every rule in ui_darwin.h
SetParent must be followed by SetSuperview and SyncEnableState
	TODO can child cache it?
adding a child must be followed by a call to SyncEnableState
SyncEnableState() must call ShouldStopSyncEnableState() first thing
Enable() and Disable() must call SyncEnableState() AFTER CHANGING WHAT Enabled() WILL RETURN