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  1. Qt
  2. QTBUG-97504

Mouse reaction delay in qml

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    • Android, Linux/X11, Windows

      Working on a project where small "windowing" system is implemented.
      Essentially user can instantiate controls within main window, drag them around or resize them.
      All of those interactions are implemented via qml.

      There is substantial observable delay between mouse input and the UI response to it.
      It creates a rubber banding effect.
      The results vary based on the platform and RHI used - in all cases the delay is observable by the user.

      I've attached minimal qml file as an example that demonstrates this issue.
      It contains mouse area and rectangle that is centered on the mouse position and is supposed to show mouse location.

      Steps to reproduce:

      • Launch the file via `qml --rhi file.qml`
      • Move the mouse around (diagonal/circular mouse motion produces most visible results)

      Actual results:

      • System mouse indicator "escapes" the area when in motion
      • There seems to be a bit of a rubber banding effect

      Expected results:

      • Rectangle is observably always centered on the system mouse indicator

      Tested this on windows/linux with vulkan,opengl and dx3d11 backends, with Qt6.2 and Qt5.15.6
      Attached a movie file from single reproduction

        1. 144hz.mp4
          1.38 MB
        2. file.qml
          0.4 kB
        3. mouse-issue.mp4
          72 kB
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            axelspoerl Axel Spoerl
            bnmann Bartłomiej Neumann
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              Created:
              Updated:
              Resolved:

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