611 lines
19 KiB
ReStructuredText
611 lines
19 KiB
ReStructuredText
.. _doc_guidelines:
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Documentation Guidelines
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########################
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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 build the documentation using the Makefile
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on Linux systems, or make.bat on Windows, to
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generate the HTML content. The HTML content can then be viewed using a
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web browser. This same .rst content is also fed into the
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`Zephyr documentation`_ website (with a different theme applied).
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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/guides/documentation/index.rst\``` that will
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show up as :zephyr_file:`doc/guides/documentation/index.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/guides/documentation/index.rst\``` role that will
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link to the "raw" content,
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:zephyr_file:`doc/guides/documentation/index.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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.. code-block:: rst
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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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.. code-block:: rst
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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 z_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 z_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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You can specify other languages for the ``code-block`` directive,
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including ``c``, ``python``, and ``rst``, and also ``console``,
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``bash``, or ``shell``. If you want no syntax highlighting, use the
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language ``none``, 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
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paragraph with a double colon (``::``) and indent the code block content
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by three spaces. On output, only one colon will be shown. The
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highlighting package makes a best guess at the type of content in the
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block and highlighting purposes.
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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
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as needed, generally at least 500 px wide but no more than 1000 px, and
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no more than 250 KB unless a particularly large image is needed for
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clarity.
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Tabs, spaces, and indenting
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***************************
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Indenting is significant in reST file content, and using spaces is
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preferred. Extra indenting can (unintentionally) change the way content
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is rendered too. For lists and directives, indent the content text to
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the first non-white space in the preceding line. For example::
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* List item that spans multiple lines of text
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showing where to indent the continuation line.
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1. And for numbered list items, the continuation
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line should align with the text of the line above.
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.. code-block::
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The text within a directive block should align with the
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first character of the directive name.
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Keep the line length for documentation less than 80 characters to make
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it easier for reviewing in GitHub. Long lines because of URL references
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are an allowed exception.
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zephyr-app-commands Directive
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*****************************
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.. include:: ../../extensions/zephyr/application.py
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:start-line: 10
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:start-after: '''
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:end-before: '''
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For example, the ``.. zephyr-app-commands`` listed above would
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render like this in the generated HTML output:
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.. zephyr-app-commands::
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:zephyr-app: samples/hello_world
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:board: qemu_x86
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:goals: build
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Alternative Tabbed Content
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**************************
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As introduced in the :ref:`getting_started`, you can provide alternative
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content to the reader via a tabbed interface. When the reader clicks on
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a tab, the content for that tab is displayed, for example::
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.. tabs::
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.. tab:: Apples
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Apples are green, or sometimes red.
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.. tab:: Pears
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Pears are green.
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.. tab:: Oranges
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Oranges are orange.
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will display as:
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.. tabs::
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.. tab:: Apples
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Apples are green, or sometimes red.
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.. tab:: Pears
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Pears are green.
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.. tab:: Oranges
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Oranges are orange.
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Tabs can also be grouped, so that changing the current tab in one area
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changes all tabs with the same name throughout the page. For example:
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.. tabs::
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.. group-tab:: Linux
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Linux Line 1
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.. group-tab:: macOS
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macOS Line 1
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.. group-tab:: Windows
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Windows Line 1
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.. tabs::
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.. group-tab:: Linux
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Linux Line 2
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.. group-tab:: macOS
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macOS Line 2
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.. group-tab:: Windows
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Windows Line 2
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In this latter case, we're using ``.. group-tab::`` instead of simply
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``.. tab::``. Under the hood, we're using the `sphinx-tabs
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<https://github.com/djungelorm/sphinx-tabs>`_ extension that's included
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in the Zephyr setup. Within a tab, you can have most any content *other
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than a heading* (code-blocks, ordered and unordered lists, pictures,
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paragraphs, and such). You can read more about sphinx-tabs from the
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link above.
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Instruction Steps
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*****************
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Also introduced in the :ref:`getting_started` is a style that makes it
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easy to create tutorial guides with clearly identified steps. Add
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the ``.. rst-class:: numbered-step`` directive immediately before a
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second-level heading (by project convention, a heading underlined with
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asterisks ``******``, and it will be displayed as a numbered step,
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sequentially numbered within the document. For example::
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.. rst-class:: numbered-step
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|
Put your right hand in
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**********************
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.. rst-class:: numbered-step
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|
Put your right hand in
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**********************
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See the :zephyr_raw:`doc/getting_started/index.rst` source file and compare
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with the :ref:`getting_started` to see a full example. As implemented,
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only one set of numbered steps is intended per document.
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For instructions on building the documentation, see :ref:`zephyr_doc`.
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