Fix flickering in the OCC Viewer.

diff --git a/src/OCCViewer/OCCViewer_ViewPort.cxx b/src/OCCViewer/OCCViewer_ViewPort.cxx
index 0ce25d0df19a41d4a432681623473881ec2c2d5e..d6cca3173e96a9785872ea5ebda943e1e7ad5f2a 100755 (executable)
--- a/src/OCCViewer/OCCViewer_ViewPort.cxx
+++ b/src/OCCViewer/OCCViewer_ViewPort.cxx
@@ -218,7 +218,7 @@ void OCCViewer_ViewPort::initialize()
   setBackgroundRole( QPalette::NoRole );//NoBackground );
   // set focus policy to threat QContextMenuEvent from keyboard  
   setFocusPolicy( Qt::StrongFocus );
-#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0) && OCC_VERSION_LARGE < 0x07000000
+#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0) && OCC_VERSION_LARGE < 0x07000000) || QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
   setAttribute( Qt::WA_PaintOnScreen );
 #endif
   setAttribute( Qt::WA_NoSystemBackground );