GTK3 Interface
From Lazarus wiki
GTK3 interface
Started as of lazarus 1.1 r41811
Currently it's in alpha status, and if you want to test it
you must uncomment USEGTK3ALPHA define in lcl/interfaces/gtk3/gtk3defines.inc.
MINIMUM REQUIREMENTS
- Gtk3 v 3.6.4
- glib2 2.34
- cairo 1.10
- pango 1.30