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  1. Qt
  2. QTBUG-43296

Threaded render loop and vsync animation driver results in inaccurate animation timing

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Details

    • Bug
    • Resolution: Out of scope
    • P2: Important
    • None
    • 5.4.0
    • Quick: SceneGraph
    • None
    • Arch Linux x86_64
      ATI Radeon HD 5450
      mesa 10.3.5
      xf86-video-ati 7.5.0 (open source driver)

    Description

      Using a threaded render loop with the vsync animation driver (which is default rather of walltime animation driver) results in loss of animation timing accuracy.

      The following results are measuring the animation transition time for StackView (which is 400 ms in Qt 5.4 and 300 ms in Qt 5.3.2 and earlier).

      Basic render loop (QT_LOGGING_RULES=qt.scenegraph.info=true qmlscene QTBUG-43296.qml):

      qt.scenegraph.info: QSG: basic render loop
...
qt.scenegraph.info: texture atlas dimensions: 512x512
qt.scenegraph.info: R/G/B/A Buffers:    8 8 8 0
qt.scenegraph.info: Depth Buffer:       24
qt.scenegraph.info: Stencil Buffer:     8
qt.scenegraph.info: Samples:            -1
qt.scenegraph.info: GL_VENDOR:          X.Org
qt.scenegraph.info: GL_RENDERER:        Gallium 0.4 on AMD CEDAR
qt.scenegraph.info: GL_VERSION:         3.0 Mesa 10.3.5
qml: Transition took 400 ms
qml: Transition took 401 ms
qml: Transition took 401 ms
qml: Transition took 403 ms
qml: Transition took 401 ms
qml: Transition took 401 ms
qml: Transition took 400 ms
qml: Transition took 401 ms
qml: Transition took 401 ms
qml: Transition took 401 ms

      Threaded render loop and vsync animation driver (QML_FORCE_THREADED_RENDERER=1 QT_LOGGING_RULES=qt.scenegraph.info=true qmlscene QTBUG-43296.qml):

      qt.scenegraph.info: threaded render loop
qt.scenegraph.info: Using sg animation driver
...
qt.scenegraph.info: Animation Driver: using vsync: 16.67 ms
qt.scenegraph.info: texture atlas dimensions: 512x512
qt.scenegraph.info: R/G/B/A Buffers:    8 8 8 0
qt.scenegraph.info: Depth Buffer:       24
qt.scenegraph.info: Stencil Buffer:     8
qt.scenegraph.info: Samples:            -1
qt.scenegraph.info: GL_VENDOR:          X.Org
qt.scenegraph.info: GL_RENDERER:        Gallium 0.4 on AMD CEDAR
qt.scenegraph.info: GL_VERSION:         3.0 Mesa 10.3.5
qml: Transition took 384 ms
qml: Transition took 381 ms
qml: Transition took 383 ms
qml: Transition took 374 ms
qml: Transition took 374 ms
qml: Transition took 388 ms
qml: Transition took 387 ms
qml: Transition took 385 ms
qml: Transition took 376 ms
qml: Transition took 376 ms

      This is a regression from Qt 5.3.2.

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        Issue Links

          relates to

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-42699 QML Timer too fast with Animation on Windows

          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
          • Closed
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              janichol Andy Nichols
              net147 Jonathan Liu
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              Dates

                Created:
                Updated:
                Resolved:

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