Wayland protocols ----------------- wayland-protocols contains Wayland protocols that add functionality not available in the Wayland core protocol. Such protocols either add completely new functionality, or extend the functionality of some other protocol either in Wayland core, or some other protocol in wayland-protocols. A protocol in wayland-protocols consists of a directory containing a set of XML files containing the protocol specification, and a README file containing detailed state and a list of maintainers. Protocol directory tree structure ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Protocols may be 'stable', 'unstable' or 'deprecated', and the interface and protocol names as well as place in the directory tree will reflect this. A stable protocol is a protocol which has been declared stable by the maintainers. Changes to such protocols will always be backward compatible. An unstable protocol is a protocol currently under development and this will be reflected in the protocol and interface names. See <<Unstable naming convention>>. A deprecated protocol is a protocol that has either been replaced by some other protocol, or declared undesirable for some other reason. No more changes will be made to a deprecated protocol. Depending on which of the above states the protocol is in, the protocol is placed within the toplevel directory containing the protocols with the same state. Stable protocols are placed in the +stable/+ directory, unstable protocols are placed in the +unstable/+ directory, and deprecated protocols are placed in the +deprecated/+ directory. Protocol development procedure ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To propose a new protocol, create a GitLab merge request adding the relevant files and Makefile.am entry to the repository with the explanation and motivation in the commit message. Protocols are organized in namespaces describing their scope ("wp", "xdg" and "ext"). There are different requirements for each namespace, see GOVERNANCE section 2 for more information. If the new protocol is just an idea, open an issue on the GitLab issue tracker. If the protocol isn't ready for complete review yet and is an RFC, create a merge request and add the "WIP:" prefix in the title. To propose changes to existing protocols, create a GitLab merge request. If the changes are backward incompatible changes to an unstable protocol, see <<Unstable protocol changes>>. Interface naming convention ~~~~~~~~~~~~~~~~~~~~~~~~~~~ All protocols should avoid using generic namespaces or no namespaces in the protocol interface names in order to minimize risk that the generated C API collides with other C API. Interface names that may collide with interface names from other protocols should also be avoided. For generic protocols not limited to certain configurations (such as specific desktop environment or operating system) the +wp_+ prefix should be used on all interfaces in the protocol. For protocols allowing clients to configure how their windows are managed, the +xdg_+ prefix should be used. For operating system specific protocols, the interfaces should be prefixed with both +wp_+ and the operating system, for example +wp_linux_+, or +wp_freebsd_+, etc. For more information about namespaces, see GOVERNANCE section 2.1. Unstable naming convention ~~~~~~~~~~~~~~~~~~~~~~~~~~ Unstable protocols have a special naming convention in order to make it possible to make discoverable backward incompatible changes. An unstable protocol has at least two versions: the major version, which represents backward incompatible changes, and the minor version, which represents backward compatible changes to the interfaces in the protocol. The major version is part of the XML file name, the protocol name in the XML, and interface names in the protocol. Minor versions are the version attributes of the interfaces in the XML. There may be more than one minor version per protocol, if there are more than one global. The XML file and protocol name also has the word 'unstable' in them, and all of the interfaces in the protocol are prefixed with +z+ and suffixed with the major version number. For example, an unstable protocol called foo-bar with major version 2 containing the two interfaces wp_foo and wp_bar both minor version 1 will be placed in the directory +unstable/foo-bar/+ consisting of one file called +README+ and one called +foo-bar-unstable-v2.xml+. The XML file will consist of two interfaces called +zwp_foo_v2+ and +zwp_bar_v2+ with the +version+ attribute set to +1+. Unstable protocol changes ~~~~~~~~~~~~~~~~~~~~~~~~~ During the development of a new protocol it is possible that backward incompatible changes are needed. Such a change needs to be represented in the major and minor versions of the protocol. Assuming a backward incompatible change is needed, the procedure for how to do so is the following: . Make a copy of the XML file with the major version increased by +1+. . Increase the major version number in the protocol XML by +1+. . Increase the major version number in all of the interfaces in the XML by +1+. . Reset the minor version number (interface version attribute) of all the interfaces to +1+. Backward compatible changes within a major unstable version can be done in the regular way as done in core Wayland or in stable protocols. Declaring a protocol stable ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Once it is decided that a protocol should be declared stable, meaning no more backward incompatible changes will ever be allowed, one last breakage is needed. The procedure of doing this is the following: . Create a new directory in the +stable/+ toplevel directory with the same name as the protocol directory in the +unstable/+ directory. . Copy the final version of the XML that is the version that was decided to be declared stable into the new directory. The target name should be the same name as the protocol directory but with the +.xml+ suffix. . Rename the name of the protocol in the XML by removing the 'unstable' part and the major version number. . Remove the +z+ prefix and the major version number suffix from all of the interfaces in the protocol. . Reset all of the interface version attributes to +1+. . Update the +README+ file in the unstable directory and create a new +README+ file in the new directory. There are other requirements for declaring a protocol stable, see GOVERNANCE section 2.3. Releases ~~~~~~~~ Each release of wayland-protocols finalizes the version of the protocols to their state they had at that time.