Hey!

From the specification:

Version 1.5 adds monitors

• A 'Monitor' is a rectangular subset of the screen which represents
a coherent collection of pixels presented to the user.

• Each Monitor is be associated with a list of outputs (which may be
empty).

• When clients define monitors, the associated outputs are removed from
existing Monitors. If removing the output causes the list for that
monitor to become empty, that monitor will be deleted.

• For active CRTCs that have no output associated with any
client-defined Monitor, one server-defined monitor will
automatically be defined of the first Output associated with them.

• When defining a monitor, setting the geometry to all zeros will
cause that monitor to dynamically track the bounding box of the
active outputs associated with them

This new object separates the physical configuration of the hardware
from the logical subsets the screen that applications should
consider as single viewable areas.