code: func (w *Window) SetPos(pos pixel.Vec) {
  	mainthread.Call(func() {
  		left, top := int(pos.X), int(pos.Y)
  		w.window.SetPos(left, top)
  	})
  }
docs: // SetPos sets the position, in screen coordinates, of the upper-left corner
  // of the client area of the window. Position can be fractional, but the actual position
  // of the window will be rounded to integers.
  //
  // If it is a full screen window, this function does nothing.