[PATCH weston] README: introduce libweston
giuliocamuffo at gmail.com
Wed Jul 15 00:51:34 PDT 2015
Hi, one comment below but it looks ok to me, also with Bryce's comments.
2015-07-14 13:07 GMT+03:00 Pekka Paalanen <ppaalanen at gmail.com>:
> From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> What is libweston and where do we intend to go with it.
> Cc: Giulio Camuffo <giuliocamuffo at gmail.com>
> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> README | 139 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 138 insertions(+), 1 deletion(-)
> diff --git a/README b/README
> index 3821e5d..beab3df 100644
> --- a/README
> +++ b/README
> @@ -1,4 +1,5 @@
> + Weston
> + ======
> Weston is the reference implementation of a Wayland compositor, and a
> useful compositor in its own right. Weston has various backends that
> @@ -16,3 +17,139 @@ weston and its dependencies.
> The test suite can be invoked via `make check`; see
> http://wayland.freedesktop.org/testing.html for additional details.
> + Libweston
> + =========
> +Writing a full-fledged Wayland compositor from scratch is lots of
> +work. Libweston is an effort to separate the re-usable parts of Weston
> +into a library. Libweston's aim is to provide most of the boring and
> +tedious bits of correctly implementing core Wayland protocols and
> +interfacing with input and output systems, so that people who just
> +want to write a new "Wayland WM" or a small DE can focus on the WM
> +The libweston effort started landing on the Weston 1.9 development
> +cycle, and is expected to continue through many Weston releases
> +towards a stable API and feature completeness.
> +API (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
> +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 can break any time without any warning or any version bumps.
> +Libweston API or ABI will not be broken between Weston's stable
> +releases 1.x.0 and 1.x.y, where y < 90.
> +To make things tolerable for libweston users in spite of ABI
> +breakages, libweston is designed to be perfectly parallel-installable.
> +An ABI-version is defined for libweston, and it is bumped for releases
> +as needed. Different ABI-versions of libweston can be installed in
> +parallel, so that external projects can easily depend on a particular
> +ABI-version, and they do not have to fight over which ABI-version is
> +installed in a user's system.
> +Note, that versions of Weston itself will not be parallel-installable,
> +only libweston is.
> +Libweston design goals
> +The high-level goal of libweston is that what used to be shell plugins
> +will be main executables. Instead of launching 'weston' with various
> +arguments to choose the shell, one would be launching
> +'weston-desktop', 'weston-ivi', 'orbital', etc. The main executable
That's ok, though splitting weston in various executables is not my
goal so i don't think i'm going to do it :P.
> +(the hosting program) links to libweston for a fundamental compositor
> +implementation. Libweston is also intended for use by other projects
> +who want to create new "Wayland WMs".
> +The libweston API/ABI will be separating the shell logic and main
> +program from the rest of the "Weston compositor" (libweston
> +- All configuration and user interfaces will be outside of libweston.
> + This includes command line parsing, configuration files, and runtime
> + (graphical) UI.
> +- The hosting program (main executable) will be in full control of all
> + libweston options. Libweston should not have user settable options
> + that would work behind the hosting program's back, except perhaps
> + debugging features and such.
> +- Signal handling will be outside of libweston.
> +- Child process execution and management will be outside of libweston.
> +- The different backends (drm, fbdev, x11, etc) will be an internal
> + detail of libweston. Libweston will not support third party
> + backends. However, hosting programs need to handle
> + backend-specific configuration due to differences in behaviour and
> + available features.
> +- Renderers will be libweston internal details too, though again the
> + hosting program may affect the choice of renderer if the backend
> + allows, and maybe set renderer-specific options.
> +- plugin design ???
> +- xwayland ???
> +There are still many more details to be decided.
> +For packagers
> +Always build Weston with --with-cairo=image.
> +The Weston project is (will be) intended to be split into several
> +binary packages, each with its own dependencies. The maximal split
> +would be roughly like this:
> +- libweston (minimal dependencies):
> + + headless backend
> + + wayland backend
> +- gl-renderer (depends on GL libs etc.)
> +- drm-backend (depends on libdrm, libgbm, libudev, libinput, ...)
> +- x11-backend (depends of X11/xcb libs)
> +- xwayland (depends on X11/xcb libs)
> +- rpi-backend (depends on DispmanX, libudev, ...)
> +- fbdev-backend (depends on libudev...)
> +- rdp-backend (depends on freerdp)
> + + screen-share
> +- weston (the executable, not parallel-installable):
> + + desktop shell
> + + ivi-shell
> + + fullscreen shell
> + + weston-info, weston-terminal, etc. we install by default
> +- weston demos (not parallel-installable)
> + + weston-simple-* programs
> + + possibly all the programs we build but do not install by
> + default
> +- and possibly more...
> +Everything should be parallel-installable across libweston
> +ABI-versions, except those explicitly mentioned.
> +Weston's build may not sanely allow this yet, but this is the
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