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  1. Qt
  2. QTBUG-140340

[REG: 5->6] Input event delivery performance regression in Qt 6

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    • Linux/Wayland

      There is a big regression in delivering input events in Qt Quick. Attached example in callgrind shows:

      Qt 5.15.18

      ==1572525== I   refs:      15,930,854,003

      Qt 6.9.2

      ==1572827== I   refs:      64,225,641,185

      And QQuickItemPrivate::itemToParentTransform() seems to jump out. It is the highest cost function in Qt 5.15.18 also, but in Qt 6 this function is now called many more times for a single event than it used to in Qt 5.

      This causes issues with lower end devices where simple mouse moves take 4x as much CPU time as before.

        1. QTBUG-140340.tar.gz
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        For Gerrit Dashboard: QTBUG-140340
        # Subject Branch Project Status CR V
        682467,12 WIP Cache result from QQItemPrivate::windowToItemTransform() dev qt/qtdeclarative Status: NEW -2 0
        684204,12 Reduce QTransform use in event delivery and cursor-finding functions dev qt/qtdeclarative Status: NEW +2 0
        685993,1 Combine findCursorItemAndHandler and deliverHoverEventRecursive dev qt/qtdeclarative Status: NEW 0 0
        686883,3 WIP make hover and cursor the responsibility of moving items dev qt/qtdeclarative Status: NEW -2 -1
        686884,1 Add QQItemPrivate::effectivelyClipsChildren; skip hover when irrelevant dev qt/qtdeclarative Status: NEW 0 0
        686885,1 WIP findCursorItemAndHandler: skip items that clip children dev qt/qtdeclarative Status: NEW -2 0
        687384,2 Add dev-only item counters and QQItemPrivate::allItems() dev qt/qtdeclarative Status: NEW 0 0
        682427,3 WIP stop sending non-enter hover events from handleMouseEvent() dev qt/qtdeclarative Status: ABANDONED -2 0
        684203,1 WIP Revert "Fix for global position in hover events" but keep the autotest dev qt/qtdeclarative Status: ABANDONED -2 0

            srutledg Shawn Rutledge
            poikelin Joni Poikelin
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              Created:
              Updated: