Cfrgtkky

I am working at a new beamer theme and I am wondering if it is possible to retrieve the height of the last shipped out beamercolorbox. To set up a reasonable minimal (although horribly looking) working example, let us focus on the frametitle template and let us assume (like it is in many themes) that the frame title is basically put into a beamercolorbox.

documentclass{beamer}

usetheme{Madrid}



makeatletter

defbeamertemplate*{frametitle}{myFrametitle}[1][left]

{

  begin{beamercolorbox}[sep=0.3cm,wd=textwidth]{frametitle}

    usebeamerfont{frametitle}%

    strutinsertframetitlestrutpar%

    {%

      ifxinsertframesubtitle@empty%

      else%

      {usebeamerfont{framesubtitle}usebeamercolor[fg]{framesubtitle}insertframesubtitlestrutpar}%

      fi

    }%

  end{beamercolorbox}%

  %-----

  % Here I would like to have a length with the height of the

  % above beamercolorbox, to be used to adapt dynamically stuff

  %-----

}

makeatother



setbeamertemplate{frametitle}[myFrametitle]



begin{document}



    begin{frame}{Frame title}

        A frame

    end{frame}



    begin{frame}{Frame title}{with subtitle}

        Another frame

    end{frame}



 end{document}

Is there an elegant way to retrieve the height of the box in the last beamercolorbox environment?

More information

• 
  

  Reading the beamerbasecolor.sty file, I thought that I might redefine the beamercolorbox environment adding a line like

  
  
  

  globalsetlength{@lastbeamercolorboxheight}{htbeamer@tempbox}%
  
  

  
  
  

  before each boxbeamer@tempbox%, where @lastbeamercolorboxheight would be an internal length of my theme. However, I do not like the idea of copying tons of beamer code just for a minimal add-on and, moreover, it does not look neither so elegant nor the way to go (see below to have a concrete example of this approach).

  
  



• I am aware that I might use the ht and dp keys of the beamercolorbox to fix the height of the box, but this is not a valid approach in my case. It is more like, the user puts whatever she/he want in the frame title/subtitle and I act dynamically accordingly.




• I am glad to receive any general hint and possibly slightly different approaches are welcome.




• If the elegant solution is not to use a beamercolorbox at all, well, I will then think to an alternative from a more general perspective.

Redefining the beamercolorbox environment

Although this is not an elegant way to retrieve the height of the box, it gives access to the desired length. However, there are probably many drawbacks, but the code here might help readers suggesting better approaches.

