f06913a2d1
Previously if we had no measurements then `compute_max_render_time_us`
would pessimise its answer to ensure triple buffering could be reached:
if (frame_clock->state >= CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE)
ret += refresh_interval_us;
But that also meant entering triple buffering even when not required.
Now we make `compute_max_render_time_us` more honest and return failure
if the answer isn't known (or is disabled). This in turn allows us to
optimize `calculate_next_update_time_us` for this special case, ensuring
triple buffering can be used, but isn't blindly always used. So when
TIMESTAMP_QUERY support is missing we now take the same path as if
presentation timestamps are missing (introduced in 56fc09151d and
improved in 0555a5bbc1), which has the benefit of naturally switching
from double to triple buffering as required without actually having to
measure render times.
This makes a visible difference to the latency when dragging windows in
Xorg, but will also help Wayland sessions on platforms lacking
TIMESTAMP_QUERY such as Raspberry Pi.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1441>
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
- Multi-GPU
API Reference
- Meta: https://mutter.gnome.org/meta/
- Clutter: https://mutter.gnome.org/clutter/
- Cogl: https://mutter.gnome.org/cogl/
- Mtk: https://mutter.gnome.org/mtk/
Meetings
There are recurring meetings to discuss development of GNOME Shell, mutter and related components.
License
Mutter is distributed under the terms of the GNU General Public License, version 2 or later. See the COPYING file for detalis.