Redefine options in TikZ-UML sequence diagrams

Question

I have several TikZ-UML sequence diagrams and mostly I always set the options dt=5 and padding=3 for all umlcall. Is it possible to set these two variables for these values as default?

\documentclass{report}
\usepackage{tikz}
\usepackage{tikz-uml}
\begin{document}

\begin{tikzpicture}
      \begin{umlseqdiag}
        \umlbasicobject{B}
        \umlbasicobject[x=6]{C}

        \begin{umlcall}[op=msg1, return={r0, r1}, dt=4, padding=3]{C}{B}
        \end{umlcall}

        \begin{umlcall}[op=callback, return={ok}, dt=5, padding=3]{B}{C}
        \end{umlcall}

        \begin{umlcall}[op=msg2, return=r2, dt=5, padding=3]{C}{B}
        \end{umlcall}

      \end{umlseqdiag}
\end{tikzpicture}

\end{document}

Answer 1

The umlcall environment does

\pgfkeys{/tikzuml/call/.cd,%
   dt/.initial={tikzumlEmpty},%
   padding/.initial=2,%
   [...]

so there's no way to pass different initial values except correcting the environment's definition. Here's a way with xpatch.

\documentclass{report}
\usepackage{tikz}
\usepackage{tikz-uml}

\usepackage{xpatch}
\xpatchcmd{\umlcall}
  {dt/.initial={tikzumlEmpty}}
  {dt/.initial=5}
  {}{}
\xpatchcmd{\umlcall}
  {padding/.initial=2}
  {padding/.initial=3}
  {}{}

\begin{document}

\begin{tikzpicture}
      \begin{umlseqdiag}
        \umlbasicobject{B}
        \umlbasicobject[x=6]{C}

        \begin{umlcall}[op=msg1, return={r0, r1}, dt=4, padding=3]{C}{B}
        \end{umlcall}

        \begin{umlcall}[op=callback, return={ok}, dt=5, padding=3]{B}{C}
        \end{umlcall}

        \begin{umlcall}[op=msg2, return=r2, dt=5, padding=3]{C}{B}
        \end{umlcall}

      \end{umlseqdiag}
\end{tikzpicture}

\begin{tikzpicture}
      \begin{umlseqdiag}
        \umlbasicobject{B}
        \umlbasicobject[x=6]{C}

        \begin{umlcall}[op=msg1, return={r0, r1}, dt=4]{C}{B}
        \end{umlcall}

        \begin{umlcall}[op=callback, return={ok}]{B}{C}
        \end{umlcall}

        \begin{umlcall}[op=msg2, return=r2]{C}{B}
        \end{umlcall}

      \end{umlseqdiag}
\end{tikzpicture}

\end{document}

I typeset the original call and the new one where the values are not specified in order to see they're identical.

Answer 2

Here, I created a new environment, Umlcall which has your desired defaults. I changed up your MWE parameters a bit to show that one can override the defaults, and that the method works without any optional argument, as well. The defaults are defined in the macro \umldefaults.

\documentclass{report}
\usepackage{tikz}
\usepackage{tikz-uml}
\newcommand\umldefaults{dt=5, padding=3, }
\newenvironment{Umlcall}[3][]{\expandafter\umlcall\expandafter[\umldefaults #1]{#2}{#3}}%
  {\endumlcall}
\begin{document}

\begin{tikzpicture}
      \begin{umlseqdiag}
        \umlbasicobject{B}
        \umlbasicobject[x=6]{C}

        \begin{Umlcall}[op=msg1, return={r0, r1}, dt=7, padding=5]{C}{B}
        \end{Umlcall}

        \begin{Umlcall}[op=callback, return={ok}]{B}{C}
        \end{Umlcall}

        \begin{Umlcall}[op=msg2, return=r2]{C}{B}
        \end{Umlcall}

        \begin{Umlcall}{C}{B}
        \end{Umlcall}

      \end{umlseqdiag}
\end{tikzpicture}

\end{document}

Answer 3

You're right. tikz-uml offers a way to define global default value thanks to the command \tikzumlset but I only activated it for drawing purpose, namely draw, fill and text options of each available UML element. I added the possibility to define global default value for quite every option of every element. This will be available soon in the new release of tikz-uml.