixed at 0.15. If this is not the
case, we reduce (by 1pt):

\lstinline+\g__letgutbanner_banner_vertical_contents_width_dim+

and loop until it is the case.
\begin{lstlisting}
\dim_do_until:nNnn {
  \g__letgutbanner_between_letters_vertical_space_dim
}
>
{
  \fp_use:N\c__letgutbanner_leading_minimum_percent_fp
  \g__letgutbanner_largest_LETR_box_height_dim
}{
\end{lstlisting}
Resize the largest of these boxes to the width of the text embedded in the "L".
\begin{lstlisting}
\box_gresize_to_wd:Nn \g__letgutbanner_largest_LETR_box {
  \g__letgutbanner_banner_vertical_contents_width_dim
}
\end{lstlisting}
Height of this resized larger box.
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_largest_LETR_box_height_dim {
  \box_ht:N \g__letgutbanner_largest_LETR_box
}
\end{lstlisting}
Resize the boxes for each of the letters in the word "LETTRE" so that they are
all the same height as the widest of them.
\begin{lstlisting}
\box_gresize_to_ht:Nn \g__letgutbanner_L_box {
  \g__letgutbanner_largest_LETR_box_height_dim
}
\box_gresize_to_ht:Nn \g__letgutbanner_E_box {
  \g__letgutbanner_largest_LETR_box_height_dim
}
\box_gresize_to_ht:Nn \g__letgutbanner_T_box {
  \g__letgutbanner_largest_LETR_box_height_dim
}
\box_gresize_to_ht:Nn \g__letgutbanner_R_box {
  \g__letgutbanner_largest_LETR_box_height_dim
}
\end{lstlisting}
Resize the box containing "La" to the width of the text embedded in the "L"
vertical bar.
\begin{lstlisting}
\box_gresize_to_wd:Nn \g__letgutbanner_La_box {
  \g__letgutbanner_banner_vertical_contents_width_dim
}
\end{lstlisting}
Determine the height (\(h\)) and depth (\(d\)) of the resized box containing "La".
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_La_height_dim {
  \box_ht:N \g__letgutbanner_La_box
}
\dim_gset:Nn \g__letgutbanner_La_depth_dim  {
  \box_dp:N \g__letgutbanner_La_box
}
\end{lstlisting}
Determining the size of the vertical offset of the resized box containing "La"
so that its top is, relative to the top of the "L", offset by the same amount as
the bottom of the box containing "GUTenberg" is offset from the bottom of the
"L" (i.e., the distance from the top of the page to the top of "La" and the
distance from the bottom of the page to the baseline of "GUTenberg" are
identical).
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_La_yoffset_dim {
  \c__letgutbanner_banner_height_dim
  -
  \c__letgutbanner_GUTenberg_yoffset_dim
  -
  \g__letgutbanner_La_height_dim
  +
  \g__letgutbanner_La_depth_dim
}
\end{lstlisting}
For the following, the area containing the letters of the word "LETTRE" aligned
vertically is fixed, defined as follows:
\begin{itemize}
\item its top is the baseline of "La",
\item its bottom is the baseline of "GUTenberg".
\end{itemize}
Determination of the height of this area.
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_area_height_dim {
  \g__letgutbanner_La_yoffset_dim
  -
  \g__letgutbanner_La_depth_dim
  -
  \c__letgutbanner_GUTenberg_yoffset_dim
}
\end{lstlisting}
Determining the vertical jump (\(s\)) between the letters in the word "LETTRE"
with the constraints that:
\begin{itemize}
\item the top of the 1st letter ("L") is \(3e/2\) below the top of the area (where
\(e\) is the common vertical space separating the letters of the word
"LETTRE"),
\item the baseline of the last letter ("E") is merged with the bottom of the area,
\item this jump must not be less than 20 \% of the common height \(h\) to all these
letters i.e.:

\lstinline+\g__letgutbanner_largest_LETR_box_height_dim+

otherwise the size of the largest of these boxes is reduced to less than the
width of the text embedded in the "L".
\end{itemize}

