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>
I messed up and released 40.alpha at the same time as 3.38.2, when it's
supposed to be in January. In order to re-align with the schedule, change
the upcoming version to 40.alpha2 so we don't have to skip a release and
will be back on track in time of 40.beta.
In order to support OpenExtensionPrefs()'s parentWindow parameter,
we will need the ability to make a window transient to an external
window identified by a string handle.
This takes the corresponding code from xdg-desktop-portal-gtk and
brings it into an introspectable form, likewise the counterpart in
libportal to export a string handle for a GtkWindow.
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1087
