psclip2.tex

\documentclass[a4paper]{article}

\usepackage{adjustbox}

\makeatletter

\def\OLD@clipbox#1#2#3#4#5{%
  \@trimbox{#1}{#2}{#3}{#4}{#5}%
  \sbox#5{%
    \special{ps: gsave}%
    \hbox{\special{ps: currentpoint pop /llx exch def}}%
    \hbox to 0pt{\hskip\wd#5\special{ps: currentpoint pop /urx exch def}\hss}%
    \raise-\dp#5\hbox{\special{ps: currentpoint /lly exch def pop}}%
    \raise\ht#5\hbox{\special{ps: currentpoint /ury exch def pop}}%
    \special{ps: llx lly urx llx sub ury lly sub rectclip}%
    \box#5%
    \special{ps: grestore}%
  }%
}

\ifpdf\else
\def\@clipbox#1#2#3#4#5{%
  \@trimbox{#1}{#2}{#3}{#4}{#5}%
  \sbox#5{%
    \special{ps: gsave}%
    \hbox to 0pt{%
        \raise-\dp#5\hbox{\special{ps: /llx currentpoint pop def /lly currentpoint exch pop def}}%
        \hskip \wd#5%
        \raise \ht#5\hbox{\special{ps: /urx currentpoint pop def /ury currentpoint exch pop def}}%
        \hss
    }%
    \special{ps: llx lly urx llx sub ury lly sub rectclip}%
    \box#5%
    \special{ps: grestore}%
  }%
}
\fi

\makeatother

\begin{document}

x\clipbox{0pt 0pt 0pt 0pt}{Foo q Bar \textit{i}}x\par
x\clipbox{1pt .5pt 1pt .5pt}{Foo q Bar \textit{i}}x\par
x\clipbox{0 {\depth} {.5\width} 0}{gXXXXg}x\par

\clipbox{1pt 1pt 1pt 1pt}{x\clipbox{0 {\depth} {.5\width} 0}{gXXXXg}x}\par

\end{document}