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Re: [Discuss-gnuradio] QT GUI FFTSINK in C++ Flowgraph

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] QT GUI FFTSINK in C++ Flowgraph
Date: Mon, 17 Dec 2012 10:35:34 -0500

On Sun, Dec 16, 2012 at 5:23 PM, Daniel Labarowski <address@hidden> wrote:
I've been toying around with this a bit more. I added "#include <QWidget>" to the top of my program. I also added "QWidget* parent = new QWidget;" before my call to qtgui_make_sink_c and replaced "QWidget *parent=NULL" white "parent". I am now getting the following error

top_block.cc:(.text+0x8cd): undefined reference to `QWidget::QWidget(QWidget*, QFlags<Qt::WindowType>)'
top_block.cc:(.text+0x94f): undefined reference to `qtgui_make_sink_c(int, int, double, double, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, bool, bool, bool, bool, QWidget*)'

I've double checked what little documentation I can find on qtgui_make_sink_c and I think that I am passing appropriate parameters. Any thoughts on what might be wrong?


This suggests that you are not linking against libgnuradio-qtgui.so. Make sure you are (-lgnuradio-qtgui should be used when linking).

You probably also want to use NULL for the parent. As it is now, you're using an empty QWidget, and I'm not sure what will happen with that, but it probably won't work as expected.

From your first email, it looks like you are passing "QWiget* parent=NULL" as the last parameter. Just say "NULL" here, instead.

I've never tried to use QTGUI in C++ apps, so I'm curious to know if you can get it to work.



On 12/15/2012 02:07 AM, Daniel Labarowski wrote:
I am attempting to use qt gui widgets in a C++ flowgraph. I managed to get all of the build dependencies figured out, which was no easy task in itself and required a lot of direct includes. Anyway, the error that I am getting now deals directly with the make function. The line that is giving me trouble is as follows

qtgui_sink_c_sptr qtsink = qtgui_make_sink_c (fftsize, gr_firdes::WIN_HAMMING, 0, 1.0, "Spectrum Display", true, true, true, true, QWidget *parent=NULL);

Information on this function is available here. The error that I am getting is that parent is undefined. I really don’t know what to put for this. Note that I have also tried putting just NULL or just 0 and it throws an undefined reference error (for the function call). I was wondering if someone could give me some pointers on what to use for parent? While I would eventually like to have both an fft and a time domain view in a single window, I am currently just trying to get the fft to show in its own window. Thanks ahead of time!


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