streamline DatabasePager::requiresUpdateSceneGraph()

would trigger unnecessary redraws when there were pending file requests or active database threads

tested ok with and without IncrementalCompileOperation

src/osgDB/DatabasePager.cpp

@@ -1371,10 +1371,7 @@ bool DatabasePager::getRequestsInProgress() const
 {
     if (getFileRequestListSize()>0) return true;
 
-    if (getDataToCompileListSize()>0)
-    {
-        return true;
-    }
+    if (getDataToCompileListSize()>0) return true;
 
     if (getDataToMergeListSize()>0) return true;
 
@@ -1595,7 +1592,11 @@ void DatabasePager::setDatabasePagerThreadPause(bool pause)
 
 bool DatabasePager::requiresUpdateSceneGraph() const
 {
-    return !(_dataToMergeList->empty());
+    if (getDataToCompileListSize()>0) return true;
+
+    if (getDataToMergeListSize()>0) return true;
+
+    return false;
 }
 
 void DatabasePager::updateSceneGraph(const osg::FrameStamp& frameStamp)

src/osgViewer/Scene.cpp

@@ -116,7 +116,7 @@ void Scene::setImagePager(osgDB::ImagePager* ip)
 bool Scene::requiresUpdateSceneGraph() const
 {
     // check if the database pager needs to update the scene
-    if (getDatabasePager()->requiresUpdateSceneGraph() || getDatabasePager()->getRequestsInProgress()) return true;
+    if (getDatabasePager()->requiresUpdateSceneGraph()) return true;
 
     // check if the image pager needs to update the scene
     if (getImagePager()->requiresUpdateSceneGraph()) return true;

src/osgViewer/View.cpp

@@ -1135,7 +1135,7 @@ bool View::requiresUpdateSceneGraph() const
     // check if there are camera update callbacks
     if (_camera->getUpdateCallback()) return true;
 
-    // check if there scene requires an update traversal
+    // check if the scene requires an update traversal
     if (_scene.valid() && _scene->requiresUpdateSceneGraph()) return true;
 
     return false;