Reset text depth (or text height)

Question

Here Align line with caption in Tikz pgfplot legend the legend alignment are wrong because of an entry that goes below the preset text depth=0.15em - see "default every axis legend style" on page 260 in the manual.

If the text depth is already set, how can it be unset? I tried text depth=false, text depth=none and text depth=\empty - of cause non of that worked.

MWE:

\documentclass[tikz, border=1cm]{standalone}
\begin{document}
\begin{tikzpicture}[text depth=0pt]
\node[draw=red, inner sep=0pt] {$\frac{1}{2}$};
\end{tikzpicture}
\end{document}

Wanted output without removing [text depth=0pt]:

Answer 1

The code for text depth is

\tikzoption{text depth}{\def\tikz@text@depth{#1}}

and the initial value for \tikz@text@depth is empty.

Reset it locally to empty.

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[text depth=0pt]
\node[draw=red, inner sep=0pt,text depth=] {$\frac{1}{2}$};
\end{tikzpicture}

\end{document}