unset rowcolor in eqnarray

Question

I have a document with a defined \rowcolors

Now in a math environment, a cases element is rendered with this table background overlapping the brace:

This can be fixed by adding \rowcolors{1}{}{}

Unfortunately, this does not work in an eqnarray environment.

has no effect and putting it in the cases statement only makes both rows with a white background, still overlaying the brace.

\documentclass[11pt, a4paper, titlepage, german, final]{scrreprt}

\usepackage[table]{xcolor}
\usepackage{color}
\usepackage{multirow}
\usepackage{colortbl}      %puts colors in tables

\definecolor{tr_color1}{HTML}{FFFFFF} %Weiß
\definecolor{tr_color2}{HTML}{E5F2FF} %Blau
\rowcolors{1}{tr_color1}{tr_color2}

\usepackage{amsmath, amssymb, amstext, amsfonts, mathrsfs} % Mathematische Symbole
\begin{document}
\[
    PD(t)= \begin{cases}
    1 : x \\
    0 : y
    \end{cases}
\]

\[\rowcolors{1}{}{}
    PD(t)= \begin{cases}
    1 : x \\
    0 : y
    \end{cases}
\]

\begin{eqnarray*}
    \rowcolors{}{}{}
    d & = & \begin{cases} 1 : PD(i)=1 \\ 0 : PD(i)=0 \end{cases}\\
    z & = & xx
\end{eqnarray*}

\begin{eqnarray*}
    d & = & \begin{cases}\rowcolors{}{}{} 1 : PD(i)=1 \\ 0 : PD(i)=0 \end{cases}\\
    z & = & xx
\end{eqnarray*}
\end{document}

The tip from here (\csname CT@everycr\endcsname{}) does not work either.

So how can I unset the rowcolors inside the eqnarray environmnent?

Answer 1

This seems to work; basically, we nullify the action of \@rowc@lors in the amsmath alignments. Of course, I do nothing to eqnarray that should never be used.

\documentclass{article}

\usepackage{amsmath}
\usepackage[table]{xcolor}
\usepackage{etoolbox}

\makeatletter
\pretocmd\env@cases{\def\@rowc@lors{}}{}{}
\pretocmd\start@align{\def\@rowc@lors{}}{}{}
\makeatother

\definecolor{tr_color1}{HTML}{FFFFFF} %Weiß
\definecolor{tr_color2}{HTML}{E5F2FF} %Blau
\rowcolors{1}{tr_color1}{tr_color2}

\begin{document}

\begin{center}
\begin{tabular}{cc}
a & a \\
b & b \\
c & c
\end{tabular}
\end{center}

\[
    PD(t)= \begin{cases}
    1 : x \\
    0 : y
    \end{cases}
\]

\begin{align*}
    d & = \begin{cases} 1 : PD(i)=1 \\ 0 : PD(i)=0 \end{cases}\\
    z & = xx
\end{align*}

\begin{gather*}
a = b \\
c = d
\end{gather*}

\begin{multline*}
a + b \\
c + d
\end{multline*}

\end{document}

Answer 2

You can also disable the rowcolors (locally) with \@rowcolorsfalse (and with \everydisplay{\@rowcolorsfalse} for all display math). But imho the more interesting question is how to color the cases without overwriting the brace. It is not so easy to change the overhang, but this seems to work:

\documentclass[11pt, a4paper, titlepage, german, final]{scrreprt}

\usepackage[table]{xcolor}%
\usepackage{multirow}

\definecolor{tr_color1}{HTML}{FFFFFF} %Weiß
\definecolor{tr_color2}{HTML}{E5F2FF} %Blau
\rowcolors{1}{tr_color1}{tr_color2}

\usepackage{amsmath}
\usepackage{etoolbox,array}

\begin{document}

\makeatletter

\[ \@rowcolorsfalse
    PD(t)=
    \begin{cases}
    1 : x \\
    0 : y
    \end{cases}
\]


\[
    PD(t)=
    \begin{cases}
    1 : x \\
    0 : y
    \end{cases}
\]

\patchcmd\env@cases{@{}l}{@{}>{\columncolor{white}[0.2pt][\tabcolsep]}l}{}{}%


\[
    PD(t)= 
    \begin{cases}
    1 : x \\
    0 : y
    \end{cases}
\]


\end{document}

Answer 3

Thanks to @david-carlisle for the answer. (seems he doesn't need the answer reputation :D)

So far the original question is not answered. But the problem arises in a \cases-statement inside an \eqnarray where the rowcolor cannot be unset so far.

This can be bypassed by using normal math environment, where rowcolor unset works and using the aligned-environment from amsmath-package.

\[
    \rowcolors{1}{}{}
    \begin{aligned}
        d & = \begin{cases} 1 : PD(i)=1 \\ 0 : PD(i)=0 \end{cases}\\
        z & = xx
    \end{aligned}
\]

I leave that open in case some can answer the actual question too.