line-to in dc-path%
Extends the path's open sub-path with a line to the given point. If
the path has no open sub-path, an exn:fail:contract exception is raised.
A path is not connected to any particular dc<%> object, so
setting a dc<%> origin or scale does not affect path
operations. Instead, a dc<%>'s origin and scale apply at the
time that the path is drawn or used to set a region.