C#

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows;

using SdPoint = System.Drawing.Point;
using SwPoint = System.Windows.Point;
using SdSize = System.Drawing.Size;
using SwSize = System.Windows.Size;

using GraphicsPath = System.Drawing.Drawing2D.GraphicsPath;
using GReg = System.Drawing.Region;
using GMat2d = System.Drawing.Drawing2D.Matrix;
using GMatMed = System.Windows.Media.Matrix;

namespace GeomLib_August_2021_III
{
    public enum ShapeType
    {
        Line,
        Arc,
        Rectangle,
        Parallelogram,
        Circle,
        Ellipse,
        RegPolygon,
        IrregPolygon,
        Grid,
        Star
    }

    public interface IShape
    {
        string ShpName { get; }
        string ShpComment { get; }
        DateTime ShpTimeStamp { get; }
        ShapeType ShpType { get; }

        Rect SwRect { get; }
        SwPoint CenterF { get; }
        SwPoint[] PathPoints { get; }

        double GetArea();
        double GetPerimeter();
        SwPoint GetCenter();
        GraphicsPath GetGPath();
        Region GetRegion();

        IShape GetUnion(IShape s1, IShape s2);
        IShape GetIntersection(IShape s1, IShape s2);

        IShape Translate(IShape s1, Matrix m1);
        IShape Rotate(IShape s1, Matrix m1);
        IShape Scale(IShape s1, Matrix m1);

        SwPoint[] Flatten();
        void Render();
        void Save();
        void Load()
    }
}

IShape Union(IShape shape);

Quote:

The Shp properties all feel like they should be in a separate class. Again, it feels to me like these are metadata items, rather than being intrinsic parts of the base interface. I would probably move these out into a separate metadata class and drop the Shp parts of the name.

Quote:

The Union and Intersection methods also appear to be wrong, unless you are looking to determine whether this shape intersects with more than one shape - the first parameter of these methods is probably going to be the current instance so why pass it in?