The CanvasFactory is used to create the Canvas
objects, evaluating the user's configuration preferences from
/org.openoffice.VCL/Settings/Canvas/PreferredServices.
The latter specifies a string list of service names to use.
Instantiating this service, you can use its
::com::sun::star::lang::XMultiComponentFactory
interface to create Canvas objects, passing an empty string
as service specifier (default).
If you want to manually override the configured service list, you can pass
a service name to try first.
