Fullwidth Note-Box (tikzpicture) in and tufte-book like layout with margins

Question

I am trying to create a special box for tables/pictures/text that spans the while width of the page, where the page's geometry is set to provide a margin (left/right alternating with odd/even). I would like to be able to customize the looks of the box frame and fill, so I opted for the tikz package because it lets me draw quite anything so far. To get an overall idea of what I am trying to accomplish have a look at POB1. There 'BOX 3.2' is such an framed environment that has many complex children like figures and text etc.

The many stack-exchange posts regarding similar questions could not provide a working solution to my problem (or I am just to stupid to integrate it).

For starters, I would love the 'figure' in my MWE (see below) to occupy the full width (minus the 1.5cm thin margin) effectively ignoring the margin defaults of 5cm set with 'geometry'. Also, this should work anywhere (even and odd pages).

\documentclass[twoside,openany]{book} 

\usepackage[paper=a4paper,margin=1in]{geometry}
\usepackage{tikz}
\usepackage{lipsum}
\usepackage{kantlipsum}

\definecolor{LightOcean}{RGB}{81, 147, 229 }
\definecolor{DeepOcean}{RGB}{51, 131, 229}

\begin{document}

\newgeometry{top=3cm,bottom=3cm,left=1.5cm,right=5cm,headsep=10pt}
\lipsum[1-6]

\begin{figure}
  \begin{tikzpicture}
    \draw (0,0) node[fill=LightOcean!10, text width=\textwidth, text justified, rectangle, draw=DeepOcean, thick, rounded corners=8pt, minimum height=6em]
      {\kant[2]};
  \end{tikzpicture}
  \caption{\kant[1]}
\end{figure}

\lipsum[3-10]

\end{document}

I was thinking of a minipage to encapsulate ... sub-minipages? But how would one tell tikzpicture where to draw the frames?

Many thanks in advance.

Answer 1

I think tcolorbox is a better solution than TikZ to draw framed (floating or not) boxes:

\documentclass[twoside,openany]{book} 

\usepackage[a4paper, vmargin={3cm, 3cm}, hmargin={1.5cm, 5cm}, headsep=10pt]{geometry}
\usepackage{tikz}
\usepackage{lipsum}
\usepackage{kantlipsum}
\usepackage[most]{tcolorbox}
\usepackage{multicol}

\definecolor{LightOcean}{RGB}{81, 147, 229 }
\definecolor{DeepOcean}{RGB}{51, 131, 229}

\newtcolorbox{mybox}[1][]{%
    float, 
    floatplacement=t,
    enhanced, 
    colback=LightOcean!10, 
    colframe=DeepOcean,
%   show bounding box,
    notitle,
    grow to right by=\marginparsep+\marginparwidth-15mm,
    toggle enlargement=evenpage,
    #1
}

\begin{document}


\lipsum[1-3]

\begin{mybox}
\begin{multicols}{2}
\kant[1]
\end{multicols}

\begin{minipage}[c]{.4\linewidth}
\centering
\includegraphics[width=.8\linewidth]{example-image-a}
\end{minipage}\hfill
\begin{minipage}[c]{.55\linewidth}
\kant[1]
\end{minipage}
\end{mybox}

\lipsum[3-6]

\begin{mybox}
\kant[2]
\end{mybox}

\end{document}