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  1. Qt
  2. QTBUG-103305

Quick threaded renderer first frames fluctuate

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      For a short description see the attached video. I would like to see smooth frame time staying ~0.0167 and not go initially down & up.

      I have been testing the threaded render loop (QSG_RENDER_LOOP=threaded). When stopping QAbstractAnimationJob and then starting it again, I'm seeing fluctuating frame times in the beginning. First there are 5-7 too fast (~5ms) frames, then 3-7 too slow (~33ms) frames, and only after that the frame times are stable (~16ms). This can be seen with manual tester in FrameAnimation patch https://codereview.qt-project.org/c/qt/qtdeclarative/+/408992/ when adding debug prints into maybeTick(). This is what I see when toggling animation run -> pause -> unpause:

      updateState, paused: true
      updateState, paused: false
      frameTime: 0.0058909
      frameTime: 0.0064895
      frameTime: 0.0056598
      frameTime: 0.0058617
      frameTime: 0.0062807
      frameTime: 0.0058258
      frameTime: 0.0075679
      frameTime: 0.0169868
      frameTime: 0.0499563
      frameTime: 0.0332207
      frameTime: 0.0334878
      frameTime: 0.0334512
      frameTime: 0.0332658
      frameTime: 0.0165824
      frameTime: 0.0166191
      frameTime: 0.0167426
      ...

        1. FrameAnimation_Tester_frametimes.mp4
          429 kB
          Kaj Grönholm
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            kagro Kaj Grönholm
            kagro Kaj Grönholm
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