662 lines
21 KiB
ReStructuredText
662 lines
21 KiB
ReStructuredText
.. _doc_guidelines:
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Documentation Guidelines
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########################
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.. highlight:: rst
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.. note::
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For instructions on building the documentation, see :ref:`zephyr_doc`.
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Zephyr Project content is written using the `reStructuredText`_ markup
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language (.rst file extension) with Sphinx extensions, and processed
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using Sphinx to create a formatted standalone website. Developers can
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view this content either in its raw form as .rst markup files, or (with
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Sphinx installed) they can :ref:`build the documentation <zephyr_doc>` locally
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to generate the documentation in HTML or PDF format. The HTML content can
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then be viewed using a web browser. This same .rst content is served by the
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`Zephyr documentation`_ website.
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You can read details about `reStructuredText`_
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and about `Sphinx extensions`_ from their respective websites.
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.. _Sphinx extensions: http://www.sphinx-doc.org/en/stable/contents.html
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.. _reStructuredText: http://docutils.sourceforge.net/docs/ref/rst/restructuredtext.html
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.. _Sphinx Inline Markup: http://sphinx-doc.org/markup/inline.html#inline-markup
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.. _Zephyr documentation: https://docs.zephyrproject.org
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This document provides a quick reference for commonly used reST and
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Sphinx-defined directives and roles used to create the documentation
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you're reading.
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Headings
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********
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While reST allows use of both and overline and matching underline to
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indicate a heading, we only use an underline indicator for headings.
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* Document title (h1) use "#" for the underline character
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* First section heading level (h2) use "*"
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* Second section heading level (h3) use "="
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* Third section heading level (h4) use "-"
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The heading underline must be at least as long as the title it's under.
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For example::
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This is a title heading
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#######################
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some content goes here
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First section heading
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*********************
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Content Highlighting
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********************
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Some common reST inline markup samples:
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* one asterisk: ``*text*`` for emphasis (*italics*),
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* two asterisks: ``**text**`` for strong emphasis (**boldface**), and
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* two backquotes: ````text```` for ``inline code`` samples.
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If asterisks or backquotes appear in running text and could be confused with
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inline markup delimiters, you can eliminate the confusion by adding a
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backslash (``\``) before it.
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Lists
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*****
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For bullet lists, place an asterisk (``*``) or hyphen (``-``) at
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the start of a paragraph and indent continuation lines with two
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spaces.
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The first item in a list (or sublist) must have a blank line before it
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and should be indented at the same level as the preceding paragraph
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(and not indented itself).
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For numbered lists
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start with a 1. or a. for example, and continue with autonumbering by
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using a ``#`` sign. Indent continuation lines with three spaces::
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* This is a bulleted list.
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* It has two items, the second
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item and has more than one line of reST text. Additional lines
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are indented to the first character of the
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text of the bullet list.
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1. This is a new numbered list. If the wasn't a blank line before it,
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it would be a continuation of the previous list (or paragraph).
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#. It has two items too.
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a. This is a numbered list using alphabetic list headings
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#. It has three items (and uses autonumbering for the rest of the list)
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#. Here's the third item
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#. This is an autonumbered list (default is to use numbers starting
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with 1).
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#. This is a second-level list under the first item (also
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autonumbered). Notice the indenting.
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#. And a second item in the nested list.
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#. And a second item back in the containing list. No blank line
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needed, but it wouldn't hurt for readability.
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Definition lists (with a term and its definition) are a convenient way
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to document a word or phrase with an explanation. For example this reST
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content::
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The Makefile has targets that include:
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html
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Build the HTML output for the project
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clean
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Remove all generated output, restoring the folders to a
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clean state.
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Would be rendered as:
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The Makefile has targets that include:
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html
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Build the HTML output for the project
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clean
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Remove all generated output, restoring the folders to a
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clean state.
