The error UI comprises the bits that are actually custom. Splitting them
out from the off-the-shelf window makes it easier to replace the dialog
with libadwaita's dedicated preference window.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2012>
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
Similar to the previously added org.freedesktop.Notifications proxy,
this exposes the org.gnome.Shell.Extensions API and forwards any
request to the real implementation in gnome-shell.
The motivation differs though: We want to be able to package the
extension app as flatpak and distribute it separately, but the
extension prefs dialog is hard to impossible to sandbox:
- filenames need translating between host and sandbox, and we
can only do that in some cases (serializing/deserializing
extensions), but not others (extension settings that refer
to files)
- system extensions install their GSettings schemas in the system
path; the best we can do there is assume a host prefix of /usr
and set GSETTINGS_SCHEMA_DIR in the flatpak (eeks)
- extensions may rely on additional typelibs that are present on
the host (for example because gnome-shell itself depends on
them), but not inside the sandbox - unless we bundle all of
gnome-shell's dependencies
- if gjs/mozjs differ between host and sandbox, extensions must
handle different runtimes for the extension and its prefs
And all those issues occur despite a very permissive sandbox (full
host filesystem access, full dconf access, full org.gnome.Shell
access (including Eval()!)).
This new service will give us an alternative place for handling
the preference dialog:
- it runs outside of gnome-shell process, so can open windows
- it runs on the host, so the extension's prefs get to run
in the same namespace as the extension itself
That is, the service will provide portal-like functionality (albeit
not using the org.freedesktop.portal.* namespace, as extension
management is an inherently privileged operation).
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1106
