Change \headheight in Beamer, Copenhagen

Question

I want to increase the \headheight in Beamer, Copenhagen.

I tried, \setlength{\headheight}{10in}, did not seem to work.

Answer 1

Edit: My previous answer was actually valid with the Sidebar outer theme, it is not as simple with Split, which is used by Copenhagen. It explains the error you got, since \beamer@headheight is not defined in Split.

Answer:

You can use the following

\makeatletter
\newdimen\beamer@headheight
\beamer@headheight=10in

\setbeamertemplate{headline}{
  \leavevmode%
  \@tempdimb=2.4375ex%
  \ifnum\beamer@subsectionmax<\beamer@sectionmax%
    \multiply\@tempdimb by\beamer@sectionmax%
  \else%
    \multiply\@tempdimb by\beamer@subsectionmax%
  \fi%
  \ifnum\@tempdimb<\beamer@headheight
    \setlength{\@tempdimb}{\beamer@headheight}
  \fi
  \ifdim\@tempdimb>0pt%
    \advance\@tempdimb by 1.125ex%
    \begin{beamercolorbox}[wd=.5\paperwidth,ht=\@tempdimb]{section in head/foot}%
      \vbox to\@tempdimb{\vfil\insertsectionnavigation{.5\paperwidth}\vfil}%
    \end{beamercolorbox}%
    \begin{beamercolorbox}[wd=.5\paperwidth,ht=\@tempdimb]{subsection in head/foot}%
      \vbox to\@tempdimb{\vfil\insertsubsectionnavigation{.5\paperwidth}\vfil}%
    \end{beamercolorbox}%
  \fi%  
}
\makeatother

You define a new length \beamer@headheight you can modify easily. This is a modification of the Split outer theme that will check if your new head height is larger than the one set by Beamer; if it is true, it will use this new length. If not, it won't change anything to avoid to mess up the headline. If you always want to force the headline to have the \beamer@headheight height, you can simply use

\makeatletter
\newdimen\beamer@headheight
\beamer@headheight=20pt

\setbeamertemplate{headline}{
  \leavevmode%
  \begin{beamercolorbox}[wd=.5\paperwidth,ht=\beamer@headheight]{section in head/foot}%
    \vbox to\@tempdimb{\vfil\insertsectionnavigation{.5\paperwidth}\vfil}%
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.5\paperwidth,ht=\beamer@headheight]{subsection in head/foot}%
    \vbox to\@tempdimb{\vfil\insertsubsectionnavigation{.5\paperwidth}\vfil}%
  \end{beamercolorbox}%
}
\makeatother