using a custom widget

**GrahamLabdon** · 21st March 2011, 14:50

Hi
So I have a custom widget and want to use it in another project.
In the .pro file for the new project I have

Qt Code:

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LIBS += C://QTProjects/cccc-build-desktop/debug/mycustomwidgetplugin.dll

LIBS += C://QTProjects/cccc-build-desktop/debug/mycustomwidgetplugin.dll

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When I compile the project I get

Qt Code:

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debug/MainWindow.o:C:\QTProjects\cccc-build-desktop/./ui_MainWindow.h:43: undefined reference to `MyCustomWidget::MyCustomWidget(QWidget*)'

debug/MainWindow.o:C:\QTProjects\cccc-build-desktop/./ui_MainWindow.h:43: undefined reference to `MyCustomWidget::MyCustomWidget(QWidget*)'

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Any ideas?

Graham

**high_flyer** · 21st March 2011, 15:08

did you specify in your project where to find the headers of your custom widgets?

**GrahamLabdon** · 21st March 2011, 15:09

Hi
I have hard coded these for now
#include "C:/QTProjects/MyCustomWidget/MyCustomWidget.h"

**high_flyer** · 21st March 2011, 15:13

where?
The error comes from an ui file - and it gets generated by the uic... if you are using your custom widget there - you should promote a widget to your custom widget so that the uic will include the correct file.

**GrahamLabdon** · 21st March 2011, 15:22

hi
I have now added the include path the .pro file
My custom widget is built in a dll and is accessible in QtDesigner (although not in QtCreator)
To get my application that uses the custom widget to compile I added an include path to the . pro file
I also added the dll to the LIBS -

Qt Code:

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#-------------------------------------------------
#
# Project created by QtCreator 2011-03-21T11:54:03
#
#-------------------------------------------------
 
QT       += core gui
 
TARGET = cccc
TEMPLATE = app
 
 
SOURCES += main.cpp\
        MainWindow.cpp
 
HEADERS  += MainWindow.h
 
FORMS    += MainWindow.ui
 
INCLUDEPATH = C:/QTProjects/MyCustomWidget
win32::LIBS += C:/QTProjects/MyCustomWidget-build-desktop/release/mycustomwidgetplugin.dll

#-------------------------------------------------
#
# Project created by QtCreator 2011-03-21T11:54:03
#
#-------------------------------------------------

QT       += core gui

TARGET = cccc
TEMPLATE = app


SOURCES += main.cpp\
        MainWindow.cpp

HEADERS  += MainWindow.h

FORMS    += MainWindow.ui

INCLUDEPATH = C:/QTProjects/MyCustomWidget
win32::LIBS += C:/QTProjects/MyCustomWidget-build-desktop/release/mycustomwidgetplugin.dll

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When I build I get a undefined reference -
/ui_MainWindow.h:43: undefined reference to `MyCustomWidget::MyCustomWidget(QWidget*)'

I am struggling to understand why this is

Any help appreciated

Graham

**high_flyer** · 21st March 2011, 15:24

I am struggling to understand why this is

read my last post again.

**GrahamLabdon** · 21st March 2011, 15:30

Hi
In Qt Designer I can see my custom widget and can drag it onto a form.
This generates a ui file with an #include for the custom widget, which is located because of the INCLUDEPATH directive in the .pro file.
If I drag a widget onto the form and try to promote it I get an error stating that the class already exists
So I am confused!!

**high_flyer** · 21st March 2011, 15:36

Hi
In Qt Designer I can see my custom widget and can drag it onto a form.
This generates a ui file with an #include for the custom widget, which is located because of the INCLUDEPATH directive in the .pro file.

That piece of information you want to give at the beginning, and that is - that you have a designer plug in for your custom widget!!
So there is no need for promotion.

does your custom widget have a constructor that take a QWidget parent defined?
Post the header for your custom widget.

