Split title page template into sub-templates

source/beamerinnerthememetropolis.dtx

@@ -156,102 +156,29 @@
 %    \end{macrocode}
 %
 % \begin{macro}{title page}
-%   Template for the title page.
+%   Template for the title page. Each element is only typset if it is defined
+%   by the user. If |\subtitle| is empty, for example, it won't leave a blank
+%   space on the title slide.
 %    \begin{macrocode}
 \setbeamertemplate{title page}{
   \begin{minipage}[b][\paperheight]{\textwidth}
-%    \end{macrocode}
-%
-%   If the user has set a |titlegraphic|, we set it in a zero-height box so
-%   it doesn't change the position of other elements.
-%
-%    \begin{macrocode}
-    \ifx\inserttitlegraphic\@empty\else{%
-      \vbox to 0pt {
-        \vspace*{2em}
-        \usebeamercolor[fg]{titlegraphic}%
-        \inserttitlegraphic%
-      }%
-      \nointerlineskip%
-    }
-    \fi
+    \ifx\inserttitlegraphic\@empty\else\usebeamertemplate*{title graphic}\fi
     \vfill%
+    \ifx\inserttitle\@empty\else\usebeamertemplate*{title}\fi
+    \ifx\insertsubtitle\@empty\else\usebeamertemplate*{subtitle}\fi
+    \usebeamertemplate*{title separator}
 %    \end{macrocode}
 %
-%   We set the title and subtitle, but only if they are defined by the user.
-%   If |\subtitle| is empty, for example, it won't leave a blank space on the
-%   title slide.
-%
-%    \begin{macrocode}
-    \ifx\inserttitle\@empty\else{{%
-      \raggedright%
-      \linespread{1.0}%
-      \usebeamerfont{title}%
-      \usebeamercolor[fg]{title}%
-      \@metropolis@titleformat{\inserttitle}%
-      \par%
-      \vspace*{0.5em}
-    }}
-    \fi
-    \ifx\insertsubtitle\@empty\else{{%
-      \usebeamerfont{subtitle}%
-      \usebeamercolor[fg]{subtitle}%
-      \insertsubtitle%
-      \par%
-      \vspace*{0.5em}
-    }}
-    \fi
-%    \end{macrocode}
-%
-%   A horizontal rule (drawn in TikZ) separates the title and subtitle from
-%   the author, date, and institution.
-%
-%    \begin{macrocode}
-    \begin{tikzpicture}
-      \usebeamercolor{title separator}
-      \draw[fg] (0, 0) -- (\textwidth, 0);
-    \end{tikzpicture}%
-    \par%
-    \vspace*{1em}%
-%    \end{macrocode}
-%
-%   Like the title and subtitle, we display the author only when it is defined.
-%   But beamer's definition of |\insertauthor| is always nonempty, so we have
+%   Beamer's definition of |\insertauthor| is always nonempty, so we have
 %   to test another macro initialized by |\author{...}| to see if the user has
 %   defined an author. This solution was suggested by Enrico Gregorio in an
 %   answer to \href{https://tex.stackexchange.com/questions/241306/}{this
 %   Stack Exchange question}.
 %
 %    \begin{macrocode}
-    \ifx\beamer@shortauthor\@empty\else{{%
-      \usebeamerfont{author}%
-      \usebeamercolor[fg]{author}%
-      \insertauthor%
-      \par%
-      \vspace*{0.25em}
-    }}
-    \fi
-%    \end{macrocode}
-%
-%   The date and institute are set after the author, again provided they are
-%   nonempty. Note that the default date in \LaTeX{} is |\today|, not |\empty|.
-%
-%    \begin{macrocode}
-    \ifx\insertdate\@empty\else{{%
-      \usebeamerfont{date}%
-      \usebeamercolor[fg]{date}%
-      \insertdate%
-      \par%
-    }}
-    \fi
-    \ifx\insertinstitute\@empty\else{{%
-      \vspace*{3mm}
-      \usebeamerfont{institute}%
-      \usebeamercolor[fg]{institute}%
-      \insertinstitute%
-      \par%
-    }}
-    \fi
+    \ifx\beamer@shortauthor\@empty\else\usebeamertemplate*{author}\fi
+    \ifx\insertdate\@empty\else\usebeamertemplate*{date}\fi
+    \ifx\insertinstitute\@empty\else\usebeamertemplate*{institute}\fi
     \vfill
     \vspace*{1mm}
   \end{minipage}
@@ -285,6 +212,90 @@
 % \end{macro}
 % \end{macro}
 %
+% \begin{macro}{title graphic}
+%   Set the title graphic in a zero-height box, so it doesn't change the
+%   position of other elements.
+%    \begin{macrocode}
+\setbeamertemplate{title graphic}{
+  \vbox to 0pt {
+    \vspace*{2em}
+    \inserttitlegraphic%
+  }%
+  \nointerlineskip%
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{title}
+%   Set the title on the title page.
+%    \begin{macrocode}
+\setbeamertemplate{title}{
+  \raggedright%
+  \linespread{1.0}%
+  \@metropolis@titleformat{\inserttitle}%
+  \par%
+  \vspace*{0.5em}
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{subtitle}
+%   Set the subtitle on the title page.
+%    \begin{macrocode}
+\setbeamertemplate{subtitle}{
+  \insertsubtitle%
+  \par%
+  \vspace*{0.5em}
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{title separator}
+%   Template to set the title graphic in a zero-height box. (It won't
+%   change the position of other elements.)
+%    \begin{macrocode}
+\setbeamertemplate{title separator}{
+  \begin{tikzpicture}
+    \draw[fg] (0, 0) -- (\textwidth, 0);
+  \end{tikzpicture}%
+  \par%
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{author}
+%   Set the author on the title page.
+%    \begin{macrocode}
+\setbeamertemplate{author}{
+  \vspace*{2em}
+  \insertauthor%
+  \par%
+  \vspace*{0.25em}
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{date}
+%   Set the date on the title page.
+%    \begin{macrocode}
+\setbeamertemplate{date}{
+  \insertdate%
+  \par%
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{institute}
+%   Set the institute on the title page.
+%    \begin{macrocode}
+\setbeamertemplate{institute}{
+  \vspace*{3mm}
+  \insertinstitute%
+  \par%
+}
+%    \end{macrocode}
+% \end{macro}
+%
 %
 %
 % \subsubsection{Section page}