How to remove the leading unnecessary white spaces when using linerange option?

Question

To be honest, I am looking for people who already read the listings documentation completely. If those people also cannot solve it, then the documentation does not mention anything about it. Sorry for this inconvenience.

But at least I can show my effort by providing you with the minimal working example.

\documentclass[preview,border=12pt,12pt]{standalone}
\usepackage{filecontents}

\begin{filecontents*}{Program.cs}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Delegate
{
    class Program
    {
        // start
        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }
        // stop
    }
}
\end{filecontents*}


\usepackage{accsupp}
\newcommand*{\noaccsupp}[1]{\BeginAccSupp{ActualText={}}#1\EndAccSupp{}}

\usepackage{xcolor}
\usepackage{listings}


\lstdefinestyle{Common}
{   
    language={[Sharp]C},
    numbers=left,
    numbersep=1em,
    numberstyle=\tiny\noaccsupp,
    frame=single,
    framesep=\fboxsep,
    framerule=\fboxrule,
    rulecolor=\color{red},
    xleftmargin=\dimexpr\fboxsep+\fboxrule,
    xrightmargin=\dimexpr\fboxsep+\fboxrule,
    breaklines=true,
    breakindent=0pt,
    tabsize=2,
    columns=flexible,
    includerangemarker=false,
    rangeprefix=//\ ,
}


\lstdefinestyle{A}
{
    style=Common,
    backgroundcolor=\color{yellow!10},
    basicstyle=\scriptsize\ttfamily,
    keywordstyle=\color{blue}\bf,
    identifierstyle=\color{black},
    stringstyle=\color{red},
    commentstyle=\color{green}
}

\begin{document}
\section*{Full Code}
\lstinputlisting[style=A]{Program.cs}
\section*{Code Snippet}
\lstinputlisting[style=A,linerange=start-stop]{Program.cs}
\end{document}*

My question is how to remove the leading white space when using linerange option?

Edit

Consider some extreme cases below.

Case 1

namespace Delegate
{
    class Program
    {
        // start
        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }      
    }        
}
// stop

The code should be rendered as follows

with includrangemarker=true

        // start
        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }      
    }        
}
// stop

with includerangemarker=false

        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }      
    }        
}

Case 2

namespace Delegate
{
    class Program
    {
    // start
        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }      
    }        
}
    // stop

The code should be rendered as follows

with includerangemarker=true,

    // start
        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }      
    }        
}
    // stop

with includerangermarker=false

        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }      
    }        
}

Answer 1

Here is a solution. More details follow.

Limitations of the gobble option (provided by listings)

The listings package provides a key called gobble, which allows the user to specify a fixed number of characters (spaces or otherwise) to be gobbled at the beginning of each line. However, gobble suffers from the following limitations.

• It lacks automation: the user has to look at the listing beforehand to determine how many spaces should be gobbled.
• The gobble key is only compatible with embedded listings (i.e. typeset using an lstlisting environment), most emphatically not with listings residing in standalone files (i.e. typeset using \lstinputlisting).

Limitations of the autogobble option (provided by lstautogobble)

The lstautogobble package provides a Boolean key called autogobble, which automates the gobbling of leading spaces; more specifically, it measures the leading spaces on the very first line (whether it be typeset or not) of the whole listing and passes that value to the gobble key. However, autogobble suffers from the following limitations.

• Because it counts leading white spaces on the very first line of the listing, it may not remove the appropriate amount of leading white space if the range of lines typeset doesn't start by line 1.
• Because it is based on the gobble key, it inherits the latter's incompatibility with \lstinputlisting.

A new key for removing leading white space: autounindent autodedent

The approach below defines a Boolean key called autounindent autodedent, which,

• if set, removes leading white space even if only a range of lines are typeset (i.e. if either the firstline option or the linerange option is used),
• is compatible with both lstlisting and \lstinputlisting.

Known limitations

The code below doesn't handle tab characters properly yet.

Moreover, the desired behaviour in the extreme cases covered in your edit seems very tricky to implement, because it would require two passes. I'm out of my depth! The best I can do is to gobble as many spaces as there are at the beginning of the line right after the // start marker (i.e. the line starting by static void in your code).

Please notify me of any other problem.

Update: I've renamed the key to autodedent (which is easier to read and write than autounindent). I also corrected a problem reported by the OP, according to this answer by Heiko Oberdiek. Finally, for convenience, I've implemented that feature in a small package called lstautodedent; the alpha version is available at https://github.com/jubobs/lstautodedent

Code

\documentclass[preview,border=12pt,12pt]{standalone}
\usepackage{filecontents}
\begin{filecontents*}{Program.cs}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Delegate
{
    class Program
    {
        // start
        static void Main(string[] args)
        {
            for (int x = 0; x < 10; x++)
                Console.WriteLine(x);
        }
        // stop
    }
}
\end{filecontents*}
\usepackage{accsupp}
\newcommand*{\noaccsupp}[1]{\BeginAccSupp{ActualText={}}#1\EndAccSupp{}}
\usepackage{xcolor}
\usepackage{listings}
\usepackage{lstautodedent}
\lstdefinestyle{Common}
{

    language={[Sharp]C},
    numbers=left,
    numbersep=1em,
    numberstyle=\tiny\noaccsupp,
    frame=single,
    framesep=\fboxsep,
    framerule=\fboxrule,
    rulecolor=\color{red},
    xleftmargin=\dimexpr\fboxsep+\fboxrule,
    xrightmargin=\dimexpr\fboxsep+\fboxrule,
    breaklines=true,
    breakindent=0pt,
    tabsize=2,
    columns=flexible,
    includerangemarker=false,
    rangeprefix=//\ ,
}
\lstdefinestyle{A}
{
    style=Common,
    backgroundcolor=\color{yellow!10},
    basicstyle=\scriptsize\ttfamily,
    keywordstyle=\color{blue}\bf,
    identifierstyle=\color{black},
    stringstyle=\color{red},
    commentstyle=\color{green}
}
\begin{document}
\section{Full Code}
\lstinputlisting[style=A]{Program.cs}
\section{Code Snippet}
\lstinputlisting[style=A,linerange=start-stop,autodedent]{Program.cs}
\end{document}*