**GrahamLabdon** · 21st March 2011, 15:38

Header File

Qt Code:

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#ifndef MYCUSTOMWIDGET_H
#define MYCUSTOMWIDGET_H
 
#include <QtGui/QWidget>
 
class MyCustomWidget : public QWidget
{
    Q_OBJECT
 
public:
    MyCustomWidget(QWidget *parent = 0);
};
 
#endif

#ifndef MYCUSTOMWIDGET_H
#define MYCUSTOMWIDGET_H

#include <QtGui/QWidget>

class MyCustomWidget : public QWidget
{
    Q_OBJECT

public:
    MyCustomWidget(QWidget *parent = 0);
};

#endif

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cpp

Qt Code:

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#include "MyCustomWidget.h"
 
MyCustomWidget::MyCustomWidget(QWidget *parent) :
    QWidget(parent)
{
}

#include "MyCustomWidget.h"

MyCustomWidget::MyCustomWidget(QWidget *parent) :
    QWidget(parent)
{
}

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Thanks for your help!

**high_flyer** · 21st March 2011, 15:45

ok, show the include section of ui_MainWindow.h

**GrahamLabdon** · 21st March 2011, 15:48

Here ya go

Qt Code:

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#ifndef UI_MAINWINDOW_H
#define UI_MAINWINDOW_H
 
#include <QtCore/QVariant>
#include <QtGui/QAction>
#include <QtGui/QApplication>
#include <QtGui/QButtonGroup>
#include <QtGui/QHeaderView>
#include <QtGui/QMainWindow>
#include <QtGui/QMenuBar>
#include <QtGui/QStatusBar>
#include <QtGui/QToolBar>
#include <QtGui/QWidget>
#include "MyCustomWidget.h"

#ifndef UI_MAINWINDOW_H
#define UI_MAINWINDOW_H

#include <QtCore/QVariant>
#include <QtGui/QAction>
#include <QtGui/QApplication>
#include <QtGui/QButtonGroup>
#include <QtGui/QHeaderView>
#include <QtGui/QMainWindow>
#include <QtGui/QMenuBar>
#include <QtGui/QStatusBar>
#include <QtGui/QToolBar>
#include <QtGui/QWidget>
#include "MyCustomWidget.h"

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**high_flyer** · 21st March 2011, 15:55

and the custom widget header is under C:/QTProjects/MyCustomWidget?
Then I don't see where the problem is...

**GrahamLabdon** · 21st March 2011, 15:57

I found this link
http://stackoverflow.com/questions/2...491825#2491825
But don't really know how to create the other lib

**high_flyer** · 21st March 2011, 16:03

you are getting a compile error, not a link error.
You have a definitive path problem that's all, I just can't tell where.
What is said in that post you linked to is not correct.
I link my apps to my custom widgets against their designer plugin dll with no problem.

**GrahamLabdon** · 21st March 2011, 16:17

Hi
Im not certain that its a compiler error
Here is the output from the build

Qt Code:

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Running build steps for project cccc...
Starting: "C:/mingw/bin/mingw32-make.exe" clean -w
mingw32-make: Entering directory `C:/QTProjects/cccc-build-desktop'
 
C:/mingw/bin/mingw32-make -f Makefile.Release clean
 
mingw32-make[1]: Entering directory `C:/QTProjects/cccc-build-desktop'
 
del release\moc_MainWindow.cpp
 
del ui_MainWindow.h
 
del release\main.o release\MainWindow.o release\moc_MainWindow.o
 
mingw32-make[1]: Leaving directory `C:/QTProjects/cccc-build-desktop'
 
C:/mingw/bin/mingw32-make -f Makefile.Debug clean
 
mingw32-make[1]: Entering directory `C:/QTProjects/cccc-build-desktop'
 
del debug\moc_MainWindow.cpp
 
del ui_MainWindow.h
 
del debug\main.o debug\MainWindow.o debug\moc_MainWindow.o
 
mingw32-make[1]: Leaving directory `C:/QTProjects/cccc-build-desktop'
 
mingw32-make: Leaving directory `C:/QTProjects/cccc-build-desktop'
 
