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Re: [Discuss-gnuradio] question about using qtgui_sink_c from c++

From: Nick Foster
Subject: Re: [Discuss-gnuradio] question about using qtgui_sink_c from c++
Date: Sat, 19 May 2012 12:00:30 -0700

On Sat, May 19, 2012 at 11:09 AM, Steve <address@hidden> wrote:
On 05/19/2012 11:06 AM, Tom Rondeau wrote:

> Alright, but that sounds like it's in the right direction. You
> probably need to get a reference to the qApp and then execute that.
> Take a look at some of the Python examples and how they work with the
> qApp and then run the "exec_()" method with it. That gets the Qt
> engine running.

Calling the block function exec_() (which calls exec() for the
QApplication) was what was needed. And setting the widget to be visible.
That makes a window pop up with the spectrum. But for some reason the
performance is very bad.

I'm working on Qt performance in a separate branch. For now, though, if by "performance is very bad" you mean "update rate is slow", then change the line in qtgui_sink_c which says: 


This will use a 20fps update rate instead of the default (strangely) 2fps.


A couple of other things.  exec() does not return till the QApplication
exits. And it must be called from the main thread. At least that is the
error output I got when I tried to call it from a boost thread. To use
it I would have to redesign my application. So I probably won't be
spending any more time with it.


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