QQuickListView: prevent mouse delivery in floating header or footer

Earlier we reimplemented the contains() method of ListView to prevent
dragging in an Overlay or Pullback header or footer. But in QQuickWindow
(QQuickWindowPrivate::pointerTargets()), an early check prevents
delivery of pointer events to an item that is clipped and for which
contains() returns false, and also to its children.  In that case, the
header or footer no longer responds to a mouse event even if you put a
MouseArea in it.

Reverts 6ad3445f1e159d9beea936b66d267dcaacdc5d6c; reimplemented using
similar logic in a new QQuickListViewPrivate::wantsPointerEvent()
method, overriding QQuickFlickablePrivate::wantsPointerEvent(), which
is now checked in event-handling code in addition to checking the
interactive flag.

Done-with: Wang Chuan <ouchuanm@outlook.com>
Pick-to: 5.15
Task-number: QTBUG-74046
Fixes: QTBUG-85302
Change-Id: I9474f035d26b74ee36c0ac19e45a77de2e694bf1
Reviewed-by: Wang Chuan <ouchuanm@outlook.com>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 47 insertions, 9 deletions

diff --git a/src/quick/items/qquicklistview.cpp b/src/quick/items/qquicklistview.cpp
index c2285c38ea..ced9e27855 100644
--- a/src/quick/items/qquicklistview.cpp
+++ b/src/quick/items/qquicklistview.cpp
@@ -58,6 +58,8 @@ QT_BEGIN_NAMESPACE
 #define QML_FLICK_SNAPONETHRESHOLD 30
 #endif
 
+Q_LOGGING_CATEGORY(lcEvents, "qt.quick.listview.events")
+
 class FxListItemSG;
 
 class QQuickListViewPrivate : public QQuickItemViewPrivate
@@ -143,6 +145,9 @@ public:
 
     void fixupHeader();
     void fixupHeaderCompleted();
+
+    bool wantsPointerEvent(const QEvent *event) override;
+
     QQuickListView::Orientation orient;
     qreal visiblePos;
     qreal averageSize;
@@ -179,6 +184,7 @@ public:
 
     bool correctFlick : 1;
     bool inFlickCorrection : 1;
+    bool wantedMousePress : 1;
 
     QQuickListViewPrivate()
         : orient(QQuickListView::Vertical)
@@ -192,7 +198,7 @@ public:
         , sectionCriteria(nullptr), currentSectionItem(nullptr), nextSectionItem(nullptr)
         , overshootDist(0.0), desiredViewportPosition(0.0), fixupHeaderPosition(0.0)
         , headerNeedsSeparateFixup(false), desiredHeaderVisible(false)
-        , correctFlick(false), inFlickCorrection(false)
+        , correctFlick(false), inFlickCorrection(false), wantedMousePress(false)
     {
         highlightMoveDuration = -1; //override default value set in base class
     }
@@ -3819,20 +3825,52 @@ QQuickListViewAttached *QQuickListView::qmlAttachedProperties(QObject *obj)
     return new QQuickListViewAttached(obj);
 }
 
-bool QQuickListView::contains(const QPointF &point) const
+/*! \internal
+    Prevents clicking or dragging through floating headers (QTBUG-74046).
+*/
+bool QQuickListViewPrivate::wantsPointerEvent(const QEvent *event)
 {
-    bool ret = QQuickItemView::contains(point);
-    // QTBUG-74046: if a mouse press "falls through" a floating header or footer, don't allow dragging the list from there
-    if (ret) {
-        if (auto header = headerItem()) {
-            if (headerPositioning() != QQuickListView::InlineHeader && header->contains(mapToItem(header, point)))
+    Q_Q(const QQuickListView);
+    bool ret = true;
+
+    QPointF pos;
+    // TODO switch not needed in Qt 6: use points().first().position()
+    switch (event->type()) {
+    case QEvent::Wheel:
+        pos = static_cast<const QWheelEvent *>(event)->position();
+        break;
+    case QEvent::MouseButtonPress:
+        pos = static_cast<const QMouseEvent *>(event)->position();
+        break;
+    default:
+        break;
+    }
+
+    if (!pos.isNull()) {
+        if (auto header = q->headerItem()) {
+            if (q->headerPositioning() != QQuickListView::InlineHeader &&
+                    header->contains(q->mapToItem(header, pos)))
                 ret = false;
         }
-        if (auto footer = footerItem()) {
-            if (footerPositioning() != QQuickListView::InlineFooter && footer->contains(mapToItem(footer, point)))
+        if (auto footer = q->footerItem()) {
+            if (q->footerPositioning() != QQuickListView::InlineFooter &&
+                    footer->contains(q->mapToItem(footer, pos)))
                 ret = false;
         }
     }
+
+    switch (event->type()) {
+    case QEvent::MouseButtonPress:
+        wantedMousePress = ret;
+        break;
+    case QEvent::MouseMove:
+        ret = wantedMousePress;
+        break;
+    default:
+        break;
+    }
+
+    qCDebug(lcEvents) << q << (ret ? "WANTS" : "DOESN'T want") << event;
     return ret;
 }