4 files changed, 157 insertions, 17 deletions
diff --git a/src/quick/items/qquickevents.cpp b/src/quick/items/qquickevents.cpp
index 0c697739fa..b5644d55e6 100644
--- a/src/quick/items/qquickevents.cpp
+++ b/src/quick/items/qquickevents.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtQuick module of the Qt Toolkit.
@@ -448,7 +448,7 @@ Item {
 */
 
 /*!
-    \qmlproperty int QtQuick::WheelEvent::inverted
+    \qmlproperty bool QtQuick::WheelEvent::inverted
 
     Returns whether the delta values delivered with the event are inverted.
 
@@ -1431,6 +1431,135 @@ QQuickEventPoint *QQuickSinglePointEvent::point(int i) const
     return nullptr;
 }
 
+
+/*!
+    \qmltype PointerScrollEvent
+    \instantiates QQuickPointerScrollEvent
+    \inqmlmodule QtQuick
+    \ingroup qtquick-input-events
+    \brief Provides information about a scrolling event, such as from a mouse wheel.
+
+    \sa WheelHandler
+*/
+
+/*!
+    \internal
+    \class QQuickPointerScrollEvent
+*/
+
+/*!
+    \readonly
+    \qmlproperty PointerDevice QtQuick::PointerScrollEvent::device
+
+    This property holds the device that generated the event.
+*/
+
+/*!
+    \qmlproperty int QtQuick::PointerScrollEvent::buttons
+
+    This property holds the mouse buttons pressed when the wheel event was generated.
+
+    It contains a bitwise combination of:
+    \list
+    \li \l {Qt::LeftButton} {Qt.LeftButton}
+    \li \l {Qt::RightButton} {Qt.RightButton}
+    \li \l {Qt::MiddleButton} {Qt.MiddleButton}
+    \endlist
+*/
+
+/*!
+    \readonly
+    \qmlproperty int QtQuick::PointerScrollEvent::modifiers
+
+    This property holds the \l {Qt::KeyboardModifier}{keyboard modifier} keys
+    that were pressed immediately before the event occurred.
+
+    It contains a bitwise combination of the following flags:
+    \value Qt.NoModifier
+        No modifier key is pressed.
+    \value Qt.ShiftModifier
+        A Shift key on the keyboard is pressed.
+    \value Qt.ControlModifier
+        A Ctrl key on the keyboard is pressed.
+    \value Qt.AltModifier
+        An Alt key on the keyboard is pressed.
+    \value Qt.MetaModifier
+        A Meta key on the keyboard is pressed.
+    \value Qt.KeypadModifier
+        A keypad button is pressed.
+
+    For example, to react to a Shift key + Left mouse button click:
+    \qml
+    Item {
+        TapHandler {
+            onTapped: {
+                if ((event.button == Qt.LeftButton) && (event.modifiers & Qt.ShiftModifier))
+                    doSomething();
+            }
+        }
+    }
+    \endqml
+*/
+
+/*!
+    \qmlproperty point QtQuick::PointerScrollEvent::angleDelta
+
+    This property holds the distance that the wheel is rotated in wheel degrees.
+    The x and y cordinate of this property holds the delta in horizontal and
+    vertical orientation.
+
+    A positive value indicates that the wheel was rotated up/right;
+    a negative value indicates that the wheel was rotated down/left.
+
+    Most mouse types work in steps of 15 degrees, in which case the delta value is a
+    multiple of 120; i.e., 120 units * 1/8 = 15 degrees.
+*/
+
+/*!
+    \qmlproperty point QtQuick::PointerScrollEvent::pixelDelta
+
+    This property holds the delta in screen pixels and is available in platforms that
+    have high-resolution trackpads, such as \macos.
+    The x and y coordinates of this property hold the delta in horizontal and
+    vertical orientation. The value should be used directly to scroll content on screen.
+
+    For platforms without high-resolution touchpad support, pixelDelta will
+    always be (0,0), and angleDelta should be used instead.
+*/
+
+/*!
+    \qmlproperty bool QtQuick::PointerScrollEvent::hasAngleDelta
+
+    Returns whether the \l angleDelta property has a non-null value.
+*/
+
+/*!
+    \qmlproperty bool QtQuick::PointerScrollEvent::hasPixelDelta
+
+    Returns whether the \l pixelDelta property has a non-null value.
+*/
+
+/*!
+    \qmlproperty bool QtQuick::PointerScrollEvent::inverted
+
+    Returns whether the delta values delivered with the event are inverted.
+
+    Normally, a vertical wheel will produce a PointerScrollEvent with positive delta
+    values if the top of the wheel is rotating away from the hand operating it.
+    Similarly, a horizontal wheel movement will produce a PointerScrollEvent with
+    positive delta values if the top of the wheel is moved to the left.
+
+    However, on some platforms this is configurable, so that the same
+    operations described above will produce negative delta values (but with the
+    same magnitude). In a QML component (such as a tumbler or a slider) where
+    it is appropriate to synchronize the movement or rotation of an item with
+    the direction of the wheel, regardless of the system settings, the wheel
+    event handler can use the inverted property to decide whether to negate the
+    \l angleDelta or \l pixelDelta values.
+
+    \note Many platforms provide no such information. On such platforms,
+    \c inverted always returns false.
+*/
 QQuickPointerEvent *QQuickPointerScrollEvent::reset(QEvent *event)
 {
     m_event = static_cast<QInputEvent*>(event);
diff --git a/src/quick/items/qquickitemsmodule.cpp b/src/quick/items/qquickitemsmodule.cpp
index 7bc6eefe0a..86253e770f 100644
--- a/src/quick/items/qquickitemsmodule.cpp
+++ b/src/quick/items/qquickitemsmodule.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtQuick module of the Qt Toolkit.
@@ -494,6 +494,8 @@ static void qt_quickitems_defineModule(const char *uri, int major, int minor)
 #endif
 #if QT_CONFIG(wheelevent)
     qmlRegisterType<QQuickWheelHandler>(uri, 2, 14, "WheelHandler");
+    qmlRegisterUncreatableType<QQuickPointerScrollEvent>(uri, 2, 14, "PointerScrollEvent",
+        QQuickPointerHandler::tr("PointerScrollEvent is only available via the WheelHandler::wheel signal"));
 #endif
     qmlRegisterUncreatableType<QQuickImageBase, 14>(uri, 2, 14, "ImageBase",
         QQuickPointerHandler::tr("ImageBase is an abstract base class"));
diff --git a/src/quick/items/qquickitemview.cpp b/src/quick/items/qquickitemview.cpp
index 66be3c79f8..a931abca58 100644
--- a/src/quick/items/qquickitemview.cpp
+++ b/src/quick/items/qquickitemview.cpp
@@ -1505,7 +1505,7 @@ QQuickItemViewPrivate::QQuickItemViewPrivate()
     , inLayout(false), inViewportMoved(false), forceLayout(false), currentIndexCleared(false)
     , haveHighlightRange(false), autoHighlight(true), highlightRangeStartValid(false), highlightRangeEndValid(false)
     , fillCacheBuffer(false), inRequest(false)
-    , runDelayedRemoveTransition(false), delegateValidated(false)
+    , runDelayedRemoveTransition(false), delegateValidated(false), isClearing(false)
 {
     bufferPause.addAnimationChangeListener(this, QAbstractAnimationJob::Completion);
     bufferPause.setLoopCount(1);
@@ -1681,6 +1681,10 @@ void QQuickItemViewPrivate::updateCurrent(int modelIndex)
 void QQuickItemViewPrivate::clear(bool onDestruction)
 {
     Q_Q(QQuickItemView);
+
+    isClearing = true;
+    auto cleanup = qScopeGuard([this] { isClearing = false; });
+
     currentChanges.reset();
     bufferedChanges.reset();
     timeline.clear();
@@ -1908,21 +1912,25 @@ void QQuickItemViewPrivate::layout()
 
