\documentclass{beamer}
\usepackage{soulutf8}
\usepackage{atbegshi}
\usepackage{etoolbox}
\usepackage{tikz}
\usetikzlibrary{tikzmark,calc,decorations.pathmorphing}


\colorlet{tdcolor}{gray!50}

\newlength{\LineWidth}
\setlength{\LineWidth}{0.7pt}

\newlength{\CornerRadius}
\setlength{\CornerRadius}{5pt}

\newlength{\BorderDispl}
\setlength{\BorderDispl}{2pt}

\makeatletter

\newlength{\txtdec@depth}
\setlength{\txtdec@depth}{.45ex}
\newlength{\txtdec@height}
\setlength{\txtdec@height}{\f@size pt} % sensible default

\newcounter{txtdec@hyphmark}
\newcounter{txtdec@decormark}
\newcounter{txtdec@hyphdraw}
\setcounter{txtdec@hyphdraw}{1}
\newcounter{txtdec@decordraw}
\setcounter{txtdec@decordraw}{1}

\newcounter{txtdec@thenextpage}

\newtoggle{txtdec@unfinisheddecor}
\newtoggle{txtdec@stayonpage}
\newtoggle{txtdec@stayondecor}
\newtoggle{txtdec@stayonline}

% from https://tex.stackexchange.com/a/33765/105447
\newcommand{\gettikzxy}[3]{%
  \tikz@scan@one@point\pgfutil@firstofone#1\relax
  \edef#2{\the\pgf@x}%
  \edef#3{\the\pgf@y}%
}

% the drawing macros

\newcommand{\txtdec@draw@all}{%
  \draw[tdcolor, line width=\LineWidth, rounded corners=\CornerRadius] ($(\Xbegin,\Ybegin)+(-\BorderDispl,-\txtdec@depth)$) rectangle ($(\Xend,\Yend)+(\BorderDispl,\txtdec@height-\txtdec@depth)$) ;
}

\newcommand{\txtdec@draw@begin}{%
  \draw[tdcolor, line width=\LineWidth, rounded corners=\CornerRadius]
    ($(\Xlineend,\Ylineend)+(0,\txtdec@height-\txtdec@depth)$) --
    ($(\Xbegin,\Ybegin)+(-\BorderDispl,\txtdec@height-\txtdec@depth)$) --
    ($(\Xbegin,\Ybegin)+(-\BorderDispl,-\txtdec@depth)$) --
    ($(\Xlineend,\Ylineend)+(0,-\txtdec@depth)$) ;
}

\newcommand{\txtdec@draw@middle}{%
  \draw[tdcolor, line width=\LineWidth] ($(\Xlinebegin,\Ylinebegin)+(0,-\txtdec@depth)$) -- ($(\Xlineend,\Ylineend)+(0,-\txtdec@depth)$) ;
  \draw[tdcolor, line width=\LineWidth] ($(\Xlinebegin,\Ylinebegin)+(0,\txtdec@height-\txtdec@depth)$) -- ($(\Xlineend,\Ylineend)+(0,\txtdec@height-\txtdec@depth)$) ;
}

\newcommand{\txtdec@draw@end}{%
  \draw[tdcolor, line width=\LineWidth, rounded corners=\CornerRadius]
  ($(\Xlinebegin,\Ylinebegin)+(0,\txtdec@height-\txtdec@depth)$) --
  ($(\Xend,\Yend)+(\BorderDispl,\txtdec@height-\txtdec@depth)$) --
  ($(\Xend,\Yend)+(\BorderDispl,-\txtdec@depth)$) --
  ($(\Xlinebegin,\Ylinebegin)+(0,-\txtdec@depth)$)   ;
}

% using soul to set tikzmarks

\def\SOUL@tdleaders{%
  \stepcounter{txtdec@hyphmark}%
  \tikzmark{p\thepage.d\arabic{txtdec@decormark}.\arabic{txtdec@hyphmark}}%
  \leaders\hrule\@depth\z@\@height\z@\relax
}