The sum of :
\begin{itemize}
\item the 5 vertical spaces (\(5e\)) between the letters in the word "LETTRE",
\item the 6 common heights (\(6h\)) to all these letters,
\item \(3e/2\),
\end{itemize}
must equal the height (\(H\)) of the zone. So we have \(H=3e/2+5e+6h\), that is
\(e=2(H-6h)/13\). Once initialized, the vertical jump between the letters is
\(s=e+h\) that is \(s=(2H+h)/13\). Therefore:

\begin{enumerate}
\item Determine the vertical half-space between the letters.
\begin{lstlisting}
\dim_set:Nn \l_tmpa_dim {
  (
  \g__letgutbanner_area_height_dim
  -
  6\g__letgutbanner_largest_LETR_box_height_dim
  )/13
}
\end{lstlisting}
\item Vertical space between letters.
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_between_letters_vertical_space_dim {
  2\l_tmpa_dim
}
\end{lstlisting}
\item If this space does not check the condition explained above, we reduce:

\lstinline+\g__letgutbanner_banner_vertical_contents_width_dim+

and loop.
\begin{lstlisting}
\dim_gsub:Nn \g__letgutbanner_banner_vertical_contents_width_dim {
  1pt
  }
}
\end{lstlisting}
\end{enumerate}
The width allocated to the text embedded in the vertical bar of the "L" may have
been re-evaluated, so the padding (which must be symmetrical) may have changed
as well.
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_banner_padding_dim {
  (
  \c__letgutbanner_banner_thickness_dim
  -
  \g__letgutbanner_banner_vertical_contents_width_dim
  )/2
}
\end{lstlisting}
\begin{enumerate}
\item Determination of the vertical offset of the 1st letter ("L").
\begin{lstlisting}
\dim_const:Nn \c__letgutbanner_first_letter_yoffset_dim {
  \g__letgutbanner_La_yoffset_dim
  -
  \g__letgutbanner_largest_LETR_box_height_dim
  -
  \fp_use:N \c__letgutbanner_leading_La_factor_fp
  \g__letgutbanner_between_letters_vertical_space_dim
}
\end{lstlisting}
\item Determination of the vertical jump between letters.
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_between_letters_yoffset_dim {
  \g__letgutbanner_between_letters_vertical_space_dim
  +
  \g__letgutbanner_largest_LETR_box_height_dim
}
\end{lstlisting}
\end{enumerate}
Resize the box containing "g" to the width of the text.
\begin{lstlisting}
\box_gresize_to_wd:Nn \g__letgutbanner_g_box {
  \fp_to_dim:n {
    \g__letgutbanner_watermark_scale_tl
    *
    \g__letgutbanner_textwidth_dim
  }
}
\end{lstlisting}
Calculates the size by which the height of the text box on the 1st page must be
reduced so that the banner does not encroach on the text. Relative to the top of
the page:
\begin{itemize}
\item the top of the horizontal bar of "L" is at a distance equal to the sum of :
\begin{itemize}
\item the distance between this top of page and the top of the vertical bar of
"L", equal to the height (\(p\)) of the paper minus the height (\(l\)) of "L"
\end{itemize}
\end{itemize}
\begin{lstlisting}
\dim_gset:Nn \g__letgutbanner_first_page_shrink_dim {
  \c__letgutbanner_tmargin_dim
  +
  \c__letgutbanner_textheight_dim
  +
  \c__letgutbanner_banner_thickness_dim
  -
  .5\paperheight
  -
  .5\c__letgutbanner_banner_height_dim
  +
  .5\baselineskip
}
\end{lstlisting}

