Extend a curve until it hits a boundary shape.

Input parameters:

1. Cr → Curve to extend.
2. Ce → Curve ends to extend.
   • 0 → None
   • 1 → Start
   • 2 → End
   • 3 → Both
3. Ty → Extension type.
   • 0 → Line
   • 1 → Arc
   • 2 → Smooth
4. Bn → Boundary shapes.

Output parameters:

1. Cr → Extended curve.