function bindAttachment(props, attachProps, optionName) {
    var bindTarget = {props: props, optionName: optionName};
    if (props.attachments.indexOf(attachProps) < 0 &&
        (!attachProps.conf.bind || attachProps.conf.bind(attachProps, bindTarget))) {
      props.attachments.push(attachProps);
      attachProps.boundTargets.push(bindTarget);
      return true;
    }
    return false;
  }
@param {props} props - `props` of `LeaderLine` instance.
@param {attachProps} attachProps - `attachProps` of `LeaderLineAttachment` instance.
@param {string} optionName - Name of bound option.
@returns {boolean} `true` when binding succeeded.