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The overrides for Canvas.Draw that would accept any type that implements the Drawable interface are missing. Currently the options are

• (Shape)
• (Shape, RenderStates)
• (Sprite)
• (Sprite, RenderStates)
• (Text)
• (Text, RenderStates)
• (VertexArray)
• (VertexArray, RenderStates)
• (Vertex[], PrimitiveType)
• (Vertex[], PrimitiveType, RenderStates)
• (Vertex[], uint start, uint count, PrimitiveType)
• (Vertex[], uint start, uint count, PrimitiveType, RenderStates)

Ideally I would think this method group would match the standard sfml Window.Draw which instead only includes the following

• (Drawable)
• (Drawable, RenderStates)
• (Vertex[], PrimitiveType)
• (Vertex[], PrimitiveType, RenderStates)
• (Vertex[], uint start, uint count, PrimitiveType)
• (Vertex[], uint start, uint count, PrimitiveType, RenderStates)

I'm also curious as to why this is preferred over something like just supplying a RenderTexture to a Widget, similar to the way you would wrap a RenderTexture in a Sprite. This would avoid the confusing "Draw" - some object into Canvas vs "Draw" - canvas into some RenderTarget. Is there a way I could do this instead?

General advice on extending the Widget system in .net would be really appreciated as well, such as how I might implement a wrapper like I've described, or for example a Widget that uses shader effects.

If I write the following code

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RenderWindow window = new RenderWindow(new VideoMode(400, 300), "TGUI.Net test");
Gui gui = new Gui(window);

Picture picture = new Picture("background.jpg");
gui.Add(picture);

// ... gui.Add various test elements ...

Vertex[] test =  {
                new Vertex(new Vector2f(), Color.White),
                new Vertex(new Vector2f(400, 0), Color.Magenta),
                new Vertex(new Vector2f(400, 75), Color.Cyan),
                new Vertex(new Vector2f(0, 75), Color.Yellow)
            };

while (window.IsOpen) {
    window.DispatchEvents();

    window.Clear();

    window.Draw(test, PrimitiveType.Quads);

    gui.Draw(); // crash, Exception Unhandled

    window.Display();
}



I get a

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System.AccessViolationException: 'Attempted to read or write protected memory. This is often an indication that other memory is corrupt.'



But if I comment out

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gui.Add(picture) it works fine and all other tgui elements and my sfml primitives draw correctly....

Alternatively if I comment out

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window.Draw(test, PrimitiveType.Quads); it works as well

Or if I change the order

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gui.Draw();
window.Draw(test, PrimitiveType.Quads);


it works but of course my "game content" draws on top of my gui

I also notice that standard builtin sfml types work, such as Sprite. It seems the problem arises only when used in conjunction with this window.Draw(Vertex[], PrimitiveType) signature, but I also tried abstracting this into a class that can be called with window.Draw(instance)

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class MyTestDrawable : Transformable, Drawable {
        private Vertex[] _Vertices;

        public MyTestDrawable() {
            _Vertices = new Vertex[] {
                new Vertex(new Vector2f(), Color.White),
                new Vertex(new Vector2f(400, 0), Color.Magenta),
                new Vertex(new Vector2f(400, 75), Color.Cyan),
                new Vertex(new Vector2f(0, 75), Color.Yellow)
            };
        }

        public void Draw(RenderTarget target, RenderStates states) {
            states.Transform *= Transform;
            target.Draw(_Vertices, PrimitiveType.Quads, states);
        }
    }
to no avail

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Further testing has revealed that if I first draw a standard sfml type like Sprite, I can then draw with (Vertex[], PrimitiveType)

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window.Draw(spriteInstance);

window.Draw(test, PrimitiveType.Quads);

gui.Draw();

with no errors.