Fix for possible crash in QSGDefaultLayer::grab

When QQuickItem::setParentItem set to NULL, derefWindow can
be called.  And for it item QSGNode will be destroyed.
If this item used for QQuickEffectShaderSource we will have
access to invalid QSGNode when "live" flag is enabled.

Change-Id: If785e5328a044ec9d2564a82361470f1b8091fc5
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
(cherry picked from commit 1c5de027d0c31d1d6697bd0557128d92207763d8)

2 files changed, 9 insertions, 0 deletions

diff --git a/src/quick/items/qquickshadereffectsource.cpp b/src/quick/items/qquickshadereffectsource.cpp
index b298ed74da..4f61d61309 100644
--- a/src/quick/items/qquickshadereffectsource.cpp
+++ b/src/quick/items/qquickshadereffectsource.cpp
@@ -344,6 +344,7 @@ void QQuickShaderEffectSource::setSourceItem(QQuickItem *item)
             d->refFromEffectItem(m_hideSource);
             d->addItemChangeListener(this, QQuickItemPrivate::Geometry);
             connect(m_sourceItem, SIGNAL(destroyed(QObject*)), this, SLOT(sourceItemDestroyed(QObject*)));
+            connect(m_sourceItem, SIGNAL(parentChanged(QQuickItem*)), this, SLOT(sourceItemParentChanged(QQuickItem*)));
         } else {
             qWarning("ShaderEffectSource: sourceItem and ShaderEffectSource must both be children of the same window.");
             m_sourceItem = nullptr;
@@ -363,6 +364,13 @@ void QQuickShaderEffectSource::sourceItemDestroyed(QObject *item)
 }
 
 
+void QQuickShaderEffectSource::sourceItemParentChanged(QQuickItem *parent)
+{
+    if (!parent && m_texture)
+        m_texture->setItem(0);
+}
+
+
 /*!
     \qmlproperty rect QtQuick::ShaderEffectSource::sourceRect
 
diff --git a/src/quick/items/qquickshadereffectsource_p.h b/src/quick/items/qquickshadereffectsource_p.h
index c0a1ccab78..4deb6c70a3 100644
--- a/src/quick/items/qquickshadereffectsource_p.h
+++ b/src/quick/items/qquickshadereffectsource_p.h
@@ -173,6 +173,7 @@ Q_SIGNALS:
 private Q_SLOTS:
     void sourceItemDestroyed(QObject *item);
     void invalidateSceneGraph();
+    void sourceItemParentChanged(QQuickItem *parent);
 
 protected:
     void releaseResources() override;