Version bump for GTK+ 3.20(.3?) http://ftp.gnome.org/pub/gnome/sources/gtk+/3.20/
We know about these, yes. Lots of external themes apparently break, help welcome in investigating that. Otherwise it's pending addition together with full GNOME 3.20.
I mean, a gtk+ 3.20 is available in the gnome overlay https://gitweb.gentoo.org/proj/gnome.git/tree/x11-libs/gtk+ Various gtk3 themes in x11-themes/ apparently break with it, as they introduced the CSS gadgets or whatever concepts. On the plus side, they now more or less stabilized the theming interface and naming, so hopefully from now on, once themes are 3.20 compatible, they will continue working with future version (3.22, 3.23, etc) without needing fixes. Because of the potential breakage to non-default themes, we haven't introduced gtk+ bump separately from GNOME 3.20. Help welcome in testing the affect of the theme breakage and seeing if some of the popular ones have fixes, etc.
Relatedly applications that did their own custom extra theme stuff also broke as with the stabilization, things were renamed. So for example gnumeric is completely broken at places, because it ships some extra CSS of its own for cell highlighting or whatever.
I want to update the theme used by RawTherapee as breakage was reported, for that I need gtk+-3.20.*. How do I get it?
*** This bug has been marked as a duplicate of bug 578452 ***
