[Qt-interest] Linker Error I do not understand

[Matthias Pospiech]

Hi,
I have a project which fails at a single class in linking. I get these 
errors:

mainwindow.obj:-1: error:  unresolved external symbol 
"__declspec(dllimport) public: __thiscall 
QCameraWidget::QCameraWidget(class QWidget *)" 
(__imp_??0QCameraWidget@@QAE at PAVQWidget@@@Z) referenced in function 
"public: void __thiscall Ui_MainWindowClass::setupUi(class QMainWindow 
*)" (?setupUi at Ui_MainWindowClass@@QAEXPAVQMainWindow@@@Z)
mainwindow.obj:-1: error:  unresolved external symbol "protected: 
virtual void __thiscall QCameraWidget::paintEvent(class QPaintEvent *)" 
(?paintEvent at QCameraWidget@@MAEXPAVQPaintEvent@@@Z)

and such, for all methods of the QCameraWidget class, all failting to 
link in mainwindow.obj

However I load the header in the cpp file, as well in the ui_* file.

#include "QCameraWidget.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindowClass)
    , camera(new QuEyeCamera)
{
...


the Class is build in a dll, which is linked with
debug:LIBS += -L../lib/$${COMPILER}/debug/ -l$${LIBRARY_NAME}

in the pro file. All other classed do not fail, so I expect that the 
library .lib file is loaded actually.

So now I do not know what to check else. Any ideas?

Matthias