Make `llap` respect bottom margin

Question

I'm using \llap in a custom environment to write some text in the document left margin, aligned with a code listing (code listing is done using lstlisting). Whenever the code listing is at the bottom of the page, the llap label stays on the previous page, whereas the code listing moves to the next page. An example is shown below (dark rectangles represent the document's margins):

The problem in this example being that the Out [9]: label is below the page's bottom margin, and the associated code listing is on the next page.

I need long code listings to break on multiple pages, so I do not want to wrap both the label and the listing inside a minipage (which would work, but not allow page breaks inside the code listing).

Is there any way to make llap respect the bottom margin? Below is an MWE.

---

\documentclass{article}

\usepackage{listings}
\usepackage[breakable]{tcolorbox}
\usepackage{ifthen}
\usepackage{xcolor}
\usepackage{lipsum}
\usepackage{showframe}

% custom colors
\definecolor{incolor}{HTML}{868686}
\definecolor{outcolor}{HTML}{868686}
\definecolor{cellbackground}{HTML}{F7F7F7}

% prompt
\makeatletter
\newcommand{\boxspacing}{\kern\kvtcb@left@rule\kern\kvtcb@boxsep}
\makeatother

\newcounter{cellcounter}

\lstdefinestyle{style}{
    language=Python, 
    aboveskip=-1.4\medskipamount,
    belowskip=0.5em,
    backgroundcolor=\color{cellbackground}, 
    numbers=none,
}

\makeatletter
\lst@Key{showprompt}{true}{\def\showprompt{#1}}
\lst@Key{promptnumber}{\thecellcounter}{\def\promptnumber{#1}}
\makeatother

\lstnewenvironment{code}[1][]
{   
    \lstset{
        style=style,
        #1
    }
    \addtocounter{cellcounter}{1}
    \ifthenelse{\boolean{\showprompt}}
        {\footnotesize\ttfamily\llap{{\color{outcolor}Out\,[\thecellcounter]:\hspace{3pt}\boxspacing}}}
        {\phantom{\footnotesize\ttfamily\llap{{\color{outcolor}Out\,[\thecellcounter]:\hspace{3pt}\boxspacing}}}}
}{
}

%----------------------------------------------------------------------------------------
%   DOCUMENT
%----------------------------------------------------------------------------------------

\setlength\parindent{0pt}
\setlength\parskip{83pt}
\begin{document}

\lipsum[70]
\lipsum[70]

\lipsum[70]
\lipsum[66]

\begin{code}
df.head()
\end{code}
\begin{code}
0         False       False  ...
1         False       False  ...
3         False       False  ...
4         False       False  ...
...         ...         ...  ...
9064      False       False  ...
9065      False       False  ...
9066      False       False  ...
9067      False       False  ...
\end{code}

\end{document}

Answer 1

I think It will be tricky to get this to work using your approach of inserting the label explicitly in the second mandatory argument of \lstnewenviroment. This has nothing to do with \llap, but is due to the fact that this argument is intended for set-up of the environment rather than for inserting text. Page breaks are explicitly allowed before the listing really begins, which is after your label is inserted.

You could, however, achieve the same effect by putting your label in the title field. Since page breaks are not allowed after the title, your label will then always appear on the same page as the first line of content. I'm setting belowcaptionskip=-\baselineskip field to get the title on the same line as the content and put the label in a \makebox of width \linewidth because it would be centred otherwise.

---

Here is a modified version of your MWE. Changes are marked as either ADDED or REMOVED.

\documentclass{article}

\usepackage{listings}
\usepackage[breakable]{tcolorbox}
\usepackage{ifthen}
\usepackage{xcolor}
\usepackage{lipsum}
\usepackage{showframe}

% custom colors
\definecolor{incolor}{HTML}{868686}
\definecolor{outcolor}{HTML}{868686}
\definecolor{cellbackground}{HTML}{F7F7F7}

% prompt
\makeatletter
\newcommand{\boxspacing}{\kern\kvtcb@left@rule\kern\kvtcb@boxsep}
\makeatother

\newcounter{cellcounter}

%% Following commands are ADDED:
\newcommand*\hbotcodefont{\footnotesize\ttfamily}
\newcommand*\hbotoutlabeltext[1]{Out\,[#1]:\hspace{3pt}}
\newcommand*{\hbotOutTitle}{%
    \hbotcodefont
    \ifthenelse{\boolean{\showprompt}}{%
        \makebox[\linewidth][l]{\llap{%
            \color{outcolor}%
            \hbotoutlabeltext{\thecellcounter}\boxspacing
        }}%
    }{}%
}

