lua-widow-control.sty

% lua-widow-control
% https://github.com/gucci-on-fleek/lua-widow-control
% SPDX-License-Identifier: MPL-2.0+
% SPDX-FileCopyrightText: 2022 Max Chernoff

% Formats built after 2015 include \LuaTeX{}Base, so this is the absolute
% minimum version that we will run under.
\NeedsTeXFormat{LaTeX2e}[2015/01/01]

% For _really_ old formats
\providecommand\DeclareRelease[3]{}
\providecommand\DeclareCurrentRelease[2]{}

\DeclareRelease{}{0000-00-00}{lua-widow-control-2022-02-22.sty}
\DeclareRelease{v1.1.6}{2022-02-22}{lua-widow-control-2022-02-22.sty}
\DeclareCurrentRelease{v2.2.2}{2022-08-23} %%version %%dashdate

% If this version of LaTeX doesn't support command hooks, then we load
% the last v1.1.X version of the package.
\providecommand\IfFormatAtLeastTF{\@ifl@t@r\fmtversion}
\IfFormatAtLeastTF{2020/10/01}{}{\input{lua-widow-control-2022-02-22.sty}}
\IfFormatAtLeastTF{2020/10/01}{}{\endinput}

\ProvidesExplPackage
    {lua-widow-control}
    {2022/08/23} %%slashdate
    {v2.2.2} %%version
    {Use Lua to remove widows and orphans}

% Message and String Constants
\str_const:Nn \c__lwc_name_str { lua-widow-control }

\msg_new:nnn
    { \c__lwc_name_str }
    { no-luatex }
    {
        LuaTeX~ is~ REQUIRED! \\
        Make~ sure~ to~ compile~ your~ document~ with~ `lualatex'.
    }

\msg_new:nnn
    { \c__lwc_name_str }
    { patch-failed }
    {
        Patching~ \c_backslash_str #1~ failed. \\
        Please~ ensure~ that~ \c_backslash_str #1~ exists.
    }

\msg_new:nnn
    { \c__lwc_name_str }
    { old-format-patch }
    {
        Patching~ not~ supported~ with~ old~ LaTeX. \\
        Please~ use~ a~ LaTeX~ format~ >=~ 2021/06/01.
    }

\msg_new:nnn
    { \c__lwc_name_str }
    { old-command }
    {
        \c_backslash_str #1~ has~ been~ REMOVED! \\
        Please~ use~ \c_backslash_str setuplwc \c_left_brace_str #2
        \c_right_brace_str\ instead.
    }

% Don't let the user proceed unless they are using \LuaTeX{}.
\sys_if_engine_luatex:F {
    \msg_critical:nn { \c__lwc_name_str } { no-luatex }
}

% Define (most of) the keys
\cs_generate_variant:Nn \keys_define:nn { Vn }

\keys_define:Vn { \c__lwc_name_str } {
    emergencystretch .dim_gset:N       = \g__lwc_emergencystretch_dim,
    emergencystretch .value_required:n = true,
    emergencystretch .initial:x        = \dim_max:nn { 3em } { 30pt },

    draftoffset .dim_gset:N       = \g__lwc_draftoffset_dim,
    draftoffset .value_required:n = true,
    draftoffset .initial:x        = \dim_max:nn { \parindent } { 12pt },

    max-cost .int_gset:N       = \g__lwc_maxcost_int,
    max-cost .value_required:n = true,
    max-cost .initial:x        = \c_max_int,

    widowpenalty .code:n = \int_gset:Nn \tex_widowpenalty:D        { #1 }
                           \int_gset:Nn \tex_displaywidowpenalty:D { #1 },
    widowpenalty .value_required:n = true,
    widowpenalty .initial:n        = 1,

    orphanpenalty .code:n = \int_gset:Nn \tex_clubpenalty:D  { #1 }
                            \int_gset:Nn \@clubpenalty       { #1 },
    orphanpenalty .value_required:n = true,
    orphanpenalty .initial:n        = 1,

    brokenpenalty .int_gset:N       = \tex_brokenpenalty:D,
    brokenpenalty .value_required:n = true,
    brokenpenalty .initial:n        = 1,

    microtype .bool_gset:N      = \g__lwc_use_microtype_bool,
    microtype .value_required:n = true,
    microtype .initial:n        = true,
    microtype .usage:n          = preamble,

    disablecmds .clist_gset:N     = \g__lwc_disablecmds_cl,
    disablecmds .value_required:n = false,
    disablecmds .initial:n        = { \@sect,           % LaTeX default
                                      \@ssect,          % LaTeX starred
                                      \M@sect,          % Memoir
                                      \@mem@old@ssect,  % Memoir Starred
                                      \ttl@straight@ii, % titlesec normal
                                      \ttl@top@ii,      % titlesec top
                                      \ttl@part@ii,     % titlesec part
                                    },
    disablecmds .usage:n          = preamble,
}

% Load the Lua code
\cs_if_exist:NTF \lua_load_module:n {
    \lua_load_module:n { lua-widow-control }
} {
    \lua_now:n { require "lua-widow-control" }
}

% Here, we enable font expansion/contraction. It isn't strictly necessary for
% \lwc/'s functionality; however, it is required for the
% lengthened paragraphs to not have terrible spacing.
\hook_gput_code:nnn { begindocument / before } { \c__lwc_name_str } {
    \bool_if:NT \g__lwc_use_microtype_bool {
        \@ifpackageloaded { microtype } {} {
            \RequirePackage[
                final,
                activate = { true, nocompatibility }
            ]
            { microtype }
        }
    }
}

