nx-x11proto-damage-dev 2:3.5.99.23-1 (amd64 binary) in ubuntu focal

 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 Damage extension, used to notify clients of changes made to
 particular areas.