\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{packages/slides-partners}[2026/10/11 Automatic title-page partner logos]
\RequirePackage{graphicx}
\RequirePackage{expl3}
\RequirePackage{xparse}

\ExplSyntaxOn
\seq_new:N \g__slides_partners_seq
\prop_new:N \g__slides_partner_files_prop
\seq_new:N \l__slides_partner_files_seq
\seq_new:N \l__slides_partner_ratios_seq
\box_new:N \l__slides_partner_box
\tl_new:N \l__slides_partner_file_tl
\tl_new:N \l__slides_partner_resolved_tl
\int_new:N \l__slides_partner_count_int
\int_new:N \l__slides_partner_columns_int
\int_new:N \l__slides_partner_rows_int
\fp_new:N \l__slides_partner_minratio_fp
\fp_new:N \l__slides_partner_maxratio_fp
\fp_new:N \l__slides_partner_candidate_fp
\fp_new:N \l__slides_partner_scale_fp
\dim_new:N \l__slides_partner_width_dim
\dim_new:N \l__slides_partner_maxheight_dim
\dim_new:N \l__slides_partner_xgap_dim
\dim_new:N \l__slides_partner_ygap_dim
\dim_new:N \l__slides_partner_cellwidth_dim
\dim_new:N \l__slides_partner_cellheight_dim

% Selection is ordered and idempotent. File lookup is delayed until rendering,
% so a declaration can appear before or after its corresponding selection.
\NewDocumentCommand{\partner}{m}
  {
    \seq_if_in:NnF \g__slides_partners_seq {#1}
      { \seq_gput_right:Nn \g__slides_partners_seq {#1} }
  }
\NewDocumentCommand{\declarepartner}{mm}
  { \prop_gput:Nnn \g__slides_partner_files_prop {#1} {#2} }

\cs_new_protected:Npn \__slides_partners_collect:
  {
    \seq_clear:N \l__slides_partner_files_seq
    \seq_clear:N \l__slides_partner_ratios_seq
    \seq_map_inline:Nn \g__slides_partners_seq
      {
        \prop_get:NnNF \g__slides_partner_files_prop {##1}
          \l__slides_partner_file_tl
          { \tl_set:Nn \l__slides_partner_file_tl {packages/partners/##1} }
        \tl_clear:N \l__slides_partner_resolved_tl
        \file_if_exist:VTF \l__slides_partner_file_tl
          { \tl_set_eq:NN \l__slides_partner_resolved_tl \l__slides_partner_file_tl }
          {
            \clist_map_inline:nn {png,pdf,jpg,jpeg}
              {
                \file_if_exist:nT {\l__slides_partner_file_tl .####1}
                  {
                    \tl_set:Nx \l__slides_partner_resolved_tl
                      {\l__slides_partner_file_tl .####1}
                    \clist_map_break:
                  }
              }
          }
        \tl_if_empty:NTF \l__slides_partner_resolved_tl
          {
            \PackageWarning{slides-partners}
              {Logo~for~partner~`##1'~not~found~at~
               `\tl_use:N \l__slides_partner_file_tl'.~Skipping~it}
          }
          {
            \seq_put_right:NV \l__slides_partner_files_seq
              \l__slides_partner_resolved_tl
            \hbox_set:Nn \l__slides_partner_box
              { \includegraphics{\tl_use:N \l__slides_partner_resolved_tl} }
            \seq_put_right:Nx \l__slides_partner_ratios_seq
              {
                \fp_eval:n
                  { \dim_to_fp:n {\box_wd:N \l__slides_partner_box} /
                    \dim_to_fp:n {\box_ht:N \l__slides_partner_box +
                                  \box_dp:N \l__slides_partner_box} }
              }
          }
      }
  }

