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setting QT_DEVICE_PIXEL_RATIO for a specific application

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  • F Offline
    F Offline
    floatingWoods
    wrote on last edited by
    #7

    I am using Qt 5.5

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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #8

      As a workaround you could try calling qsetenv before instantiating your QApplication

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      • F Offline
        F Offline
        floatingWoods
        wrote on last edited by
        #9

        Thanks again!

        This works on Windows:

        qputenv("QT_DEVICE_PIXEL_RATIO",QByteArray("2"));
        

        Any similar functionality for Linux (and optionally Mac, but as far as I have tested it, Mac always recognizes high dpi displays)?

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        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #10

          qputenv works also on OS X and Linux. IIRC yes OS X already handles that

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • F Offline
            F Offline
            floatingWoods
            wrote on last edited by
            #11

            Excellent, you are right, that also works on Linux.
            Thanks a lot!

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            • F floatingWoods

              Hello,

              under Windows 8.1, I can force the pixel ratio by setting the system's environmnent variable QT_DEVICE_PIXEL_RATIO.
              This is however applied to all my Qt applications.
              Is it possible to set that variable specifically to one application?
              I read about qt.conf file, but I am not sure what I have to put in there. e.g.

              [Environment]
              setx QT_DEVICE_PIXEL_RATIO 2
              

              But that has no effect. The qt.conf file is located in the same folder as my application's executable.

              S Offline
              S Offline
              soudi00
              wrote on last edited by
              #12

              @floatingWoods

              Hi, I need to change the QT_DEVICE_PIXEL_RATIO to "auto" in windows 10.

              I'm not a software developer and I have no idea how to do this I really appreciate if you can help me with this.

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #13

                Hi and welcome to devnet,

                If it's to test your application while using Qt Creator: go to the run part of the Project panel. There you can edit the environment variables. Add a new variable with the name QT_DEVICE_PIXEL_RATIO and in value write auto.

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                N 1 Reply Last reply
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                • SGaistS SGaist

                  Hi and welcome to devnet,

                  If it's to test your application while using Qt Creator: go to the run part of the Project panel. There you can edit the environment variables. Add a new variable with the name QT_DEVICE_PIXEL_RATIO and in value write auto.

                  N Offline
                  N Offline
                  nikit
                  wrote on last edited by
                  #14

                  @SGaist said:

                  QT_DEVICE_PIXEL_RATIO

                  Hi,
                  I did set the variable to AUTO as you mentioned.
                  My app run fines on 1366768 screen resolution size. But if I keep my screen resolution to 1024768, UI gets cut. (cannot see buttons of my UI app).
                  What would be the probable way to fix my app to all resolution of screen?

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                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #15

                    Are you using layouts to handle your widgets ?

                    Interested in AI ? www.idiap.ch
                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                    • N Offline
                      N Offline
                      nikit
                      wrote on last edited by
                      #16

                      Yes I am using Layouts.

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                      • SGaistS Offline
                        SGaistS Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on last edited by
                        #17

                        If your application needs a minimal size then you can put your main widget in a QScrollArea. That way if your application doesn't fit, you'll have scroll bars to move up/down to access the rest of your UI.

                        Interested in AI ? www.idiap.ch
                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                        • N Offline
                          N Offline
                          nikit
                          wrote on last edited by
                          #18

                          Thank you.
                          Guess this is the last option to add Scroll in my app to support low end resolution screens

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                          • SGaistS Offline
                            SGaistS Offline
                            SGaist
                            Lifetime Qt Champion
                            wrote on last edited by
                            #19

                            Not really a last option. If the design of your UI is big enough to not fit some screen resolution you can either change the design to fit a larger set of screen resolution. or make it more modular under a certain size. A scrolling area is not a bad solution otherwise how would you browse internet ?

                            Interested in AI ? www.idiap.ch
                            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                            • N Offline
                              N Offline
                              nikit
                              wrote on last edited by
                              #20

                              Yeah true. Well my app gets cut in low end resolution (1024*764). On large screen resolution its fine.

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