Function difference_polygon 

pub fn difference_polygon(
    poly1: &Polygon,
    poly2: &Polygon,
) -> Result<Vec<Polygon>>

Computes the difference of two polygons (poly1 - poly2)

Returns the portion of poly1 that does not overlap with poly2. Handles:

• Disjoint polygons (returns poly1)
• poly2 contains poly1 (returns empty)
• poly1 contains poly2 (returns poly1 with poly2 as hole)
• Partial overlap (simplified result)
• Existing interior rings (holes) in both polygons

Interior Ring Handling

• Holes in poly1: Preserved unless they are completely covered by poly2
• Holes in poly2: If poly2 is inside poly1, poly2’s holes become new polygon regions (since subtracting a hole means keeping that area)
• New holes: Created when poly2 is entirely contained within poly1

Arguments

• poly1 - The polygon to subtract from
• poly2 - The polygon to subtract

Returns

Vector of polygons representing the difference

Errors

Returns error if polygons are invalid