Documentation for Symbulation Documentation

This is a quick primer on how to document things within Symbulation.

Symbulation makes use of the Sphinx documentation system based off of XML information gathered from Doxygen via a plugin named Breathe. This means that Doxygen will automatically build documentation for anything written in a C++ source file and Sphinx will be used to organize how that documentation is displayed.


You’ll need to install some additional things to build the documentation locally. If you make additions to the documentation, please build it locally to make sure that it is formatted well before making a pull request.

You need to install

  • Doxygen

  • Sphinx

  • pip/pip3

For Homebrew users, that looks like this:

brew install sphinx
brew install doxygen
brew install pip3

You can then use pip3 to install the rest of the requirements:

cd SymbulationEmp/docs
pip3 install -r requirements.txt

Building Documentation Locally

You are then ready to make your local documentation and run it:

make html
cd _build/html/
python3 -m http.server

How to Comment for Doxygen Autodoc

Doxygen has an entire documentation section on how to comment your code. We’ll provide a trimmed version here so that you can get started quickly.

Doxygen will examine all comments to determine if they are documentation comments or just code comments. To make a documentation comment you must add either an extra * or /, depending on the kind of comment:

 * This is a documentation comment
 * across several lines
 * This comment will be associated with the function immediately following.
void somefunc(sometype param)


// this is a comment that doxygen will ignore
// note how it only has two leading slashes, like a normal comment
/// This is a comment that will be included in the documentation
/// Note the extra leading slash
/// Huzzah, documentation


Doxygen requires a minimum of three triple slash’d lines before a block is considered documentation:

/// This line will be ignored
int somefunc() { return 5; }

/// This line will be included
void otherfunc() { ; }

If you wish to make a more visible comment block, e.g. a header for a class, then you may do something like the following:

* Here is some text inside a visible block


Doxygen will view this as any other documentation comment and will not render it any differently than a ‘normal’ documentation comment–it is simply more visible within the source code.

How to include Doxygen’s autodocs within Sphinx files

Through the use of the Breathe extension it is incredibly easy to include Doxygen autodocs within a Sphinx documentation file.

Suppose we have a C++ implementation file name lily.h that has inline comment documentation as detailed above and that lily.h is a component of a module named flowers that was just created.

To document them, you must create a file within the Symbulation Library documentation source to hold the module’s documentation:

    touch doc/library/

Within you can make an introduction to the module, etc., and then add in the sphinx directives to include auto-documentation. Your file should look something like the following:

    # This is the flowers documentation!

    This is a very short introduction.

    ## lily.h

    .. doxygenfile:: lily.h
       :project: Symbulation

When the docs are built Sphinx will automatically pull the available documentation from Doxygen’s XML files to construct the docs.

Additional directives exist to include auto-documentaiton from different levels, the full breakdown of which is available within the Breathe Documentation.

How to add docs to the Sphinx documentation

Sphinx is the system used to generate the developer guide and similar reference documentation. A primer to using ReStructured Text, the markup language used by Sphinx, can be found here. You can also look at any of the [.rst]{.title-ref} files in the [doc/]{.title-ref} directory to get a feel for how thinks work.

New documents must be included in the toctree in the file for the directory the added file lives in. For example, if you add to the CoolFacts/ directory you must add to the toctree found in CoolFacts/

    # Cool Facts

    A bunch of cool facts!