% Equal-area logos in equal-width cells give seals and wide wordmarks comparable
% visual weight. Try every column count, maximizing the common area scale while
% fitting the tallest and widest logos into the available title-page rectangle.
\cs_new_protected:Npn \__slides_partners_layout:
  {
    \int_set:Nn \l__slides_partner_count_int
      { \seq_count:N \l__slides_partner_files_seq }
    % Keep a margin on the left so a full grid stays clear of the affiliations.
    \dim_set:Nn \l__slides_partner_width_dim {.82\linewidth}
    \dim_set:Nn \l__slides_partner_maxheight_dim {.24\paperheight}
    \dim_set:Nn \l__slides_partner_xgap_dim
      { \fp_to_dim:n {min(.04 * \dim_to_fp:n {\linewidth},
          .25 * \dim_to_fp:n {\linewidth} / max(1,\l__slides_partner_count_int-1))} }
    \dim_set:Nn \l__slides_partner_ygap_dim
      { \fp_to_dim:n {min(.015 * \dim_to_fp:n {\paperheight},
          .25 * \dim_to_fp:n {\l__slides_partner_maxheight_dim} /
          max(1,\l__slides_partner_count_int-1))} }
    \fp_set:Nn \l__slides_partner_minratio_fp {inf}
    \fp_zero:N \l__slides_partner_maxratio_fp
    \seq_map_inline:Nn \l__slides_partner_ratios_seq
      {
        \fp_set:Nn \l__slides_partner_minratio_fp
          {min(\l__slides_partner_minratio_fp,##1)}
        \fp_set:Nn \l__slides_partner_maxratio_fp
          {max(\l__slides_partner_maxratio_fp,##1)}
      }
    \fp_zero:N \l__slides_partner_scale_fp
    \int_set:Nn \l__slides_partner_columns_int {1}
    \int_step_inline:nnnn {\l__slides_partner_count_int} {-1} {1}
      {
        \int_set:Nn \l__slides_partner_rows_int
          { \fp_eval:n {ceil(\l__slides_partner_count_int / ##1)} }
        \fp_set:Nn \l__slides_partner_candidate_fp
          { min(.14 * \dim_to_fp:n {\paperheight},
              (\dim_to_fp:n {\l__slides_partner_maxheight_dim} -
               (\l__slides_partner_rows_int-1) *
               \dim_to_fp:n {\l__slides_partner_ygap_dim}) /
               \l__slides_partner_rows_int * sqrt(\l__slides_partner_minratio_fp),
              (\dim_to_fp:n {\l__slides_partner_width_dim} -
               (##1-1) * \dim_to_fp:n {\l__slides_partner_xgap_dim}) /
                ##1 / sqrt(\l__slides_partner_maxratio_fp)) }
        % Break equal-size ties by minimizing unused cells in the final row.
        \fp_compare:nT
          { \l__slides_partner_candidate_fp > \l__slides_partner_scale_fp + .0001 ||
            (abs(\l__slides_partner_candidate_fp - \l__slides_partner_scale_fp) <= .0001 &&
             ##1 * \l__slides_partner_rows_int <
             \l__slides_partner_columns_int *
             ceil(\l__slides_partner_count_int / \l__slides_partner_columns_int)) }
          {
            \fp_set_eq:NN \l__slides_partner_scale_fp \l__slides_partner_candidate_fp
            \int_set:Nn \l__slides_partner_columns_int {##1}
          }
      }
    % Size cells to the widest rendered logo, not the entire available column.
    % The enclosing row still right-aligns the compact grid in the title footer.
    \dim_set:Nn \l__slides_partner_cellwidth_dim
      { \fp_to_dim:n {\l__slides_partner_scale_fp * sqrt(\l__slides_partner_maxratio_fp)} }
    \dim_set:Nn \l__slides_partner_cellheight_dim
      { \fp_to_dim:n {\l__slides_partner_scale_fp / sqrt(\l__slides_partner_minratio_fp)} }
  }

\cs_new_protected:Npn \__slides_partners_typeset:
  {
    \vbox
      {
        \offinterlineskip
        \int_step_inline:nn {\l__slides_partner_count_int}
          {
            \int_compare:nNnT
              {\int_mod:nn {##1-1} {\l__slides_partner_columns_int}} = {0}
              {
                \int_compare:nNnT {##1} > {1}
                  { \vskip \l__slides_partner_ygap_dim }
                \hbox_to_wd:nn {\linewidth}
                  {
                    \hfil
                    \int_step_inline:nnn {##1}
                      {\int_min:nn {##1+\l__slides_partner_columns_int-1}
                                   {\l__slides_partner_count_int}}
                      {
                        \int_compare:nNnT {####1} > {##1}
                          { \hskip \l__slides_partner_xgap_dim }
                        \vbox_to_ht:nn {\l__slides_partner_cellheight_dim}
                          {
                            \vfil
                            \hbox_to_wd:nn {\l__slides_partner_cellwidth_dim}
                              {
                                \hfil
                                \includegraphics[height=\fp_to_dim:n
                                  {\l__slides_partner_scale_fp / sqrt(
                                    \seq_item:Nn \l__slides_partner_ratios_seq {####1})}]
                                  {\seq_item:Nn \l__slides_partner_files_seq {####1}}
                                \hfil
                              }
                            \vfil
                          }
                      }
                  }
              }
          }
      }
  }

\NewDocumentCommand{\insertpartnerlogos}{}
  {
    \group_begin:
    \seq_if_empty:NTF \g__slides_partners_seq
      { \inserttitlegraphic } % Backwards compatibility with existing slides.
      {
        \__slides_partners_collect:
        \seq_if_empty:NF \l__slides_partner_files_seq
          {
            \__slides_partners_layout:
            \__slides_partners_typeset:
          }
      }
    \group_end:
  }
\ExplSyntaxOff
\endinput