How to setup linkage for OpenCV and Qt to use createButton?

Question

I'm looking at opencv highgui samples (like connectedcomponents.cpp) and trying to get used to adding GUI elements. Currently I'm trying to add a button:

void on_button(int, void*){
    cout << "click" << end;
}
//in main()
createButton("test",on_button);

but I get a link error:

g++ -c -pipe -g -gdwarf-2 -arch x86_64 -Xarch_x86_64 -mmacosx-version-min=10.5 -Wall -W -DQT_CORE_LIB -I../../../QtSDK/Desktop/Qt/474/gcc/mkspecs/macx-g++ -I. -I../../../QtSDK/Desktop/Qt/474/gcc/lib/QtCore.framework/Versions/4/Headers -I../../../QtSDK/Desktop/Qt/474/gcc/include/QtCore -I../../../QtSDK/Desktop/Qt/474/gcc/include -I/opt/local/include -I../../../QtSDK/Desktop/Qt/474/gcc/include -I. -F/Users/george/QtSDK/Desktop/Qt/474/gcc/lib -o main.o main.cpp
g++ -headerpad_max_install_names -arch x86_64 -Xarch_x86_64 -mmacosx-version-min=10.5 -o CVConnectedComponent main.o   -F/Users/george/QtSDK/Desktop/Qt/474/gcc/lib -L/Users/george/QtSDK/Desktop/Qt/474/gcc/lib /opt/local/lib/libopencv_core.dylib /opt/local/lib/libopencv_contrib.dylib /opt/local/lib/libopencv_highgui.dylib /opt/local/lib/libopencv_objdetect.dylib /opt/local/lib/libopencv_imgproc.dylib /opt/local/lib/libopencv_features2d.dylib /opt/local/lib/libopencv_video.dylib -framework QtCore -F/Users/george/Documents/Qt/CVConnectedComponent/../../../QtSDK/Desktop/Qt/474/gcc/lib/ 
Undefined symbols:
  "cv::createButton(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, void (*)(int, void*), void*, int, bool)", referenced from:
      _main in main.o
make: Leaving directory `/Users/george/Documents/Qt/CVConnectedComponent'
ld: symbol(s) not found

As far as I can understand I'm not linking against the QtCore library properly. I've this:

mac: LIBS += -framework QtCore

and this:

mac: LIBS += -F$$PWD/../../../QtSDK/Desktop/Qt/474/gcc/lib/ -framework QtCore

INCLUDEPATH += $$PWD/../../../QtSDK/Desktop/Qt/474/gcc/include
DEPENDPATH += $$PWD/../../../QtSDK/Desktop/Qt/474/gcc/include

In the .pro file of the Qt project, but with no luck. I'm using OpenCV 2.4.1 with Qt 4.7.4 on osx 10.6.8.

What's the correct way to link to QtCore in Qt Creator to use createButton in OpenCV ?

Answer 1

I've reinstalled OpenCV, this time with Qt support and the code worked. Still it's worth remembering that buttons will go into the Control Panel by default, as I found out by reading some documentation :