# Constellation plot in c++ using qtgui

**URL:** <https://www.ruby-forum.com/t/constellation-plot-in-c-using-qtgui/240917>\
**Category:** GNU Radio\
**Created:** [May 6, 2014, 4:31pm UTC](https://www.ruby-forum.com/t/constellation-plot-in-c-using-qtgui/240917 "2014-05-06T16:31:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [May 6, 2014, 4:31pm UTC](https://www.ruby-forum.com/t/constellation-plot-in-c-using-qtgui/240917/1 "2014-05-06T16:31:03Z")

</div>

hello everybody,

I wanted to use constellation plot of gnuradio in my top block in c++. I  
actually use qtcreator in ubuntu and gnuradio 3.7.3. After I found out  
that  
I must add “-lgnuradio-qtgui” to the .pro file of qtcreator for using  
qtgui  
of gnuradio, I ran the program but it didn’t open any GUI!!!

my code is like this :

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////  
#include \<gnuradio/qtgui/const\_sink\_c.h\>

#include \<QtGui/QApplication\>  
#include \<qapplication.h\>  
#include

using namespace gr;

int main()  
{  
// some blocks here …

```
 qtgui::const_sink_c::sptr constellation =

```

qtgui::const\_sink\_c::make(10, “constellation”, 1, NULL);

```
  // some connections ....

  tb->run();

  return 0;

```

}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

What is the problem!? Why I can’t see any GUI?

best

---

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**Author:** ![mostafa\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mostafa\_a](https://www.ruby-forum.com/u/mostafa_a)\
**Post date:** [May 6, 2014, 5:02pm UTC](https://www.ruby-forum.com/t/constellation-plot-in-c-using-qtgui/240917/2 "2014-05-06T17:02:26Z")

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On Tue, May 6, 2014 at 10:29 AM, Mostafa A.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)wrote:

> 

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

> ```
> // some blocks here ....
> 
> ```

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

> What is the problem!? Why I can’t see any GUI?
> 
> best

You haven’t don’t anything to get the qApplication and start it.

Tom

---

<div class="post-metadata">

**Author:** ![mostafa\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mostafa\_a](https://www.ruby-forum.com/u/mostafa_a)\
**Post date:** [May 6, 2014, 5:06pm UTC](https://www.ruby-forum.com/t/constellation-plot-in-c-using-qtgui/240917/3 "2014-05-06T17:06:08Z")

</div>

On Tue, May 6, 2014 at 11:00 AM, Tom R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > int main()  
> > return 0;
> 
> You haven’t don’t anything to get the qApplication and start it.
> 
> Tom

You haven’t “done” anything to get the qApplication and start it.

Tom