The xdg-output protocol aims at describing outputs in way which is more in line with the concept of an output on desktop oriented systems.
For now it just features the position and logical size which describe the output position and size in the global compositor space.
This is however much useful for Xwayland to advertise the output size and position to X11 clients which need this to configure their surfaces in the global compositor space as the compositor may apply a different scale from what is advertised by the output scaling property (to achieve fractional scaling, for example).
This was added in wayland-protocols 1.10.
da8de2a7f xwayland: Add optional xdg-output support
configure.ac | 2 +-
hw/xwayland/Makefile.am | 9 +++-
hw/xwayland/meson.build | 3 ++
hw/xwayland/xwayland-output.c | 119 ++++++++++++++++++++++++++++++++++++++----
hw/xwayland/xwayland.c | 5 ++
hw/xwayland/xwayland.h | 8 +++
meson.build | 2 +-
7 files changed, 135 insertions(+), 13 deletions(-)