Superflous leading dot in biblatex/numeric and beamer

Question

The combination of beamer and biblatex with the numeric style leads to an undesired dot and space at the beginning of @MISC entries.

\begin{filecontents}{mybib.bib}
@MISC{www,
   title={TeX.SX},
   url={www.tex.stackexchange.com},
   urldate={2012-02-02},
}
\end{filecontents}

\documentclass{beamer}

\usepackage[backend=biber,style=numeric]{biblatex}
\addbibresource{mybib.bib}

\begin{document}
\frame{Test \cite{www}}

\frame{\printbibliography}
\end{document}

Since this only happens with beamer and not scrarticle I guess it’s a beamer problem/imcompability. Is it possible to fix it?

Answer 1

This seems to be a bug in beamerbaselocalstructure.sty. You can temporarily fix it by adding

 \makeatletter
 \patchcmd{\abx@macro@title}{\blx@unitpunct\blx@postpunct}{}{}
 \makeatother

right after \begin{document} in your file.

The same problem will arise with an empty title field in an entry. This is not so easily fixed at the moment, however.

(IMO this is safer than making your own local copy of beamerbaselocalstructure.sty. In my experience, it's very easy to forget such local modifications and then be bitten down the road if the package is updated.)

Answer 2

In beamerbaselocalstructure.sty you will find

\AtBeginDocument{
  \@ifpackageloaded{biblatex}
    {
      \apptocmd\blx@env@bibliography{\let\makelabel\beamer@biblabeltemplate}{}{}
      \pretocmd{\abx@macro@author}{\usebeamercolor[fg]{bibliography entry author}}{}{}
      \pretocmd{\abx@macro@editor}{\usebeamercolor[fg]{bibliography entry author}}{}{}
      \pretocmd{\abx@macro@title}{\blx@unitpunct\blx@postpunct\newblock\usebeamercolor[fg]{bibliography entry title}}{}{}
      \apptocmd{\abx@macro@title}{\blx@unitpunct\blx@postpunct\newblock\usebeamercolor[fg]{bibliography entry note}}{}{}
    }
    {}
}

The issue can be removed by using a modified version of this file which instead reads

\AtBeginDocument{
  \@ifpackageloaded{biblatex}
    {
      \apptocmd\blx@env@bibliography{\let\makelabel\beamer@biblabeltemplate}{}{}
      \pretocmd{\abx@macro@author}{\usebeamercolor[fg]{bibliography entry author}}{}{}
      \pretocmd{\abx@macro@editor}{\usebeamercolor[fg]{bibliography entry author}}{}{}
      \pretocmd{\abx@macro@title}{\newblock\usebeamercolor[fg]{bibliography entry title}}{}{}
      \apptocmd{\abx@macro@title}{\blx@unitpunct\blx@postpunct\newblock\usebeamercolor[fg]{bibliography entry note}}{}{}
    }
    {}
}

Looking at this again, I'm not sure why that extra punctuation is there at all: I will update beamer with this fix.

Answer 3

Patches to the low-level bibliography macros need to generate punctuation in some cases - otherwise the color of unit punctuation set outside the macros won't match the color of the preceding field. In this new hook the punctuation at the beginning of title is set if labelname is defined. The punctuation at the end is set if title is defined.

\AtBeginDocument{%
  \@ifpackageloaded{biblatex}
    {\apptocmd\blx@env@bibliography{\let\makelabel\beamer@biblabeltemplate}{}{}
     \apptocmd{\abx@macro@begentry}{\usebeamercolor[fg]{bibliography entry author}}{}{}
     \pretocmd{\abx@macro@title}
       {\ifcsundef{abx@name@labelname}{}{\blx@unitpunct\blx@postpunct}%
        \newblock\usebeamercolor[fg]{bibliography entry title}}{}{}
     \apptocmd{\abx@macro@title}
       {\ifcsundef{abx@field@title}{}{\blx@unitpunct\blx@postpunct}%
        \newblock\usebeamercolor[fg]{bibliography entry note}}{}{}}
    {}}

I've also included a patch to begentry. Names from editor or translator form labelname when author undefined, but the original patches to the author and editor macros don't appear to handle this case properly.

The above hook should replace the one found in beamerbaselocalstructure.sty. Otherwise the original hook can be patched after \begin{document}. Here's an example.

\documentclass{beamer}
\usepackage[backend=biber,style=numeric]{biblatex}

\begin{filecontents}{\jobname.bib}
@MISC{www,
   title={TeX.SX},
   url={www.tex.stackexchange.com},
   urldate={2012-02-02},}
@MISC{www2,
   url={www.tex.stackexchange.com},
   urldate={2012-02-02},}
\end{filecontents}

\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}

\begin{document}
\makeatletter
  \apptocmd{\abx@macro@begentry}{\usebeamercolor[fg]{bibliography entry author}}{}{}
  \patchcmd{\abx@macro@title}
    {\blx@unitpunct\blx@postpunct\newblock\usebeamercolor[fg]{bibliography entry title}}
    {\ifcsundef{abx@name@labelname}{}{\blx@unitpunct\blx@postpunct}%
     \newblock\usebeamercolor[fg]{bibliography entry title}}{}{}
  \patchcmd{\abx@macro@title}
    {\blx@unitpunct\blx@postpunct\newblock\usebeamercolor[fg]{bibliography entry note}}
    {\ifcsundef{abx@field@title}{}{\blx@unitpunct\blx@postpunct}%
     \newblock\usebeamercolor[fg]{bibliography entry note}}{}{}
\makeatother
\frame{Test \cite{www,companion,www2,moraux,gaonkar}}
\frame{\printbibliography}
\end{document}