Could Not Find C:\QTProjects\cccc-build-desktop\debug\moc_MainWindow.cpp
 
Could Not Find C:\QTProjects\cccc-build-desktop\ui_MainWindow.h
 
Could Not Find C:\QTProjects\cccc-build-desktop\debug\main.o
 
The process "C:/mingw/bin/mingw32-make.exe" exited normally.
Configuration unchanged, skipping qmake step.
Starting: "C:/mingw/bin/mingw32-make.exe" -w
mingw32-make: Entering directory `C:/QTProjects/cccc-build-desktop'
 
C:/mingw/bin/mingw32-make -f Makefile.Release
 
mingw32-make[1]: Entering directory `C:/QTProjects/cccc-build-desktop'
 
c:\Qt\4.7.2\bin\uic.exe ..\cccc\MainWindow.ui -o ui_MainWindow.h
 
g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -o release\main.o ..\cccc\main.cpp
 
g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -o release\MainWindow.o ..\cccc\MainWindow.cpp
 
C:\Qt\4.7.2\bin\moc.exe -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -D__GNUC__ -DWIN32 ..\cccc\MainWindow.h -o release\moc_MainWindow.cpp
 
g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -o release\moc_MainWindow.o release\moc_MainWindow.cpp
 
g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc -Wl,-s -mthreads -Wl -Wl,-subsystem,windows -o release\cccc.exe release/main.o release/MainWindow.o release/moc_MainWindow.o  -L"c:\Qt\4.7.2\lib" -lmingw32 -lqtmain C:/QTProjects/MyCustomWidget-build-desktop/release/mycustomwidgetplugin.dll -lQtGui4 -lQtCore4 
 
mingw32-make[1]: Leaving directory `C:/QTProjects/cccc-build-desktop'
 
mingw32-make: Leaving directory `C:/QTProjects/cccc-build-desktop'
 
release/MainWindow.o:MainWindow.cpp:(.text$_ZN13Ui_MainWindow7setupUiEP11QMainWindow[Ui_MainWindow::setupUi(QMainWindow*)]+0x129): undefined reference to `MyCustomWidget::MyCustomWidget(QWidget*)'
 
collect2: ld returned 1 exit status
 
mingw32-make[1]: *** [release\cccc.exe] Error 1
 
mingw32-make: *** [release] Error 2
 
The process "C:/mingw/bin/mingw32-make.exe" exited with code %2.
Error while building project cccc (target: Desktop)
When executing build step 'Make'

Running build steps for project cccc...
Starting: "C:/mingw/bin/mingw32-make.exe" clean -w
mingw32-make: Entering directory `C:/QTProjects/cccc-build-desktop'

C:/mingw/bin/mingw32-make -f Makefile.Release clean

mingw32-make[1]: Entering directory `C:/QTProjects/cccc-build-desktop'

del release\moc_MainWindow.cpp

del ui_MainWindow.h

del release\main.o release\MainWindow.o release\moc_MainWindow.o

mingw32-make[1]: Leaving directory `C:/QTProjects/cccc-build-desktop'

C:/mingw/bin/mingw32-make -f Makefile.Debug clean

mingw32-make[1]: Entering directory `C:/QTProjects/cccc-build-desktop'

del debug\moc_MainWindow.cpp

del ui_MainWindow.h

del debug\main.o debug\MainWindow.o debug\moc_MainWindow.o

mingw32-make[1]: Leaving directory `C:/QTProjects/cccc-build-desktop'

mingw32-make: Leaving directory `C:/QTProjects/cccc-build-desktop'

Could Not Find C:\QTProjects\cccc-build-desktop\debug\moc_MainWindow.cpp

Could Not Find C:\QTProjects\cccc-build-desktop\ui_MainWindow.h

Could Not Find C:\QTProjects\cccc-build-desktop\debug\main.o

The process "C:/mingw/bin/mingw32-make.exe" exited normally.
Configuration unchanged, skipping qmake step.
Starting: "C:/mingw/bin/mingw32-make.exe" -w
mingw32-make: Entering directory `C:/QTProjects/cccc-build-desktop'

