Re: [Discuss-gnuradio] Rounding values in QT Number

[John Ackermann N8UR]

Thanks, Marcus!

First, there's something goofy because I am getting 6 decimal places, 
not 4.  See the attached screen shot.

Second, unfortunately at the moment I'm using the Ubuntu packages.  I 
used to always use the build-gnuradio script, but last summer I started 
having problems with librtlsdr when I did that, so I reverted to the 
packaged version because it still worked.  So I'm not set up to build 
gnuradio from sources without going back to ground zero. (Though I 
suppose I could do the whole deb-source thing.  *Shudder*)

Is there a reasonable process to take an existing GRC block and convert 
it to an OOT module?  I'd be happy to do that but don't know how to go 
about it.

Thanks,
John
----

On 03/06/2018 08:47 AM, Müller, Marcus (CEL) wrote:
> Hi John,
>
> there's no dumb questions, maybe badly researched ones, and you
> definitely don't have the habit of posting the latter, so: Good
> question!
>
> It all boils down to this line in gnuradio/gr-
> qtgui/lib/numberdisplayform.cc:
>
>        d_text_box[i]->setText(QString("%1 %2").arg(f, 4, ' ').\
>                               arg(QString(d_unit[i].c_str())));
>
> in which the current value `f` is displayed with four digits after the
> decimal dot.
>
> I'd agree this is probably not what's desirable in any application.
>
> Now, this can be changed; for example, we could add a way to set the
> number of digits variably instead of to 4. However, that'll be a source
> code and API change, so it'll require recompilation of GNU Radio and
> relinking of everything that use gr-qtgui. Does that help you?
>
> Best regards,
> Marcus
>
> On Mon, 2018-03-05 at 16:36 -0500, John Ackermann N8UR wrote:
> > I hate to put such a dumb question to the list, but I'm going nuts
> > trying to do something that ought to be simple.
> >
> > I am using a QT Number Sink to display dB values in float format.  It is
> > showing many more decimal places than have any meaning.  I'd like to
> > round the display to one or two decimal places.
> >
> > I tried making an embedded python block to do the rounding and finally
> > succeeded (it was a long and painful process, and frankly I don't
> > understand why I had to do what I did to get it to work), but the number
> > sink is still printing all the extra decimal places, they're just now
> > set to zero.
> >
> > Is there any trick to round or even just truncate the number of decimal
> > places shown in the QT Number Sink?
> >
> > Thanks,
> > John
> >
> > _______________________________________________
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Screenshot from 2018-03-06 08-58-11.png
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