// Copyright 2017-2021 The Khronos Group Inc. // SPDX-License-Identifier: CC-BY-4.0

= OpenGL-Registry

== OpenGL, OpenGL ES, and OpenGL ES-SC API and Extension Registry

This site contains the API and Extension registries for the OpenGL family APIs - OpenGL, OpenGL ES, and OpenGL SC. It includes API specifications; specifications of Khronos- and vendor-approved extensions; header files corresponding to the specifications; the XML API Registry defining each API; and related tools and scripts.

It does not contain the OpenGL and OpenGL ES Reference Pages, which are in the KhronosGroup/OpenGL-Refpages repository.

If you want to add an extension specification to the Registry, correct an existing specification, request allocation of enumerants and other controlled resources in the OpenGL / GLX / WGL namespaces, or otherwise change the Registry, propose a pull request against the OpenGL-Registry repository and adding the appropriate extension specifications, making changes to the appropriate XML file, etc. Note that any changes you propose to reserved values in the registry are not official until your pull request is accepted into the main branch.

Feel free to post issues on the repository if it's unclear how to do something you need to with extensions, or if you find any problems.

== Please Don't File API And GLSL Bugs Here!

The OpenGL-Registry repository isn't the right place to report problems with the OpenGL and OpenGL ES API and Shading Language Specifications.

For API (both core and extension) issues, please use the issue tracker in the https://github.com/KhronosGroup/OpenGL-API repository.

For Shading Language (both core and extension) issues, please use the issue tracker in the https://github.com/KhronosGroup/OpenGL-GLSL repository.

Please tag your issues with +[OpenGL]+ or +[OpenGL ES]+ in the title, if they are specific to that API and/or Shading Language.

Reporting problems with the registry itself, including missing or badly formed extension documents, headers, or XML files, should be done using the OpenGL-Registry issue tracker.

=== Defining New Extensions

To create a new extension specification, take these steps:

• Request one or more blocks of unused enumerants for GL, GLX, or WGL depending on the needs of your extension, by adding the reservation(s) to the end of gl.xml, glx.xml, and/or wgl.xml.
• Once the pull request modifying the XML files is accepted into main, you have control of those enumerant blocks.
• Create an extension specification, following the model of existing vendor specifications under extensions/vendor/ .
• Obtain whatever degree of review, implementation, and signoff you need from affected parties before declaring the extension complete.
• Add the extension specification under extensions/vendor/extension .
• Modify extensions/registry.py to include the extension, using the next free ARB, GL, and/or ES extension numbers (depending on which API the extension is defined for). Execute the python script nextfree.py in the extensions/ directory to find the next free numbers.
• Once registry.py is updated, 'make' in extensions/ to update the PHP include files which are used to show an index of extensions on the registry website. This requires GNU make and Python 3.
• Add the extension number(s) to the extension specification in the 'Number' block.
• Add the extension interfaces and enumerant assignments to xml/gl.xml, glx.xml, and/or wgl.xml following existing examples. Verify that the relevant extension headers are generated with the correct interfaces by running 'make' in xml/. This requires the lxml Python module.
• Once the pull request adding the extension specification and modifying registry.py is accepted, your extension is registered.

There are some documents under the docs/ directory describing some of the processes for making extensions, but they are largely out of date. They may be updated or removed over time:

• link:docs/rules.html[How to create extensions]
• link:docs/enums.html[Enumerant allocation policies]
• link:docs/template.txt[Extension specification template]
• link:docs/promoting.html[Extension promotion guidelines]
• link:docs/reserved.txt[GLX opcode registry (rarely updated)]
• link:docs/syntaxrules.txt[OpenGL Syntax Rules (updated 2006/12/13)]
• link:docs/GLSLExtensionRules.txt[OpenGL Shading Language Extension Conventions (updated 2006/12/18)]
• link:docs/fog_coord.txt[Extension Specification Example]

=== Repository Contents

• ABI - OpenGL ABI for Linux
• api - Header files for all APIs api/ES - Headers for OpenGL ES api/GL - Headers for OpenGL api/SC - Headers for OpenGL SC Note that the OpenGL ES and OpenGL SC headers all depend on the shared https://www.khronos.org/registry/EGL/api/KHR/khrplatform.h[khrplatform.h] This file is maintained in the http://www.khronos.org/registry/EGL/[EGL Registry].
• docs - Miscellaneous documentation on creating extensions, mostly out of date.
• extensions - Extension specifications for all APIs extensions/registry.py - combined extension registry for all APIs extensions/makeindex.py - create HTML extension indices from registry.py
• index_{es,gl,sc}.php - Index files for the website, linking to specifications, headers, and extensions relevant to each API
• specs - API and Shading Language Specifications for all APIs specs/es - OpenGL ES Specifications specs/gl - OpenGL Specifications ** specs/sc - OpenGL SC Specifications
• xml - XML API Registry and related tools

=== There Sure Is A Lot Of Stuff In Here!

Yes, there sure is. The specs/ directory contains over 125 MB of PDFs, including the latest specs for each version of OpenGL and OpenGL ES. While this may be somewhat distressing to people who just want to add a single extension, due to the repository download time, the primary purpose of this repository is to be the backing store for the web registry on khronos.org. Fortunately git is very efficient, so once you've done the initial repository clone, updates will be small and quick.