Question: I have a Qt application wrapped up inside a DLL for plugging into 3rd party applications. When those 3rd party applications start the Qt application, the toolbar tooltips in the 3rd party applications stop working. As soon as I close the Qt application, they work again.

I recreated the problem in Visual Studio by creating a non-Qt executable (in this case an MFC MDI application with out-of-the-box settings), and a Qt Application (which I changed to a DLL). I added a menu item to the non-Qt executable, and handled the event as follows:

```
void MFCApp::OnFileLaunch()
{
   QtApp qtApp;
   qtApp.Launch();
}

```

The QtApp class doesn't expose the Qt API at all, and Launch() is implemented as follows:

```
int QtApp::Launch()
{
   int argc = 0;
   char *argv = 0;
   QApplication a(argc, &argv);
   MyMainWindow w;
   w.show();
   return a.exec();
}

```

The non-Qt application remains fully responsive while the Qt application is displayed, apart from the toolbar tooltips (and also keyboard shortcuts such as Ctrl A for Select All).

I suspect this is might be a Qt bug, but just wanted to check anyway in case it's my Launch code that's wrong.

I'm using Qt 4.5.2 by the way.

Thanks

Answer: 
( value == 0.00 )

Never gets true.
Or, it takes so many runs of the function that the it runs into, well, stack overflow :P
You should take another look at how you made your function. Right now it is not even useful, it can only ever return 0.
don't compare float values with constants, always check if they fall under a lower-bound.
change your value == 0.00 to value <= 0.0001 for example