Constant PATCH 

const PATCH: [[f32; 2]; 6];

The patch in its own space, in draw order.

The shape is chosen so every topology draws something a reader can tell apart: a point list draws six dots down it, a line list three separate strokes, a line strip one connected zigzag, a triangle list two detached triangles and a triangle strip a filled band.

Every consecutive triple winds the same way, because the triangle list culls back faces: two triangles of opposite winding would draw as one, and the snapshot would no longer show what the topology does.