The new tiling code, instead of based around "tiling states", is instead
based around constrained edges. This allows us to have windows that have
three constrained edges, but keep one free-floating, e.g. a window tiled
to the left has the left, top, and bottom edges constrained, but the
right edge can be left resizable.
This system also is easily extended to support corner tiling. We also,
using the new "size state" system, also keep normal, tiled, and
maximized sizes independently, allowing the maximize button to bounce
between maximized and tiled states without reverting to normal in
between. Dragging from the top will always restore the normal state,
though.
https://bugzilla.gnome.org/show_bug.cgi?id=751857
50e3e3b929