Vulkan-Docs/styleguide.txt

// Copyright (c) 2014-2019 Khronos Group. This work is licensed under a
// Creative Commons Attribution 4.0 International License; see
// http://creativecommons.org/licenses/by/4.0/

= Vulkan^®^ Documentation and Extensions: Procedures and Conventions
Jon Leech, Tobias Hector
:data-uri:
:icons: font
:toc2:
:toclevels: 3
:max-width: 100
:numbered:
:doctype: book
:imagewidth: 800
:fullimagewidth: width="800"
:cl: :

// Various special / math symbols. This is easier to edit with than Unicode.
include::config/attribs.txt[]

:leveloffset: 1

<<<<

include::copyright-ccby.txt[]

<<<<

[[introduction]]
= Introduction

This document contains required procedures and conventions when writing
specifications for new Vulkan APIs, extensions and layers, or related
Khronos^{reg}^ documentation such as white papers and tutorials; or
contributing to existing Vulkan specifications.
These are collectively referred to as _Vulkan Documentation_ or just
_documentation_ below.
The primary focus is the API Specification and API extensions, although all
of the markup and most of the writing style is equally applicable to other
documentation.

The primary purpose is to achieve consistency across the API, as well as
across all of our source and output documents.
Consistency makes it easier for developers, editors, reviewers, and users of
our documentation to understand and modify it.

This document is now formally voted on and approved by the Vulkan Working
Group.
This means that unless explicitly stated otherwise, the procedures and
conventions must be followed.
If you have a strong desire to modify the procedures and conventions, such
changes must be made through the normal Vulkan Working Group processes.


[[introduction-terminology]]
== Terminology

The key words *must*, *required*, *should*, *recommend*, *may*, and
*optional* in this document are to be interpreted as described in RFC 2119
and by the Vulkan 1.1 Specification in the "`Terminology`" section.


[[introduction-structure]]
== Document Structure

The style guide is broken into four sections:

  * <<naming,API Naming Conventions>> - the required rules for choosing
    names of Vulkan identifiers of all types.
  * <<extensions,Extensions and Layers>> - the required procedures for
    creating formal Vulkan extensions and layers.
  * <<markup,Markup Style>> - the required and recommended markup style for
    writing asciidoc and XML source that follows consistent formatting and
    layout guidelines, tags special terms and phrases for proper processing
    by the spec generation tools, etc.
  * <<writing,Writing Style>> - the required and recommended writing style
    for overall and fine-grained structure and conventions, normative
    language use, API naming conventions, common words and phrases to use
    and to avoid, linking and cross-referencing, etc.


[[introduction-asciidoc]]
== Asciidoc Markup

Vulkan Documentation is primarily written in Asciidoc, a form of text markup
language.
Specifically we're using the version of Asciidoc that is actively maintained
by asciidoctor, which is documented on its website at
https://asciidoctor.org.

References to the Asciidoctor User Manual are to sections in the document at
https://asciidoctor.org/docs/user-manual/.

Asciidoctor is implemented in Ruby (https://www.ruby-lang.org/), which is
available for Linux, MacOS, and Microsoft Windows.
Multiple preview tools also exist for the language, primarily using
AsciidoctorJ (https://github.com/asciidoctor/asciidoctorj) or asciidoctor.js
(https://github.com/asciidoctor/asciidoctor.js).
In particular, GitHub and GitLab both have asciidoc previews for .adoc or
.asciidoc files in repositories, and live preview extensions exist for
Chrome and Firefox.

The Asciidoctor toolchain and build process are not addressed by this
document, which concentrates solely on source documents.


[[introduction-normative]]
== Normative References

Normative references are references to external documents or resources to
which documentation authors must comply.

[[acm-references]]
Association for Computing Machinery.
_Citation Style and Reference Formats_.
Retrieved July 27, 2019.
https://www.acm.org/publications/authors/reference-formatting .

[[iso-8601]]
International Organization for Standardization.
_Data elements and interchange formats -- Information interchange --
Representation of dates and times_ (2004-12-01).
https://www.iso.org/standard/40874.html .
Also see https://www.w3.org/QA/Tips/iso-date for colloquial examples.

[[vulkan-docs]]
Khronos Vulkan Working Group.
`KhronosGroup/Vulkan-Docs` project on GitHub (July 5, 2016).
https://github.com/KhronosGroup/Vulkan-Docs .

[[vulkan-spec]]
Khronos Vulkan Working Group.
_Vulkan 1.1.116 - A Specification_ (July 20, 2019).
https://www.khronos.org/registry/vulkan/ .

Version 1.1.116 is the latest patch release of the Vulkan API Specification
as of the time this reference was created, but that Specification is
frequently updated with minor bugfixes and clarifications.
When a more recent patch release is made, it becomes the normative reference
for the API.


