%
% lltjp-atbegshi.sty
%

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{lltjp-atbegshi}[2021-04-29 Patching \string\shipout\space hooks for LuaTeX-ja]

% concept: execute all hooks inside yoko direction \vbox

\ifltj@ltfilehook@avail
%<*ltshipout>-----------------------------------
%
\RequirePackage{expl3}
\ExplSyntaxOn\makeatletter
\box_new:N \l__platex_shipout_dummy_box
\if_cs_exist:N \__shipout_execute_main_cont:Nnnn %% 2021-06-01
\cs_new_eq:NN \__platex_original_shipout_execute_main_cont:Nnnn
              \__shipout_execute_main_cont:Nnnn
\cs_set:Npn \__shipout_execute_main_cont:Nnnn #1#2#3#4 {
  % if the box #1 is not a \yoko-box (= horizontal writing),
  % then make it a \yoko-box behorehand.
  \platex_if_box_yoko:NF #1 {
    \vbox_set:Nn #1 { \platex_direction_yoko: \box_use:N #1 }
  }
  % if the current direction is not \yoko,
  % then enclose \__shipout_execute_main_cont:Nnnn with
  % a dummy \yoko-box named \l__platex_shipout_dummy_box.
  \platex_if_direction_yoko:TF {
    \__platex_original_shipout_execute_main_cont:Nnnn { #1 } { #2 } { #3 } { #4 }
  }{
    \vbox_set:Nn \l__platex_shipout_dummy_box {
      \platex_direction_yoko:
      \__platex_original_shipout_execute_main_cont:Nnnn { #1 } { #2 } { #3 } { #4 }
    }
    % [Limitation] the code above may discard some contents,
    % so we'd like to put it back by \box\l__platex_shipout_dummy_box.
    % however, an infinite loop occurs if we uncomment the line below
    % so we can't.
    %\box_use:N \l__platex_shipout_dummy_box
  }
}

\else: %% 2020-10-01
\cs_new_eq:NN \__platex_original_shipout_execute_cont: \__shipout_execute_cont:
\cs_set:Npn \__shipout_execute_cont:
{
  \platex_if_box_yoko:NF \l_shipout_box {
    \vbox_set:Nn \l_shipout_box { \platex_direction_yoko: \box_use:N \l_shipout_box }
  }
  \platex_if_direction_yoko:TF {
    \__platex_original_shipout_execute_cont:
  }{
    \vbox_set:Nn \l__platex_shipout_dummy_box {
      \platex_direction_yoko: \__platex_original_shipout_execute_cont:
    }
  }
}
\fi:
%</ltshipout>-----------------------------------
\ExplSyntaxOff
\expandafter\endinput
\fi
\RequirePackage{atbegshi}
%<*atbegshi>-------------------------------------
% patching atbegshi.sty
%%%  following codes are almost copied from
%%%  pxatbegshi.sty 2019/09/07 v0.5 (in platex-tools bundle, by H. Yamashita).

\ifdefined\AtBeginShipoutOriginalShipout
  \let\AtBeginShipoutOriginalShipout\ltj@shipout
\fi
\AtBeginShipoutInit
\DeclareRobustCommand \AtBeginDvi [1]{%
  \global \setbox \@begindvibox
    \vbox{\yoko\unvbox \@begindvibox #1}%
}
%% internal macros are locally effective
\begingroup

% helpers
%% unique tokens
\def\pxabgs@mark{\pxabgs@mark@}
\def\pxabgs@fin{\pxabgs@fin@}

%% \pxabgs@patch@cmd\CMD{<orig>}{<new>}
\def\pxabgs@patch@cmd#1#2#3{%
  \ifx#1\relax\else
  \def\pxabgs@next##1#2##2\pxabgs@mark##3\pxabgs@fin{%
    \ifx\pxabgs@mark##3\pxabgs@mark\let#1\relax
    \else
      \def\pxabgs@fragment{##2}\def#1{##1#3##2}%
    \fi}%
  \expandafter\pxabgs@next#1\pxabgs@mark#2\pxabgs@mark\pxabgs@fin
  \fi
}

% prepare
\ifdefined\AtBegShi@Output
  \let\pxabgs@AtBegShi@Output\AtBegShi@Output
\else\let\pxabgs@AtBegShi@Output\relax\fi
% try first patch
\pxabgs@patch@cmd\pxabgs@AtBegShi@Output
  {\let\AtBegShi@OrgProtect\protect}%
  {\setbox8\vbox\bgroup\yoko\let\AtBegShi@OrgProtect\protect}
\pxabgs@patch@cmd\pxabgs@AtBegShi@Output
  {\AtBeginShipoutOriginalShipout\box\AtBeginShipoutBox}%
  {\AtBeginShipoutOriginalShipout\box\AtBeginShipoutBox\egroup}
\pxabgs@patch@cmd\pxabgs@AtBegShi@Output
  {%
    \begingroup
      \setbox\AtBeginShipoutBox\box\AtBeginShipoutBox
    \endgroup
    \let\protect\AtBegShi@OrgProtect
  }{%
    \begingroup
      \setbox\AtBeginShipoutBox\box\AtBeginShipoutBox
    \endgroup
    \let\protect\AtBegShi@OrgProtect
    \egroup
  }
% commit the change only when successful
\ifx\pxabgs@AtBegShi@Output\relax
  \@PackageWarningNoLine{lltjp-atbegshi}{%
    Failed in patching \string\AtBegShi@Output.\MessageBreak
    This may cause error in tate direction%
  }
\else
  \global\let\AtBegShi@Output\pxabgs@AtBegShi@Output
\fi

\endgroup
%% internal macros are no longer effective
%</atbegshi>-------------------------------------
\endinput
