Project ERROR: Unknown module(s) in QT: designer

  • I have downloaded 5.9.1 source files using the installer and cross compiled for Raspberry Pi 3 using a Ubuntu 17.04 Host. If I start an example project and add

    QT       += designer

    to my .pro file I can compile for the Desktop but when I try to compile for the Raspberry Pi I get this error. I have compiled all the source modules (specifically qttools which I believe has the designer module) so I'm not sure what I need to add in order for the cross compile to find the designer module.

    I have tested other projects and core, gui, and widgets all can be successfully cross compiled.

    Thanks in advance for your help.

  • Lifetime Qt Champion


    IIRC, the designer related classes are not available when cross-compiling as it is a host tool.

  • Thanks for that. What my ultimate goal was to install and use Qwt widgets and in order to use it the install instructions said you need to add designer to your Pro file. Is there another way to do this?

  • Lifetime Qt Champion

    Only if you plan to use designer to create your widgets and in that case, it's still a "host plugin" so just don't build it when cross-compiling.

  • I'm sorry but I'm a little confused by your reply. If I want to use the Qwt plugin to add one of their widgets I need to use designer to place the widget and then I would need to cross compile and transfer to the Raspberry Pi to run on the Pi.

    Could you add some details on how I would install, use, and cross compile for the Pi?


  • Lifetime Qt Champion

    I mean that the plugin must be compiled for the same architecture as Designer is running on. So for development you need to build Qwt twice: once for your desktop machine and once for your Pi.

    When cross-compiling you'll be linking to your cross-compiled Qwt the same way you'd be linking with your Desktop build of Qwt while building your application on your desktop machine.

  • OK, I think I'm getting there, thanks. so for the Host build I would issue:

    qmake -spec linux-g++
    sudo make install

    which would install it at /usr/local/qwt-6.3.1 on the Ubunutu Host

    and then for the Raspberry Pi I would issue:

    qmake -spec device/linux-rasp-pi3-g++
    make install

    But I need to direct the output to go into the ~/raspi/sysroot/usr or some other place like ~raspi/build/qt5.9/bin?

    When I ran the .config for cross compiling on the Ubuntu Host the configure used these values:

    -sysroot ~/raspi/sysroot
    -prefix /usr/local/qt5.9
    -extprefix ~/raspi/build/qt5.9
    -hostprefix ~/raspi/build/qt5.9-host

  • Lifetime Qt Champion

    Use the full path to the qmake binary of the version of Qt you want to use.

    As for cross-compilation, again, use the the full path to the qmake binary from your cross-compiled Qt.

  • Dear Sirs,

    I am facing the same issue. I also stop at Project ERROR: Unknown module(s) in QT: designer

    My procedure is:

    1. Use QT creator open
    2. select Desktop QT5.8.0 GCC 64bit to build project
    3. result is OK.(no error)
    4. switch to "Raspberry Pi" then build project. (/rpi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-g++)
    5. result is " Unknown module(s) in QT: designer"

    According to this discussion:
    It same as @SGaist 's suggestion, it needs to compiler twice(if using cross-compiler).
    Do I have to comment out designer for the fourth step (the 2nd compiler) ?
    How to do it ? Does it means QT+=designer in (manual add for step2) or the

    QWT_INSTALL_PLUGINS   = $${QWT_INSTALL_PREFIX}/plugins/designer 

    in qwtconfig.pri ??

    Is there anyone have similar experience ?

    Thanks for any help.

  • Lifetime Qt Champion

    IIRC, you need to disable the QWT_CONFIG += QwtDesigner line in qwtconfig.pri.

  • Dear @SGaist ,

    Yes, your suggestion is correct. After comment out

    QWT_CONFIG += QwtDesigner

    I can use rpi(/arm-linux-gnueabihf-g++) compiler the qwt project without error.

    Though I still don't know how to add qwt into designer correctly, this may belong to different topic. I will arrange my test procedure and create different topic.


  • Lifetime Qt Champion

    The plugin for Designer must be built with the same version of Qt than Designer/Creator was built with (on Windows this includes compiler version).

    That's why it's recommended to split the plugin project in two:

    • One is a library with all the widget(s)
    • One is the plugin itself

    The plugin will be used to design your widget while the library will be used to link the application thus when you cross-compile you only need the library for the target.

  • I installed QT Creator into the ubuntu 16.04,

    After first compiler by linux-g++, was created.
    and then I open terminal and run "sudo make install" in /build-qwt-Desktop_Qt_5_8_0_GCC_64bit-Debug/. Then I can see qwt-6.1.3 folder was generated to /usr/local

    then as @SGaist said, I comment out qwtdesigner, then run 2nd compiler.
    2nd compiler is linux-rasp-pi-g++, then generate ../build-qwt-Raspberry_Pi-Debug.

    1. Where should I copy to ??
      I expect after this process, I should able to see qwt widget in designer, right ?
      I had tried copy to ~/Qt5.8.0/5.8/gcc_64/plugins/designer , but not working.

    2. Should I do sudo make install in the ../build-qwt-Raspberry_Pi-Debug after 2nd compiler ?

    3. After 2nd compiler, I think I should copy all ../build-qwt-Raspberry_Pi-Debug/lib to some place, but where ?? Replace everything in the /usr/local/qwt-6.1.3/lib ??

    Appreciate for any help~

  • Lifetime Qt Champion

    The plugin should go within the installation of Qt Creator

    You should have your cross-compiled Qwt in it's own folder.

  • Dear Sirs,

    I want to make qwt widget show on designer first, so I copy to below foler, one by one.

    /Qt5.8.0/Tools/QtCreator/bin/designer <--manual create bin/designer folder
    /usr/local/qwt-6.1.3/plugins/designer <--manual create plugins/designer folder

    Unfortunately, none of them work... Any idea ?

    PS. I re-open Qt Creator after copy to the folder each time.

  • Lifetime Qt Champion

    Did you check that you are using the same version of Qt that was used to build Qt Creator ?

  • Dear @SGaist ,

    I think they are the same, when I install qt creator I just download *.run file to complete the installation, so I think it use default make to build qt creator. Default gcc version is:

    When compiler qwt desktop(ubuntu) version, I didn't export different compiler. So Qwt and qt creator should use the same make and gcc version.

    Is there any point I can check ?

  • Lifetime Qt Champion

    You can start Qt Creator on the command line after setting the QT_DEBUG_PLUGINS environment variable to 1 so you can see what is happening with your plugin.

  • Dear @SGaist ,

    I reinstall QT Creator and copy to
    ~/Qt5.8.0/Tools/QtCreator/lib/Qt/plugins/designer/, then I can see qwt widget in the designer.

    I have not complete the whole process, but this is a good start. Thanks.

  • Lifetime Qt Champion

    What do you mean by "all process" ?

  • Dear @SGaist ,

    I can run on Ubuntu. Then I rebuild by Raspberry and did:

    sudo make install

    then copy lib to


    then build Qwt example OK, but when I run it, it show:

    error while loading shared libraries:

    So I think I didn't complete all process~

  • Dear All,

    After surf the Internet, it can be solved easily by

    Just copy *.so to RPi then add path to /etc/

    Thanks everyone.

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