Signal/Slot between a QT application and a non qt c++ code

[ademmler]

Hi there,

How do i realize Signal/Slot between a QT application and
a non qt c++ code (Like a foreign SDK - which is a black box)?

As example to set progress on a progress bar.
The sdk needs to set the "progress" in the main app.

thx

[Pablo J. Rogina]

@ademmler said in Signal/Slot between a QT application and a non qt c++ code:

But he asked me how I will use it in qt

I'd say it doesn't matter from the point of view of the SDK (and the SDK developer). Just make the SDK provide a callback function, as it will be used by any C++ program or one just happening to use Qt framework.

[Christian Ehrlicher]

Create a helper object and call the SDK api function in a slot there.

[ademmler]

@Christian-Ehrlicher

Hi Christian,

you mean something like this:

void myHelper() {
int err = mySDKroutine(parameters );
}

But still I do not see how the sdk can tell me how far the progress went ...

[Christian Ehrlicher]

@ademmler But where's the Qt problem here? If your SDK returns a progress value e.g. due to a callback then set it to a function in your helper class and emit a signal then.

[ademmler]

@Christian-Ehrlicher said in Signal/Slot between a QT application and a non qt c++ code:

If your SDK returns a progress value e.g. due to a callback then set it to a function in your helper class and emit a signal then.

I have not said there is a qt problem. I was asking for the best practise.
Single line answers are ambiguous to understand.
As far as I know "callbacks" are not available in qt.
May somebody posts a link to a working sample or some code lines here?

[Christian Ehrlicher]

@ademmler said in Signal/Slot between a QT application and a non qt c++ code:

As far as I know "callbacks" are not available in qt.

I said when your SDK provides a callback to report the progress you can set it to a function of your helper class.

[ademmler]

@Christian-Ehrlicher It does not give a callback.

[Christian Ehrlicher]

@ademmler So when your SDK does not provide a progress indicator you can't display any progress, or?

[ademmler]

@Christian-Ehrlicher You are right - that's why I asked the SDK developer to do so. But he asked me how I will use it in qt .... I am just in the middle of question ;-) that's why I asked for some example :-)
thx for your help.

[Christian Ehrlicher]

@ademmler He should provide a function to report the progress as callback function. So you can pass a function pointer to your helper class function.

[Pablo J. Rogina]

@ademmler said in Signal/Slot between a QT application and a non qt c++ code:

But he asked me how I will use it in qt

I'd say it doesn't matter from the point of view of the SDK (and the SDK developer). Just make the SDK provide a callback function, as it will be used by any C++ program or one just happening to use Qt framework.

[ademmler]

@Pablo-J-Rogina and @Christian-Ehrlicher

thx for your ideas.

[ademmler]

@Christian-Ehrlicher and @Pablo-J-Rogina

Hi Pablo and christian, I do not get this connection between sdk callback and qt application to work.
Is there a real live example somewhere - from what I can learn?
Would you be so kind to point me to this?

[Pablo J. Rogina]

@ademmler said in Signal/Slot between a QT application and a non qt c++ code:

sdk callback

at a very least, you should have already provided a link to such SDK...

[ademmler]

@Pablo-J-Rogina yes your are right - but it am not allowed to. It's private.

I get this error "no known conversion from 'void (SpectraProof::)(int)' to 'FuncPtrInt' (aka 'void ()(int)') for 6th argument"

What I have in the header file fo the SDK:
typedef void (*FuncPtrInt)(int);

In my main qt app (stripped code):
void myFunctionCallingTheSDK
{
err = chamo_nChanneltoRGB(nChannel_TIFF.toStdString(), RGB_TIFF.toStdString(), IP, jobSpotDefinitions.toStdString(), cmmPath.toStdString(), &updateProgress);
}

void SpectraProof::updateProgress(int percent)
{
qDebug() << "Progress: " + QString::number(percent);
ui->progressBar->setValue(percent);
}

[JonB]

@ademmler said in Signal/Slot between a QT application and a non qt c++ code:

typedef void (*FuncPtrInt)(int);

Before you go any farther: that looks like it's expecting a simple C-style function? You will need a C++ expert here to confirm: I don't think you can call a C++ class member method (your SpectraProof::updateProgress(int)) like this, there's no this?

[Christian Ehrlicher]

@JonB said in Signal/Slot between a QT application and a non qt c++ code:

I don't think you can call a C++ class member method

correct. That's why some callback functions take a function pointer + a custom 'void* userData' which takes e.g. this as userData. If this is not available you need a global ptr.

[ademmler]

@Christian-Ehrlicher @JonB

Ok gentlemen - it is really hard for me to follow your advices because I got lost ...
Would it be possible to give me some lines of code to illustrate your words?