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Transform slow?

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

    Hi,

    I have a slow embedded device and I notice that the user interface could be more responsive. I have already used the Loader element to dynamically load/unload qml files and i'm trying to do some more optimalisations.

    I'm wondering about the transform element that I use to rotate my screens:

    @
    Rectangle {
    transform: { Rotation { origin.x: 120; origin.y: 120; angle 270 }
    showSomeStuyff
    }
    @

    Will this slow down my userinterface noticeable? I reckon for every change the cpu has to calculate the rotated rectangle?

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    • B Offline
      B Offline
      bkamps
      wrote on last edited by
      #2

      I also use transform to rotate images:

      @
      Rectangle {
      transform: { Rotation { origin.x: 120; origin.y: 120; angle 270 }
      BorderImage {
      source: "myimage.png"
      }
      }
      @

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      • A Offline
        A Offline
        aabc
        wrote on last edited by
        #3

        What device do you use ?

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

          Embedded linux, omap ARM 300 mhz. How does the transform function work?

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          • A Offline
            A Offline
            aabc
            wrote on last edited by
            #5

            What is your display device ?

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            • B Offline
              B Offline
              bkamps
              wrote on last edited by
              #6

              It's an omap l138:

              Video Port Interface (VPIF):
              Two 8-bit SD (BT.656), Single 16-bit Video Display Channels

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              • C Offline
                C Offline
                chriadam
                wrote on last edited by
                #7

                I'm not 100% certain, but I seem to recall someone saying that transform with QGV is much slower than with scenegraph rendering (ie, Qt 4.8 will be slower than Qt 5.0, in that QtQuick 1.1 will be slower than QtQuick 2.0, for transform operations) - although I can't remember why, now. Perhaps scenegraph allows partial-update and thus only the transformed element needs to be redrawn? Not sure.

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