These coordinates contain the all-time accumulated buffer attach point,
which is a way to perform incremental client-side initiated movement of
windows, intended as a way to maintain logical window positioning while
compensating for layout changes such as folding in a left side panel.
This value is not useful for implementing this feature, and break things
if they ever become non-zero. Their inclusion in calculations also tend
to cause confusion.
Remove usage of these coordinates, removing the ability for clients to
move themselves. This may again be supported if a better API is made
available from wlroots.
7ec9d07fc5