Fixes: NB#201968 - MContainer should either take ownership of the centralWidget or not.

RevBy: Stanislav Ionascu

Details: The MContainer shall takes ownership by default of the central widget.

Merged with updated documentation for the MContainer::setCentralWidget.

4 files changed, 58 insertions, 10 deletions

diff --git a/src/corelib/widgets/mcontainer.cpp b/src/corelib/widgets/mcontainer.cpp
index 334e8dc2..d43e65fe 100644
--- a/src/corelib/widgets/mcontainer.cpp
+++ b/src/corelib/widgets/mcontainer.cpp
@@ -72,16 +72,20 @@ QGraphicsWidget *MContainer::centralWidget()
 
 void MContainer::setCentralWidget(QGraphicsWidget *centralWidget, bool destroy)
 {
-    if (centralWidget != NULL) {
-        const QGraphicsWidget *oldCentralWidget = model()->centralWidget();
-
-        // Set the new central widget
-        model()->setCentralWidget(centralWidget);
-
-        // Destroy the old central widget if requested
-        if (destroy) {
-            delete oldCentralWidget;
-        }
+    QGraphicsWidget *oldCentralWidget = model()->centralWidget();
+
+    // Set the new central widget
+    model()->setCentralWidget(centralWidget);
+
+    // Destroy the old central widget if requested
+    if (destroy) {
+        delete oldCentralWidget;
+    } else {
+        // pass the ownership back to the caller.
+        oldCentralWidget->setParentItem(0);
+        oldCentralWidget->setParent(0);
+        if (scene())
+            scene()->removeItem(oldCentralWidget);
     }
 }
 
diff --git a/src/corelib/widgets/mcontainer.h b/src/corelib/widgets/mcontainer.h
index 9b891e96..f1e35231 100644
--- a/src/corelib/widgets/mcontainer.h
+++ b/src/corelib/widgets/mcontainer.h
@@ -133,6 +133,11 @@ public:
 
     /*!
      * \brief Sets the central widget for container.
+     * By default MContainer takes ownership of the centralWidget.
+     *
+     * When centralWidget is replaced and destroy parameter is passed as false, the old
+     * centralWidget is removed from graphics hierarchy and scene, and it's ownership of
+     * is passed to caller.
      */
     void setCentralWidget(QGraphicsWidget *centralWidget, bool destroy = true);
 
diff --git a/tests/ut_mcontainer/ut_mcontainer.cpp b/tests/ut_mcontainer/ut_mcontainer.cpp
index 48e50d62..29ecceb9 100644
--- a/tests/ut_mcontainer/ut_mcontainer.cpp
+++ b/tests/ut_mcontainer/ut_mcontainer.cpp
@@ -21,6 +21,7 @@
 #include <QGraphicsLinearLayout>
 #include <QGraphicsSceneMouseEvent>
 #include <QSignalSpy>
+#include <QWeakPointer>
 
 #include <mcontainer.h>
 #include "mcontainer_p.h"
@@ -72,6 +73,42 @@ void Ut_MContainer::setCentralWidget()
     QVERIFY(m_subject->centralWidget() == tmp);
 }
 
+void Ut_MContainer::replaceCentralWidget()
+{
+    QGraphicsWidget *widget = new QGraphicsWidget;
+    QWeakPointer<QGraphicsWidget> widgetPointer(widget);
+
+    m_subject->setCentralWidget(widget);
+
+    QVERIFY(m_subject->centralWidget() == widget);
+
+    m_subject->setCentralWidget(0);
+
+    QVERIFY(m_subject->centralWidget() == 0);
+    QCOMPARE(widgetPointer.isNull(), true);
+}
+
+void Ut_MContainer::replaceCentralWidgetWithoutDestroying()
+{
+    QGraphicsWidget *widget = new QGraphicsWidget;
+    QWeakPointer<QGraphicsWidget> widgetPointer(widget);
+
+    m_subject->setCentralWidget(widget);
+
+    QVERIFY(m_subject->centralWidget() == widget);
+
+    m_subject->setCentralWidget(0, false);
+
+    QVERIFY(m_subject->centralWidget() == 0);
+    QCOMPARE(widgetPointer.isNull(), false);
+    QVERIFY(widget->parentItem() == 0);
+    QVERIFY(widget->parent() == 0);
+    QVERIFY(widget->scene() == 0);
+
+    // clean up
+    delete widget;
+}
+
 void Ut_MContainer::title()
 {
     QString myQString("testing title()");
diff --git a/tests/ut_mcontainer/ut_mcontainer.h b/tests/ut_mcontainer/ut_mcontainer.h
index 98df3716..888f0d26 100644
--- a/tests/ut_mcontainer/ut_mcontainer.h
+++ b/tests/ut_mcontainer/ut_mcontainer.h
@@ -39,6 +39,8 @@ private slots:
 
     void centralWidget();
     void setCentralWidget();
+    void replaceCentralWidget();
+    void replaceCentralWidgetWithoutDestroying();
 
     void title();
     void text();