code: func (q *commandQueue) Enqueue(command command) {
  	// TODO: If dst is the screen, reorder the command to be the last.
  	q.commands = append(q.commands, command)
  }
docs: // Enqueue enqueues a drawing command other than a draw-image command.
  //
  // For a draw-image command, use EnqueueDrawTrianglesCommand.