The dialog is now displayed by calling gtk_dialog_run and
gtk_window_set_transient_for in the window displaying the dialog.
Cleanup is handled using gtk_widget_destroy.
Destructors in the windows using the dialog no longer cleanup the dialog
as it is assumed it will be either cleaned up after the response
callback, or handled by the destroy_with_parent property set on the
dialog itself.
G_IS_OBJECT checks fail when calling g_signal_connect_object because
PpPPDSelectionDialog is a struct, not a type descending from G_OBJECT.
This makes the changes required for PpPPDSelectionDialog to be a
GObject, and defines PpPPDSelectionDialog as a GObject. It also updates
consumers of PpPPDSelectionDialog to destroy created PpPPDSelectionDialogs as GObjects.
https://gitlab.gnome.org/GNOME/gnome-control-center/-/issues/1126
This commit adds popup window which when activated allows
user to select PPD from local database of installed PPDs,
select directly PPD from filesystem or select one from 3
recommended PPDs (#678637).
The popup is activated by clicking on model field (the panel
has to be unlocked). It starts to search for the best PPDs
available immediately after its popup.
All operations are asynchronous.
