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QXcbConnection: Could not connect to display

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  • m.sueM m.sue

    Hi @MHermann

    Did you connect via ssh -X or such from the Ubuntu 15 machine for this start test or did you try it directly on the Ubuntu 16 machine?

    -Michael.

    M Offline
    M Offline
    MHermann
    wrote on last edited by MHermann
    #7

    @m.sue :
    I tried it directly on the Ubuntu 16 machine.
    Is it possible to use QtCreator with ssh -X?

    m.sueM 1 Reply Last reply
    0
    • M MHermann

      @m.sue :
      I tried it directly on the Ubuntu 16 machine.
      Is it possible to use QtCreator with ssh -X?

      m.sueM Offline
      m.sueM Offline
      m.sue
      wrote on last edited by
      #8

      Hi @MHermann

      I would assume that QtCreator does this on its own for remote debugging?

      Please try also with ssh -X from the Ubuntu 16 command line. If this works the problem lies within QtCreator's connection to the remote machine.

      -Michael.

      M 1 Reply Last reply
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      • m.sueM m.sue

        Hi @MHermann

        I would assume that QtCreator does this on its own for remote debugging?

        Please try also with ssh -X from the Ubuntu 16 command line. If this works the problem lies within QtCreator's connection to the remote machine.

        -Michael.

        M Offline
        M Offline
        MHermann
        wrote on last edited by
        #9

        @m.sue :
        I tried it with ssh -X from the Ubuntu 16 command line.
        This is also not working.
        It gives me the following error messages:

        Failed to create OpenGL context for format QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 24, redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1, stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::SwapBehavior(DoubleBuffer), swapInterval 1, profile  QSurfaceFormat::OpenGLContextProfile(NoProfile)) 
        

        Any idea about this?

        m.sueM 1 Reply Last reply
        0
        • M MHermann

          @m.sue :
          I tried it with ssh -X from the Ubuntu 16 command line.
          This is also not working.
          It gives me the following error messages:

          Failed to create OpenGL context for format QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 24, redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1, stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::SwapBehavior(DoubleBuffer), swapInterval 1, profile  QSurfaceFormat::OpenGLContextProfile(NoProfile)) 
          

          Any idea about this?

          m.sueM Offline
          m.sueM Offline
          m.sue
          wrote on last edited by m.sue
          #10

          Hi @MHermann

          You will have to solve this OpenGL forwarding problem to make QtCreator remote debugging of a QML program possible.

          You will have to wait for someone else to take over here.

          -Michael.

          M 1 Reply Last reply
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          • m.sueM m.sue

            Hi @MHermann

            You will have to solve this OpenGL forwarding problem to make QtCreator remote debugging of a QML program possible.

            You will have to wait for someone else to take over here.

            -Michael.

            M Offline
            M Offline
            MHermann
            wrote on last edited by
            #11

            @m.sue :
            I am not sure if I understand you right here.
            For summerize:

            • I can compile and debug the app directly on my Ubuntu 16.

            • I can also compile remote debug the app on and Raspberry Pi.

            • I have only problems with remote debugging on Ubuntu 15.

            So the QtCreator is able to remote debug QML programs.

            m.sueM 1 Reply Last reply
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            • M MHermann

              @m.sue :
              I am not sure if I understand you right here.
              For summerize:

              • I can compile and debug the app directly on my Ubuntu 16.

              • I can also compile remote debug the app on and Raspberry Pi.

              • I have only problems with remote debugging on Ubuntu 15.

              So the QtCreator is able to remote debug QML programs.

              m.sueM Offline
              m.sueM Offline
              m.sue
              wrote on last edited by m.sue
              #12

              Hi @MHermann

              Yes but I think you have a problem to run a QML program on Ubuntu 15 remotely on Ubuntu 16. That is independent of QtCreator. The problem is to realize OpenGL commands generated in the program running on Ubuntu 15 on the graphics card of your Ubuntu 16 machine. This can be a configuration issue, a general problem, who knows.

              -Michael.

              M 1 Reply Last reply
              0
              • m.sueM m.sue

                Hi @MHermann

                Yes but I think you have a problem to run a QML program on Ubuntu 15 remotely on Ubuntu 16. That is independent of QtCreator. The problem is to realize OpenGL commands generated in the program running on Ubuntu 15 on the graphics card of your Ubuntu 16 machine. This can be a configuration issue, a general problem, who knows.

                -Michael.

                M Offline
                M Offline
                MHermann
                wrote on last edited by
                #13

                Has somebody else an idea how I can resolve this problem???

                M 1 Reply Last reply
                0
                • M MHermann

                  Has somebody else an idea how I can resolve this problem???

                  M Offline
                  M Offline
                  MHermann
                  wrote on last edited by
                  #14

                  I found the solution.
                  Maybe someone is interested in it...

                  In QtCreator > Run Settings > Run Environment it is necessary to set two environment variables:

                  • DISPLAY
                  • XAUTHORITY

                  After that the debugging works without problems.

                  1 Reply Last reply
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                  • D Offline
                    D Offline
                    da_ebeng
                    wrote on last edited by
                    #15

                    Hi @MHermann ,
                    I have the same problem. i tried to fix it by setting these evironment variables (DISPLAY, XAUTHORITY) but I still get this error:
                    qt.qpa.screen: QXcbConnection: Could not connect to display <VALUE>
                    Could not connect to any X display.
                    I did not set the values of the environment variables. How did you set the values?

                    1 Reply Last reply
                    0
                    • O Offline
                      O Offline
                      obertini
                      wrote on last edited by
                      #16

                      Hi,
                      Maybe that can help.

                      Cross-compiling Qt-5.10 on Raspberry Pi 3 running Raspbian Stretch
                      In Qt Creator, the Run parameters for the device are:
                      Use System Environment and
                      Set DISPLAY to :0
                      Set XAUTHORITY to /home/pi/.Xauthority

                      Note that I have also set the run argument as -platform xcb

                      1 Reply Last reply
                      1
                      • afyaA Offline
                        afyaA Offline
                        afya
                        wrote on last edited by
                        #17

                        Just as normal user authorize root, to connect to your display :)
                        xhost +SI:localuser:root

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                        • P Offline
                          P Offline
                          pakainfo
                          Banned
                          wrote on last edited by
                          #18
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