% !TeX root = ./testing/test.tex
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% The rainbow colour theme 
% A beamer colour theme which alternates theme colours on every frame
% Maintained by samcarter
%
% Project repository and bug tracker:
% https://github.com/samcarter/beamertheme-rainbow
%
% Released under the LaTeX Project Public License v1.3c or later
% See https://www.latex-project.org/lppl.txt
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\ProvidesPackage{beamercolorthemerainbow}[2024/11/14 version v1.0 Beamer colour theme with alternating theme colours]

\mode<presentation>

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Default colours
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\definecolor{rainbow@0}{HTML}{e50000}
\definecolor{rainbow@1}{HTML}{ff8d00}
\definecolor{rainbow@2}{HTML}{ffee00}
\definecolor{rainbow@3}{HTML}{028121}
\definecolor{rainbow@4}{HTML}{004cff}
\definecolor{rainbow@5}{HTML}{770088}
\colorlet{beamer@structure@color}{rainbow@0}
\setbeamercolor{structure}{fg=beamer@structure@color}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Reading theme options
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\DeclareOptionBeamer{colors}{\def\rainbow@colors{#1}}
\DeclareOptionBeamer{auto}{\def\rainbow@auto{#1}}
\ExecuteOptionsBeamer{colors={rainbow@0,rainbow@1,rainbow@2,rainbow@3,rainbow@4,rainbow@5},auto=frame}
\ProcessOptionsBeamer

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Defining colours
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\ExplSyntaxOn

% list to store colour list
\clist_new:N \l_rainbow_clist
\clist_set:Nx \l_rainbow_clist \rainbow@colors

\newcounter{rainbow@count}

% macro to switch to next colour
\newcommand{\rainbow}{
  \addtocounter{rainbow@count}{1}
  \colorlet{beamer@structure@color}{
    \clist_item:Nn \l_rainbow_clist {
      \int_eval:n {
        \int_mod:nn { \value{rainbow@count} }{ 
          \clist_count:N \l_rainbow_clist
        } + 1
      }
    }
  }
}

% switch colour at start of frame
\str_if_eq:eeT { \rainbow@auto } { frame } { 
  \pretocmd{\beamer@@@frame}{
    \ifnum\thepage>1
      \rainbow
    \fi
  }{}{}
}

% switch colour at start of section
\str_if_eq:eeT { \rainbow@auto } { section } { 
  \AddToHook{cmd/section/before}{%
    \ifnum\thepage>1
      \rainbow
    \fi
  }
}

% switch colour at start of subsection
\str_if_eq:eeT { \rainbow@auto } { subsection } { 
  \AddToHook{cmd/subsection/before}{%
    \ifnum\thepage>1
      \rainbow
    \fi
  }
}

% initially use first colour from the list 
\AtBeginDocument{
  \setcounter{rainbow@count}{-1}
  \rainbow
}

\ExplSyntaxOff

\mode
<all>
