Seems to fix wireframe crashes

apps/nifosgtest/test.cpp

@@ -17,9 +17,8 @@
 class WireframeKeyHandler : public osgGA::GUIEventHandler
 {
 public:
-    WireframeKeyHandler(osg::Node* node)
+    WireframeKeyHandler()
         : mWireframe(false)
-        , mNode(node)
     {
 
     }
@@ -32,12 +31,7 @@ public:
             if (adapter.getKey() == osgGA::GUIEventAdapter::KEY_W)
             {
                 mWireframe = !mWireframe;
-                osg::PolygonMode* mode = new osg::PolygonMode;
-                mode->setMode(osg::PolygonMode::FRONT_AND_BACK,
-                              mWireframe ? osg::PolygonMode::LINE : osg::PolygonMode::FILL);
-                mNode->getOrCreateStateSet()->setAttributeAndModes(mode, osg::StateAttribute::ON);
-                mNode->getOrCreateStateSet()->setMode(GL_CULL_FACE, mWireframe ? osg::StateAttribute::OFF
-                                                                               : osg::StateAttribute::ON);
+                // applying state from an event handler doesn't appear to be safe, so do it in the frame update
                 return true;
             }
         default:
@@ -46,9 +40,13 @@ public:
         return false;
     }
 
+    bool getWireframe() const
+    {
+        return mWireframe;
+    }
+
 private:
     bool mWireframe;
-    osg::Node* mNode;
 };
 
 int main(int argc, char** argv)
@@ -93,11 +91,28 @@ int main(int argc, char** argv)
     viewer.setUpViewInWindow(0, 0, 800, 600);
     viewer.realize();
     viewer.setCameraManipulator(new osgGA::TrackballManipulator());
-    viewer.addEventHandler(new WireframeKeyHandler(root));
+
+    WireframeKeyHandler* keyHandler = new WireframeKeyHandler;
+
+    viewer.addEventHandler(keyHandler);
     viewer.addEventHandler(new osgViewer::StatsHandler);
 
+    bool wireframe = false;
+
     while (!viewer.done())
     {
+
+        if (wireframe != keyHandler->getWireframe())
+        {
+            wireframe = keyHandler->getWireframe();
+            osg::PolygonMode* mode = new osg::PolygonMode;
+            mode->setMode(osg::PolygonMode::FRONT_AND_BACK,
+                          wireframe ? osg::PolygonMode::LINE : osg::PolygonMode::FILL);
+            root->getOrCreateStateSet()->setAttributeAndModes(mode, osg::StateAttribute::ON);
+            root->getOrCreateStateSet()->setMode(GL_CULL_FACE, wireframe ? osg::StateAttribute::OFF
+                                                                           : osg::StateAttribute::ON);
+        }
+
         viewer.frame();
 
         for (unsigned int i=0; i<controllers.size(); ++i)