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  1. Qt
  2. QTBUG-86317

Flickable is unaware of non-60Hz displays



    • Type: Bug
    • Status: Reported
    • Priority: P2: Important
    • Resolution: Unresolved
    • Affects Version/s: 5.15.0
    • Fix Version/s: None
    • Labels:
    • Environment:
      Ubuntu 20.04, KDE, AMD RX 480 8 gigabyte, LG B9 55" (which can be set to 24, 25, 30, 50, 60, 100, and 120 hz), Dell P2415Q monitor as a 60hz control
    • Platform/s:


      Flickables do not seem to behave correctly when flicked by the mouse on a non-60Hz display.

      At 60Hz, it's buttery smooth. When dragging the flickable at constant velocity and releasing the mouse button, the flickable's initial velocity matches the cursor perfectly before decaying due to the deceleration.

      There is some jank visible when on sub-60Hz displays, including 24, 30, and 50 Hz (tested on my LG B9 55"), but flick velocities seem okay when releasing the mouse button when dragging.

      At higher framerates (both 100Hz and 120Hz in my testing), all motion is very smooth. However, when dragging the mouse at constant velocity and releasing the mouse button, the flickable's initial velocity is higher than the mouse cursor's velocity, by a factor of about 2x at 120Hz. This can cause the flickable to severely overtake the mouse.

      This can be best seen with the flickable displaying something significantly larger than the viewport, like a long list or a zoomed view of an image.

      It came up in my project Filmulator; you can try editing a photo with the AppImage; when zooming in on images in the Filmulate tab and attempting to pan around with flicking, this issue comes up.


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            qt.team.quick.subscriptions Qt Quick and Widgets Team
            carvac Carlo Vaccari
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