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Multi-column lists
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******************
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If you have a long bullet list of items, where each item is short, you
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can indicate the list items should be rendered in multiple columns with
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a special ``.. rst-class:: rst-columns`` directive. The directive will
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apply to the next non-comment element (e.g., paragraph), or to content
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indented under the directive. For example, this unordered list::
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.. rst-class:: rst-columns
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* A list of
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* short items
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* that should be
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* displayed
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* horizontally
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* so it doesn't
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* use up so much
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* space on
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* the page
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would be rendered as:
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.. rst-class:: rst-columns
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* A list of
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* short items
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* that should be
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* displayed
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* horizontally
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* so it doesn't
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* use up so much
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* space on
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* the page
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A maximum of three columns will be displayed, and change based on the
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available width of the display window, reducing to one column on narrow
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(phone) screens if necessary. We've deprecated use of the ``hlist``
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directive because it misbehaves on smaller screens.
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Tables
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******
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There are a few ways to create tables, each with their limitations or
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quirks. `Grid tables
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<http://docutils.sourceforge.net/docs/ref/rst/restructuredtext.html#grid-tables>`_
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offer the most capability for defining merged rows and columns, but are
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hard to maintain::
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+------------------------+------------+----------+----------+
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| Header row, column 1 | Header 2 | Header 3 | Header 4 |
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| (header rows optional) | | | |
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+========================+============+==========+==========+
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| body row 1, column 1 | column 2 | column 3 | column 4 |
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+------------------------+------------+----------+----------+
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| body row 2 | ... | ... | you can |
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+------------------------+------------+----------+ easily +
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| body row 3 with a two column span | ... | span |
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+------------------------+------------+----------+ rows +
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| body row 4 | ... | ... | too |
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+------------------------+------------+----------+----------+
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This example would render as:
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+------------------------+------------+----------+----------+
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| Header row, column 1 | Header 2 | Header 3 | Header 4 |
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| (header rows optional) | | | |
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+========================+============+==========+==========+
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| body row 1, column 1 | column 2 | column 3 | column 4 |
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+------------------------+------------+----------+----------+
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| body row 2 | ... | ... | you can |
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+------------------------+------------+----------+ easily +
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| body row 3 with a two column span | ... | span |
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+------------------------+------------+----------+ rows +
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| body row 4 | ... | ... | too |
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+------------------------+------------+----------+----------+
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`List tables
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<http://docutils.sourceforge.net/docs/ref/rst/directives.html#list-table>`_
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are much easier to maintain, but don't support row or column spans::
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.. list-table:: Table title
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:widths: 15 20 40
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:header-rows: 1
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* - Heading 1
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- Heading 2
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- Heading 3
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* - body row 1, column 1
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- body row 1, column 2
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- body row 1, column 3
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* - body row 2, column 1
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- body row 2, column 2
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- body row 2, column 3
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This example would render as:
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.. list-table:: Table title
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:widths: 15 20 40
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:header-rows: 1
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* - Heading 1
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- Heading 2
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- Heading 3
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* - body row 1, column 1
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- body row 1, column 2
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- body row 1, column 3
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* - body row 2, column 1
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- body row 2, column 2
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- body row 2, column 3
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The ``:widths:`` parameter lets you define relative column widths. The
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default is equal column widths. If you have a three-column table and you
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want the first column to be half as wide as the other two equal-width
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columns, you can specify ``:widths: 1 2 2``. If you'd like the browser
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to set the column widths automatically based on the column contents, you
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can use ``:widths: auto``.
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File names and Commands
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***********************
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Sphinx extends reST by supporting additional inline markup elements (called
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"roles") used to tag text with special
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meanings and allow style output formatting. (You can refer to the `Sphinx Inline Markup`_
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documentation for the full list).
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For example, there are roles for marking :file:`filenames`
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(``:file:`name```) and command names such as :command:`make`
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(``:command:`make```). You can also use the \`\`inline code\`\`
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markup (double backticks) to indicate a ``filename``.
