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Touchscreen bounces with Qt app.

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  • B Offline
    B Offline
    bask185
    wrote on last edited by
    #1

    Today I got a new panel PC, I believe it may be the cheapest one available. The thing has an Ltd eGalax touchscreen and with Ubuntu 16.04 LTS installed it works out of the box like a charm.

    But when I run my Qt application, the touchscreen bounces.....alot. When I boot to the desktop there seems to be no problem at all. The virtual keyboard of ubuntu also works perfect. My fancy Qtumbler does not work now :(

    My application is run on it's own desktop (so it can run fullscreen).

    I do not know where the problem might be. The problem might be related to Qt (5.8) or it might related to the separate desktop. But I have no way to test this.

    I don't know if there are any known issues between Qt apps and certain touchscreen drivers??

    raven-worxR 1 Reply Last reply
    0
    • B bask185

      Today I got a new panel PC, I believe it may be the cheapest one available. The thing has an Ltd eGalax touchscreen and with Ubuntu 16.04 LTS installed it works out of the box like a charm.

      But when I run my Qt application, the touchscreen bounces.....alot. When I boot to the desktop there seems to be no problem at all. The virtual keyboard of ubuntu also works perfect. My fancy Qtumbler does not work now :(

      My application is run on it's own desktop (so it can run fullscreen).

      I do not know where the problem might be. The problem might be related to Qt (5.8) or it might related to the separate desktop. But I have no way to test this.

      I don't know if there are any known issues between Qt apps and certain touchscreen drivers??

      raven-worxR Offline
      raven-worxR Offline
      raven-worx
      Moderators
      wrote on last edited by
      #2

      @bask185 said in Touchscreen bounces with Qt app.:

      But when I run my Qt application, the touchscreen bounces.....alot.

      what exactly does this mean?

      --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
      If you have a question please use the forum so others can benefit from the solution in the future

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      • B Offline
        B Offline
        bask185
        wrote on last edited by
        #3

        I mean it bounces just like a bouncing switch. When I hold my finger on a pushbutton (yes, autorepeat is disabled), I see the state toggling and events are being executed continously instead of just one time. This prevents me from using the Qtumbler :(

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        • B Offline
          B Offline
          bask185
          wrote on last edited by
          #4

          So nobody has a clue why Qt on this systems behaves like this?

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          • SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #5

            Hi,

            Do you have the same strange behaviour if you compile your application your distribution provided Qt ?

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

            B 1 Reply Last reply
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            • SGaistS SGaist

              Hi,

              Do you have the same strange behaviour if you compile your application your distribution provided Qt ?

              B Offline
              B Offline
              bask185
              wrote on last edited by
              #6

              @SGaist No I only have it on this particular panel PC. The PC has ubuntu installed like my host pc and other panel PCs

              Unfortunately this thing must be shipped out as a pilot. So I have to fix the flickering. I tried using QThread::msleep(); but that does not solve the problem it only makes it slower.

              If I push a button and the msleep is set at 300ms I am still getting 3 events instead of just 1.

              I think I came up with a viable simple solution. When I push a button I want to set a boolean variable true and let it go to false after a time has expired. When the boolean is set to true, no actions will happen.

              example:

              void on_pushbutton_clicked()
              {
                 if(boolean == false) {
              
              }
              
              }
              
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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #7

                Usually de-bouncing is done using a single shot timer that is connected to the actual slot that will do something.

                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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