Qt5 port: workaround to keep multi-sampling when undocking mdi window

src/Gui/Quarter/QuarterWidget.cpp

@@ -147,8 +147,10 @@ using namespace SIM::Coin3D::Quarter;
 #if defined(HAVE_QT5_OPENGL)
 class CustomGLWidget : public QOpenGLWidget {
 public:
+    QSurfaceFormat myFormat;
+
     CustomGLWidget(const QSurfaceFormat& format, QWidget* parent = 0, const QOpenGLWidget* shareWidget = 0, Qt::WindowFlags f = 0)
-     : QOpenGLWidget(parent, f)
+     : QOpenGLWidget(parent, f), myFormat(format)
     {
         Q_UNUSED(shareWidget);
         QSurfaceFormat surfaceFormat(format);
@@ -299,6 +301,20 @@ QuarterWidget::constructor(const QtGLFormat & format, const QtGLWidget * sharewi
   initialized = false;
 }
 
+void
+QuarterWidget::replaceViewport()
+{
+#if defined(HAVE_QT5_OPENGL)
+  CustomGLWidget* oldvp = static_cast<CustomGLWidget*>(viewport());
+  CustomGLWidget* newvp = new CustomGLWidget(oldvp->myFormat, this);
+  PRIVATE(this)->replaceGLWidget(newvp);
+  setViewport(newvp);
+
+  setAutoFillBackground(false);
+  viewport()->setAutoFillBackground(false);
+#endif
+}
+
 /*! destructor */
 QuarterWidget::~QuarterWidget()
 {

src/Gui/Quarter/QuarterWidget.h

@@ -189,6 +189,9 @@ public Q_SLOTS:
 Q_SIGNALS:
   void devicePixelRatioChanged(qreal dev_pixel_ratio);
 
+private Q_SLOTS:
+  void replaceViewport();
+
 protected:
   virtual void paintEvent(QPaintEvent*);
   virtual void resizeEvent(QResizeEvent*);

src/Gui/Quarter/QuarterWidgetP.cpp

@@ -179,6 +179,14 @@ QuarterWidgetP::removeFromCacheContext(QuarterWidgetP_cachecontext * context, co
   }
 }
 
+void
+QuarterWidgetP::replaceGLWidget(const QtGLWidget * newviewport)
+{
+  QtGLWidget* oldviewport = static_cast<QtGLWidget*>(this->master->viewport());
+  cachecontext->widgetlist.removeItem(oldviewport);
+  cachecontext->widgetlist.append(newviewport);
+}
+
 /*!
 
  */

src/Gui/Quarter/QuarterWidgetP.h

@@ -110,6 +110,7 @@ public:
   mutable ContextMenu * contextmenu;
 
   static bool nativeEventFilter(void * message, long * result);
+  void replaceGLWidget(const QtGLWidget * newviewport);
 
  private:
   QuarterWidgetP_cachecontext * findCacheContext(QuarterWidget * widget, const QtGLWidget * sharewidget);

src/Gui/View3DInventor.cpp

@@ -1006,6 +1006,16 @@ void View3DInventor::setCurrentViewMode(ViewMode newmode)
 
     MDIView::setCurrentViewMode(newmode);
 
+#if defined(HAVE_QT5_OPENGL)
+    // Internally the QOpenGLWidget switches of the multi-sampling and there is no
+    // way to switch it on again. So as a workaround we just re-create a new viewport
+    // The method is private but defined as slot to avoid to call it by accident.
+    int index = _viewer->metaObject()->indexOfMethod("replaceViewport()");
+    if (index >= 0) {
+        _viewer->qt_metacall(QMetaObject::InvokeMetaMethod, index, 0);
+    }
+#endif
+
     // This widget becomes the focus proxy of the embedded GL widget if we leave 
     // the 'Child' mode. If we reenter 'Child' mode the focus proxy is reset to 0.
     // If we change from 'TopLevel' mode to 'Fullscreen' mode or vice versa nothing