nx-x11proto-scrnsaver-dev 2:3.5.99.16-1 (amd64 binary) in ubuntu bionic

 NX is a software suite which implements very efficient
 compression of the X11 protocol. This increases performance when
 using X applications over a network, especially a slow one.
 .
 This package provides development headers describing the wire protocol
 for the MIT-SCREEN-SAVER extension, used to notify the server of client
 screen saver events.