code: @Override
      public int doStartTag() {
  
          // get the flex controller
          CmsFlexController controller = CmsFlexController.getController(pageContext.getRequest());
  
          // get the device selector
          I_CmsJspDeviceSelector selector = OpenCms.getSystemInfo().getDeviceSelector();
  
          List<String> supportedDevices = selector.getDeviceTypes();
          List<String> selectedDevices = CmsStringUtil.splitAsList(m_type, ",", true);
  
          // check if the selected device is in the list of supported devices
          for (String selectedDevice : selectedDevices) {
              if (supportedDevices.contains(selectedDevice)) {
                  // get the current device from the request
                  HttpServletRequest req = controller.getTopRequest();
                  String device = (String)req.getAttribute(I_CmsJspDeviceSelector.REQUEST_ATTRIBUTE_DEVICE);
  
                  if (CmsStringUtil.isEmptyOrWhitespaceOnly(device)) {
                      // device not found in request
                      device = selector.getDeviceType(req);
                      if (CmsStringUtil.isNotEmpty(device)) {
                          // put the detected device into the request
                          req.setAttribute(I_CmsJspDeviceSelector.REQUEST_ATTRIBUTE_DEVICE, device);
                      }
                  }
  
                  // check if the detected device is in the list of given types
                  if (selectedDevices.contains(device)) {
                      return EVAL_BODY_INCLUDE;
                  } else {
                      return SKIP_BODY;
                  }
              } else {
                  LOG.error(
                      Messages.get().getBundle().key(
                          Messages.LOG_WRONG_DEVICE_TYPE_2,
                          selectedDevice,
                          controller.getCurrentRequest().getElementUri()));
              }
          }
          return SKIP_BODY;
      }
docs: Decides on the base of the device selector interface whether the user's device is in
  the selected device types or not.<p>
  
  If the user's device is in the list of possible devices the content inside the tag is printed out
  and otherwise the content won't be printed out.<p>
  
  @return {@link #EVAL_BODY_INCLUDE}<br/>{@link #SKIP_BODY}