Add page about gdextension docs generation (#9667)

* Adding page about gdextension docs generation

---------

Co-authored-by: Max Hilbrunner <[email protected]>

tutorials/scripting/gdextension/gdextension_docs_system.rst

@@ -0,0 +1,172 @@
+.. _doc_gdextension_docs_system:
+
+GDExtension documentation system
+================================
+
+.. note::
+
+    Adding documentation for GDExtensions is only possible for Godot 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 :ref:`GDExtension C++ Example <doc_gdextension_cpp_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 Godot demo project directory of your GDExtension directory, run the following terminal command:
+
+.. code-block:: none
+
+    # Replace "godot" with the full path to a Godot editor binary
+    # if Godot is not installed in your `PATH`.
+    godot --doctool ../ --gdextension-docs
+
+This command calls upon the Godot editor binary to generate documentation via the ``--doctool``
+and ``--gdextension-docs`` commands. The ``../`` addition is to let Godot know where the GDExtension
+SConstruct file is located. By calling this command, Godot 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:
+
+.. code-block:: py
+
+    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 Godot editor or later and open the documentation of your extension class
+either by :kbd:`Ctrl + Click` in the script editor or the Editor help dialog you will see something like this:
+
+.. image:: img/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 :ref:`RichTextLabels <doc_bbcode_in_richtextlabel>`.
+You can set text as bold, italic, underlined, colored, codeblocks etc. by embedding them in tags like this:
+
+.. code-block:: none
+
+    [b]this text will be shown as bold[/b]
+
+Currently they supported tags for the GDExtension documentation system are:
+
+.. list-table::
+  :class: wrap-normal
+  :width: 100%
+  :widths: 60 40
+
+  * - 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 the mono font and styles the text color and background like a shortcut.
+
+    - ``[code]{text}[/code]``
+
+  * - | **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.
+      | **Must be handled with the "meta_clicked" signal to have an effect,** see :ref:`doc_bbcode_in_richtextlabel_handling_url_tag_clicks`.
+
+    - | ``[url]{link}[/url]``
+      | ``[url={link}]{text}[/url]``
+
+  * - | **img**
+      | Inserts an image from the ``{path}`` (can be any valid :ref:`class_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 :ref:`doc_bbcode_in_richtextlabel_image_and_table_alignment`.
+      | Supports configuration options, see :ref:`doc_bbcode_in_richtextlabel_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
+        :ref:`doc_bbcode_in_richtextlabel_named_colors`) or using the HEX format (e.g.
+        ``#ff00ff``, see :ref:`doc_bbcode_in_richtextlabel_hex_colors`).
+
+    - ``[color={code/name}]{text}[/color]``

tutorials/scripting/gdextension/gdextension_file.rst

@@ -1,4 +1,4 @@
-.. _doc_gdextension_file_sections:
+.. _doc_gdextension_file:
 
 The .gdextension file
 =====================

tutorials/scripting/gdextension/index.rst

@@ -10,3 +10,4 @@ GDExtension
    what_is_gdextension
    gdextension_cpp_example
    gdextension_file
+   gdextension_docs_system