Provide feedback about (no) incoming messages

[rhaschke]

Provide (status) feedback on:

• no message received at all
• no message received within last timeout seconds
• message display failing due to missing (or too old) TF In https://github.com/ubi-agni/tactile_toolbox/pull/13#issuecomment-705113442, @guihomework remarked that rviz states "not yet published" although messages are published but just don't have a matching TF.

[guihomework]

• no message received at all :

  • should not be per group, too verbose
  • should consider valid, the empty messages, because tactile_merger currently publishes empty messages all the time and this is not a "no message received at all"

• no message received within the last timeout seconds

  • I don't care if there was no message on the topic (even no empty one) for a while. This is not important and can be verified outside (just rostopic echo the topic and one sees it, but seeing a time is outdated with rostopic echo is not easy for a human due to using epochs)

• NEW message received is outdated

  • message received, but its timestamp is in the past, out of the timeout, and hence won't be displayed.
  • this is very valuable, it was missing several times in the past, usually when forgetting to set use_sim_time to true, while playing a bag file with data in the past or when forgetting to publish the clock of the bagfile etc...
  • maybe per group but I would appreciate at least one message for the whole topic

• message display failing due to missing or too old TF

  • is different than contact data being outdated, so should indeed be a different message

not sure if all status can be seen at the same time, in case 2 errors happen at the same time.