> Chromium defaults to drawing the title bar itself as part of the window, > for the same space-saving reasons. GTK+ applications using the header > bar still have window buttons too - by default a close button, but > optionally minimize/maximize. > > Anyway, I'm pointing them out as the applications that popularized this > feature, not as applications *only* providing this choice. The main reason for HeaderBar widget on core apps of Gnome is Wayland. This is a protocol to develop compositors in replacement of the old and beloved Xorg. In Wayland world there is no Windows Manager, so windows decoration are in apps. That's the main reason.
