How to create gradient text boxes as wide as paperwidth

Question

In a beamer presentation I would like to create boxes without frame but filled with gradient from left (light grey) to right (dark grey) and text in the box. I also want the box to touch the edge of the paper (top, left, right), so put it on the slide without any margins. It is possible to do this with tcolorboxes?

Answer 1

Upon my EDIT, I still don't have a clue what I am doing, but I did manage to get things into beamer. The use of physical dimensions, notably 4.2in for the \makebox and 4.65in for the \tcbox width, are given in physical dimensions because I don't know what the corresponding variable names are for beamer margin widths, etc. They may, therefore need changing depending on your beamer template.

\documentclass{beamer}
\usepackage{tcolorbox,lipsum}
\tcbuselibrary{skins}
\begin{document}
\begin{frame}
\raisebox{4cm}{\makebox[4.2in]{
\tcbox[enhanced, boxrule=0pt, arc=0pt, width=4.65in, top=.2in,bottom=.3in,
  interior style={left color=gray!05,right color=gray!50}]
{\begin{minipage}{4.65in}
\lipsum[1]
\end{minipage}
}}}
\end{frame}
\end{document}

---

I employed bits and pieces from these three answers:

How to make more than two fancy gradient stripes in tcolorbox?

Sharp corners to tcolorbox

and

How do I draw a box with tcolorbox

Answer 2

This is a variant of the answer of Steven B. Segletes. I made a new environment gradientbox which takes optional tcolorbox parameters. I tried to use dimension settings from the beamer style files. Still, there is a fixed kerning of 2mm for the top space which I could not find in reasonable time in the beamer implementation.

Frame should be used with the [t] option and without title to get the box to the very top of the slide.

\documentclass{beamer}
\usepackage{tcolorbox,lipsum}
\tcbuselibrary{skins}

\makeatletter%
\newtcolorbox{gradientbox}[1][]{%
  enhanced,boxrule=0pt,boxsep=0pt,sharp corners,
  before=\nointerlineskip\kern-2mm,%
  width=\paperwidth,
  enlarge left by=-\beamer@leftmargin-\beamer@leftsidebar,
  enlarge right by=-\beamer@rightmargin-\beamer@rightsidebar,
  frame hidden,interior style={left color=gray!05,right color=gray!50},
  #1
}
\makeatother%

\begin{document}

\begin{frame}[t]
  \begin{gradientbox}
    \lipsum[1]
  \end{gradientbox}
\end{frame}

\begin{frame}[t]
  \begin{gradientbox}[top=8mm,bottom=8mm,left=10mm,right=10mm]
    \lipsum[1]
  \end{gradientbox}
\end{frame}

\end{document}