QQuickHoverHandler: listen for parent changes, and update hasHoverInChild

A QQuickHoverHandler is normally created by the QML engine, but
can sometimes also be created directly from C++. And for
the latter case, QQuickHoverHandler::componentComplete() will
not be called. This causes a problem, since it takes care of
subscribing for hover events on the parent item.

To support creating hover handlers from c++, we therefore need
to also subscribe to hover events from the constructor.
Moreover, since the parentItem can change at runtime, we also
need a virtual function that informs it when the parent item
changes, so that we can remove hover subscription from the old
parent, and subscribe for it on the new parent.

Change-Id: I52f3cd16d6bbfbbe2e4c3c019efdc7f06c5f2c31
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
(cherry picked from commit 7db67e59d45b47e45a2723808f23e8cdadf5065c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 39 insertions, 12 deletions

diff --git a/src/quick/handlers/qquickhoverhandler.cpp b/src/quick/handlers/qquickhoverhandler.cpp
index 2a2208c567..072ca626a6 100644
--- a/src/quick/handlers/qquickhoverhandler.cpp
+++ b/src/quick/handlers/qquickhoverhandler.cpp
@@ -40,35 +40,58 @@ class QQuickHoverHandlerPrivate : public QQuickSinglePointHandlerPrivate
 
 public:
     void onEnabledChanged() override;
+    void onParentChanged(QQuickItem *oldParent, QQuickItem *newParent) override;
+
+    void updateHasHoverInChild(QQuickItem *item, bool hasHover);
 };
 
 void QQuickHoverHandlerPrivate::onEnabledChanged()
 {
     Q_Q(QQuickHoverHandler);
 
-    if (auto parent = q->parentItem()) {
-        QQuickItemPrivate *itemPriv = QQuickItemPrivate::get(parent);
-        itemPriv->setHasHoverInChild(enabled);
-        // The DA needs to resolve which items and handlers should now be hovered or unhovered.
-        // Marking the parent item dirty ensures that flushFrameSynchronousEvents() will be called from the render loop,
-        // even if this change is not in response to a mouse event and no item has already marked itself dirty.
-        itemPriv->dirty(QQuickItemPrivate::Content);
-    }
+    if (auto parent = q->parentItem())
+        updateHasHoverInChild(parent, enabled);
     if (!enabled)
         q->setHovered(false);
+
+    QQuickSinglePointHandlerPrivate::onEnabledChanged();
+}
+
+void QQuickHoverHandlerPrivate::onParentChanged(QQuickItem *oldParent, QQuickItem *newParent)
+{
+    if (oldParent)
+        updateHasHoverInChild(oldParent, false);
+    if (newParent)
+        updateHasHoverInChild(newParent, true);
+
+    QQuickSinglePointHandlerPrivate::onParentChanged(oldParent, newParent);
+}
+
+void QQuickHoverHandlerPrivate::updateHasHoverInChild(QQuickItem *item, bool hasHover)
+{
+    QQuickItemPrivate *itemPriv = QQuickItemPrivate::get(item);
+    itemPriv->setHasHoverInChild(hasHover);
+    // The DA needs to resolve which items and handlers should now be hovered or unhovered.
+    // Marking the parent item dirty ensures that flushFrameSynchronousEvents() will be called from the render loop,
+    // even if this change is not in response to a mouse event and no item has already marked itself dirty.
+    itemPriv->dirty(QQuickItemPrivate::Content);
 }
 
 QQuickHoverHandler::QQuickHoverHandler(QQuickItem *parent)
     : QQuickSinglePointHandler(*(new QQuickHoverHandlerPrivate), parent)
 {
+    Q_D(QQuickHoverHandler);
     // Tell QQuickPointerDeviceHandler::wantsPointerEvent() to ignore button state
-    d_func()->acceptedButtons = Qt::NoButton;
+    d->acceptedButtons = Qt::NoButton;
+    if (parent)
+        d->updateHasHoverInChild(parent, true);
 }
 
 QQuickHoverHandler::~QQuickHoverHandler()
 {
+    Q_D(QQuickHoverHandler);
     if (auto parent = parentItem())
-        QQuickItemPrivate::get(parent)->setHasHoverInChild(false);
+        d->updateHasHoverInChild(parent, false);
 }
 
 /*!
@@ -105,9 +128,13 @@ bool QQuickHoverHandler::event(QEvent *event)
 
 void QQuickHoverHandler::componentComplete()
 {
+    Q_D(QQuickHoverHandler);
     QQuickSinglePointHandler::componentComplete();
-    if (auto par = parentItem())
-        QQuickItemPrivate::get(par)->setHasHoverInChild(true);
+
+    if (d->enabled) {
+        if (auto parent = parentItem())
+            d->updateHasHoverInChild(parent, true);
+    }
 }
 
 bool QQuickHoverHandler::wantsPointerEvent(QPointerEvent *event)