About Gtk3/Gtk2 in 4.12

[Nick Schermer]

Folks,

We've ported a couple of parts of Xfce to Gtk3 and IMO it is better to 
stick with Gtk2 for 4.12. Beside that fact that it is an awful amount of 
work, the resulting applications are visibly slower (large treeviews 
mostly), consume more resources and hardly any advantages (api 
technically).
So for me porting the core of Xfce in the state Gtk3 currently is, is 
for me a no-go.

That said we can still prepare for this to make the switch easier in 
the future.

- Depend on Gtk 2.24.
- Use new API (compile with GSEAL) as much as possible and drop 
deprecated API.
- In a number of places we use Gtk widgets instead of our own versions.
- Libraries (libxfce4ui and exo) can provide a gtk2 and gtk3 version of 
the lib.
- Some core modules (xfce4-appfinder for example) can optionally 
compile against gtk3. This allows us to track Gtk3 progress and possibly 
help finding issues.

This will give us more time to port parts to Gtk3, because with the 
complexity it brings, it will consume a lot of time, leaving not much 
room for adding new features. Not to mention the fact porting (and only 
porting) takes to fun out of the project, for me at least.

It might even be possible to run gtk3 panel plugins in a gtk2 panel 
(externally), so also for goodies it will give a better migration path.

We've already discussed this a bit on IRC/private, and Jannis and Peter 
agree with this path. Hopefully others do as well, because then we can 
assign the porting parts and work on the 4.12 roadmap.

Nick