With the previous preparations in place, it is time to take the plunge.
As both the app and the portal use the same small library for handling
external windows, port everything at once to avoid the hassle of building
and installing two versions of the library.
With the portal using GTK4 now, all extensions must port their preference
widgets as well.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1495>
We currently use separate frames for the details expander and the
expanded details. That layout works as long as frames are boxy (as
in the default GTK3 style), but breaks down with rounded corners
(as in the default GTK4 style).
In order to work with either style, adapt the layout to use a single
surrounding frame and appropriate borders as separator.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1495>
There's little point in setting properties to their default value,
so stop doing that.
(GtkFrame:shadow-type actually defaults to "edged-in" rather than "in",
but all types other than "none" are treated the same nowadays)
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1495>
As outlined earlier, in order to turn the Extensions app into a properly
sandboxed application, we need to split out the extension prefs dialog
and move it elsewhere.
With "elsewhere" being the new Extensions D-Bus service, effectively
turning it into a shell extensions portal.
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1106
