Initial thoughts about F14 / GNOME3

[Matthias Clasen]

This Fedora cycle will see more drastic changes in the GNOME stack than
usual, with GNOME3 getting rolled out. We should start early to think
about how to best organize this transition in Fedora. Here are some
unsorted thoughts on this:

1) GConf is getting phased out in favor of GSettings+DConf [1].
GSettings has already landed in rawhide, as part of GLib 2.25.x. For a
first example of an application that has been ported from GConf to
GSettings, look at evince in rawhide.

GSettings relies on backends for actual data storage. The only non-toy
backend that is available in rawhide right now is the GConf backend that
is included in GConf 2.31. It is only meant as a transition help (it
allows to switch applications to the GSettings API without migrating the
user data to another storage). Any day now, dconf will be available as
the main settings backend that will replace GConf.

Making applications use dconf as the settings backend requires migration
of existing user data. GConf comes with a tool that is intended to help
with this, gsettings-data-convert(1). I plan to try this out with evince
or another early-adopter application as soon as dconf is available, and
then write some more detailed instructions on how to best deal with this
on the packaging level.

I expect that we will have a mixture of GConf- and GSettings-using
applications in F14.

2) GTK+ gets a major new version, GTK3. Packages are currently under
review [2]. GTK3 will be fully parallel-installable with gtk2, and
applications can be ported at their own speed.

>From a packaging perspective, the most important consequence of this is
that packages that provides modules for GTK+ (such as image loaders,
theme engines, input methods) need to provide them for both gtk2 and
gtk3. As soon as the gtk3 package is in rawhide, I'll try this out for a
simple example like librsvg2.

Some of the notable features in GTK3 that applications may want to make
use of are support for symbolic icons and dark themes. Theme packagers
may want to look into providing dark variants for the themes they
package. At least we should make sure that our default theme has such a
variant.

Here too, it is clear that F14 will still include plenty of gtk2-using
applications.

3) gnome-shell will be the designated user experience. For practical
reasons, the 'classical GNOME2' experience with gnome-panel+metacity
will still be available, and we need a reasonable way to fall back to
the GNOME2 experience if the shell does not work for some reason.

I expect this to be worked out between the shell team and the
gnome-session/gdm maintainers, but it is something to keep an eye on.

It would also be good to start a discussion on the if/when/how of
switching to the shell as the default user experience (on supported
hardware).


Matthias


[1]http://mail.gnome.org/archives/devel-announce-list/2010-April/msg00000.html
[2]https://bugzilla.redhat.com/show_bug.cgi?id=591222