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GDExtension documentation system

Note

Adding documentation for GDExtensions is only possible for Redot 4.3 and later. The support can be integrated into your project regardless because the snippet will check if you use the appropriate godot-cpp version. If you set the compatability_minimum to 4.2 and you load a project with the extension through a 4.2 editor, the documentation page for that class will be empty. The extension itself will still work.

The GDExtension documentation system works in a similar manner to the built-in engine documentation. It uses a series of XML files (one per class) to document the exposed constructors, properties, methods, constants, signals, and theme items of each class.

Note

We are assuming you are using the project files explained in the GDExtension C++ Example with the following structure:

gdextension_cpp_example/  # GDExtension directory
|
+--demo/                  # game example/demo to test the extension
|   |
|   +--main.tscn
|   |
|   +--bin/
|       |
|       +--gdexample.gdextension
|
+--godot-cpp/             # C++ bindings
|
+--src/                   # source code of the extension we are building
|   |
|   +--register_types.cpp
|   +--register_types.h
|   +--gdexample.cpp
|   +--gdexample.h

Inside the Redot demo project directory of your GDExtension directory, run the following terminal command:

# Replace "godot" with the full path to a Redot editor binary
# if Redot is not installed in your `PATH`.
redot --doctool ../ --gdextension-docs

This command calls upon the Redot editor binary to generate documentation via the --doctool and --gdextension-docs commands. The ../ addition is to let Redot know where the GDExtension SConstruct file is located. By calling this command, Redot generates a doc_classes directory inside the project directory in which it generates XML files for the GDExtension classes. Those files can then be edited to add information about member variables, methods, signals, and more.

To add the now edited documentation to the GDExtension and let the editor load it, you need to add the following lines to your SConstruct file:

if env["target"] in ["editor", "template_debug"]:
try:
    doc_data = env.GodotCPPDocData("src/gen/doc_data.gen.cpp", source=Glob("doc_classes/*.xml"))
    sources.append(doc_data)
except AttributeError:
    print("Not including class reference as we're targeting a pre-4.3 baseline.")

The if-statement checks if we are compiling the GDExtension library with the editor and template_debug flags. SCons then tries to load all the XML files inside the doc_classes directory and appends them to the sources variable which already includes all the source files of your extension. If it fails it means we are currently trying to compile the library when the godot_cpp is set to a version before 4.3.

After loading the extension in a 4.3 Redot editor or later and open the documentation of your extension class either by Ctrl + Click in the script editor or the Editor help dialog you will see something like this:

../../../_images/gdextension_docs_generation.webp

Documentation styling

To style specific parts of text you can use BBCode tags similarly to how they can be used in RichTextLabels. You can set text as bold, italic, underlined, colored, codeblocks etc. by embedding them in tags like this:

[b]this text will be shown as bold[/b]

Currently they supported tags for the GDExtension documentation system are:

Tag	Example
b Makes `{text}` use the bold (or bold italics) font of `RichTextLabel`.	`[b]{text}[/b]`
i Makes `{text}` use the italics (or bold italics) font of `RichTextLabel`.	`[i]{text}[/i]`
u Makes `{text}` underlined.	`[u]{text}[/u]`
s Makes `{text}` strikethrough.	`[s]{text}[/s]`
kbd Makes `{text}` use a grey beveled background, indicating a keyboard shortcut.	`[kbd]{text}[/kbd]`
code Makes inline `{text}` use the mono font and styles the text color and background like code.	`[code]{text}[/code]`
codeblocks Makes multiline `{text}` use the mono font and styles the text color and background like code. The addition of the `[gdscript]` tag highlights the GDScript specific syntax.	`[codeblocks]` `[gdscript]` `{text}` `[/gdscript]` `[/codeblocks]`
center Makes `{text}` horizontally centered. Same as `[p align=center]`.	`[center]{text}[/center]`
url Creates a hyperlink (underlined and clickable text). Can contain optional `{text}` or display `{link}` as is.	`[url]{link}[/url]` `[url={link}]{text}[/url]`
img Inserts an image from the `{path}` (can be any valid Texture2D resource). If `{width}` is provided, the image will try to fit that width maintaining the aspect ratio. If both `{width}` and `{height}` are provided, the image will be scaled to that size. Add `%` to the end of `{width}` or `{height}` value to specify it as percentages of the control width instead of pixels. If `{valign}` configuration is provided, the image will try to align to the surrounding text, see Image and table vertical alignment. Supports configuration options, see Image options.	`[img]{path}[/img]` `[img={width}]{path}[/img]` `[img={width}x{height}]{path}[/img]` `[img={valign}]{path}[/img]` `[img {options}]{path}[/img]`
color Changes the color of `{text}`. Color must be provided by a common name (see Named colors) or using the HEX format (e.g. `#ff00ff`, see Hexadecimal color codes).	`[color={code/name}]{text}[/color]`

Publishing documentation online

You may want to publish an online reference for your GDExtension, similar to this website. The most important step is to build reStructuredText (.rst) files from your XML class reference:

# You need a version.py file, so download it first.
curl -sSLO https://raw.githubusercontent.com/godotengine/godot/refs/heads/master/version.py

# Edit version.py according to your project before proceeding.
# Then, run the rst generator. You'll need to have Python installed for this command to work.
curl -sSL https://raw.githubusercontent.com/redot-engine/redot-engine/master/doc/tools/make_rst.py | python3 - -o "docs/classes" -l "en" doc_classes

Your .rst files will now be available in docs/classes/. From here, you can use any documentation builder that supports reStructuredText syntax to create a website from them.

redot-docs uses Sphinx. You can use the repository as a basis to build your own documentation system. The following guide describes the basic steps, but they are not exhaustive: You will need a bit of personal insight to make it work.

Add redot-docs as a submodule to your docs/ folder.
Copy over its conf.py, index.rst, .readthedocs.yaml files into /docs/. You may later decide to copy over and edit more of redot-docs' files, like _templates/layout.html.
Modify these files according to your project. This mostly involves adjusting paths to point to the redot-docs subfolder, as well as strings to reflect it's your project rather than Redot you're building the docs for.
Create an account on readthedocs.org. Import your project, and modify its base .readthedocs.yaml file path to /docs/.readthedocs.yaml.

Once you have completed all these steps, your documentation should be available at <repo-name>.readthedocs.io.