How to recognize when tf has stopped publishing?

edit

hello,

you may check out waitForTransform()

bool tf::TransformListener::waitForTransform (const std::string &target_frame, const std::string &source_frame, const ros::Time &time, const ros::Duration &timeout, const ros::Duration &polling_sleep_duration=ros::Duration(0.01), std::string *error_msg=NULL) const

Test if source_frame can be transformed to target_frame at time time. The waitForTransform() methods return a bool whether the transform can be evaluated. It will sleep and retry every polling_duration until the duration of timeout has been passed. It will not throw. If you pass a non NULL string pointer it will fill the string error_msg in the case of an error. (Note: That this takes notably more resources to generate the error message.)

or

The canTransform() methods return a bool whether the transform can be evaluated. It will not throw. If you pass a non NULL string pointer it will fill the string error_msg in the case of an error.

bool tf::TransformListener::canTransform (const std::string &target_frame, const std::string &source_frame, const ros::Time &time, std::string *error_msg=NULL) const