Clang: make ViewManager instance a proper singleton.

src/calamares/CalamaresWindow.cpp

@@ -142,7 +142,7 @@ CalamaresWindow::CalamaresWindow( QWidget* parent )
     CalamaresUtils::unmarginLayout( sideLayout );
     CalamaresUtils::unmarginLayout( mainLayout );
 
-    Calamares::ViewManager* vm = new Calamares::ViewManager( this );
+    Calamares::ViewManager* vm = Calamares::ViewManager::instance( this );
 
     mainLayout->addWidget( vm->centralWidget() );
 }

src/libcalamaresui/ViewManager.cpp

@@ -42,13 +42,20 @@ ViewManager::instance()
     return s_instance;
 }
 
+ViewManager*
+ViewManager::instance( QObject* parent )
+{
+    Q_ASSERT( !s_instance );
+    s_instance = new ViewManager( parent );
+    return s_instance;
+}
+
 ViewManager::ViewManager( QObject* parent )
     : QObject( parent )
     , m_widget( new QWidget() )
     , m_currentStep( 0 )
 {
     Q_ASSERT( !s_instance );
-    s_instance = this;
 
     QBoxLayout* mainLayout = new QVBoxLayout;
     m_widget->setLayout( mainLayout );

src/libcalamaresui/ViewManager.h

@@ -43,12 +43,10 @@ class UIDLLEXPORT ViewManager : public QObject
 public:
     /**
      * @brief instance access to the ViewManager singleton.
-     * @return
+     * @return pointer to the singleton instance.
      */
     static ViewManager* instance();
-
-    explicit ViewManager( QObject* parent = nullptr );
-    virtual ~ViewManager();
+    static ViewManager* instance( QObject* parent );
 
     /**
      * @brief centralWidget always returns the central widget in the Calamares main
@@ -115,6 +113,9 @@ signals:
     void currentStepChanged();
 
 private:
+    explicit ViewManager( QObject* parent = nullptr );
+    virtual ~ViewManager();
+
     void insertViewStep( int before, ViewStep* step );
 
     static ViewManager* s_instance;