No change/archive event sent when attribute value transitions to/from NaN and quality factor does not change
cppTango does not send any change/archive event when a DevDouble (probably the same with DevFloat) attribute value changes to NaN if the quality factor did not change.
This is in the use case when the server is sending events (via Tango polling thread or pushing events by code with criteria managed by library) and let the cpptango library do the check whether an event should be sent or not based on the configured change/archive event threshold.
In the same way, no event is sent when the value changes from NaN to the attribute value from before the NaN value if the quality factor does not change.
Edited by Reynald Bourtembourg