message WindowList

Every window the compositor has, and which workspace is on screen.

A whole list every time rather than deltas, and that is a deliberate trade rather than laziness. A desktop has tens of windows, not thousands; a snapshot is a few hundred bytes; and a shell that receives one is correct rather than correct-if-it-applied-every-previous-message. Deltas would be machinery whose only purpose is to make a resynchronisation bug possible.

currentWorkspace rides along because a dock showing "what is open here" needs both halves and they change together — a workspace switch changes which windows are relevant without changing any window.