Commit 72416979 authored by Pekka Paalanen's avatar Pekka Paalanen
Browse files

README: updates on libweston versioning



We have agreed to use the major as the ABI-version, so talk about major
to avoid confusion.

Remove unncessary or incorrect wording related to breaking ABI on minor
bumps.

Explain a little about the weston vs. libweston version numbers.

v2:
- Add a paragraph about ABI breaks between alpha and .0 releases.
- clarify pre-release definition
- Add two paragraphs about libweston versions differing from weston
  version and how to use pkg-config properly.
Signed-off-by: Pekka Paalanen's avatarPekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Morgane Glidic's avatarQuentin Glidic <sardemff7+git@sardemff7.net>
Reviewed-by: Jonas Ådahl's avatarJonas Ådahl <jadahl@gmail.com>
Reviewed-by: Emil Velikov's avatarEmil Velikov <emil.velikov@collabora.com>
parent bfb392e0
......@@ -36,7 +36,7 @@ input and output systems, so that people who just want to write a new
"Wayland window manager" (WM) or a small desktop environment (DE) can
focus on the WM part.
Libweston was first introduced in Weston 1.9, and is expected to
Libweston was first introduced in Weston 1.12, and is expected to
continue evolving through many Weston releases before it achieves a
stable API and feature completeness.
......@@ -45,23 +45,24 @@ API/ABI (in)stability and parallel installability
-------------------------------------------------
As libweston's API surface is huge, it is impossible to get it right
in one go. Therefore developers reserve the right to break the API/ABI
between every 1.x.0 Weston release (minor version bumps), just like
Weston's plugin API does. For git snapshots of the master branch, the
API/ABI can break any time without warning or version bump.
in one go. Therefore developers reserve the right to break the API/ABI and bump
the major version to signify that. For git snapshots of the master branch, the
API/ABI can break any time without warning.
Libweston API or ABI will not be broken between Weston's stable
releases 1.x.0 and 1.x.y, where y < 90.
Libweston major can be bumped only once during a development cycle. This should
happen on the first patch that breaks the API or ABI. Further breaks before the
next Weston major.0.0 release do not cause a bump. This means that libweston
API and ABI are allowed to break also after an alpha release, up to the final
release. However, breaks after alpha should be judged by the usual practices
for allowing minor features, fixes only, or critical fixes only.
To make things tolerable for libweston users despite API/ABI breakages,
libweston is designed to be perfectly parallel-installable. An
API/ABI-version is defined for libweston, and it is bumped for releases as
needed. Different non-backward compatible ABI versions of libweston can be
installed in parallel, so that external projects can easily depend on a
particular ABI-version. Thus they do not have to fight over which ABI-version
is installed in a user's system. This allows a user to install many
different compositors each requiring a different libweston ABI-version
without tricks or conflicts.
different libweston major versions are designed to be perfectly
parallel-installable. This way external projects can easily depend on a
particular API/ABI-version. Thus they do not have to fight over which
ABI-version is installed in a user's system. This allows a user to install many
different compositors each requiring a different libweston ABI-version without
tricks or conflicts.
Note, that versions of Weston itself will not be parallel-installable,
only libweston is.
......@@ -82,6 +83,26 @@ The document provides the full details, with the gist summed below:
- Minor - new backward compatible features.
- Patch - internal (implementation specific) fixes.
Weston and libweston have separate version numbers in configure.ac. All
releases are made by the Weston version number. Libweston version number
matches the Weston version number in all releases except maybe pre-releases.
Pre-releases have the Weston micro version 91 or greater.
A pre-release is allowed to install a libweston version greater than the Weston
version in case libweston major was bumped. In that case, the libweston version
must be Weston major + 1 and with minor and patch versions zero.
Pkg-config files are named after libweston major, but carry the Weston version
number. This means that Weston pre-release 2.1.91 may install libweston-3.pc
for the future libweston 3.0.0, but the .pc file says the version is still
2.1.91. When a libweston user wants to depend on the fully stable API and ABI
of a libweston major, he should use (e.g. for major 3):
PKG_CHECK_MODULES(LIBWESTON, [libweston-3 >= 3.0.0])
Depending only on libweston-3 without a specific version number still allows
pre-releases which might have different API or ABI.
Forward compatibility
---------------------
......
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