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diff --git a/Help/dev/documentation.rst b/Help/dev/documentation.rst new file mode 100644 index 0000000..c302790 --- /dev/null +++ b/Help/dev/documentation.rst @@ -0,0 +1,530 @@ +CMake Documentation Guide +************************* + +The following is a guide to the CMake documentation source for developers. +See documentation on `CMake Development`_ for more information. + +.. _`CMake Development`: README.rst + +Help +==== + +The ``Help`` directory contains CMake help manual source files. +They are written using the `reStructuredText`_ markup syntax and +processed by `Sphinx`_ to generate the CMake help manuals. + +.. _`reStructuredText`: http://docutils.sourceforge.net/docs/ref/rst/introduction.html +.. _`Sphinx`: http://sphinx-doc.org + +Markup Constructs +----------------- + +In addition to using Sphinx to generate the CMake help manuals, we +also use a C++-implemented document processor to print documents for +the ``--help-*`` command-line help options. It supports a subset of +reStructuredText markup. When authoring or modifying documents, +please verify that the command-line help looks good in addition to the +Sphinx-generated html and man pages. + +The command-line help processor supports the following constructs +defined by reStructuredText, Sphinx, and a CMake extension to Sphinx. + +.. + Note: This list must be kept consistent with the cmRST implementation. + +CMake Domain directives + Directives defined in the `CMake Domain`_ for defining CMake + documentation objects are printed in command-line help output as + if the lines were normal paragraph text with interpretation. + +CMake Domain interpreted text roles + Interpreted text roles defined in the `CMake Domain`_ for + cross-referencing CMake documentation objects are replaced by their + link text in command-line help output. Other roles are printed + literally and not processed. + +``code-block`` directive + Add a literal code block without interpretation. The command-line + help processor prints the block content without the leading directive + line and with common indentation replaced by one space. + +``include`` directive + Include another document source file. The command-line help + processor prints the included document inline with the referencing + document. + +literal block after ``::`` + A paragraph ending in ``::`` followed by a blank line treats + the following indented block as literal text without interpretation. + The command-line help processor prints the ``::`` literally and + prints the block content with common indentation replaced by one + space. + +``note`` directive + Call out a side note. The command-line help processor prints the + block content as if the lines were normal paragraph text with + interpretation. + +``parsed-literal`` directive + Add a literal block with markup interpretation. The command-line + help processor prints the block content without the leading + directive line and with common indentation replaced by one space. + +``productionlist`` directive + Render context-free grammar productions. The command-line help + processor prints the block content as if the lines were normal + paragraph text with interpretation. + +``replace`` directive + Define a ``|substitution|`` replacement. + The command-line help processor requires a substitution replacement + to be defined before it is referenced. + +``|substitution|`` reference + Reference a substitution replacement previously defined by + the ``replace`` directive. The command-line help processor + performs the substitution and replaces all newlines in the + replacement text with spaces. + +``toctree`` directive + Include other document sources in the Table-of-Contents + document tree. The command-line help processor prints + the referenced documents inline as part of the referencing + document. + +Inline markup constructs not listed above are printed literally in the +command-line help output. We prefer to use inline markup constructs that +look correct in source form, so avoid use of \\-escapes in favor of inline +literals when possible. + +Explicit markup blocks not matching directives listed above are removed from +command-line help output. Do not use them, except for plain ``..