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Akihiko Odaki a41c30338f backend/native: Calculate refresh rate in double-precision 
The old calculation was introduced to improve the precision
with commit c16a5ec1cf.

Here, I call the calculation as "revision 2", and the
calculation even older as "revision 1", and the new
calculation introduced with this commit as "reivion 3".

Revision 2 has two problems:
1. The calculation is mixed with fixed-point numbers and
   floating-point numbers.

To overcome the precision loss of fixed-point numbers division,
it first "calculates refresh rate in milliHz first for extra
precision", but this requires converting the value back to Hz.
An extra calculation has performance and precision costs.
It is also hard to understand for programmers.

2. The calculation has a bias.

In the process, it does:
refresh += (drm_mode->vtotal / 2);
It prevents the value from being rounded to a smaller value in
a fixed-point integer arithmetics, but it only adds a small
bias (0.0005) and consumes some fraction bits for
floating point arithmetic.

Revision 3, introduced with this commit always uses
double-precision floating-point values for true precision and
to ease understanding of this code. It also removes the bias.

Another change is that it now has two internal values, numerator
and denominator. Revision 1 also calculated those two values
first, and later performed a division with them, which minimizes
the precision loss caused by divisions. This method has risks of
overflowing the two values and revision 1 caused problems due to
that, but revision 3 won't thanks to double-precision. Therefore,
revision 3 will theoretically have the result identical with
the calculation with infinite-precision.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1737>
2021-03-05 14:37:48 +00:00
.gitlab/issue_templates gitlab: Add missing < in markdown comment tag 2020-02-14 03:10:28 +00:00
.gitlab-ci ci: Install Xwayland from git 2021-01-25 15:14:35 +00:00
clutter clutter/keymap: Make caps and num lock state properties 2021-03-04 17:39:08 +00:00
cogl cogl: Stop using GSlice 2021-02-22 13:51:30 +01:00
data data: Updated exposed keybindings 2021-02-04 00:09:57 +01:00
doc Add MetaGravity and replace X11 equivalent with it 2020-02-29 21:01:50 +00:00
meson build: Add postinstall script 2019-08-27 09:57:54 +00:00
po Update Basque translation 2021-02-28 18:55:03 +00:00
src backend/native: Calculate refresh rate in double-precision 2021-03-05 14:37:48 +00:00
subprojects build: bump ABI to sysprof-capture-4 2020-07-28 11:13:30 -07:00
tools tools: Remove obsolete ppa-magic.py 2018-11-30 11:12:12 +08:00
.gitignore build: bump ABI to sysprof-capture-4 2020-07-28 11:13:30 -07:00
.gitlab-ci.yml ci: Update ci-fairy image 2021-03-04 11:13:41 +00:00
config.h.meson xwayland: Check for listenfd option 2021-01-22 11:40:30 +01:00
COPYING Updated obsolete FSF postal address in COPYING 2014-01-12 08:44:30 +07:00
meson_options.txt xwayland: Check X11 clients prior to terminate Xwayland 2021-01-18 17:52:22 +01:00
meson.build Post-release version bump 2021-02-22 15:52:04 +01:00
mutter.doap mutter.doap: Add marge-bot as a maintainer 2020-11-16 11:59:45 +01:00
NEWS Tag release 40.beta 2021-02-22 15:44:43 +01:00
README.md README: Elaborate coding style and commit message guidelines 2020-10-28 07:28:55 +00:00

README.md

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.h types instead of GLib fundamental types, except for gboolean, and guint/gulong for GSource ids and signal handler ids. That means e.g. uint64_t instead of guint64, int instead of gint, unsigned int instead of guint if unsignedness is of importance, uint8_t instead of guchar, 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 of g_slice_new0().

  • Initialize and assign floating point variables (i.e. float or double) using the form floating_point = 3.14159 or ratio = 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.