d31b781efb
We might get told to restore the old monitor configuration by the monitor configuration prompt, in case the user pressed "revert" or equivalent. This might be in response to a button press, and those happen during frame clock dispatch. If we would restore an old configuration during dispatch, it means we would reconfigure the monitors including their stage views while dispatching, which means we'd destroy the frame clock while it's dispatching. Doing that causes problems, as the frame clock isn't expecting to be destroyed mid-function. Specifically, We'd enter clutter_frame_clock_dispatch (clutter-frame-clock.c:811) frame_clock_source_dispatch (clutter-frame-clock.c:839) g_main_dispatch (gmain.c:3454) g_main_context_dispatch (gmain.c:4172) g_main_context_iterate.constprop.0 (gmain.c:4248) g_main_loop_run (gmain.c:4448) meta_context_run_main_loop (meta-context.c:482) main (main.c:663) which would first call _clutter_process_event (clutter-main.c:920) _clutter_stage_process_queued_events (clutter-stage.c:757) handle_frame_clock_before_frame (clutter-stage-view.c:1150) which would emit e.g. a button event all the way to a button press handler, which would e.g. deny the new configuration: restore_previous_config (meta-monitor-manager.c:1931) confirm_configuration (meta-monitor-manager.c:2866) meta_monitor_manager_confirm_configuration (meta-monitor-manager.c:2880) meta_plugin_complete_display_change (meta-plugin.c:172) That would then regenerate the monitor configuration and stage view layout, which would destroy the old stage view and frame clock. meta_stage_native_rebuild_views (meta-stage-native.c:68) meta_backend_native_update_screen_size (meta-backend-native.c:457) meta_backend_sync_screen_size (meta-backend.c:266) meta_backend_monitors_changed (meta-backend.c:337) meta_monitor_manager_notify_monitors_changed (meta-monitor-manager.c:3595) meta_monitor_manager_rebuild (meta-monitor-manager.c:3683) meta_monitor_manager_native_apply_monitors_config (meta-monitor-manager-native.c:343) meta_monitor_manager_apply_monitors_config (meta-monitor-manager.c:704) After returning back to the original clutter_frame_clock_dispatch() frame, various state in the frame clock will be gone and we'd crash. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2901>
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/
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.