`` comments +that are removed by Sphinx too. + +Note that nested indentation of blocks is not recognized by the +command-line help processor. Therefore: + +* Explicit markup blocks are recognized only when not indented + inside other blocks. + +* Literal blocks after paragraphs ending in ``::`` but not + at the top indentation level may consume all indented lines + following them. + +Try to avoid these cases in practice. + +CMake Domain +------------ + +CMake adds a `Sphinx Domain`_ called ``cmake``, also called the +"CMake Domain". It defines several "object" types for CMake +documentation: + +``command`` + A CMake language command. + +``generator`` + A CMake native build system generator. + See the `cmake(1)`_ command-line tool's ``-G`` option. + +``manual`` + A CMake manual page, like the `cmake(1)`_ manual. + +``module`` + A CMake module. + See the `cmake-modules(7)`_ manual + and the `include()`_ command. + +``policy`` + A CMake policy. + See the `cmake-policies(7)`_ manual + and the `cmake_policy()`_ command. + +``prop_cache, prop_dir, prop_gbl, prop_sf, prop_inst, prop_test, prop_tgt`` + A CMake cache, directory, global, source file, installed file, test, + or target property, respectively. See the `cmake-properties(7)`_ + manual and the `set_property()`_ command. + +``variable`` + A CMake language variable. + See the `cmake-variables(7)`_ manual + and the `set()`_ command. + +Documentation objects in the CMake Domain come from two sources. +First, the CMake extension to Sphinx transforms every document named +with the form ``Help/<type>/<file-name>.rst`` to a domain object with +type ``<type>``. The object name is extracted from the document title, +which is expected to be of the form:: + + <object-name> + ------------- + +and to appear at or near the top of the ``.rst`` file before any other +lines starting in a letter, digit, or ``<``. If no such title appears +literally in the ``.rst`` file, the object name is the ``<file-name>``. +If a title does appear, it is expected that ``<file-name>`` is equal +to ``<object-name>`` with any ``<`` and ``>`` characters removed. + +Second, the CMake Domain provides directives to define objects inside +other documents: + +.. code-block:: rst + + .. command:: <command-name> + + This indented block documents <command-name>. + + .. variable:: <variable-name> + + This indented block documents <variable-name>. + +Object types for which no directive is available must be defined using +the first approach above. + +.. _`Sphinx Domain`: http://sphinx-doc.org/domains.html +.. _`cmake(1)`: https://cmake.org/cmake/help/latest/manual/cmake.1.html +.. _`cmake-modules(7)`: https://cmake.org/cmake/help/latest/manual/cmake-modules.7.html +.. _`cmake-policies(7)`: https://cmake.org/cmake/help/latest/manual/cmake-policies.7.html +.. _`cmake-properties(7)`: https://cmake.org/cmake/help/latest/manual/cmake-properties.7.html +.. _`cmake-variables(7)`: https://cmake.org/cmake/help/latest/manual/cmake-variables.7.html +.. _`cmake_policy()`: https://cmake.org/cmake/help/latest/command/cmake_policy.html +.. _`include()`: https://cmake.org/cmake/help/latest/command/include.html +.. _`set()`: https://cmake.org/cmake/help/latest/command/set.html +.. _`set_property()`: https://cmake.org/cmake/help/latest/command/set_property.html + +Cross-References +---------------- + +Sphinx uses reStructuredText interpreted text roles to provide +cross-reference syntax. The `CMake Domain`_ provides for each +domain object type a role of the same name to cross-reference it. +CMake Domain roles are inline markup of the forms:: + + :type:`name` + :type:`text <name>` + +where ``type`` is the domain object type and ``name`` is the +domain object name. In the first form the link text will be +``name`` (or ``name()`` if the type is ``command``) and in +the second form the link text will be the explicit ``text``. +For example, the code: + +.. code-block:: rst + + * The :command:`list` command. + * The :command:`list(APPEND)` sub-command. + * The :command:`list() command <list>`. + * The :command:`list(APPEND) sub-command <list>`. + * The :variable:`CMAKE_VERSION` variable. + * The :prop_tgt:`OUTPUT_NAME_<CONFIG>` target property. + +produces: + +* The `list()`_ command. +* The `list(APPEND)`_ sub-command. +* The `list() command`_. +* The `list(APPEND) sub-command`_. +* The `CMAKE_VERSION`_ variable. +* The `OUTPUT_NAME_<CONFIG>`_ target property. + +Note that CMake Domain roles differ from Sphinx and reStructuredText +convention in that the form ``a<b>``, without a space preceding ``<``, +is interpreted as a name instead of link text with an explicit target. +This is necessary because we use ``<placeholders>`` frequently in +object names like ``OUTPUT_NAME_<CONFIG>``. The form ``a <b>``, +with a space preceding ``<``, is still interpreted as a link text +with an explicit target. + +.. _`list()`: https://cmake.org/cmake/help/latest/command/list.html +.. _`list(APPEND)`: https://cmake.org/cmake/help/latest/command/list.html +.. _`list(APPEND) sub-command`: https://cmake.org/cmake/help/latest/command/list.html +.. _`list() command`: https://cmake.org/cmake/help/latest/command/list.html +.. _`CMAKE_VERSION`: https://cmake.org/cmake/help/latest/variable/CMAKE_VERSION.html +.. _`OUTPUT_NAME_<CONFIG>`: https://cmake.org/cmake/help/latest/prop_tgt/OUTPUT_NAME_CONFIG.html + +Style +----- + +Style: Section Headers +^^^^^^^^^^^^^^^^^^^^^^ + +When marking section titles, make the section decoration line as long as +the title text. Use only a line below the title, not above. For +example: + +.. code-block:: rst + + Title Text + ---------- + +Capitalize the first letter of each non-minor word in the title. + +The section header underline character hierarchy is + +* ``#``: Manual group (part) in the master document +* ``*``: Manual (chapter) title +* ``=``: Section within a manual +* ``-``: Subsection or `CMake Domain`_ object document title +* ``^``: Subsubsection or `CMake Domain`_ object document section +* ``"``: Paragraph or `CMake Domain`_ object document subsection + +Style: Whitespace +^^^^^^^^^^^^^^^^^ + +Use two spaces for indentation. Use two spaces between sentences in +prose. + +Style: Line Length +^^^^^^^^^^^^^^^^^^ + +Prefer to restrict the width of lines to 75-80 columns. This is not a +hard restriction, but writing new paragraphs wrapped at 75 columns +allows space for adding minor content without significant re-wrapping of +content. + +Style: Prose +^^^^^^^^^^^^ + +Use American English spellings in prose. + +Style: Starting Literal Blocks +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Prefer to mark the start of literal blocks with ``::`` at the end of +the preceding paragraph. In cases where the following block gets +a ``code-block`` marker, put a single ``:`` at the end of the preceding +paragraph. + +Style: CMake Command Signatures +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Command signatures should be marked up as plain literal blocks, not as +cmake ``code-blocks``. + +Signatures are separated from preceding content by a section header. +That is, use: + +.. code-block:: rst + + ... preceding paragraph. + + Normal Libraries + ^^^^^^^^^^^^^^^^ + + :: + + add_library(<lib> ...) + + This signature is used for ... + +Signatures of commands should wrap optional parts with square brackets, +and should mark list of optional arguments with an ellipsis (``...``). +Elements of the signature which are specified by the user should be +specified with angle brackets, and may be referred to in prose using +``inline-literal`` syntax. + +Style: Boolean Constants +^^^^^^^^^^^^^^^^^^^^^^^^ + +Use "``OFF``" and "``ON``" for boolean values which can be modified by +the user, such as ``POSITION_INDEPENDENT_CODE``. Such properties +may be "enabled" and "disabled". Use "``True``" and "``False``" for +inherent values which can't be modified after being set, such as the +``IMPORTED`` property of a build target. + +Style: Inline Literals +^^^^^^^^^^^^^^^^^^^^^^ + +Mark up references to keywords in signatures, file names, and other +technical terms with ``inline-literal`` syntax, for example: + +.. code-block:: rst + + If ``WIN32`` is used with :command:`add_executable`, the + :prop_tgt:`WIN32_EXECUTABLE` target property is enabled. That command + creates the file ``<name>.exe`` on Windows. + +Style: Cross-References +^^^^^^^^^^^^^^^^^^^^^^^ + +Mark up linkable references as links, including repeats. +An alternative, which is used by wikipedia +(`<http://en.wikipedia.org/wiki/WP:REPEATLINK>`_), +is to link to a reference only once per article. That style is not used +in CMake documentation. + +Style: Referencing CMake Concepts +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +If referring to a concept which corresponds to a property, and that +concept is described in a high-level manual, prefer to link to the +manual section instead of the property. For example: + +.. code-block:: rst + + This command creates an :ref:`Imported Target <Imported Targets>`. + +instead of: + +.. code-block:: rst + + This command creates an :prop_tgt:`IMPORTED` target. + +The latter should be used only when referring specifically to the +property. + +References to manual sections are not automatically created by creating +a section, but code such as: + +.. code-block:: rst + + .. _`Imported Targets`: + +creates a suitable anchor. Use an anchor name which matches the name +of the corresponding section. Refer to the anchor using a +cross-reference with specified text. + +Imported Targets need