How to Center a Sentence at the Center of a Bclogo

Question

I would like to automatically center a sentence within a Bclogo box; that is, I would like to place the sentence such that its center lies (technically) at the midpoint of the diagonal endpoints of the rectangular-shaped bclogo.

Based on how one might automatically center a divider in the TOC, I tried the following code:

\documentclass{book}
\usepackage{xcolor}
\usepackage[tikz]{bclogo}
\usetikzlibrary{calc,shapes.callouts,shapes.arrows}

\begin{document}
\thispagestyle{empty}
\Huge
\begin{center} 
\begin{bclogo}[couleur=red!10,  %couleur=blue!14, %couleur=blue!20, 
epBord=3.5, arrondi=0, %logo=\bcplume, %\bclampe,marge=8, 
logo= ,
%ombre=true, blur, couleurBord=blue!14, %couleurBord=blue!60,
barre=none, %barre=snake, tailleOndu=1.5
]{\hfil{This sentence is not centered.}\hfil}
\end{bclogo}
\end{center}
\end{document}

which produces

I have noticed, surprisingly to me, that if I replace \hfil by \hfill I get the following:

which looks pretty much like a goof horizontal centering, but clearly, not vertically centered.

In the past, I have spent a considerable amount of time trying to center a sentence by many manual trial-and-error adjustments; and so, I would like to pose the following question.

QUESTION: How may I center a sentence in the described Bclogo such that it is automatically both vertically and horizontally centered? Also, does anyone know why \hfil does not do the job as it seems to when I have used it to center an item in a TOC: and also, why is the vertical centering so egregiously off when I use \hfill?

Thank you.

Answer 1

The mandatory argument to bclogo is the title. You want

\begin{bclogo}[<options>]{}
  text for the box
\end{bclogo}

but you first need to remove the space reserved for the title, that's inserted no matter what.

\documentclass{book}
\usepackage{xcolor}
\usepackage[tikz]{bclogo}
\usetikzlibrary{calc,shapes.callouts,shapes.arrows}

\pagestyle{empty}

\begin{document}

\begin{bclogo}[
  couleur=red!10,
  %couleur=blue!14,
  %couleur=blue!20,
  epBord=1.5,
  arrondi=0,
  logo=,
  %logo=\bcplume,
  %logo=\bclampe,
  %marge=8, 
  %ombre=true,
  %blur,
  %couleurBord=blue!14,
  %couleurBord=blue!60,
  barre=none,
  %barre=snake,
  %tailleOndu=1.5
]{}
\vspace*{-\ht\strutbox}
\vspace*{-\dp\strutbox}

\vspace{1cm}

\centering This sentence is centered.

\vspace{1cm}

\end{bclogo}

\end{document}

Without the two \vspace{1cm} instructions you'd get