Fix the frameNumber not being incremented in certain frames

apps/openmw/mwgui/loadingscreen.cpp

@@ -282,7 +282,13 @@ namespace MWGui
         MWBase::Environment::get().getInputManager()->update(0, true, true);
 
         //osg::Timer timer;
-        mViewer->frame(mViewer->getFrameStamp()->getSimulationTime());
+        // at the time this function is called we are in the middle of a frame,
+        // so out of order calls are necessary to get a correct frameNumber for the next frame.
+        // refer to the advance() and frame() order in Engine::go()
+        mViewer->eventTraversal();
+        mViewer->updateTraversal();
+        mViewer->renderingTraversals();
+        mViewer->advance(mViewer->getFrameStamp()->getSimulationTime());
         //std::cout << "frame took " << timer.time_m() << std::endl;
 
         //if (mViewer->getIncrementalCompileOperation())

apps/openmw/mwgui/windowmanagerimp.cpp

@@ -859,7 +859,13 @@ namespace MWGui
                 mMessageBoxManager->onFrame(0.f);
                 MWBase::Environment::get().getInputManager()->update(0, true, false);
 
-                mViewer->frame(mViewer->getFrameStamp()->getSimulationTime());
+                // at the time this function is called we are in the middle of a frame,
+                // so out of order calls are necessary to get a correct frameNumber for the next frame.
+                // refer to the advance() and frame() order in Engine::go()
+                mViewer->eventTraversal();
+                mViewer->updateTraversal();
+                mViewer->renderingTraversals();
+                mViewer->advance(mViewer->getFrameStamp()->getSimulationTime());
             }
         }
     }
@@ -1756,7 +1762,13 @@ namespace MWGui
         {
             MWBase::Environment::get().getInputManager()->update(0, true, false);
 
-            mViewer->frame(mViewer->getFrameStamp()->getSimulationTime());
+            // at the time this function is called we are in the middle of a frame,
+            // so out of order calls are necessary to get a correct frameNumber for the next frame.
+            // refer to the advance() and frame() order in Engine::go()
+            mViewer->eventTraversal();
+            mViewer->updateTraversal();
+            mViewer->renderingTraversals();
+            mViewer->advance(mViewer->getFrameStamp()->getSimulationTime());
         }
         mVideoWidget->stop();
 

apps/openmw/mwrender/renderingmanager.cpp

@@ -521,10 +521,18 @@ namespace MWRender
         osg::ref_ptr<NotifyDrawCompletedCallback> callback (new NotifyDrawCompletedCallback);
         rttCamera->setFinalDrawCallback(callback);
 
-        mViewer->frame(mViewer->getFrameStamp()->getSimulationTime());
+        // at the time this function is called we are in the middle of a frame,
+        // so out of order calls are necessary to get a correct frameNumber for the next frame.
+        // refer to the advance() and frame() order in Engine::go()
+        mViewer->eventTraversal();
+        mViewer->updateTraversal();
+        mViewer->renderingTraversals();
 
         callback->waitTillDone();
 
+        // now that we've "used up" the current frame, get a fresh framenumber for the next frame() following after the screenshot is completed
+        mViewer->advance(mViewer->getFrameStamp()->getSimulationTime());
+
         rttCamera->removeChildren(0, rttCamera->getNumChildren());
         rttCamera->setGraphicsContext(NULL);
         mRootNode->removeChild(rttCamera);