QmlDesigner: Fix potential crash

The new selected ModelNode (m_selectedNode) was set to early, since
we defer the creation of the QML frontend.

We have to set m_selectedNode when the QML frontend is actually created.
Otherwise, we might access an uninitialized QML frontend.

Change-Id: I630b103246c414c737c977e233180723df0c3160
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

2 files changed, 24 insertions, 16 deletions

diff --git a/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.cpp b/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.cpp
index 9dd0a2da24..cacdab072e 100644
--- a/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.cpp
+++ b/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.cpp
@@ -389,6 +389,8 @@ void PropertyEditorView::resetView()
     if (model() == nullptr)
         return;
 
+    setSelelectedModelNode();
+
     m_locked = true;
 
     if (debug)
@@ -526,21 +528,16 @@ void PropertyEditorView::removePropertyFromModel(const PropertyName &propertyNam
     m_locked = false;
 }
 
-void PropertyEditorView::selectedNodesChanged(const QList<ModelNode> &selectedNodeList,
-                                          const QList<ModelNode> &lastSelectedNodeList)
+void PropertyEditorView::selectedNodesChanged(const QList<ModelNode> &,
+                                          const QList<ModelNode> &)
 {
-    Q_UNUSED(lastSelectedNodeList);
-
-    if (selectedNodeList.isEmpty())
-        select(ModelNode());
-    else
-        select(selectedNodeList.constFirst());
+    select();
 }
 
 void PropertyEditorView::nodeAboutToBeRemoved(const ModelNode &removedNode)
 {
     if (m_selectedNode.isValid() && removedNode.isValid() && m_selectedNode == removedNode)
-        select(m_selectedNode.parentProperty().parentModelNode());
+        select();
 }
 
 void PropertyEditorView::modelAttached(Model *model)
@@ -686,19 +683,29 @@ void PropertyEditorView::nodeIdChanged(const ModelNode& node, const QString& new
     }
 }
 
-void PropertyEditorView::select(const ModelNode &node)
+void PropertyEditorView::select()
 {
     if (m_qmlBackEndForCurrentType)
         m_qmlBackEndForCurrentType->emitSelectionToBeChanged();
 
-    if (QmlObjectNode(node).isValid())
-        m_selectedNode = node;
-    else
-        m_selectedNode = ModelNode();
-
     delayedResetView();
 }
 
+void PropertyEditorView::setSelelectedModelNode()
+{
+    const auto selectedNodeList = selectedModelNodes();
+
+    m_selectedNode = ModelNode();
+
+    if (selectedNodeList.isEmpty())
+        return;
+
+    const ModelNode node = selectedNodeList.constFirst();
+
+    if (QmlObjectNode(node).isValid())
+            m_selectedNode = node;
+}
+
 bool PropertyEditorView::hasWidget() const
 {
     return true;
diff --git a/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.h b/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.h
index e7f57cf186..20047fde40 100644
--- a/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.h
+++ b/src/plugins/qmldesigner/components/propertyeditor/propertyeditorview.h
@@ -105,7 +105,8 @@ private: //functions
     void updateSize();
     void setupPanes();
 
-    void select(const ModelNode& node);
+    void select();
+    void setSelelectedModelNode();
 
     void delayedResetView();
     void setupQmlBackend();