\lstdefinestyle{style}{
    language=Python,
    title=\hbotOutTitle, %% <- ADDED
    belowcaptionskip=-\baselineskip, %% <- ADDED
    %% <- REMOVED aboveskip=...
    backgroundcolor=\color{cellbackground},
    numbers=none,
}

\makeatletter
\lst@Key{showprompt}{true}{\def\showprompt{#1}}
\lst@Key{promptnumber}{\thecellcounter}{\def\promptnumber{#1}}
\makeatother

\lstnewenvironment{code}[1][]
{
    \lstset{style=style,#1}
    \hbotcodefont
    \addtocounter{cellcounter}{1}
    %% <- REMOVED label insertion code
}{
}

%----------------------------------------------------------------------------------------
%   DOCUMENT
%----------------------------------------------------------------------------------------

\setlength\parindent{0pt}
\setlength\parskip{83pt}
\begin{document}

\lipsum[70]
\lipsum[70]

\lipsum[70]
\lipsum[66]

\begin{code}
df.head()
\end{code}
\begin{code}
0         False       False  ...
1         False       False  ...
3         False       False  ...
4         False       False  ...
...         ...         ...  ...
9064      False       False  ...
9065      False       False  ...
9066      False       False  ...
9067      False       False  ...
\end{code}

\end{document}

Answer 2

Following the answer of @David Carlisle in this post and as I said in comment, you can replace \llap with \makebox[0pt][r] in your environment definition.

Here is the code you proposed with two changes:

• \llap replaced (two times) with \makebox[0pt][r]
• removed \lipsum[xx] with several blabla\par to get more precision in pagebreak testing.

You can uncomment some of the blabla\par to get the effect described in comments:

I hope this will help you solving your problem.

This "answer" is just to show you the code so you can tell me if it works as you expect.

\documentclass{article}


\usepackage{listings}
\usepackage[breakable]{tcolorbox}
\usepackage{ifthen}
\usepackage{xcolor}
\usepackage{lipsum}
\usepackage{showframe}

% custom colors
\definecolor{incolor}{HTML}{868686}
\definecolor{outcolor}{HTML}{868686}
\definecolor{cellbackground}{HTML}{F7F7F7}

% prompt
\makeatletter
\newcommand{\boxspacing}{\kern\kvtcb@left@rule\kern\kvtcb@boxsep}
\makeatother

\newcounter{cellcounter}

\lstdefinestyle{style}{
    language=Python, 
    aboveskip=-1.4\medskipamount,
    belowskip=0.5em,
    backgroundcolor=\color{cellbackground}, 
    numbers=none,
}

\makeatletter
\lst@Key{showprompt}{true}{\def\showprompt{#1}}
\lst@Key{promptnumber}{\thecellcounter}{\def\promptnumber{#1}}
\makeatother

\lstnewenvironment{code}[1][]
{   
    \lstset{
        style=style,
        #1
    }
    \addtocounter{cellcounter}{1}
    \ifthenelse{\boolean{\showprompt}}
    {\footnotesize\ttfamily\makebox[0pt][r]{{\color{outcolor}Out\,[\thecellcounter]:\hspace{3pt}\boxspacing}}}
    {\phantom{\footnotesize\ttfamily\makebox[0pt][r]{{\color{outcolor}Out\,[\thecellcounter]:\hspace{3pt}\boxspacing}}}}
}{
}

%----------------------------------------------------------------------------------------
%   DOCUMENT
%----------------------------------------------------------------------------------------

\setlength\parindent{0pt}

\begin{document}

    \lipsum[1-4]
    blabla\par
    blabla\par  
    blabla\par
    blabla\par
    blabla\par  
    blabla\par
    blabla\par
    blabla\par  
    blabla\par      % "Out [1]" and the first two lines of "Out [2]" on page 1, the rest on page 2
%   blabla\par      % "Out [1]" on the penultimate line of page 1 (last line blank)
%   blabla\par      % Only "Out [1]" on last line of page 1
%   blabla\par      % Everything on page 2
    \begin{code}
        df.head()
    \end{code}
    \begin{code}
        0         False       False  ...
        1         False       False  ...
        3         False       False  ...
        4         False       False  ...
        ...         ...         ...  ...
        9064      False       False  ...
        9065      False       False  ...
        9066      False       False  ...
        9067      False       False  ...
    \end{code}
    \begin{code}
        blabla
    \end{code}

\end{document}