This allows for compositor managed different co-ordinate space between kwin's
logical co-ordinate space and a client's logical co-ordinate space.
When combined with a modified kwin!1959 this allows us to set a DPI in xrdb and
mark all xwayland windows as being 2x (or other) and avoid upscales for xwayland
clients in a way that doesn't impact other wayland clients or require
third-party changes. Any use of fractional values is in layers we control
instead of over the wire. kwayland-server is the right place for this
abstraction as we need Outputs to differ on a per resource basis. Something we
can't control from within kwin.
Right now only protocols used by Xwayland are covered. If we covered
remaining protocols we can offer user-control on all remaining clients which
could open up other possibilities such as a user controlled dynamic resizing,
or adapt to possible future protocol changes with wayland scaling.
Be more explicit about the types, prefer passing semantically correct
parents and keep track of the pads from the object rather than relying
on them being initialised properly.
