added defaultVAO binding from QOpenGL branch

widgets/glWidget/QtBaseViewer.cc

@@ -1060,6 +1060,18 @@ void glViewer::paintGL(double _aspect)
 {
   if (!initialized_)
     initializeGL ();
+
+
+  // some drivers in core profile require a VAO object to be bound for all buffer array operations
+  if (!glstate_->compatibilityProfile())
+  {
+    if (!defaultVAO_.isSupported())
+      std::cerr << "Error - using core profile, but required VAO is not supported!" << std::endl;
+    else
+      defaultVAO_.bind();
+  }
+
+
   if (!properties_.updateLocked())
   {
     properties_.lockUpdate();

widgets/glWidget/QtBaseViewer.hh

@@ -620,6 +620,8 @@ private:
   // Used to calculate the time passed between redraws
   QTime redrawTime_;
 
+  // Default VAO needed in core profile mode
+  ACG::VertexArrayObject defaultVAO_;
 
 #if (QT_VERSION >= QT_VERSION_CHECK(5,1,0))
   // Get additional debug info from OpenGL