I don't see any issue with letting glade2 and glade3 coexist for a while. And I don't expect there to be any explicit incompatibility, I just fear that there may be some issues when using glade3 on glade files that have been produced by glade2. Either way, I really hope that we will soon see a ui builder that supports the GtkBuilder format.
Now that we are starting to see GtkBuilder support [1] in Glade3 can we finally push it as the "default on-media" package over Glade2?
Cheers, Debarshi
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