# Indentation inside tcolorbox

I have a environment solution created with xparse and tcolorbox. I do not understand why package \usepackage{indentfirst} does not work inside solution.

\documentclass[12pt]{book}
\usepackage{xparse}
\usepackage{indentfirst}
\usepackage{lipsum}
\def\Solution{Solution}
\usepackage[most, breakable, many]{tcolorbox}
\NewTColorBox[auto counter,number within=section]{solution}{+O{}}{%
breakable, enhanced,colframe=gray,colback=white,coltitle=green!40!black,
fonttitle=\bfseries,
underlay={\begin{tcbclipinterior}
\draw[help lines,step=5mm,blue!20!white,shift={(interior.north west)}]
(interior.south west) grid (interior.north east);
\end{tcbclipinterior}},
title={\Solution},
label={},
after upper={\par\hfill\textcolor{green!40!black}%
{}},
lowerbox=ignored,
#1,
}
\begin{document}
\chapter{One}
\begin{solution}
\lipsum[1-35]
\end{solution}
\end{document}

• as your image shows parindent is zero inside the box, so there is effectively no indentation for any paragraph, so it's hard to know what you expect indentfirst to do??? – David Carlisle Dec 14 '14 at 20:51
• @David Carlisleshows "parindent is zero inside the box" In what line of code you see it? – sergiokapone Dec 14 '14 at 20:59
• I didn't look too hard at the code, but the output shows several paragraphs with no indentation (which is the default for \parbox so not that surprising. – David Carlisle Dec 14 '14 at 21:03
• @ David Carlisle "which is the default for \parbox" Ok, now it is clear for me, I should to use parbox=false . Tnx, You helped me again. – sergiokapone Dec 14 '14 at 21:09
• did I:-) If it's solved perhaps you should post a self-answer:-) – David Carlisle Dec 14 '14 at 21:10

For paragraph indentation inside tcolorbox it is necesary to switch off the options parbox, e.g. parbox=false (by default it is true). Thus:

\NewTColorBox[auto counter,number within=section]{solution}{+O{}}{%
breakable,
enhanced,
colframe=gray,
colback=white,
coltitle=green!40!black,
fonttitle=\bfseries,
parbox = false,
underlay={\begin{tcbclipinterior}
\draw[help lines,step=5mm,blue!20!white,shift={(interior.north west)}]
(interior.south west) grid (interior.north east);
\end{tcbclipinterior}},
title={\Solution},
label={},