         prepareVisibleItemTransitions();
 
-        for (auto it = releasePendingTransition.begin(); it != releasePendingTransition.end(); ) {
-            auto old_count = releasePendingTransition.count();
-            auto success = prepareNonVisibleItemTransition(*it, viewBounds);
-            // prepareNonVisibleItemTransition() may invalidate iterators while in fast flicking
-            // invisible animating items are kicked in or out the viewPort
-            // use old_count to test if the abrupt erasure occurs
-            if (old_count > releasePendingTransition.count()) {
+        // We cannot use iterators here as erasing from a container invalidates them.
+        for (int i = 0, count = releasePendingTransition.count(); i < count;) {
+            auto success = prepareNonVisibleItemTransition(releasePendingTransition[i], viewBounds);
+            // prepareNonVisibleItemTransition() may remove items while in fast flicking.
+            // Invisible animating items are kicked in or out the viewPort.
+            // Recheck count to test if the item got removed. In that case the same index points
+            // to a different item now.
+            const int old_count = count;
+            count = releasePendingTransition.count();
+            if (old_count > count)
                 continue;
-            }
+
             if (!success) {
-                releaseItem(*it);
-                it = releasePendingTransition.erase(it);
-                continue;
+                releaseItem(releasePendingTransition[i]);
+                releasePendingTransition.remove(i);
+                --count;
+            } else {
+                ++i;
             }
-            ++it;
         }
 
         for (int i=0; i<visibleItems.count(); i++)
@@ -2399,7 +2407,7 @@ bool QQuickItemViewPrivate::releaseItem(FxViewItem *item)
     QQmlInstanceModel::ReleaseFlags flags = {};
     if (model && item->item) {
         flags = model->release(item->item);
-        if (!flags) {
+        if (!flags && !isClearing) {
             // item was not destroyed, and we no longer reference it.
             if (item->item->parentItem() == contentItem) {
                 // Only cull the item if its parent item is still our contentItem.
diff --git a/src/quick/items/qquickitemview_p_p.h b/src/quick/items/qquickitemview_p_p.h
index b31f53b2c0..a448cf9a38 100644
--- a/src/quick/items/qquickitemview_p_p.h
+++ b/src/quick/items/qquickitemview_p_p.h
@@ -316,6 +316,7 @@ public:
     bool inRequest : 1;
     bool runDelayedRemoveTransition : 1;
     bool delegateValidated : 1;
+    bool isClearing : 1;
 
 protected:
     virtual Qt::Orientation layoutOrientation() const = 0;