\def\SOUL@tdunderline#1{{%
    \setbox\z@\hbox{#1}%
    \dimen@=\wd\z@
    \dimen@i=\SOUL@uloverlap
    \advance\dimen@2\dimen@i
    \rlap{%
      \null
      \kern-\dimen@i
      \SOUL@ulcolor{\SOUL@tdleaders\hskip\dimen@}%
      \hskip\dimen@
    }%
    \unhcopy\z@
  }}

\def\SOUL@tdpreamble{%
  \spaceskip\SOUL@spaceskip
  \stepcounter{txtdec@decormark}%
  \setcounter{txtdec@hyphmark}{0}%
  \tikzmark{p\thepage.d\arabic{txtdec@decormark}.begin}%
}
\def\SOUL@tdeverysyllable{%
  \SOUL@tdunderline{%
    \the\SOUL@syllable
    \SOUL@setkern\SOUL@charkern
  }%
  \stepcounter{txtdec@hyphmark}%
  \tikzmark{p\thepage.d\arabic{txtdec@decormark}.\arabic{txtdec@hyphmark}}%
}
\def\SOUL@tdeveryhyphen{%
  \discretionary{%
    \unkern
    \SOUL@tdunderline{%
      \SOUL@setkern\SOUL@hyphkern
      \SOUL@sethyphenchar
    }%
    \stepcounter{txtdec@hyphmark}%
    \tikzmark{p\thepage.d\arabic{txtdec@decormark}.\arabic{txtdec@hyphmark}}%
  }{}{}%
}
\def\SOUL@tdeveryexhyphen#1{%
  \SOUL@setkern\SOUL@hyphkern
  \SOUL@tdunderline{#1}%
  \stepcounter{txtdec@hyphmark}%
  \tikzmark{p\thepage.d\arabic{txtdec@decormark}.\arabic{txtdec@hyphmark}}%
  \discretionary{}{}{%
    \SOUL@setkern\SOUL@charkern
  }%
}
\def\SOUL@tdpostamble{%
  % create an extra mark, vertically displaced, to create an exit condition for the last line
  \stepcounter{txtdec@hyphmark}%
  \raisebox{-5pt}{\tikzmark{p\thepage.d\arabic{txtdec@decormark}.\arabic{txtdec@hyphmark}}}%
  \tikzmark{p\thepage.d\arabic{txtdec@decormark}.end}%
}
\def\SOUL@tdsetup{%
  \SOUL@setup
  \let\SOUL@preamble\SOUL@tdpreamble
  \let\SOUL@everysyllable\SOUL@tdeverysyllable
  \let\SOUL@everyhyphen\SOUL@tdeveryhyphen
  \let\SOUL@everyexhyphen\SOUL@tdeveryexhyphen
  \let\SOUL@postamble\SOUL@tdpostamble
}
\DeclareRobustCommand*\textdecor{\SOUL@tdsetup\SOUL@}

