simplify to define when to use which offscreen rendering method

src/Gui/SoFCOffscreenRenderer.cpp

@@ -411,11 +411,7 @@ void SoQtOffscreenRenderer::init(const SbViewportRegion & vpr,
     this->framebuffer = NULL;
     this->numSamples = -1;
     this->cache_context = 0;
-#if !defined(HAVE_QT5_OPENGL)
-    this->pbuffer = QGLPixelBuffer::hasOpenGLPbuffers();
-#else
     this->pbuffer = false;
-#endif
 }
 
 /*!

src/Gui/View3DInventorViewer.cpp

@@ -927,14 +927,7 @@ void View3DInventorViewer::setSceneGraph(SoNode* root)
 
 void View3DInventorViewer::savePicture(int w, int h, const QColor& bg, QImage& img) const
 {
-    // If 'QGLPixelBuffer::hasOpenGLPbuffers()' returns false then
-    // SoQtOffscreenRenderer won't work. In this case we try to use
-    // Coin's implementation of the off-screen rendering.
-#if !defined(HAVE_QT5_OPENGL)
-    bool useCoinOffscreenRenderer = !QGLPixelBuffer::hasOpenGLPbuffers();
-#else
     bool useCoinOffscreenRenderer = false;
-#endif
     useCoinOffscreenRenderer = App::GetApplication().GetParameterGroupByPath
         ("User parameter:BaseApp/Preferences/Document")->
         GetBool("CoinOffscreenRenderer", useCoinOffscreenRenderer);

src/Gui/View3DPy.cpp

@@ -755,13 +755,8 @@ Py::Object View3DInventorPy::saveImage(const Py::Tuple& args)
         bg.setNamedColor(colname);
 
     QImage img;
-#if !defined(HAVE_QT5_OPENGL)
-    bool pbuffer = QGLPixelBuffer::hasOpenGLPbuffers();
-#else
-    bool pbuffer = false;
-#endif
     if (App::GetApplication().GetParameterGroupByPath
-        ("User parameter:BaseApp/Preferences/Document")->GetBool("DisablePBuffers",!pbuffer)) {
+        ("User parameter:BaseApp/Preferences/Document")->GetBool("DisablePBuffers", false)) {
         createImageFromFramebuffer(w, h, bg, img);
     }
     else {