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Use Emacs to highlight source code listings in LaTeX and HTML documents!

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# Emacs Syntax Highlighting for LaTeX

This programs processes TeX source files, adding syntax-highlighting to the contents of specially-delimited environments and macros. For example, esh2tex transforms this block:

%% ESH: c
\begin{verbatim}
int main() { return 0; }
\end{verbatim}

into something like that:

\begin{ESHBlock}
\-  \color{8CC4FF}{int} \color{FCE94F}{main}() \{ \color{B4FA70}{return} 0; \}
\end{ESHBlock}

Curious? Check out our demo PDF and give it a try! Plus, since ESH works with special comments, your documents remain compatible with plain LaTeX (for more on this see Collaborating with authors who do not use ESH below).

## Setup

Dependencies: Emacs > 24.2; XeLaTeX (best) or pdfLaTeX; Cask (optional)

Setup: Clone the repository somewhere, and add <wherever>/bin to your path (alternatively, just call <wherever>/bin/esh2tex explicitly). This program is tested only on GNU/Linux; it has been reported to work on macOS as well, and to some limited extent on Windows (see Windows support below).

Sanity check: Running make in the example directory of the Git repo should produce a (partially) syntax-highlighted example.pdf.

## Quickstart

Create a new file minimal.tex and write the following:

\documentclass{minimal}
%% ESH-preamble-here

\begin{document}
%% ESH: c
\begin{verbatim}
int main() { return 0; }
\end{verbatim}
\end{document}

Process with esh2tex minimal.tex, then compile with pdflatex minimal.esh.tex or xelatex minimal.esh.tex. Run make in the example/ directory of the Git repository for a more advanced example.

For larger documents, run esh2tex --init in a new directory to create a ready-to-use ESH setup.

## Usage

# Create a ready-to-use ESH setup in the current directory
esh2tex --init

# Process one or more tex files with embedded code blocks
esh2tex [<options>...] [<input>.tex...]

# Process one or more standalone source code listings
esh2tex --standalone [<options>...] [<input>.py|c|cpp|...]


<input>.tex should be an UTF-8 encoded text file; output goes to <input>.esh.tex. --init is special; see Options. <input> may also be an arbitrary source file; see --standalone.

In <input>, you may indicate source blocks like this:

%% ESH: <lang>
\begin{...}
...
\end{...}

<lang>-mode should be the name of an Emacs major mode (in fact, any function will do, as long as it ends in mode); the name of the environment (...) does not matter.

Additionally, <input> should load ESH's preamble before \begin{document}. For simple documents, adding the following special comment to your preamble is enough (esh2tex will replace it by appropriate set-up code):

%% ESH-preamble-here


esh2tex does not load your personal Emacs configuration (though see --no-Q); instead, it looks for a file named esh-init.el in the current directory, one of its parents, or ~/.emacs.d/. You can use that file to chose a different color theme, load extra packages (see Installing extra packages), and teach ESH about inline macros (see Inline syntax highlighting).

## Options

• --usage, --help

Show this help.

• --init

Don't process input files; instead, create a fairly complete ESH setup in the current folder, including an basic main.tex and simple Makefile.

• --standalone

Treat <input> as a standalone source file: don't look for special %% ESH comments, highlight the entire file, and save output to <input>.esh.tex. This is convenient for longer source code listings, or if your collaborators don't use ESH (see Collaborating with authors who do not use ESH below).

• --persist

Leave server running after processing <input>.tex.

• --kill-server

Kill previously-started instances of the ESH server. (You usually do not need to run this explicitly, since the server resets automatically when you edit your ESH configuration).

• --stdout

Write to stdout, instead of writing to <input>.esh.tex.

• --no-cask

Normally, when the current directory contains a Cask file and the cask binary is in your path, ESH uses cask exec emacs instead of emacs to start the syntax-highlighting daemon. With this option, ESH will stick to using the plain emacs.

• --no-Q

Load your full Emacs configuration instead of the esh-init.el file. Use this option with caution; there are subtle differences between ESH and a regular Emacs that can prevent your Emacs configuration from loading properly. In general, it's much better to extract just what you need from your .emacs and put it in an esh-init.el, as described below.

• --write-preamble

Write esh-preamble.tex to current directory. This option does not require specifying an input file.