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For references to files that are in the Zephyr GitHub tree, a special
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role can be used that creates a hyperlink to that file. For example a
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reference to the reST file used to create this document can be generated
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using ``:zephyr_file:`doc/contribute/documentation/guidelines.rst``` that will
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show up as :zephyr_file:`doc/contribute/documentation/guidelines.rst`, a link to
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the "blob" file in the github repo. There's also a
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``:zephyr_raw:`doc/contribute/documentation/guidelines.rst``` role that will
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link to the "raw" content,
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:zephyr_raw:`doc/contribute/documentation/guidelines.rst`. (You can click on
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these links to see the difference.)
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.. _internal-linking:
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Internal Cross-Reference Linking
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********************************
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Traditional ReST links are only supported within the current file using the
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notation::
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Refer to the `internal-linking`_ page
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which renders as,
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Refer to the `internal-linking`_ page
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Note the use of a trailing
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underscore to indicate an outbound link. In this example, the label was
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added immediately before a heading, so the text that's displayed is the
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heading text itself. You can change the text that's displayed as the
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link writing this as::
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Refer to the `show this text instead <internal-linking_>`_ page
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which renders as,
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Refer to the `show this text instead <internal-linking_>`_ page
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External Cross-Reference Linking
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********************************
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With Sphinx's help, we can create
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link-references to any tagged text within the Zephyr Project documentation.
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Target locations in a document are defined with a label directive::
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.. _my label name:
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Heading
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=======
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Note the leading underscore indicating an inbound link.
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The content immediately following
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this label must be a heading, and is the target for a ``:ref:`my label name```
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reference from anywhere within the Zephyr documentation.
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The heading text is shown when referencing this label.
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You can also change the text that's displayed for this link, such as::
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:ref:`some other text <my label name>`
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To enable easy cross-page linking within the site, each file should have
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a reference label before its title so it can
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be referenced from another file. These reference labels must be unique
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across the whole site, so generic names such as "samples" should be
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avoided. For example the top of this document's .rst file is::
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.. _doc_guidelines:
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Documentation Guidelines for the Zephyr Project
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###############################################
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Other .rst documents can link to this document using the ``:ref:`doc_guidelines``` tag and
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it will show up as :ref:`doc_guidelines`. This type of internal cross reference works across
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multiple files, and the link text is obtained from the document source so if the title changes,
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the link text will update as well.
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You can also define links to any URL and then reference it in your document.
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For example, with this label definition in the document::
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.. _Zephyr Wikipedia Page:
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https://en.wikipedia.org/wiki/Zephyr_(operating_system)
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you can reference it with::
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Read the `Zephyr Wikipedia Page`_ for more information about the
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project.
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\`any\` links
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*************
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Within the Zephyr project, we've defined the default role to be "any",
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meaning if you just write a phrase in back-ticks, e.g.,
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```doc_guidelines```, Sphinx will search through all domains looking for
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something called doc_guidelines to link to. In this case it will find
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the label at the top of this document, and link to `doc_guidelines`.
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This can be useful for linking to doxygen-generated links for function
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names and such, but will cause a warning such as::
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WARNING: 'any' reference target not found: doc_giudelines
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if you misspelled ```doc_guidelines``` as ```doc_giudelines```.
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Non-ASCII Characters
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********************
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You can insert non-ASCII characters such as a Trademark symbol (|trade|),
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by using the notation ``|trade|``.
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Available replacement names are defined in an include file used during the Sphinx processing
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of the reST files. The names of these replacement characters are the same as used in HTML
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entities used to insert characters in HTML, e.g., \™ and are defined in the
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file ``sphinx_build/substitutions.txt`` as listed here:
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.. literalinclude:: ../../substitutions.txt
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:language: rst
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We've kept the substitutions list small but others can be added as
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needed by submitting a change to the ``substitutions.txt`` file.
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Code and Command Examples
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*************************
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Use the reST ``code-block`` directive to create a highlighted block of
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fixed-width text, typically used for showing formatted code or console
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commands and output. Smart syntax highlighting is also supported (using the
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Pygments package). You can also directly specify the highlighting language.