// Chapters of the text are included below

include::style/naming.txt[]

include::style/extensions.txt[]

include::style/markup.txt[]

include::style/writing.txt[]

include::style/misc.txt[]

// Appendices are included below
include::style/vuid.txt[]


= Revision History

* 2019-08-13 - Add a NOTE to the <<appendix-vuid-format, Format of VUID
  Tags>> appendix specifying allowed characters in VUID tags (based on
  discussion for internal merge request 3239).
* 2019-07-27 - Add the <<writing-references, References>> section and
  rewrite external references accordingly.
* 2019-05-09 - Specify rules for defining <<extensions-new-flags-types, new
  bitmask and flags types (internal issue 1649).
* 2019-01-06 - Add details on <<extensions-reserving-bitmask-values,
  Reserving Bitmask Values>> (internal issue 1411).
* 2018-11-19 - Add details to the <<extensions-documenting-extensions,
  Changes for New Extensions>> section including the new "`Description`"
  section, and other standard parts of extension appendices.
* 2018-08-13 - Add %inline directive to the <<markup-sample-section-images,
  Figures>> section (public pull request 734).
* 2018-07-30 - Added a section on <<writing-undefined, Describing Undefined
  Behavior>> (as part of the fixes for public issue 379), and describing why
  the undefined{cl} macro should always be used.
* 2018-07-08 - Remove requirement to explicitly include extension appendices
  in the <<extensions-documenting-extensions, Changes for New Extensions>>
  section.
* 2018-06-25 - Modify the process for <<extensions-vendor-id, Registering a
  Vendor ID with Khronos>> to define vendor ID values as part of an
  enumerated type.
* 2018-03-07 - Updated for Vulkan 1.1 release.
* 2018-01-10 - Move details of mandated extension compatibility from the
  <<extensions-rules, General Rules/Guidelines>> section into the
  Fundamentals section of the API Specification, where they are changed
  slightly to allow explicit incompatibilies (public issue 638).
* 2017-10-27 - Add language about proper use of "`valid pointer`" and
  "`pointer to valid object`" for valid usage statements, in the
  <<sample-command, Sample Command Description>> section (related to public
  pull request 547).
* 2017-10-15 - Describe how to write <<writing-latexmath-in-table-cells,
  LaTeX Math in Table Cells>> (internal issue 908).
* 2017-10-15 - Add more details of <<extensions-naming-author-IDs, `KHX`
  extensions>> (public issues 536, 580).
* 2017-09-10 - Add descriptions of <<writing-arrays, how to use `each` and
  `any`>> to refer to properties of elments of arrays (internal issue 884).
* 2017-09-10 - Add <<extensions-interactions-parent, Valid Usage and
  Extension pname:pNext Chains>> language specifying where to describe
  interactions of structures in a pname:pNext chain (internal issue 715).
* 2017-09-10 - Add example of marking up an enumerated type all of whose
  values are defined by extensions (internal issue 864).
* 2017-08-25 - Add language to the <<extensions,API Versions, Extensions,
  and Layers>> chapter describing how to write new API versions (internal
  issue 892).
* 2017-06-12 - Add sections describing when to use the
  <<markup-macros-api-name, *name{cl}>> and <<markup-macros-api-text,
  *text{cl}>> markup macros instead of the *link{cl} macros, and clarify
  that slink{cl} should be used for handle as well as structure names
  (internal issue 886).
* 2017-05-08 - Add appendix describing <<appendix-vuid, Valid Usage ID
  Tags>> and how they're generated.
* 2017-03-19 - Add naming rule for <<naming-extension-structures, Extension
  Structure Names>>.
* 2017-02-11 - Finish transitioning to asciidoctor markup.
* 2016-09-28 - Add asciidoc math markup guidelines.
* 2016-09-16 - Make style guide markup more consistent with its own
  recommendations.
  Simplify some tables of preferred terms.
  Add sections on block and table markup.
* 2016-09-12 - Describe writing and markup style for labelled lists.
  Require use of the ISO 8601 date format except in rare legacy cases.
  Expand the description of <<markup-layout,Line Lengths>> and add a
  description of markup for <<markup-footnotes,Footnotes>>.
* 2016-09-08 - Add a writing section about proper use of
  <<writing-misc-a-an,"`a`" and "`an`">> (internal issue 432).
* 2016-08-30 - Remove mustnot{cl} and shouldnot{cl} macro definitions, which
  are no longer used in the Specification (internal issue 407).
* 2016-08-29 - Add spelling and compound word rules (public issue 352).
* 2016-08-23 - Modify description of specifying extensions in the
  <<extensions,Layers and Extensions>> chapter to refer to the new
  single-branch model for extensions (internal issue 397).
* 2016-07-26 - Add section describing <<writing-refpages,markup for
  automatic reference page extraction>>.
* 2016-07-18 - Add examples of function-parameter and structure-member
  markup (based on public issue 286).
* 2016-07-11 - Change the document title.
* 2016-07-07 - Rename document, change license to CC BY, clarify required
  and recommended actions, and reserve use of "`normative`" for the
  Specifications.
* 2016-06-26 - Move Layers and Extensions chapter from Appendix C of the
  Vulkan API Specification and merge content with the naming guide.
  Put extension and naming chapters into their own source files.
* 2016-06-20 - Add API naming guide.
* 2016-05-22 - Add markup and image creation rules, after fixing missing
  figure captions for public issue 219.
* 2016-05-01 - Include feedback from public issues 120 and 190.
  Use consistent conventions for defining structures.
  Use American rather than British spelling conventions.
* 2016-03-12 - Recommend against "the value of".
* 2016-02-26 - Replace use of the "maynot{cl}" macro with "may{cl} not".
* 2016-02-16 - Place asciidoc conversion post-release.
* 2016-02-09 - Added quotation mark convention.
* 2016-02-01 - Add the Oxford Comma section and issue resolution.
* 2016-01-26 - Add bullet-list style description of command parameters.
* 2016-01-11 - Add "`Numbers in Text`" section from WSI work.
* 2015-12-16 - Make "`begin / end`" preferred terms to "`start / finish`".
* 2015-12-15 - Make "`implementation`" preferred term instead of "`system`".
* 2015-12-13 - Add tlink{cl}/tname{cl} macros for function pointer types.
* 2015-12-10 - Initial release for feedback.