Backport Building the manual with Sphinx page from the `master` branch

community/contributing/building_the_manual.rst

@@ -0,0 +1,99 @@
+.. _doc_building_the_manual:
+
+Building the manual with Sphinx
+===============================
+
+This page explains how to build a local copy of the Godot manual using the
+Sphinx docs engine. This allows you to have local HTML files and build the
+documentation as a PDF, EPUB, or LaTeX file, for example.
+
+To get started, you need to:
+
+1. Clone the `godot-docs repository <https://github.com/godotengine/godot-docs/>`__.
+2. Install `Sphinx <https://www.sphinx-doc.org/>`__
+3. To build the docs as HTML files, install the `readthedocs.org theme
+   <https://github.com/snide/sphinx_rtd_theme>`__.
+4. Install the Sphinx extensions defined in the `godot-docs repository
+   <https://github.com/godotengine/godot-docs/>`__ ``requirements.txt`` file.
+
+We recommend using `pip <https://pip.pypa.io>`__, Python’s package manager to
+install all these tools. It comes pre-installed with `Python
+<https://www.python.org/>`__. Ensure that you install and use Python 3. Here are
+the commands to clone the repository and then install all requirements.
+
+.. code:: sh
+
+    git clone https://github.com/godotengine/godot-docs.git
+    pip install -r requirements.txt
+
+.. note:: On Linux distributions, you may need to write ``pip3`` instead of
+          ``pip`` because you generally have both Python 2 and 3 installed on
+          your system. Alternatively, you can explicitly ask Python 3 to execute
+          its version of pip as a module like so: ``python3 -m pip``.
+
+With the programs installed, you can build the HTML documentation from the root
+folder of this repository with the following command:
+
+.. code:: sh
+
+    # On Linux and MacOS
+    make html
+
+    # On Windows, you need to execute the ``make.bat`` file instead.
+    make.bat html
+
+If you run into errors, you may try the following command:
+
+.. code:: sh
+
+    make SPHINXBUILD=~/.local/bin/sphinx-build html
+
+Building the documentation requires at least 8 GB of RAM to run without disk
+swapping, which slows it down. If you have at least 16 GB of RAM, you can speed
+up compilation by running:
+
+.. code:: sh
+
+    # On Linux/macOS
+    make html SPHINXOPTS=-j2
+
+    # On Windows
+    set SPHINXOPTS=-j2 && make html
+
+The compilation will take some time as the ``classes/`` folder contains hundreds
+of files.
+
+You can then browse the documentation by opening ``_build/html/index.html`` in
+your web browser.
+
+In case you of a ``MemoryError`` or ``EOFError``, you can remove the
+``classes/`` folder and run ``make`` again. This will drop the class references
+from the final HTML documentation but will keep the rest intact.
+
+.. note:: If you delete the ``classes/`` folder, do not use ``git add .`` when
+          working on a pull request or the whole ``classes/`` folder will be
+          removed when you commit. See `#3157
+          <https://github.com/godotengine/godot-docs/issues/3157>`__ for more
+          detail.
+
+Alternatively, you can build the documentation by running the sphinx-build
+program manually:
+
+.. code:: sh
+
+   sphinx-build -b html ./ _build
+
+Building with Sphinx and virtualenv
+-----------------------------------
+
+If you want your Sphinx installation scoped to the project, you can install
+sphinx-build using virtualenv. To do so, run this command from this repository's
+root folder:
+
+.. code:: sh
+
+   virtualenv --system-site-packages env/
+   . env/bin/activate
+   pip install -r requirements.txt
+
+Then, run ``make html`` as shown above.

community/contributing/index.rst

@@ -12,6 +12,7 @@ Contributing
    bisecting_regressions
    code_style_guidelines
    bug_triage_guidelines
+   building_the_manual
    documentation_guidelines
    docs_writing_guidelines
    updating_the_class_reference