• --precompute-verbs-map

Instead of producing a highlighted version of <input>, produce an auxiliary file storing only highlighting information and redefinitions of \verb-like commands. See Precomputed verb maps below.

• --debug-on-error

Print stack traces for errors.

## Notes

• Starting a server can be slow if your configuration file is large. Use --persist to leave a server running after the first run and reuse it on subsequent runs.

## Tips and suggestions

All the following tricks, and more, are demonstrated in the example/example.tex file of the Git repository.

### Loading a different theme

To load a different theme, include the following line in your esh-init.el:

(load-theme '<theme-name> t) ;; tango, dichromacy, leuven, adwaita...

### Inline syntax highlighting

In addition to code blocks, ESH can highlight inline macros. Since LaTeX doesn't have inline comments, though, you need to define your own wrappers. Start by adding the following to your esh-init.el:

(esh-latex-add-inline-verb "\\python" 'python-mode)
(esh-latex-add-inline-verb "\\cpp" 'c++-mode)

These lines teach ESH about two new inline code delimiters, \python and \cpp. This lets you use \python|yield 1| or \cpp/*p++ |= *q++/ in the body of your documents, and have them syntax-highlighted by esh2tex in python-mode and c++-mode respectively.

If you want the document to remain compatible with plain LaTeX, you can trick LaTeX into thinking that \python and \cpp are aliases of \verb:

\def\python{\verb} % To remain compatible with plain LaTeX
\def\cpp{\verb}

### Using prettification

Emacs can render operators using unicode symbols, displaying → instead of ->, for example. This feature is called prettify-symbols-mode.

To enable it in ESH, add the following to your esh-init.el:

(add-hook '<mode>-hook #'prettify-symbols-mode) ;; lisp-mode, perl-mode...

XeLaTeX and LuaLaTeX are generally better at handling Unicode, but if you are stuck with pdfLaTeX we have a workaround (see the pdfLaTeX tips section).

With XeLaTeX and LuaLaTeX, you'll probably want to redefine the \ESHFallbackFont command, too (see below); something like this:

\usepackage{fontspec}
\newfontfamily{\XITSMath}{XITS Math}
\renewcommand{\ESHFallbackFontFamily}{\XITSMath}

### Inline blocks

By default, ESH blocks work in vertical mode: they start a new paragraph, and add vertical space before and after themselves. If you include them in a horizontal box, such as a math formula or a subfloat, LaTeX will complain (something is wrong -- maybe a missing \item?). Think of the difference between \begin{align} and \begin{aligned}.

To get a horizontal-mode "inline" block, use the following syntax:

%% ESHInlineBlock: <lang>
\begin{...}
...
\end{...}


### Installing extra packages

If the languages that you want to highlight are not supported by Emacs out of the box, use Cask to install the corresponding packages locally. This is much cleaner and more stable than loading your full Emacs configuration (in short, Cask is to Emacs Lisp what VirtualEnv is to Python).

The repo's example/ directory uses a Cask file to manage external dependencies.

### Customizing the output

All customizations should be placed after the %% ESH-preamble-here line (or the explicit \input{esh-preamble}).

Changing fonts:

\usepackage{fontspec}

;; Use a roman font for code blocks
\renewcommand{\ESHBlockFontFamily}{\textrm}

;; Use Ubuntu Mono for inline code
\newfontfamily{\UbuntuMono}[Mapping=tex-ansi]{Ubuntu Mono}
\renewcommand{\ESHInlineFontFamily}{\UbuntuMono}

;; Use XITS Math for special characters
\newfontfamily{\XITSMath}{XITS Math}
\renewcommand{\ESHFallbackFontFamily}{\XITSMath}

Customizing spacing:

;; Leave two blank lines before and after each code block
\setlength{\ESHSkip}{2\baselineskip}

Overriding the ESHBlock environment:

\renewenvironment{ESHBlock}{...}{...}

All these tricks, and more, are demonstrated in the example/example.tex subfolder of the repository.

### Processing standalone source files

ESH processes the input as a LaTeX source file containing code blocks to highlight. To process a plain source file, use the --standalone option:

esh2tex --standalone main.py


This is very useful to collaborate with authors who do not use ESH.

