Auto overlay table rows with \rowfont (tabu) and beamer

Question

I have a table in a presentation which I would like to color the text of each row as it is revealed. I'm currently using the beamer package and a variation of a related solution which requires specifying the slide number for each row.

Here is a MWE illustrating my current "manual" method which has the desired end result.

\documentclass{beamer}

\usepackage{tabu}

\newcommand{\rowcolor}[1]{\rowfont{\leavevmode\temporal<#1>{\color{white}}{\color{blue}}{\color{normal text.fg}}}}

\begin{document}

\begin{frame}{A Table}
    \begin{tabu}{lll}
    \rowcolor{1} cell 1 & cell 2 & cell 3\\
    \rowcolor{2} cell 4 & cell 5 & cell 6\\
    \rowcolor{3} cell 7 & cell 8 & cell 9
    \end{tabu}

\end{frame}

\end{document}

I attempted to use enclose my \rowcolor function inside an \everyrow function

...
\everyrow{\rowcolor{+}}
\begin{tabu}{lll}
...    

However, apparently \rowfont inserts its argument into each cell of the row before the contents are evaluated by beamer, so that the <+> specification will then get incremented for each cell, not just for each row.

Is there a way to increment the slide number before \rowfont is executed?Or is there a better way to auto increment the slides without specifying slide number explicitly for each row?

Answer 1

Something like this might do the trick (needs >= 2 compilations for the correct result):

\documentclass{beamer}

\usepackage{tabu}

\usepackage{totcount}
\newtotcounter{totalrows}

\begin{document}

\begin{frame}
    \frametitle{A Table}


    bla\pause 

    test\pause

     \everyrow{%
        \ifnum\thetaburow<\totvalue{totalrows}
                \only<+>{\rowfont{\leavevmode\color{blue}}}
        \fi
        }  

        \begin{tabu}{lll}
                cell 1 & cell 2 & cell 3\\
            cell 4 & cell 5 & cell 6\\
            cell 7 & cell 8 & cell 9 
            \setcounter{totalrows}{\thetaburow}           
        \end{tabu}

\end{frame}

\end{document}