[Tex/LaTex] How to change default theme title style (bold, color, margin) of title in the beginning of each slide

Question

I am interested in having a local change to the default theme of beamer.

I want every title in the beginning of a slide to be boldfaced, black (instead of purplish, black) with a horizontal line that stretches below it, with some margin between the line and the end points of the slide.

Is that possible to do with beamer?

Answer 1

One option would be to set the frametitle template to add the horizontal rule; something along these lines:

\documentclass{beamer}

\setbeamertemplate{frametitle}{\color{black}\bfseries\insertframetitle\par\vskip-6pt\hrulefill}

\begin{document}

\begin{frame}
\frametitle{Test title for the frame}
\end{frame}

\end{document}

To keep the exact formatting of the original frametitle template, you can change the default definition (I wasn't sure about the position of the rule in the case of a frame subtitle, so I opted for placing the rule below a possible frame subtitle; this can be easily modified):

\documentclass{beamer}

\makeatletter
\setbeamertemplate{frametitle}
{
  \ifbeamercolorempty[bg]{frametitle}{}{\nointerlineskip}%
  \@tempdima=\textwidth%
  \advance\@tempdima by\beamer@leftmargin%
  \advance\@tempdima by\beamer@rightmargin%
  \begin{beamercolorbox}[sep=0.3cm,left,wd=\the\@tempdima]{frametitle}
    \vbox{}\vskip-1ex%
    \if@tempswa\else\csname beamer@fteleft\endcsname\fi%
    {\strut\color{black}\bfseries\insertframetitle\strut\par%
    {%
      \ifx\insertframesubtitle\@empty%
      \else%
      {\usebeamerfont{framesubtitle}\usebeamercolor[fg]{framesubtitle}\insertframesubtitle\strut\par}%
      \fi
    }%
    \vskip-1.5ex%
    \rule{\dimexpr\paperwidth-0.6cm\relax}{0.4pt}}
    \if@tempswa\else\vskip-.3cm\fi% set inside beamercolorbox... evil here...
  \end{beamercolorbox}%
    %
}
\makeatother

\begin{document}

\begin{frame}
\frametitle{Test title for the frame}
\end{frame}

\end{document}