[Discuss-gnuradio] QT GUI Update Rates for Vector vs Number Sink

[Murphy, John]

My GRC flowgraph has a block that outputs a float and a vector of
floats, at a rate of approx 1.49 updates per second. These go to a QT
GUI Vector Sink and a QT GUI Number Sink. The number sink has a graph
type of "None" so it is just showing the number.

When I calculate and enter the actual update period (1 / 1.49 ish)
then the displays do not update at the proper interval and the update
timing is very inconsistent. So I have both QT GUI Sinks set to Update
Period of 0.

The vector sink shows every update right on cue.
The number sink reliably shows every eighth (8th) update. You can
watch both and count the regular vector sink updates and every 8 times
the number sink will update.

I have also noticed the first number update happens reliably (all
possible testing <g>) on the fifth vector update, if that helps locate
the issue.

Since the vector stream and the float stream are coming from the same
block the rate has to be the same, so I am assuming it is not my block
that is failing to output updates. And the block C++ looks correct for
the output part of the work function. My guess anyhow.

Is this a known QT GUI Number Sink bug or do I have something
configured incorrectly? Any idea what it could be?

If it is of any relevance, here is the system info:
Fedora 20 (uname -r is 3.18.9-100.fc20.x86_64)
LXDE desktop environment
GNU Radio version 3.7.6.1
UHD version 3.8.1
USRP B200 with TCXO GPSDO connected over USB3
i7-4990R brick with 16 GB RAM and SSD

Thanks,
John