The reference configuration documents the boundary for both plugins that
use the feature:
# Set hide_threshold_bytes to an integer value to automatically hide
# interface with traffic less or equal than this value
#hide_threshold_bytes=0
"less or equal than this value", with a documented default of 0, means a
rate of exactly 0 is hidden. The comparison un-hid on `>=` instead, so at
the default threshold every zero rate satisfied `0 >= 0` and the row came
straight back.
The first refresh still hides, because it has no previous view to carry
forward and falls into the `else` branch. From the second refresh on,
nothing was ever hidden again -- which is why `hide_zero=True` looked like
it worked for one frame and then stopped.
This restores the behaviour that `i[field] != 0` had before the threshold
option was introduced, and honours a non-zero threshold the way the
configuration file describes it.
Tests pin the boundary rather than any rendered message: the views dict
keeps every key either way, only `hidden` moves.
nicolargo