### Collaborating with authors who do not use ESH

ESH documents can be compiled using plain xelatex or pdflatex, but then they won't be highlighted, and there might be small spacing differences. To collaborate with non-ESH users, you can instead use the following setup:

• In your main document, replace the %% ESH-preamble-here line with \input{esh-preamble} and run esh2tex --write-preamble to save a local copy of ESH's preamble. Make sure to share this file with your collaborators (check it in your repository, for example).

• Do not use special % ESH comments; instead, save your code snippets as individual files in a separate listings directory. In your document, replace code blocks:

%% ESH: c
\begin{verbatim}
int main() {...}
\end{verbatim}


by \ESHInputBlocks:

\ESHInputBlock{listings/main.c}


or, if the block appears in a horizontal context (inside of a math formula, for example):

\ESHInputInlineBlock[t]{listings/main.c}


(the optional argument indicates the vertical alignment to use -- one of t, c, or b)

• Use ESH to highlight your source files:

esh2tex --standalone listings/main.c


(this command produces listings/main.c.esh.tex)

• For inline code snippets, use one of the following two approaches:

• Extract the code to external files, process them with --standalone, and use \ESHInputInline{snippet.c} to include them. This approach is very stable, but cumbersome for small snippets.
• Use a precomputed verbs map. Keep your inline snippets as usual in your file, make sure that it compiles with the regular esh2tex, then run esh2tex --precompute-verbs-map <your-file>.tex and \input the resulting <your-file>.esh-pv.tex. See Precomputed verb maps below for more info.

As long as you share the highlighted source files and the ESH preamble with your co-authors, they won't need to run ESH themselves.

#### Precomputed verb maps

The --precompute-verbs-map flag instructs ESH to generate a table mapping each inline code snippet in your original LaTeX file to its highlighted counterpart. This table is saved under the name <your-file>.esh-pv.tex. esh-preamble.tex includes the required machinery to manipulate these mappings, and the generated .esh-pv.tex file redefines each of your inline macros to perform the appropriate lookups (ESH learns about your inline macros from the declarations in your esh-init.el).

This works very well as long as your inline snippets are at the top level of your file. If they appear as arguments to another macro, things get tricky (remember that you can't have \verb as an argument to a macro, for catcode-related reasons). In a nutshell, if you use an inline snippet inside the argument of another macro, the snippet must contain neither unbalanced braces nor % or # signs (the former will yield "File ended while scanning use of ...", and the latter an "Illegal parameter number in definition of reserved@a." error). To work around this, you can either use an external file processed with --standalone, or use ESHSavedVerb and ESHUseVerb in conjunction with --precompute-verb-map:

\begin{ESHSavedVerb}{yuck-yuck}
\cverb|You can write anything here: %, #, and {{{|
\end{ESHSavedVerb}

Here's a reference to the saved verb: \footnote{\ESHUseVerb{yuck-yuck}}


### pdfLaTeX tips

pdfLaTeX is bad at Unicode, but ESH can use its built-in table of (Unicode → LaTeX command) mappings to substitute unicode characters before pdfLaTeX can see them and get confused. For this to work, just add the following to your esh-init.el:

(setq-default esh-substitute-unicode-symbols t)


If you want to add your own mappings, use the following examples:

(esh-latex-add-unicode-substitution "∷" "\\ensuremath{::}")
(esh-latex-add-unicode-substitution "‽" "!\!?")


Some symbols require extra packages, like MnSymbol.

### Fixing font issues

If you're having font issues, try switching to XeLaTeX or LuaLaTeX. ESH wraps each non-ASCII character in an \ESHSpecialChar{} command, which internally uses \ESHFallbackFont (by default, this is an alias of \ESHFontFamily). You may want to redefine that to a font with good Unicode coverage:

\usepackage{fontspec}
\newfontfamily{\XITSMath}{XITS Math}
\renewcommand{\ESHFallbackFontFamily}{\XITSMath}

### Using a different version of Emacs

If the Emacs in your path isn't the right one, you can use the EMACS environment variable to let ESH know about the right one:

EMACS=/Applications/Emacs.app/Contents/MacOS/Emacs esh2tex your-file.tex


### Windows support

ESH works on Windows, with the following limitations:

• Emacs 25 is required.
• --persist is not supported.

### Debugging

If you run into issues, try getting the example (in the example folder of the repository) to work. If you can't get the example to work, please open a GitHub issue.

For more advanced debugging, you can load the esh package into Emacs, and use M-x esh2tex-current-buffer on your TeX file.

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