Create a new surface that is a rectangle within the target surface. All operations drawn to this surface are then clipped and translated onto the target surface. Nothing drawn via this sub-surface outside of its bounds is drawn onto the target surface, making this a useful method for passing constrained child surfaces to library routines that draw directly onto the parent surface, i.e. with no further backend allocations, double buffering or copies.

Note: The semantics of subsurfaces have not been finalized yet unless the rectangle is in full device units, is contained within the extents of the target surface, and the target or subsurface's device transforms are not changed.