Creating a custom Beamer theme. Need to remove the footline for the title page only

Question

First of all, I'm aware of this question and it's really not what I'm asking: the solution given there is to issue

\setbeamertemplate{footline}{}

in a localized group containing the \titlepage frame. That's not what I want. As the title says, I'm creating a custom theme and I don't want to leave the suppression of the footline on the title page up to my end users. How can I go about suppressing the footline just for the title page?

Note that I already tried

\setbeamertemplate{title page}{
    \setbeamertemplate{footline}{}
    % my definitions here
}

and it didn't work.

I know that the etiquette around here is to post a MWE, but I'm not really sure what I need to post in this case. If you need me to post parts of my definition, I'll gladly do.

Answer 1

If a presentation using your theme always has a title page, which is usually the first page, then one can define the template for footline to be different for the first page.

To implement this, one can use the \ifnum expression:

\defbeamertemplate*{footline}{my footline}
{
    \ifnum \insertpagenumber=1
      <definition of footline style on page 1>
    \else
      <definition of footline style on other pages>
    \fi
}

This will define a template for footline, such that page 1 has a potentially different footline style from other pages. \insertpagenumber inserts the current page number into the template, which is checked by \ifnum to see if it's page 1. Then the appropriate clause of the "then-else" statement will be executed depending the truth value of the expression "the current page number is 1".

MWE

\documentclass{beamer}
\usetheme{Madrid}

\defbeamertemplate*{footline}{my footline}
{
    \ifnum \insertpagenumber=1
      \leavevmode%
      \hbox{%
      \begin{beamercolorbox}[wd=\paperwidth,ht=2.25ex,dp=1ex,center]{}%
        % empty environment to raise height
      \end{beamercolorbox}}%
      \vskip0pt%
    \else
      \leavevmode%
      \hbox{%
      \begin{beamercolorbox}[wd=\paperwidth,ht=2.25ex,dp=1ex,center]{title in head/foot}%
        \usebeamerfont{title in head/foot}\insertshorttitle
      \end{beamercolorbox}}%
      \vskip0pt%
    \fi
}

\setbeamertemplate{footline}[my footline]

\title{Some Title}

\begin{document}
\begin{frame}
\titlepage
\end{frame}

\begin{frame}{Frame 1}
This is a normal frame.
\end{frame}
\end{document}

Output