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For example::
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.. code-block:: c
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struct k_object {
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char *name;
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uint8_t perms[CONFIG_MAX_THREAD_BYTES];
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uint8_t type;
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uint8_t flags;
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uint32_t data;
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} __packed;
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Note the blank line between the ``code-block`` directive and the first
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line of the code-block body, and the body content is indented three
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spaces (to the first non-white space of the directive name).
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This would be rendered as:
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.. code-block:: c
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struct k_object {
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char *name;
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uint8_t perms[CONFIG_MAX_THREAD_BYTES];
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uint8_t type;
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uint8_t flags;
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uint32_t data;
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} __packed;
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Other languages are of course supported (see `languages supported by Pygments`_), and in particular,
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you are encouraged to make use of the following when appropriate:
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.. _`languages supported by Pygments`: http://pygments.org/languages/
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* ``c`` for C code
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* ``cpp`` for C++ code
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* ``python`` for Python code
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* ``console`` for console output, i.e. interactive shell sessions where commands are prefixed by a
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prompt (ex. ``$`` for Linux, or ``uart:~$`` for Zephyr's shell), and where the output is also
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shown. The commands will be highlighted, and the output will not. What's more, copying code block
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using the "copy" button will automatically copy just the commands, excluding the prompt and the
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outputs of the commands.
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* ``shell`` or ``bash`` for shell commands. Both languages get highlighted the same but you may use
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``bash`` for conveying that the commands are bash-specific, and ``shell`` for generic shell
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commands.
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.. note::
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Do not use ``bash`` or ``shell`` if your code block includes a prompt, use ``console`` instead.
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Reciprocally, do not use ``console`` if your code block does not include a prompt and is not
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showcasing an interactive session with command(s) and their output.
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.. list-table:: When to use ``bash``/``shell`` vs. ``console``
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:class: wrap-normal
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:header-rows: 1
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:widths: 20,40,40
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* - Use case
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- ``code-block`` snippet
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- Expected output
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* - One or several commands, no output
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- .. code-block:: rst
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.. code-block:: shell
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echo "Hello World!"
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- .. code-block:: shell
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echo "Hello World!"
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* - An interactive shell session with command(s) and their output
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- .. code-block:: rst
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.. code-block:: console
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$ echo "Hello World!"
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Hello World!
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- .. code-block:: console
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$ echo "Hello World!"
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Hello World!
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* - An interactive Zephyr shell session, with commands and their outputs
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- .. code-block:: rst
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.. code-block:: console
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uart:~$ version
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Zephyr version 3.5.99
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uart:~$ kernel uptime
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Uptime: 20970 ms
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- .. code-block:: console
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uart:~$ version
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Zephyr version 3.5.99
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uart:~$ kernel uptime
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Uptime: 20970 ms
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* ``bat`` for Windows batch files
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* ``cfg`` for config files with "KEY=value" entries (ex. Kconfig ``.conf`` files)
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* ``cmake`` for CMake
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* ``devicetree`` for Devicetree
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* ``kconfig`` for Kconfig
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* ``yaml`` for YAML
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* ``rst`` for reStructuredText
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When no language is specified, the language is set to ``none`` and the code block is not
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highlighted. You may also use ``none`` explicitly to achieve the same result; for example::
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.. code-block:: none
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This would be a block of text styled with a background
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and box, but with no syntax highlighting.
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Would display as:
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.. code-block:: none
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This would be a block of text styled with a background
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and box, but with no syntax highlighting.
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There's a shorthand for writing code blocks too: end the introductory paragraph with a double colon
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(``::``) and indent the code block content that follows it by three spaces. On output, only one
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colon will be shown. The code block will have no highlighting (i.e. ``none``). You may however use
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the ``.. highlight::`` directive to customize the default language used in your document (see for
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example how this is done at the beginning of this very document).
