Fix issue with context timestamp when using QVTKWidget2.

Change-Id: Ic5bc394e6cbe3d9ab8bedf1809af72912aa94411

Examples/GUI/Qt/GraphicsView/GraphicsView.hpp

@@ -44,6 +44,7 @@ class GraphicsView : public QGraphicsView
       p->beginNativePainting();
 #endif
       mWidget->GetRenderWindow()->PushState();
+      mWidget->GetRenderWindow()->OpenGLInitState();
       mWidget->GetRenderWindow()->Render();
       mWidget->GetRenderWindow()->PopState();
 #if QT_VERSION >= 0x040600

GUISupport/Qt/QVTKGraphicsItem.cxx

@@ -137,7 +137,7 @@ void QVTKGraphicsItem::Start()
   }
 
   mWin->PushState();
-  mWin->OpenGLInit();
+  mWin->OpenGLInitState();
 }
 
 void QVTKGraphicsItem::End()

GUISupport/Qt/QVTKWidget2.cxx

@@ -202,7 +202,7 @@ void QVTKWidget2::Start()
 {
   makeCurrent();
   mRenWin->PushState();
-  mRenWin->OpenGLInit();
+  mRenWin->OpenGLInitState();
 }
 
 void QVTKWidget2::End()
@@ -210,6 +210,15 @@ void QVTKWidget2::End()
   mRenWin->PopState();
 }
 
+void QVTKWidget2::initializeGL()
+{
+  if(!this->mRenWin)
+    {
+    return;
+    }
+  this->mRenWin->OpenGLInitContext();
+}
+
 /*! handle resize event
  */
 void QVTKWidget2::resizeGL(int w, int h)

GUISupport/Qt/QVTKWidget2.h

@@ -99,6 +99,8 @@ protected Q_SLOTS:
   virtual void SupportsOpenGL(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
 
 protected:
+  // overloaded initialize handler
+  virtual void initializeGL();
   // overloaded resize handler
   virtual void resizeGL(int, int);
   // overloaded paint handler

Rendering/vtkOpenGLRenderWindow.cxx

@@ -238,38 +238,18 @@ void vtkOpenGLRenderWindow::StereoUpdate(void)
 
 void vtkOpenGLRenderWindow::OpenGLInit()
 {
-  // When a new OpenGL context is created, force an update
-  // of the extension manager by calling modified on it.
-  vtkOpenGLExtensionManager *extensions = this->GetExtensionManager();
-  extensions->Modified();
+  OpenGLInitContext();
+  OpenGLInitState();
+}
 
-  this->ContextCreationTime.Modified();
+void vtkOpenGLRenderWindow::OpenGLInitState()
+{
   glMatrixMode( GL_MODELVIEW );
   glDepthFunc( GL_LEQUAL );
   glEnable( GL_DEPTH_TEST );
   glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );
 
   // initialize blending for transparency
-  
-  // We have to set the function pointer to null, otherwise the following
-  // scenario would fail on Windows (and maybe other kind of configurations):
-  // 1. Render onscreen on GPU that supports OpenGL 1.4
-  // 2. Switch to offscreen with GDI Windows implementation (1.1)
-  vtkgl::BlendFuncSeparate=0;
-  
-  // Try to initialize vtkgl::BlendFuncSeparate() if available.
-  if (extensions->ExtensionSupported("GL_VERSION_1_4"))
-    {
-    extensions->LoadExtension("GL_VERSION_1_4");
-    }
-  else
-    {
-    if (extensions->ExtensionSupported("GL_EXT_blend_func_separate"))
-      {
-      extensions->LoadCorePromotedExtension("GL_EXT_blend_func_separate");
-      }
-    }
-  
   if(vtkgl::BlendFuncSeparate!=0)
     {
     vtkgl::BlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA,
@@ -323,6 +303,34 @@ void vtkOpenGLRenderWindow::OpenGLInit()
   glPixelStorei(GL_PACK_ALIGNMENT,1);
 }
 
+void vtkOpenGLRenderWindow::OpenGLInitContext()
+{
+  // When a new OpenGL context is created, force an update
+  // of the extension manager by calling modified on it.
+  vtkOpenGLExtensionManager *extensions = this->GetExtensionManager();
+  extensions->Modified();
+
+  this->ContextCreationTime.Modified();
+
+  // We have to set the function pointer to null, otherwise the following
+  // scenario would fail on Windows (and maybe other kind of configurations):
+  // 1. Render onscreen on GPU that supports OpenGL 1.4
+  // 2. Switch to offscreen with GDI Windows implementation (1.1)
+  vtkgl::BlendFuncSeparate=0;
+
+  // Try to initialize vtkgl::BlendFuncSeparate() if available.
+  if (extensions->ExtensionSupported("GL_VERSION_1_4"))
+    {
+    extensions->LoadExtension("GL_VERSION_1_4");
+    }
+  else
+    {
+    if (extensions->ExtensionSupported("GL_EXT_blend_func_separate"))
+      {
+      extensions->LoadCorePromotedExtension("GL_EXT_blend_func_separate");
+      }
+    }
+}
 
 void vtkOpenGLRenderWindow::PrintSelf(ostream& os, vtkIndent indent)
 {

Rendering/vtkOpenGLRenderWindow.h

@@ -107,6 +107,12 @@ public:
   // Initialize OpenGL for this window.
   virtual void OpenGLInit();
 
+  // Initialize the state of OpenGL that VTK wants for this window
+  virtual void OpenGLInitState();
+
+  // Initialize VTK for rendering in a new OpenGL context
+  virtual void OpenGLInitContext();
+
   // Description:
   // Return the OpenGL name of the back left buffer.
   // It is GL_BACK_LEFT if GL is bound to the window-system-provided