ScrollView: fix crash when scrolling with zero-sized item

Check if a Flickable type was actually set as the contentItem before
accessing the pointer. Also warn that using a type other than Flickable
is not supported.

Fixes: QTBUG-93039
Pick-to: 6.1 6.0 5.15
Change-Id: I1470766c6de02b7b601edf1375791d3147f26ab5
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

2 files changed, 10 insertions, 1 deletions

diff --git a/src/quicktemplates2/qquickscrollbar.cpp b/src/quicktemplates2/qquickscrollbar.cpp
index cc338b65..843b7d86 100644
--- a/src/quicktemplates2/qquickscrollbar.cpp
+++ b/src/quicktemplates2/qquickscrollbar.cpp
@@ -1014,6 +1014,9 @@ class QQuickFriendlyFlickable : public QQuickFlickable
 
 void QQuickScrollBarAttachedPrivate::scrollHorizontal()
 {
+    if (!flickable)
+        return;
+
     QQuickFriendlyFlickable *f = reinterpret_cast<QQuickFriendlyFlickable *>(flickable);
 
     const qreal viewwidth = f->width();
@@ -1026,6 +1029,9 @@ void QQuickScrollBarAttachedPrivate::scrollHorizontal()
 
 void QQuickScrollBarAttachedPrivate::scrollVertical()
 {
+    if (!flickable)
+        return;
+
     QQuickFriendlyFlickable *f = reinterpret_cast<QQuickFriendlyFlickable *>(flickable);
 
     const qreal viewheight = f->height();
diff --git a/src/quicktemplates2/qquickscrollview.cpp b/src/quicktemplates2/qquickscrollview.cpp
index 174495f6..1f5adbb7 100644
--- a/src/quicktemplates2/qquickscrollview.cpp
+++ b/src/quicktemplates2/qquickscrollview.cpp
@@ -585,7 +585,10 @@ void QQuickScrollView::contentItemChange(QQuickItem *newItem, QQuickItem *oldIte
         // assume/require that it has an explicit content size assigned.
         d->flickableHasExplicitContentWidth = true;
         d->flickableHasExplicitContentHeight = true;
-        d->setFlickable(qobject_cast<QQuickFlickable *>(newItem), false);
+        auto newItemAsFlickable = qobject_cast<QQuickFlickable *>(newItem);
+        if (newItem && !newItemAsFlickable)
+            qmlWarning(this) << "ScrollView only supports Flickable types as its contentItem";
+        d->setFlickable(newItemAsFlickable, false);
     }
     QQuickPane::contentItemChange(newItem, oldItem);
 }