Hi, Currently the minimum required version is 3.8.
Beginning on 3.10 Gtk added support for client-side decorations and the GtkHeaderBar is the default widget to do that. https://docs.gtk.org/gtk3/ctor.HeaderBar.new.html Gtk 3.10 was released Sep/2013. Gtk4 and Gnome apps default to this behaviour. By using it we may be able to get rid of the window sizing problem on glass-gtk which is "decoration sizes" thru _NET_FRAME_EXTENTS which is very error prone (it depends on each window manager). Currently it does a lot of work-arounds to size the window properly because the server does the decoration so there is a problem getting it's size to size the window accordingly. It works, but it's far from pretty. More details here: https://discourse.gnome.org/t/understanding-window-sizing-and-decorations-on-gtk4/7290 By moving to this idea we might be more compatible with other apps and do a better job on the implementation of window sizing. If you put a pure gtk window and a javafx window on Ubuntu 20.04 there are some differences (shadow size and titlebar size). Also, if we want to support wayland we will have to require a greater gtk3 version. Or just support it on Gtk4 where I would follow the HeaderBar (client-side decorations) idea. -- Thiago.
