Row highlights conceal left parentheses

[taishi-n]

Hi there, thanks for maintaining such an awesome package!

\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{pseudo}

\begin{document}
  \begin{pseudo}
    $A \gets \begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix} \begin{bmatrix} x \\ y \end{bmatrix}$ \ct{Left parentheses are shown} \\[hl]
    $A \gets \begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix} \begin{bmatrix} x \\ y \end{bmatrix}$ \ct{Left parentheses are hidden} \\
    $A \gets \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix} \begin{pmatrix} x \\ y \end{pmatrix}$ \ct{Regardless of which parentheses} \\[hl]
    $A \gets \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix} \begin{pmatrix} x \\ y \end{pmatrix}$ \\
    $A \gets \begin{Bmatrix} 1 & 2 \\ 3 & 4 \end{Bmatrix} \begin{Bmatrix} x \\ y \end{Bmatrix}$ \ct{Regardless of which parentheses} \\[hl]
    $A \gets \begin{Bmatrix} 1 & 2 \\ 3 & 4 \end{Bmatrix} \begin{Bmatrix} x \\ y \end{Bmatrix}$
  \end{pseudo}
\end{document}

I'm running into an issue where, as shown in the attached image, highlighting a line somehow makes the left bracket disappear.
It seems like it might be a bug.
Is there a fix or a workaround for this?

I really love the elegant pseudocode your package produces, but I'm not very familiar with the ins and outs of LaTeX, so I haven't been able to debug it down to the implementation.
I'm hoping you might have an elegant solution. Thanks a lot!

[mlhetland]

Hi!

Thanks for the kind words, and the clear bug report. The issue here seems to be that the \rowcolor inserted by hl also applies to the matrix used by bmatrix. That is, you get a similar issue with the following (where the \left/\right stuff around matrix is what bmatrix does, I think):

\documentclass{article}
\usepackage{amsmath}
\usepackage[table]{xcolor}

\begin{document}
  \begin{tabular}{l}
    \rowcolor{black!12}
    $\left[\begin{matrix} 1 & 2 \\ 3 & 4 \end{matrix}\right]$
  \end{tabular}
\end{document}

The problem is that the left parenthesis is drawn before the matrix, and when the matrix has a \rowcolor, that extends over the parenthesis. An even smaller example:

$\left[\begin{matrix}\rowcolor{black!12} 1 & 2 \\ 3 & 4 \end{matrix}\right]$

Ideally, we'd like to turn off the effect of the \rowcolor for inner tables, here, and I don't immediately have a fix for that, though I'll take a look.

It would also be possible to use some other mechanism for highlighting (such as filling tikz rectangles in the background, or the like, though that seems like a bit much; or possibly using one of the custom table/array packages with specialized functionality for this kind of stuff).

So I'm not yet quite sure how best to handle this, but I'll see if I can come up with something.

[mlhetland]

A quick workaround, for now.

\documentclass{article}

\usepackage{amsmath}
\usepackage{xparse}
\usepackage{mathtools}

\NewDocumentCommand{\addbrackets}{m}{%
    \left[#1\right]%
    \!
    \mathllap{\left[\phantom{#1}\right]}
}

\begin{document}
\begin{tabular}{l}
\rowcolor{black!12}
$\addbrackets{\begin{matrix} 1 & 2 \\ 3 & 4 \end{matrix}}$
\end{tabular}
\end{document}

This draws both brackets a second time, on top. (Replace \left[ and \left] with \left( and \left), etc., for other parentheses.)

[taishi-n]

Thanks for sharing your quick workaround!
I also tried the following hack and it seems like worked:

\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{mathtools}
\usepackage{pseudo}

\begin{document}
  \begin{pseudo}
    [hl] $A \gets \begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix} \begin{Bmatrix} x \\ y \end{Bmatrix}$ \\
    [hl] $A \gets \left[\begin{array}{cc} 1 & 2 \\ 3 & 4 \end{array}\right] \begin{Bmatrix} x \\ y \end{Bmatrix}$
  \end{pseudo}
\end{document}

This is a bit tricky and cumborsome to rewrite it but I would share this for anyone else who might run into the same issue.
Thanks a lot!

[mlhetland]

This should fix the problem, by turning off the table color operation inside each pseudocode line:

\makeatletter
\let\oldctdocolor\CT@@do@color
\pseudoset{
    setup-append = {
        \let\CT@@do@color\relax\ignorespaces
    },
    eol-append = {
        \let\CT@@do@color\oldctdocolor
    }
}
\makeatother

(I.e., just add this to your preamble.)

I may add a section to the HOWTO chapter about this, or maybe add some functionality for it in the package. (Maybe make it the default behavior, which could then be turned off. Not quite sure.)

Oh, and BTW, with your code you're probably getting warnings about using hl without hpad. The intention is to use [hpad] on the main environment when one uses hl on individual lines (to get some gray to the left/right of the code line, as well). If you don't want that, you can use hl-warn=false. (See p. 18 in the current doc.)

[mlhetland]

(Also, it's a bit annoying to have to add the \ignorespaces to any append – I'll have a look at that.)

[taishi-n]

Thank you for your quick answer! My problem was solved for now.
I will leave this issue open for anyone else running into the same bug, but feel free to close it once the docs are updated.