16 lines (10 with data), 537 Bytes
What I'd like to do some time...
* Fullscreen toggle needs to account for Xinerama.
* Snap-to-edge functionality when moving windows.
* New windows tile as well as possible.
* Seems like some applications (notably audiocontrol) bring themselves
to the front whenever mapped. This breaks the simple approach to
keeping stacking order on changing desktop. So probably have to do
the structure reordering thing.
* Think of some good way of adding controllable window resizing beyond the
fullscreen/vertical maximise toggles.