code: func (q *commandQueue) appendVertices(vertices []float32) {
  	if len(q.vertices) < q.nvertices+len(vertices) {
  		n := q.nvertices + len(vertices) - len(q.vertices)
  		q.vertices = append(q.vertices, make([]float32, n)...)
  	}
  	copy(q.vertices[q.nvertices:], vertices)
  	q.nvertices += len(vertices)
  }
docs: // appendVertices appends vertices to the queue.