disable ESC button support in View3DInventor::keyEvent() for Qt5 beca…

…use changing MDI view mode causes rendering artifacts

src/Gui/View3DInventor.cpp

@@ -964,6 +964,12 @@ bool View3DInventor::eventFilter(QObject* watched, QEvent* e)
 
 void View3DInventor::keyPressEvent (QKeyEvent* e)
 {
+    // See StdViewDockUndockFullscreen::activated()
+    // With Qt5 one cannot directly use 'setCurrentViewMode'
+    // of an MDI view because it causes rendering problems.
+    // The only reliable solution is to clone the MDI view,
+    // set its view mode and close the original MDI view.
+#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
     ViewMode mode = MDIView::currentViewMode();
     if (mode != Child) {
         // If the widget is in fullscreen mode then we can return to normal mode either
@@ -972,6 +978,7 @@ void View3DInventor::keyPressEvent (QKeyEvent* e)
             setCurrentViewMode(Child);
         }
     }
+#endif
 
     QMainWindow::keyPressEvent(e);
 }