documentclass{beamer}

usetheme{Madrid}



makeatletter



newlength{@lastbeamercolorboxheight}



renewenvironment{beamercolorbox}[2]{% taken from beamerbasecolor.sty

  begingroup%

    defbeamer@colbox@coladd{0pt}%

    defbeamer@vmode{leavevmode}%

    setkeys{beamercolbox}{%

      wd=textwidth,ht={},dp={},%

      leftskip=0pt,rightskip=0pt plus1fil,%

      sep=0pt,colsep=0pt,colsep*=0pt,%

      shadow=false,rounded=false,ignorebg=false}%

    setkeys{beamercolbox}{#1}%

    ifbeamercolorempty[bg]{#2}{@tempswafalse}{@tempswatrue}%

    ifbeamer@colbox@ignorebg@tempswafalsefi%

    defbeamer@colbox@color{#2}%

    hsize=beamer@colbox@wd%

    setboxbeamer@tempbox=hboxbgroupvboxbgroup%

      leftskip=beamer@colbox@ls%

      advanceleftskip bybeamer@colbox@sep%

      rightskip=beamer@colbox@rs%

      advancerightskip bybeamer@colbox@sep%

      ifbeamer@colbox@ignorebg%

        colorlet{beamer@temp@color}{bg}%

        usebeamercolor[fg]{#2}%

        colorlet{bg}{beamer@temp@color}%

      else%

        usebeamercolor[fg]{#2}%

      fi%

      if@tempswa%

        advanceleftskip bybeamer@colbox@colsep%

        advancerightskip bybeamer@colbox@colsep%

        ifdimbeamer@colbox@colsep=0ptelsevskipbeamer@colbox@colsepfi%

        ifdimbeamer@colbox@colseps=0ptelsevskipbeamer@colbox@colsepsfi%

      fi%

      ifdimbeamer@colbox@sep=0ptelsevskipbeamer@colbox@sepfi%

      beamer@vmodeignorespaces}{%

      ifdimbeamer@colbox@sep=0ptelsevskipbeamer@colbox@sepfi%

      if@tempswaifdimbeamer@colbox@colsep=0ptelsevskipbeamer@colbox@colsepfifi%

      if@tempswaifdimbeamer@colbox@colseps=0ptelsevskipbeamer@colbox@colsepsfifi%

    egroupegroup%

    wdbeamer@tempbox=hsize%

    @tempdima=wdbeamer@tempbox%

    ifxbeamer@colbox@ht@empty%

    else%

      htbeamer@tempbox=beamer@colbox@ht%

    fi%

    ifxbeamer@colbox@dp@empty%

    else%

      dpbeamer@tempbox=beamer@colbox@dp%

    fi%

    ifbeamer@colbox@rounded%

      if@tempswa%

        begin{beamerboxesrounded}[%

          shadow=beamer@colbox@shadow,%

          lower=beamer@colbox@color,%

          upper=normal text,%

          width=beamer@colbox@wd]{}%

          globalsetlength{@lastbeamercolorboxheight}{htbeamer@tempbox}% <--- ADDED

          boxbeamer@tempbox%

        end{beamerboxesrounded}%

      else%

        ifdim@tempdima>textwidth%

          setboxbeamer@tempbox=hbox totextwidth{hssboxbeamer@tempboxhss}%

        fi%

        globalsetlength{@lastbeamercolorboxheight}{htbeamer@tempbox}%  <--- ADDED

        boxbeamer@tempbox%

      fi%

    else%

      if@tempswasetboxbeamer@tempbox=hbox{vbox{%

        usebeamercolor{beamer@colbox@color}%

        advancehsize by beamer@colbox@colsepsrelax%

        advancehsize by beamer@colbox@colsepsrelax%

        hskip-beamer@colbox@colseps%

        fboxsep=0ptcolorbox{bg}{%

          hskipbeamer@colbox@colseps%

          hbox{boxbeamer@tempbox}%

          hskipbeamer@colbox@colseps%

        }%

        hskip-beamer@colbox@colseps%

      }}fi%

      ifdim@tempdima>textwidth%

        setboxbeamer@tempbox=hbox totextwidth{hskip0pt minusbeamer@leftmarginrelaxboxbeamer@tempboxhskip0pt minusbeamer@rightmarginrelax}%

      fi%

      globalsetlength{@lastbeamercolorboxheight}{htbeamer@tempbox}%  <--- ADDED

      boxbeamer@tempbox%

    fi%

  endgroup%

}



defbeamertemplate*{frametitle}{myFrametitle}

{

  begin{beamercolorbox}[sep=0.3cm,wd=textwidth]{frametitle}

    usebeamerfont{frametitle}%

    strutinsertframetitlestrutpar%

    {%

      ifxinsertframesubtitle@empty%

      else%

      {usebeamerfont{framesubtitle}usebeamercolor[fg]{framesubtitle}insertframesubtitlestrutpar}%

      fi

    }%

  end{beamercolorbox}%

  %-----

  % Here the length @lastbeamercolorboxheight is set to the height of the box above

  textcolor{black}{the@lastbeamercolorboxheight}

}

makeatother



setbeamertemplate{frametitle}[myFrametitle]



begin{document}



    begin{frame}{Frame title}

        A frame

    end{frame}



    begin{frame}{Frame title}{with subtitle}

        Another frame

    end{frame}



 end{document}

And the result is the following.