f0a9ec0519
Because the framebuffer itself might be backed by a texture, which might have mipmapping enabled. If so then rendering to the framebuffer will make those mipmaps out of date. Technically we are flagging the framebuffer's mipmaps as dirty *before* they are, because the journal hasn't been flushed yet. But we need to do it early because ideally the next flush will both write the offscreen framebuffer contents and then read them for use in rendering to an onscreen framebuffer. And the `mipmaps_dirty` flag needs to be set before the read, so therefore we need to do it before the next journal flush. Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3146 where the offscreen framebuffer in question is meta-background's `monitor->fbo`. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1664>
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 af 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.
Coding style and conventions
The coding style used is primarily the GNU flavor of the GNOME coding style with some additions:
-
Use regular C types and
stdint.htypes instead of GLib fundamental types, except forgboolean, andguint/gulongfor GSource ids and signal handler ids. That means e.g.uint64_tinstead ofguint64,intinstead ofgint,unsigned intinstead ofguintif unsignedness is of importance,uint8_tinstead ofguchar, and so on. -
Try to to limit line length to 80 characters, although it's not a strict limit.
-
Usage of g_autofree and g_autoptr are encouraged. The style used is
g_autofree char *text = NULL;
g_autoptr (MetaSomeThing) thing = NULL;
text = g_strdup_printf ("The text: %d", a_number);
thing = g_object_new (META_TYPE_SOME_THING,
"text", text,
NULL);
thinger_use_thing (rocket, thing);
-
Declare variables at the top of the block they are used, but avoid non-trivial logic among variable declarations. Non-trivial logic can be getting a pointer that may be
NULL, any kind of math, or anything that may have side effects. -
Instead of boolean arguments in functions, prefer enums or flags when they're more expressive.
-
Use
g_new0()etc instead ofg_slice_new0(). -
Initialize and assign floating point variables (i.e.
floatordouble) using the formfloating_point = 3.14159orratio = 2.0.
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.
License
Mutter is distributed under the terms of the GNU General Public License, version 2 or later. See the COPYING file for detalis.