How to make a framebox around paragraph title

Question

I would like to have a framebox around some paragraph titles. Something like the diagram below. I would like the framebox to have a background color (e.g. cyan), round corners, and shade if possible.

+-----------------------+
|   Paragraph one       | Paragraph text starts here. 
+-----------------------+

I have been searching over the internet but only found solutions to wrap the entire paragraph or the section title which occupies a single line.

Answer 1

Without any fancy colors.

\documentclass{article}
\usepackage{titlesec}
\newcommand{\mypara}[1]{\hspace*{-\fboxsep}\fbox{\theparagraph\hskip1em #1}}
\titleformat{\paragraph}[runin]
{\normalfont\normalsize\bfseries}{}{0em}{\mypara}

\titlespacing*{\paragraph}{0pt}{3.25ex plus 1ex minus .2ex}{0.5em}
\setcounter{secnumdepth}{5}

\begin{document}
\section{some section}
\subsection{some subsection}
\subsubsection{some subsubsection}
\paragraph{A test paragraph}
Some test text.


\end{document}

With colors and powers of tikz

\documentclass{article}
\usepackage{lipsum}
\usepackage{titlesec}
\usepackage{tikz}
\newcommand{\mypara}[1]{%
\begin{tikzpicture}[baseline=(a.base)]
 \node[draw=red,line width=0.5pt,rounded corners=1ex,inner sep=2pt,fill=cyan] (a) {#1};
\end{tikzpicture}
}

\titlespacing*{\paragraph}{0pt}{3.25ex plus 1ex minus .2ex}{0.5em}

\newcommand\bparagraph[1]{%
\titleformat{\paragraph}[runin]
{\normalfont\normalsize\bfseries}{}{0em}{\mypara}
\paragraph{#1}
\titleformat{\paragraph}[runin]
{\normalfont\normalsize\bfseries}{\theparagraph}{1em}{}
}

\begin{document}
\section{some section}
\subsection{some subsection}
\subsubsection{some subsubsection}
\bparagraph{A test paragraph}
\lipsum[1]
\paragraph{A test paragraph}
\lipsum[1]


\end{document}

Answer 2

Using tcolorbox and defining two commands for regular and framed paragraphs which can be used as many times as required:

The code:

\documentclass{article}
\usepackage{titlesec}
\usepackage{lipsum}
\usepackage[many]{tcolorbox}

\newcommand\framedparagraph[1]{%
  \tcbox[
    enhanced,
    colframe=cyan,
    box align=base,
    nobeforeafter,
    top=1pt,
    bottom=1pt,
    left=2pt,
    right=2pt,
    enlarge left by=-1.2mm,
    boxsep=0pt,
    interior style={top color=orange!20,bottom color=magenta!20}
  ]{\theparagraph\hskip1em#1}%
}

\newcommand\FramedPara{%
\titleformat{\paragraph}[runin]
  {\normalfont\normalsize\bfseries}{}{0em}{\framedparagraph}
}

\newcommand\RegularPara{%
\titleformat{\paragraph}[runin]
  {\normalfont\normalsize\bfseries}{\theparagraph}{1em}{}
}

\setcounter{secnumdepth}{5}

\begin{document}
\section{some section}
\subsection{some subsection}
\subsubsection{some subsubsection}
\FramedPara
\paragraph{A test paragraph} 
\lipsum[2]
\RegularPara
\paragraph{A test paragraph}
\lipsum[4]

\end{document}

Since paragraph titles are in a "runin" style, the height and depth for the box were kept to a minimum to not disrupt the regular separation between lines.

Answer 3

Here is a no-frills version of fixed width: \cparagraph[optional-fixed-width]{name}. EDITED to allow box to grow with size of paragraph name (but must remain less than one line width). REEDITED to handle \parskip.

EDITED to automatically handle paragraph names that extend up to two lines in length.

The MWE below shows two paragraphs of variable title width, and then two of fixed width; and finally one that extends to a second line.

\documentclass{article}
\usepackage{xcolor,tabto,lipsum}
\newlength\hbuffer
\setlength\hbuffer{6pt}
\newcommand\cparagraph[2][0pt]{%
  \setbox2=\hbox{\bfseries#2\kern\hbuffer}%
  \ifdim\wd2>\textwidth\relax%
    \wd2=\dimexpr\textwidth+\hbuffer\relax\relax%
    \def\mystrut{%
      \rule[\dimexpr-\ht\strutbox-\baselineskip\relax]{0pt}{2\baselineskip}}%
  \else%
    \let\mystrut\strut%
    \ifdim#1>0pt\relax\wd2=#1\relax\fi%
  \fi%
  \setbox4=\hbox{\mystrut}%
  \fboxsep=.5pt\noindent\rule{-.5\hbuffer}{0pt}\colorbox{red}{\colorbox{cyan!15}{%
% THE 2" BOX WIDTH AND THE THE 3.25ex \vspace MAY NEED TWEAKING
  \makebox[\wd2][l]{\mystrut}}}%
  \vspace{\dimexpr-\ht4-\dp4-3.25ex+\fboxsep-\parskip\relax}%
  \paragraph{#2}\tabto*{\dimexpr\wd2-.5\hbuffer+.66ex\relax}\allowbreak}
%\parskip 1ex
\begin{document}
\cparagraph{Paragraph one}
\lipsum[4] 
\cparagraph{My other paragraph}
\lipsum[4]
\cparagraph[2in]{Paragraph one}
\lipsum[4] 
\cparagraph[2in]{My other paragraph}
\lipsum[4]
\cparagraph{My other paragraph with a very very long name 
that extends well past one line}
\lipsum[4]
\end{document}

There are at least two potential flaws with this approach:

1. For a paragraph name that ends near the end of a line, the first word of the subsequent text may lay on the same line, extending into the margin. It can be remedied by manually inserting a \\ following the close of the \cparagraph argument;

2. The algorithm determines the width of the title by setting it in a box. If the actual length is just slightly larger than \textwidth, the algorithm will believe that it extends to two lines and prepare a 2-line colorbox accordingly; however, the inter-word spaces might conceivably be reduced allowing the title to fit on a single line.