[Discuss-gnuradio] WX slider freezing when displayed with FFT sink..

Hi all

I have a problem with the WX slider freezing when I'm also displaying
a FFT sink. This is on Ubuntu Linux 18.04 LTS.

For some background, (sorry if this is a bit long and vague). I'm new
to GNU Radio. I'm working through Michael Ossmann's video course. I
only have a cheap dongle SDR but I've managed to get it receiving the
FM broadcast stations nicely. I'm eagerly waiting for my preordered
Airspy HF+ Discovery.

I'm running on an HP Pavilion laptop. It's a few years old but I think
it's still not too bad. I7 quad core (htop shows 8 cpus because of
hyperthreading), 8 GB ram.

Following Michael's course, I'm using WX widgets. The sliders are
often frozen. If I slide the mouse back and forward then the numeric
value changes but the pointer doesn't move. When I release the mouse
the value returns to the default. This happens with a simple1 kHz
waveform generator, to a throttle block to an FFT sink with 32k sample
rate. Occasionally they start working. I think a slider always works
if it's the only widget.

Another issue is that it really doesn't work well with the sound at
48kHz. Lots of underflows and sounds distorted. It works reasonably
well on 44.1kHz.

One of the exercises on the course is to try Pentoo Linux. I made a
live usb stick of Pentoo and the FM radio receiver flow works
perfectly with sliders working smoothly and sounding good at 48kHz
without underflow or overflow. I don't really want to use Pentoo as my
primary O/S. I'm not sure if it's activity maintained.

As an experiment, I made live usb sticks for several Ubuntu flavors.
Ubuntu 18.04 LTS to check if maybe something wrong with my main
install but got the same result.
Xubuntu - Same result.
Kubuntu - Sliders work well but same issue with the sound.

All this is with GNU radio 3.7.11-10 installed with apt-get.

I'd appreciate any suggestions. Maybe it's just not good hardware for
this but maybe it's something simple. I don't know enough about
desktop Linux to know what makes Pentoo work so well compared to the
others.

Thanks

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