cleanup viewer message handling

viewer/main.cpp

@@ -18,30 +18,23 @@ int main(int argc, char* argv[])
     app.setOrganizationName("WebVfx");
     app.setApplicationName("WebVfx Viewer");
 
+    Viewer viewer;
+    static Viewer* viewerPtr = &viewer;
     // Can't use a capturing lambda as a function pointer
     // https://stackoverflow.com/questions/73366933/what-does-mean-in-cpp-lambda-declaration-auto-fun1
-    // Need to ensure viewer is destroyed before we leave main and exit,
-    // otherwise it's destructor tries to clean up global state which is in the unloaded webvfx library
-
-    struct Cleanup {
-        static inline void cleanup(Viewer* pointer)
-        {
-            qInstallMessageHandler(0);
-            delete pointer;
-        }
-    };
-    static Viewer* viewer = new Viewer();
-    QScopedPointer<Viewer, Cleanup> destroyer(viewer);
-
     auto messageHandler = +[](QtMsgType type, const QMessageLogContext& context, const QString& msg) mutable {
-        viewer->messageHandler(type, context, msg);
+        if (viewerPtr)
+            viewerPtr->messageHandler(type, context, msg);
     };
     qInstallMessageHandler(messageHandler);
-    viewer->show();
+    viewer.show();
 
     QStringList args(QApplication::arguments());
     if (args.size() > 1)
-        viewer->loadFile(args.at(1));
+        viewer.loadFile(args.at(1));
 
-    return app.exec();
+    auto result = app.exec();
+    qInstallMessageHandler(0);
+    viewerPtr = nullptr;
+    return result;
 }