C:/mingw/bin/mingw32-make -f Makefile.Release

mingw32-make[1]: Entering directory `C:/QTProjects/cccc-build-desktop'

c:\Qt\4.7.2\bin\uic.exe ..\cccc\MainWindow.ui -o ui_MainWindow.h

g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -o release\main.o ..\cccc\main.cpp

g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -o release\MainWindow.o ..\cccc\MainWindow.cpp

C:\Qt\4.7.2\bin\moc.exe -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -D__GNUC__ -DWIN32 ..\cccc\MainWindow.h -o release\moc_MainWindow.cpp

g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\Qt\4.7.2\include\QtCore" -I"..\..\Qt\4.7.2\include\QtGui" -I"..\..\Qt\4.7.2\include" -I"..\MyCustomWidget" -I"..\..\Qt\4.7.2\include\ActiveQt" -I"release" -I"." -I"..\cccc" -I"." -I"..\..\Qt\4.7.2\mkspecs\win32-g++" -o release\moc_MainWindow.o release\moc_MainWindow.cpp

g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc -Wl,-s -mthreads -Wl -Wl,-subsystem,windows -o release\cccc.exe release/main.o release/MainWindow.o release/moc_MainWindow.o  -L"c:\Qt\4.7.2\lib" -lmingw32 -lqtmain C:/QTProjects/MyCustomWidget-build-desktop/release/mycustomwidgetplugin.dll -lQtGui4 -lQtCore4 

mingw32-make[1]: Leaving directory `C:/QTProjects/cccc-build-desktop'

mingw32-make: Leaving directory `C:/QTProjects/cccc-build-desktop'

release/MainWindow.o:MainWindow.cpp:(.text$_ZN13Ui_MainWindow7setupUiEP11QMainWindow[Ui_MainWindow::setupUi(QMainWindow*)]+0x129): undefined reference to `MyCustomWidget::MyCustomWidget(QWidget*)'

collect2: ld returned 1 exit status

mingw32-make[1]: *** [release\cccc.exe] Error 1

mingw32-make: *** [release] Error 2

The process "C:/mingw/bin/mingw32-make.exe" exited with code %2.
Error while building project cccc (target: Desktop)
When executing build step 'Make'

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Does this help you locate the problem?

**high_flyer** · 21st March 2011, 16:24

The error you posted now is a link error.

elease/MainWindow.o:MainWindow.cpp

.text$_ZN13Ui_MainWindow7setupUiEP11QMainWindow[Ui_MainWindow::setupUi(QMainWindow*)]+0x129): undefined reference to `MyCustomWidget::MyCustomWidget(QWidget*)'

But error you posted at the beginngin of this thread was a compile error:

debug/MainWindow.o:C:\QTProjects\cccc-build-desktop/./ui_MainWindow.h:43: undefined reference to `MyCustomWidget::MyCustomWidget(QWidget*)'

You have to be a bit more cooperative if you want effective help.

Your link line is not good:

-L"c:\Qt\4.7.2\lib" -lmingw32 -lqtmain C:/QTProjects/MyCustomWidget-build-desktop/release/mycustomwidgetplugin.dll -lQtGui4 -lQtCore4

'-l' is missing before 'C:/QTProjects/MyCustomWidget-build-desktop/release/mycustomwidgetplugin.dll'

**GrahamLabdon** · 21st March 2011, 16:27

Hi
Sorry if there has been some confusion
I had already tried '-l'
It gives this error

c:/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../mingw32/bin/ld.exe: cannot find -lC:/QTProjects/MyCustomWidget-build-desktop/release/mycustomwidgetplugin.dll

**high_flyer** · 21st March 2011, 16:34

you need to link against the *.lib file not the dll.
The dll is loaded at runtime.

**GrahamLabdon** · 21st March 2011, 16:36

I don't have a ".lib" file to link against

**high_flyer** · 21st March 2011, 16:48

Well, you should.
If you have the custom widget project source, try rebuilding it.
Without a lib you can't link against this DLL.

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