The same code works under Windows and fails under GNU/Linux

goetz

It's common to instantiate your UI class in the main function after the QApplication (-derived) object has been created.

I have not tested if that is the cause of your problem, but at least it's common coding style in Qt world.

vishwajeet

Ohhhh i apologies for too many abbreviations in my writing.
[quote author="Volker" date="1298556541"][quote author="vishwajeet" date="1298555161"]
Problem seems simple here i guess, its just you have to check the difference between win and Linux in terms of main() code execution, max u might have to go 1 layer down but that should resolve ur problem. [/quote]

[Highlighting by me]

Can you please use correct english in your writings. It's hard to read these non obvious abbreviations, especially for non-native speakers. This is neither Twitter nor SMS, we do have far more than 140 available :-) so no need to confuse people.
[/quote]

To jerome.bouat

Could you please check if @MyApp app(argc,argv);
return app.exec(); // event loop@ is getting executed in case of windows and Linux ?

jerome.bouat

The below code fragment is being executed
on Windows (because the application works properly)
and Linux (because I don't get the error if I comment it) :
@MyApp app(argc,argv);
return app.exec(); // event loop@

I moved the GUI initialization in a separate method (createWindow) :
@class MyApp : public QApplication

{

private:

Q_OBJECT

public:

bool tested;

QString program;

streambuf *coutbuf;

virtual ~MyApp();

// empty, just call super class constructor
// and initialize object attributes

MyApp(int &,char **);

void createWindow(int &,char **);

};@

Into this new method, I don't get the error message
if I comment the "show()" call
@void MyApp::createWindow(int &argc,char **argv)

{

MainWindow *mainWindow = new MainWindow(argc,argv);

mainWindow->show(); // no error if commented

}@

Thus, the issue seems to be located into the super-super class method QWidget::show().

goetz

No way to analyze this here. Can you please:

make a small test case
put it into a complete project
make sure it compiles, runs and shows the error
put the sources (and only these) into a ZIP
put the ZIP on dropbox, pastebin or make it available somewhere else
post the link here

jerome.bouat

It seems to be an OpenGL issue but the error message I reported is far from that.

I'm investigating.

jerome.bouat

Just a Qt newbie question : I assume that all calls like below should be located into header files only and not cpp files :
@QObject::connect(scrollBar, SIGNAL(valueChanged(int)), label, SLOT(setNum(int)));@
?

Or could we possibly use this call into cpp files by including the right Qt file ?

goetz

It's an ordinary call of a static method. You put it into regular method bodies. That happens mostly in the .cpp files, but can be put into headers too.

andre

What's more, in most cases the right file is already included when you call this: the header of either of the objects you want to connect. If you find that you can not use the connect call: it is to be found in the QObject header.

jerome.bouat

I assume the "emit" keyword can be used in cpp files ?

andre

Perhaps you should work through one of the basic Qt tutorials. This is all explained very well in the documentation, there is even a section called "Signals & Slots" that explains in detail how this all works.