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Images
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******
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Images are included in documentation by using an image directive::
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.. image:: ../../images/doc-gen-flow.png
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:align: center
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:alt: alt text for the image
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or if you'd like to add an image caption, use::
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.. figure:: ../../images/doc-gen-flow.png
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:alt: image description
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Caption for the figure
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The file name specified is relative to the document source file,
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and we recommend putting images into an ``images`` folder where the document
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source is found. The usual image formats handled by a web browser are
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supported: JPEG, PNG, GIF, and SVG. Keep the image size only as large
|
|
as needed, generally at least 500 px wide but no more than 1000 px, and
|
|
no more than 250 KB unless a particularly large image is needed for
|
|
clarity.
|
|
|
|
Tabs, spaces, and indenting
|
|
***************************
|
|
|
|
Indenting is significant in reST file content, and using spaces is
|
|
preferred. Extra indenting can (unintentionally) change the way content
|
|
is rendered too. For lists and directives, indent the content text to
|
|
the first non-white space in the preceding line. For example::
|
|
|
|
* List item that spans multiple lines of text
|
|
showing where to indent the continuation line.
|
|
|
|
1. And for numbered list items, the continuation
|
|
line should align with the text of the line above.
|
|
|
|
.. code-block::
|
|
|
|
The text within a directive block should align with the
|
|
first character of the directive name.
|
|
|
|
Refer to the Zephyr :ref:`coding_style` for additional requirements.
|
|
|
|
zephyr-app-commands Directive
|
|
*****************************
|
|
|
|
.. include:: ../../_extensions/zephyr/application.py
|
|
:start-line: 10
|
|
:start-after: '''
|
|
:end-before: '''
|
|
|
|
For example, the ``.. zephyr-app-commands`` listed above would
|
|
render like this in the generated HTML output:
|
|
|
|
.. zephyr-app-commands::
|
|
:zephyr-app: samples/hello_world
|
|
:board: qemu_x86
|
|
:goals: build
|
|
|
|
Alternative Tabbed Content
|
|
**************************
|
|
|
|
As introduced in the :ref:`getting_started`, you can provide alternative
|
|
content to the reader via a tabbed interface. When the reader clicks on
|
|
a tab, the content for that tab is displayed, for example::
|
|
|
|
.. tabs::
|
|
|
|
.. tab:: Apples
|
|
|
|
Apples are green, or sometimes red.
|
|
|
|
.. tab:: Pears
|
|
|
|
Pears are green.
|
|
|
|
.. tab:: Oranges
|
|
|
|
Oranges are orange.
|
|
|
|
will display as:
|
|
|
|
.. tabs::
|
|
|
|
.. tab:: Apples
|
|
|
|
Apples are green, or sometimes red.
|
|
|
|
.. tab:: Pears
|
|
|
|
Pears are green.
|
|
|
|
.. tab:: Oranges
|
|
|
|
Oranges are orange.
|
|
|
|
Tabs can also be grouped, so that changing the current tab in one area
|
|
changes all tabs with the same name throughout the page. For example:
|
|
|
|
.. tabs::
|
|
|
|
.. group-tab:: Linux
|
|
|
|
Linux Line 1
|
|
|
|
.. group-tab:: macOS
|
|
|
|
macOS Line 1
|
|
|
|
.. group-tab:: Windows
|
|
|
|
Windows Line 1
|
|
|
|
.. tabs::
|
|
|
|
.. group-tab:: Linux
|
|
|
|
Linux Line 2
|
|
|
|
.. group-tab:: macOS
|
|
|
|
macOS Line 2
|
|
|
|
.. group-tab:: Windows
|
|
|
|
Windows Line 2
|
|
|
|
In this latter case, we're using ``.. group-tab::`` instead of simply
|
|
``.. tab::``. Under the hood, we're using the `sphinx-tabs
|
|
<https://github.com/djungelorm/sphinx-tabs>`_ extension that's included
|
|
in the Zephyr setup. Within a tab, you can have most any content *other
|
|
than a heading* (code-blocks, ordered and unordered lists, pictures,
|
|
paragraphs, and such). You can read more about sphinx-tabs from the
|
|
link above.
|