aedb0f200d
This removes an incorrect implicit assumption in
calculate_next_update_time_us() that a frame may only be scheduled
once in the duration of a refresh cycle. It accomplishes this by
setting last_next_presentation_time_us on presentation feedback
instead of calculating it every time an update is scheduled.
Specifically, it corrects the intended scheduling logic in scenarios
like the following, when all of the below occur in the context of a
single refresh cycle:
1. Frame update (1) is scheduled normally, and
"is_next_presentation_time_valid" is set to TRUE
2. Frame update (1) is dispatched but ends up being "empty" (no
presentation necessary)
3. Frame update (2) is scheduled "now" and
"is_next_presentation_time_valid" is set to FALSE
4. Frame update (2) is dispatched but ends up being "empty" (no
presentation necessary)
5. Frame update (3) is scheduled normally, and since
"is_next_presentation_time_valid" is set to FALSE, the
"early presented event" logic is unintentionally skipped in
calculate_next_update_time_us().
6. Frame update (3) is dispatched and ends up being a "non-empty"
update, but its update time was calculated incorrectly because
some logic was skipped.
Scenarios such as this would become more common with the introduction
of variable refresh rate since it makes scheduling "now" a commonplace
occurrence.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3560>
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 first look at the GNOME Handbook and the documentation and API references below first.
Documentation
- Coding style and conventions
- Git conventions
- Code overview
- Building and Running
- Debugging
- Monitor configuration
API Reference
- Meta: https://mutter.gnome.org/meta/
- Clutter: https://mutter.gnome.org/clutter/
- Cally: https://mutter.gnome.org/cally/
- Cogl: https://mutter.gnome.org/cogl/
- CoglPango: https://mutter.gnome.org/cogl-pango/
- Mtk: https://mutter.gnome.org/mtk/
License
Mutter is distributed under the terms of the GNU General Public License, version 2 or later. See the COPYING file for detalis.