Provide a generic overload for IShapeF

[LokiMidgard]

Since IShapeF is an interface which is implemented by structs, those will get boxed that allocates and can trigger garbage collection.

providing an overload can prevent this. E.g. in the Shape class.

public static bool Intersects<TShapeA, TShapeB>(this TShape shapeA, TShape shapeB)
where TShape: struct, IShapeF
{
}

One could get a step further and obsolete the methods that take the interface and provide information why they should not be used.

If interested in this, I could look into and make pull requests for those changes.

[lithiumtoast]

Could I ask how you are using the IShapeF interface? Boxing is a common problem in general especially for people who are new; I would consider removing the interface altogether.

[LokiMidgard]

I currently use it with methods and objects in this library, since I have no choise ;). And when I write methods or classes I use it as a condition for generic type argument as above.

Since there are some structs, like Circle Rectangle, and maybe ellipse (if that is changed to struct), I would keep the Interface, but mark it as obsolete. Also Property's and everywhere it is used, like in interfaces. That way methods and object can just use a generic type constrained to IShapeF, struct and call themselves other generic methods. Only sings like intersect, that need to access the actual information would need to be duplicated. This would reduce the code that is written and needs maintenance drastically. Without the interface, it could be hard to communicate what type the argument would need to have.

Of course that will use a bunch of generic arguments, and probably specialized lists, that can handle multiple shapes.

If someday in the future c# supports RectangleF | CircleF as types, it could be removed without increasing the amount of code (if the underling implementation does not use boxing for this).

I just pushed some code I was testing this to github. I tried making a tile map collision there, without boxing. It's a first shot that could be improved a lot, (probably performance and usability wise) and it is not finished.

I started pulling code from this repo over like the collision calculation and some interfaces, so I could prevent boxing. The next thing would probably the QuadTree, so I no longer need to unbox if I use that...

[lithiumtoast]

So the context is mostly collision detection? If the C# interface type provides value for constraints using generics I could see it being okay.

What I'm worried about is that if people have a property like this:

public IShapeF Shape { get; set; }

And assign to it:

Shape = new CircleF(100, 100, 5);

This would cause boxing; which I think the C# interface should not be used like a traditional C# interface and only for generics; which then I think it should be removed and pushed into a collision detection library where it's not as easy to make this mistake.

[LokiMidgard]

That's the context I think I will be using it and I can't currently think of something else. So for me putting the interface to the Collision lib should be ok.

[LokiMidgard]

I thought about preventing the ussage of IShapeF, depricating it would also show a warining when it is used in the where clause.

Instead a Rosyln Analyzer could warn the user not to use this. It can check where the type is used and only warn when a Variable, parameter or field is declared. Maybe I find time in the weekend to try this in a Fork.

I'll open a seperate issue for this.

[LokiMidgard]

I tried moving everything Shape like to collisions project.

I moved

• ShapeF
• RectangleF
• RectangleExtensions
• Segment2
• Ray2
• Polyline
• Polygon
• EllipseF
• CircleF
• BoundingRectangle

I then changed

• IRectangular to only contain the interface IRectangular removing IRectangularF. Should probably moved instead of removing
• ShapExtension I removed the methods that work with the moved ones (also better moving instead)
  • FillRectangle (that takes an RectangleF)
  • DrawRectangle (3 variants that uses RectangleF)
  • DrawPolygon
  • One of the DrawCircle

After that Following files could no longer get compield since they use RectangleF

• BitmapFont
• Camera
• Sprite
• OrthographicCamera

So I currently don't think it is a good Idea to move IShape (and everything that needs it) to the collision project.

[lithiumtoast]

I'm slowly making progress on a fork of FNA which I'm going to use as the base here. It is best to wait for that first. However, I think perhaps evaluating the usages of RectangleF and see if they really need to be used would be a good idea. Perhaps they all need width and height at some sites. Or perhaps passing x, y, width, height instead would allow removing the dependency for other sites.