Automatic addition on the 1st page (only) of the banner.
\begin{lstlisting}
\AddToHookNext{shipout/background}{
\end{lstlisting}
We want the material added to this page to be not selectable in order to let the
reader who wants to copy the interesting text be able to select it.
\begin{lstlisting}
\BeginAccSupp{ActualText={}}
\end{lstlisting}
We put now the big "L" at the right place.
\begin{lstlisting}
\put(
.5\c__letgutbanner_lmargin_dim-.5\c__letgutbanner_banner_thickness_dim
,
-.5\paperheight-.5\c__letgutbanner_banner_height_dim
){
  \put(0,0){
    \rule{
      \c__letgutbanner_banner_width_dim
    }{
      \c__letgutbanner_banner_thickness_dim
    }
  }
  \put(0,0){
    \rule{
      \c__letgutbanner_banner_thickness_dim
    }{
      \c__letgutbanner_banner_height_dim
    }
  }
\end{lstlisting}
The color should not be systematically white, but should be identical to the one
chosen for the page background.
\begin{lstlisting}
  % \color_fill:nV {rgb}{ \g__letgutbanner_pagecolor_clist }
  \color[rgb]{ \g__letgutbanner_pagecolor_clist }
  \put(
  \g__letgutbanner_banner_padding_dim
  ,
  \g__letgutbanner_La_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_La_box
  }
  \put(
  \g__letgutbanner_banner_padding_dim
  ,
  \c__letgutbanner_first_letter_yoffset_dim
  -0\g__letgutbanner_between_letters_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_L_box
  }
  \put(
  \g__letgutbanner_banner_padding_dim
  ,
  \c__letgutbanner_first_letter_yoffset_dim
  -1\g__letgutbanner_between_letters_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_E_box
  }
  \put(
  \g__letgutbanner_banner_padding_dim
  ,
  \c__letgutbanner_first_letter_yoffset_dim
  -2\g__letgutbanner_between_letters_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_T_box
  }
  \put(
  \g__letgutbanner_banner_padding_dim
  ,
  \c__letgutbanner_first_letter_yoffset_dim
  -3\g__letgutbanner_between_letters_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_T_box
  }
  \put(
  \g__letgutbanner_banner_padding_dim
  ,
  \c__letgutbanner_first_letter_yoffset_dim
  -4\g__letgutbanner_between_letters_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_R_box
  }
  \put(
  \g__letgutbanner_banner_padding_dim
  ,
  \c__letgutbanner_first_letter_yoffset_dim
  -5\g__letgutbanner_between_letters_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_E_box
  }
  \put(
  \c__letgutbanner_banner_thickness_dim
  ,
  \c__letgutbanner_GUTenberg_yoffset_dim
  ){
    \box_use:N \g__letgutbanner_GUTenberg_box
  }
  % \color_fill:n {black!10}
  \color{ black!10 }
  \put(
  .5\c__letgutbanner_lmargin_dim
  +
  .5\c__letgutbanner_banner_thickness_dim
  +
  \fp_to_dim:n {
    (1-\g__letgutbanner_watermark_scale_tl)/2*\g__letgutbanner_textwidth_dim
  }
  ,
  .5\paperheight
  +
  .5\c__letgutbanner_banner_height_dim
  -
  \c__letgutbanner_tmargin_dim
  ){
    \box_move_down:nn {.5\c__letgutbanner_textheight_dim}
    {\box_use:N \g__letgutbanner_g_box}
  }
}
\end{lstlisting}
We end the part which isn't selectable.
\begin{lstlisting}
\EndAccSupp{}
}
\end{lstlisting}

We close \lstinline+\AddToHook{begindocument}+.

\begin{lstlisting}
}
\end{lstlisting}

If the package is used with another class than \class{letgut}, we reduce the
textheight of the first page of the height of the horizontal bar of the "L".

\begin{lstlisting}
\@ifclassloaded{letgut}{
}{
  \AddToHook{begindocument/end}{%
    \enlargethispage{
      - \g__letgutbanner_first_page_shrink_dim
    }
    \thispagestyle{empty}
  }
}
\end{lstlisting}

\section{Example file (\texttt{letgut-banner-example.tex})}
\label{Examplefileletgutbannerexampletex-heehxqt0fck0}
\end{document}