Mutter

Mutter is a Wayland display server and X11 window manager and compositor library.

When used as a Wayland display server, it runs on top of KMS and libinput. It implements the compositor side of the Wayland core protocol as well as various protocol extensions. It also has functionality related to running X11 applications using Xwayland.

When used on top of Xorg it acts as a X11 window manager and compositing manager.

It contains functionality related to, among other things, window management, window compositing, focus tracking, workspace management, keybindings and monitor configuration.

Internally it uses a fork of Cogl, a hardware acceleration abstraction library used to simplify usage of OpenGL pipelines, as well as a fork of Clutter, a scene graph and user interface toolkit.

Mutter is used by, for example, GNOME Shell, the GNOME core user interface, and by Gala, elementary OS's window manager. It can also be run standalone, using the command "mutter", but just running plain mutter is only intended for debugging purposes.

Contributing

To contribute, open merge requests at https://gitlab.gnome.org/GNOME/mutter.

It can be useful to look at the documentation available at the Wiki.

The API documentation is available at:

• Meta: https://gnome.pages.gitlab.gnome.org/mutter/meta/
• Clutter: https://gnome.pages.gitlab.gnome.org/mutter/clutter/
• Cally: https://gnome.pages.gitlab.gnome.org/mutter/cally/
• Cogl: https://gnome.pages.gitlab.gnome.org/mutter/cogl/
• CoglPango: https://gnome.pages.gitlab.gnome.org/mutter/cogl-pango/
• Mtk: https://gnome.pages.gitlab.gnome.org/mutter/mtk/

Coding style and conventions

See HACKING.md.

Git messages

Commit messages should follow the GNOME commit message guidelines. We require an URL to either an issue or a merge request in each commit. Try to always prefix commit subjects with a relevant topic, such as compositor: or clutter/actor:, and it's always better to write too much in the commit message body than too little.

If a commit fixes an issue and that issue should be closed, add URL to it in the bottom of the commit message and prefix with Closes:.

Do not add any Part-of: line, as that will be handled automatically when merging.

The Fixes tag

If a commit fixes a regression caused by a particular commit, it can be marked with the Fixes: tag. To produce such a tag, use

git show -s --pretty='format:Fixes: %h (\"%s\")' <COMMIT>

or create an alias

git config --global alias.fixes "show -s --pretty='format:Fixes: %h (\"%s\")'"

and then use

git fixes <COMMIT>

Example

compositor: Also consider dark matter when calculating paint volume

Ignoring dark matter when calculating the paint volume missed the case where
compositing happens in complete vacuum.

Fixes: 123abc123ab ("compositor: Calculate paint volume ourselves")
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1234

Default branch

The default development branch is main. If you still have a local checkout under the old name, use:

git checkout master
git branch -m master main
git fetch
git branch --unset-upstream
git branch -u origin/main
git symbolic-ref refs/remotes/origin/HEAD refs/remotes/origin/main

License

Mutter is distributed under the terms of the GNU General Public License, version 2 or later. See the COPYING file for detalis.