14 DAY TRIAL // Ubuntu developers are working on the 15.04 version of their operating system and they have made some interesting changes so far, but they also entertained the possibility of adopting GTK+ 3.16. Unfortunately, that wasn't meant to be.
Ubuntu devs are very particular with the packages they choose for their system. Until Ubuntu 14.10, many of the GNOME packages were from the 3.10 branch, which could be considered ancient by now. They finally made some progress with Ubuntu 15.04, which saw the adoption of the 3.14 branch. Of course, these are not the vanilla packages from GNOME, they are modified to suit the Ubuntu profile and its needs.
Having the latest packages from GNOME does present certain advantages and the latest GTK+ is quite interesting, but Ubuntu devs need to tweak them so that they work properly. They often have to make important modifications to them and GTK+ is probably among the most finicky of them. It interacts with so many components, that any big GTK+ upgrade will cause a lot of issues that need to be solved.
Ubuntu 15.04 will have to settle with GTK+ 3.14
Adopting GTK+ 3.16 sounded like a really interesting thing to do, but the devs realized that it would have created many problems that couldn't have been fixed in due time.
"We're thinking about having the released version of GTK3 in 15.04 be 3.16, which is the current in-development version to be released towards the end of March. But the main motivation from our side is that it contains an implementation of overlay scrollbars that will allow us to remove our existing GTK module which is becoming harder and taking longer to maintain over time," wrote Iain Lane, a Debian and Ubuntu developer.
Many other Ubuntu devs pitched in and it was decided that it might not be such a good idea so late in the development cycle. So, after a healthy debate, the same developer returned with this message: "We discussed this switch at the desktop team meeting on Tuesday and the consensus amongst those there is that the issues outweigh the benefits of switching, so for now we prefer to stick with what we have for 15.04."
It was nice while it lasted, but Ubuntu 15.04 will ship with GTK+ 3.14.