Selective breaking of biblatex urls?

Question

Based on Avoiding inelegant splits on URLs, I have this MWE:

\documentclass{article}
\usepackage[backend=biber]{biblatex}
\usepackage{filecontents}
\usepackage{trace}
\usepackage{hyperref}
\begin{filecontents}{\jobname.bib}
@misc{A01,
  author = {Author, A. and Buthor, B.  },
  year = {2001},
  title = {Alpha aaa},
  url = {http://www.thewebsiteurl.com/ab/XC/PYR12337.pdf},
}
@misc{A02,
  author = {Authoq, A. and Buthoq, B.  },
  year = {2002},
  title = {Betaa bbb},
  url = {http://www.trythesesites.com/cx/AB/KXY0012C.pdf},
}
\end{filecontents}
\addbibresource{\jobname.bib}

\def\mybiburlval{0}% 0 is otherwise the default
% \def\mybiburlval{1}% uncomment this to set to 1

% hyphenation does not work in URLs:
%\hyphenation{the-website-url}
% so use as per:
% https://tex.stackexchange.com/questions/30857/avoiding-inelegant-splits-on-urls

% Set low penalties for breaks at numbers, uppercase letters and lowercase letters
\setcounter{biburlnumpenalty}{\mybiburlval}
\setcounter{biburlucpenalty}{\mybiburlval}
\setcounter{biburllcpenalty}{\mybiburlval}

% Define a category to selectively print entries with a higher lowercase penalty
\DeclareBibliographyCategory{badbreaks}
\addtocategory{badbreaks}{A01} % only A01 here

\AtEveryBibitem{%
  \ifcategory{badbreaks}
    {\defcounter{biburllcpenalty}{9000}}
    {}}

\begin{document}

\noindent
A: \fullcite{A01}

B: \fullcite{A02}

\printbibliography

\end{document}

Compiled this with pdflatex test.tex && biber test && pdflatex test.tex && pdflatex test.tex, using Texlive 2014 frozen. Here is a screenshot of how evince renders this output:

So the links mostly "leak"/"spill over" the margin, except the second one, which is line-broken at a period/dot.

Now uncomment the \def\mybiburlval{1} line, and recompile again; the output now is:

Notice how all links are line-broken here at lowercase characters - even if I've only added the first (A01) citation to the badbreaks category; and even if I've set the lower case breaking penalty to the smallest possible value (1)!

So my question is - how can I selectively choose to have a URL break only for the citations which are in the badbreaks category (in this case, only A01); and otherwise typeset links as in the usual case (even if they spill over the margin)?

Maybe of note would be to recall:

$ texdef -t latex -p biblatex -f setcounter
\setcounter is defined by (La)TeX.

\setcounter:
macro:#1#2->\@ifundefined {c@#1}{\@nocounterr {#1}}{\global \csname c@#1\endcsname #2\relax }

$ texdef -t latex -p biblatex -f defcounter
\defcounter first defined in "etoolbox.sty".

\defcounter:
\protected macro:#1#2->\ifcsundef {c@#1} {\etb@noglobal \@nocounterr {#1}}{\csname c@#1\endcsname \numexpr #2\relax }

So, apparently, \setcounter is global, and \defcounter is not (is local) - but I get the same output (i.e. breaking applied nonselectively everywhere), even if I use \setcounter instead of \defcounter in the switch - and even if I specifically set a 0 in the "else" part, as in:

\AtEveryBibitem{%
  \ifcategory{badbreaks}
    {\setcounter{biburllcpenalty}{9000}}
    {\setcounter{biburllcpenalty}{0}   }}

So how can I apply url breaking at lowercase characters selectively - only to some citations?

Answer 1

The penalties are not used in a bibitem, but only in \biburlsetup which is done at the begin of the bibliography. If you want to change the settings for one bibitem, you should call the url setup again:

\AtEveryBibitem{%
  \ifcategory{badbreaks}
    {\defcounter{biburllcpenalty}{9000}\biburlsetup}
    {}}

Output with OP MWE (\def\mybiburlval{0}):