% Core Function Definitions
\cs_new_eq:NN \iflwc \__lwc_iflwc:

\prg_new_conditional:Nnn \__lwc_if_enabled: { T, F, TF } {
    \__lwc_if_enabled:
        \prg_return_true:
    \else
        \prg_return_false:
    \fi
}

% Expansion of some parts of the document, such as section headings, is quite
% undesirable, so we'll disable \lwc/ for certain commands.
\int_new:N \g__lwc_disable_int

\cs_new:Npn \__lwc_patch_pre: {
    % We should only reenable \lwc/ at the end if it was already enabled.
    \__lwc_if_enabled:T {
        \int_gincr:N \g__lwc_disable_int
        \__lwc_disable:
    }
}

\cs_new:Npn \__lwc_patch_post: {
    \int_compare:nT { \g__lwc_disable_int > 0 } {
        \__lwc_enable:
        \int_gdecr:N \g__lwc_disable_int
    }
}

\cs_new:Npn \__lwc_patch_cmd:c #1 {
    \IfFormatAtLeastTF { 2021/06/01 } {
        \hook_gput_code:nnn { cmd / #1 / before } { \c__lwc_name_str } {
            \__lwc_patch_pre:
        }
        \hook_gput_code:nnn { cmd / #1 / after } { \c__lwc_name_str } {
            \__lwc_patch_post:
        }
    } {
        \msg_warning:nn
                { \c__lwc_name_str }
                { old-format-patch }
    }
}

\cs_new:Npn \__lwc_patch_cmd:N #1 {
    \__lwc_patch_cmd:c { \cs_to_str:N #1 }
}

\cs_new:Npn \__lwc_patch_cmd:n #1 {
    % If the item provided is a single token, we'll assume that it's a \macro.
    % If it is multiple tokens, we'll assume that it's a `csname`.
    \tl_if_single:nTF { #1 } {
        \__lwc_patch_cmd:c { \cs_to_str:N #1 }
    } {
        \__lwc_patch_cmd:c { #1 }
    }
}

\hook_gput_code:nnn { begindocument / before } { \c__lwc_name_str } {
    \clist_map_function:NN \g__lwc_disablecmds_cl \__lwc_patch_cmd:n
}

%%% Class and package-specifc patches

% KOMA-Script
\cs_if_exist:NT \AddtoDoHook {
    \AddtoDoHook { heading / begingroup } { \__lwc_patch_pre:  \use_none:n }
    \AddtoDoHook { heading / endgroup   } { \__lwc_patch_post: \use_none:n }
}

% Memoir
\cs_gset_nopar:Npn \pen@ltyabovepfbreak { 23 } % Issue #32

% Define some final keys
\keys_define:Vn { \c__lwc_name_str } {
    enable .choice:,
    enable / true  .code:n     = \__lwc_enable:,
    enable / false .code:n     = \__lwc_disable:,
    enable .initial:n          = true,
    enable .default:n          = true,
    enable .value_required:n   = false,

    disable .code:n            = \__lwc_disable:,
    disable .value_forbidden:n = true,

    debug .choice:,
    debug / true  .code:n     = \__lwc_debug:n { true  },
    debug / false .code:n     = \__lwc_debug:n { false },
    debug .default:n          = true,
    debug .value_required:n   = false,

    draft .choice:,
    draft / true  .code:n     = \__lwc_draft:n { true  },
    draft / false .code:n     = \__lwc_draft:n { false },
    draft .default:n          = true,
    draft .value_required:n   = false,

    nobreak .code:n           = \__lwc_nobreak:n { #1 },
    nobreak .value_required:n = true,
    nobreak .initial:n        = keep,

    strict .meta:n = { emergencystretch = 0pt,
                       max-cost         = 5000,
                       nobreak          = warn,
                       widowpenalty     = 1,
                       orphanpenalty    = 1,
                       brokenpenalty    = 1,
                     },
    strict .value_forbidden:n = true,

    default .meta:n = { emergencystretch = 3em,
                        max-cost         = \c_max_int,
                        nobreak          = keep,
                        widowpenalty     = 1,
                        orphanpenalty    = 1,
                        brokenpenalty    = 1,
                      },
    default .value_forbidden:n = true,

    balanced .meta:n = { emergencystretch = 1em,
                         max-cost         = 10000,
                         nobreak          = keep,
                         widowpenalty     = 500,
                         orphanpenalty    = 500,
                         brokenpenalty    = 500,
                      },
    balanced .value_forbidden:n = true,
}

% Add the user interface for the keys
\IfFormatAtLeastTF { 2022-06-01 } {
    \ProcessKeyOptions [ \c__lwc_name_str ]
}{
    \RequirePackage { l3keys2e }
    \exp_args:NV \ProcessKeysOptions { \c__lwc_name_str }
}

\cs_generate_variant:Nn \keys_set:nn { Vn }
\NewDocumentCommand \lwcsetup {m} {
    \keys_set:Vn { \c__lwc_name_str }{ #1 }
}

% Legacy Commands
\NewDocumentCommand \lwcemergencystretch { } {
    \msg_error:nnnnn
        { \c__lwc_name_str }
        { old-command }
        { lwcemergencystretch }
        { emergencystretch=XXXpt }
}

\NewDocumentCommand \lwcdisablecmd { m } {
    \msg_error:nnxx
        { \c__lwc_name_str }
        { old-command }
        { lwcdisablecmd }
        { disablecmds={\c_backslash_str aaa,~ \c_backslash_str bbb} }
}

\cs_new_eq:NN \lwcenable  \__lwc_enable:
\cs_new_eq:NN \lwcdisable \__lwc_disable:

\endinput