% get the drawing done AtBeginShipout

\AtBeginShipout{%
  \AtBeginShipoutUpperLeft{%
    % getting the number of the next page
    \setcounter{txtdec@thenextpage}{\thepage}%
    \stepcounter{txtdec@thenextpage}%
    % if the current decoration occurs on this page, stay on it
    \iftikzmark{p\thepage.d\arabic{txtdec@decordraw}.\arabic{txtdec@hyphdraw}}{%
      \toggletrue{txtdec@stayonpage}}{}%
    \whileboolexpr{togl {txtdec@stayonpage}}{%
      \begin{tikzpicture}[remember picture, overlay]
        \setlength{\txtdec@height}{\f@size pt}%
        \iftikzmark{p\thepage.d\arabic{txtdec@decordraw}.begin}{%
          % if current decor begins in current page, get coordinates
          \gettikzxy{(pic cs:p\thepage.d\arabic{txtdec@decordraw}.begin)}{\Xbegin}{\Ybegin}}{%
          % if current decor begins in previous page, set to top left of the page
          \gettikzxy{(current page.north west)}{\Xbegin}{\Ybegin}}%
        \iftikzmark{p\thepage.d\arabic{txtdec@decordraw}.end}{%
          % if current decor ends in current page, get coordinates
          \gettikzxy{(pic cs:p\thepage.d\arabic{txtdec@decordraw}.end)}{\Xend}{\Yend}}{%
          % if current decor ends in future page, set to bottom right of the page
          \gettikzxy{(current page.south east)}{\Xend}{\Yend}}%
        \ifdim\Ybegin=\Yend % the simplest case, a single line
          \txtdec@draw@all
          \stepcounter{txtdec@decordraw}%
        \else % current textdecor has a line break
          \toggletrue{txtdec@stayondecor}%
          \whileboolexpr{togl {txtdec@stayondecor}}{%
            \gettikzxy{(pic cs:p\thepage.d\arabic{txtdec@decordraw}.\arabic{txtdec@hyphdraw})}{\Xlinebegin}{\Ylinebegin}%
            \edef\Xcurrent{\Xlinebegin}%
            \edef\Ycurrent{\Ylinebegin}%
            \edef\Xnext{\Xcurrent}%
            \edef\Ynext{\Ycurrent}%
            \toggletrue{txtdec@stayonline}%
            \whileboolexpr{togl {txtdec@stayonline}}{%
              \ifdim\Ycurrent=\Ynext
                \stepcounter{txtdec@hyphdraw}%
                % if the following tikzmark exists, we are at a page break
                \iftikzmark{p\arabic{txtdec@thenextpage}.d\arabic{txtdec@decordraw}.\arabic{txtdec@hyphdraw}}{%
                  \edef\Xcurrent{\Xnext}%
                  \edef\Ycurrent{\Ynext}%
                  \gettikzxy{(current page.south east)}{\Xnext}{\Ynext}
                  \togglefalse{txtdec@stayondecor}%
                }{% else, we remain on the same page
                  \iftikzmark{p\thepage.d\arabic{txtdec@decordraw}.\arabic{txtdec@hyphdraw}}{%
                    \edef\Xcurrent{\Xnext}%
                    \edef\Ycurrent{\Ynext}%
                    \gettikzxy{(pic cs:p\thepage.d\arabic{txtdec@decordraw}.\arabic{txtdec@hyphdraw})}{\Xnext}{\Ynext}}{}%
                }%
              \else
                \edef\Xlineend{\Xcurrent}%
                \edef\Ylineend{\Ycurrent}%
                % if we are on the first line of the current decoration
                \ifdim\Ylinebegin=\Ybegin
                  \txtdec@draw@begin
                \else
                  % if we are on the last line of the current decoration
                  \ifdim\Ycurrent=\Yend
                    \txtdec@draw@end
                    \stepcounter{txtdec@decordraw}%
                    \setcounter{txtdec@hyphdraw}{1}%
                    \togglefalse{txtdec@stayondecor}%
                  % if we are in a middle line of the decoration
                  \else
                    \txtdec@draw@middle
                  \fi
                \fi
                \togglefalse{txtdec@stayonline}%
              \fi
            }%
          }%
        \fi
      \end{tikzpicture}%
      % if the beginning of the next decor does not exist in this page, leave this page
      \iftikzmark{p\thepage.d\arabic{txtdec@decordraw}.begin}{}{%
        \togglefalse{txtdec@stayonpage}}%
      % if the continuation of the current decor exists in the next page, leave this page
      \iftikzmark{p\arabic{txtdec@thenextpage}.d\arabic{txtdec@decordraw}.\arabic{txtdec@hyphdraw}}{%
        \togglefalse{txtdec@stayonpage}}{}%
    }%
  }%
}

\makeatother

\begin{document}

\begin{frame}[fragile]{x}
	Lorem ipsum \textdecor{dolor sit amet, consectetuer adipiscing}
	elit. Ut purus elit, vestibulum ut, placerat ac, adipiscing vitae.\newline
	Beamer version: 3.69,  Ti\textit{k}Z version 3.1.10
\end{frame}
\end{document}