the ``IMPORTED`` term marked up with care in +particular because the term may refer to a command keyword, a target +property, or a concept. + +Where a property, command or variable is related conceptually to others, +by for example, being related to the buildsystem description, generator +expressions or Qt, each relevant property, command or variable should +link to the primary manual, which provides high-level information. Only +particular information relating to the command should be in the +documentation of the command. + +Style: Referencing CMake Domain Objects +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +When referring to `CMake Domain`_ objects such as properties, variables, +commands etc, prefer to link to the target object and follow that with +the type of object it is. For example: + +.. code-block:: rst + + Set the :prop_tgt:`AUTOMOC` target property to ``ON``. + +Instead of + +.. code-block:: rst + + Set the target property :prop_tgt:`AUTOMOC` to ``ON``. + +The ``policy`` directive is an exception, and the type us usually +referred to before the link: + +.. code-block:: rst + + If policy :policy:`CMP0022` is set to ``NEW`` the behavior is ... + +However, markup self-references with ``inline-literal`` syntax. +For example, within the ``add_executable`` command documentation, use + +.. code-block:: rst + + ``add_executable`` + +not + +.. code-block:: rst + + :command:`add_executable` + +which is used elsewhere. + +Modules +======= + +The ``Modules`` directory contains CMake-language ``.cmake`` module files. + +Module Documentation +-------------------- + +To document CMake module ``Modules/<module-name>.cmake``, modify +``Help/manual/cmake-modules.7.rst`` to reference the module in the +``toctree`` directive, in sorted order, as:: + + /module/<module-name> + +Then add the module document file ``Help/module/<module-name>.rst`` +containing just the line:: + + .. cmake-module:: ../../Modules/<module-name>.cmake + +The ``cmake-module`` directive will scan the module file to extract +reStructuredText markup from comment blocks that start in ``.rst:``. +At the top of ``Modules/<module-name>.cmake``, begin with the following +license notice: + +:: + + # Distributed under the OSI-approved BSD 3-Clause License. See accompanying + # file Copyright.txt or https://cmake.org/licensing for details. + +After this notice, add a *BLANK* line. Then, add documentation using +a `Bracket Comment`_ of the form: + +:: + + #[=======================================================================[.rst: + <module-name> + ------------- + + <reStructuredText documentation of module> + #]=======================================================================] + +Any number of ``=`` may be used in the opening and closing brackets +as long as they match. Content on the line containing the closing +bracket is excluded if and only if the line starts in ``#``. + +Additional such ``.rst:`` comments may appear anywhere in the module file. +All such comments must start with ``#`` in the first column. + +For example, a ``Findxxx.cmake`` module may contain: + +:: + + # Distributed under the OSI-approved BSD 3-Clause License. See accompanying + # file Copyright.txt or https://cmake.org/licensing for details. + + #[=======================================================================[.rst: + FindXxx + ------- + + This is a cool module. + This module does really cool stuff. + It can do even more than you think. + + It even needs two paragraphs to tell you about it. + And it defines the following variables: + + ``VAR_COOL`` + this is great isn't it? + ``VAR_REALLY_COOL`` + cool right? + #]=======================================================================] + + <code> + + #[=======================================================================[.rst: + .. command:: xxx_do_something + + This command does something for Xxx:: + + xxx_do_something(some arguments) + #]=======================================================================] + macro(xxx_do_something) + <code> + endmacro() + +Test the documentation formatting by running +``cmake --help-module <module-name>``, and also by enabling the +``SPHINX_HTML`` and ``SPHINX_MAN`` options to build the documentation. +Edit the comments until generated documentation looks satisfactory. To +have a .cmake file in this directory NOT show up in the modules +documentation, simply leave out the ``Help/module/<module-name>.rst`` +file and the ``Help/manual/cmake-modules.7.rst`` toctree entry. + +.. _`Bracket Comment`: https://cmake.org/cmake/help/latest/manual/cmake-language.7.html#bracket-comment |