server: Fix cursor alignment

I can't seem to get these values right. I measured them in Photoshop,
but they still seem off. I wonder if my picking is off inside server.js
itself...
server: Fix error throwing for exclusive events
server: Add more cursors
server: Rework viewability

When windows were unmapped, the inferiors of it wouldn't become
unviewable, since the logic was wrong. Fix that.
demo-common: Handle bounded mode when the child is smaller