Redirecting the notifier

The OSG output message always includes important information about the running state, graphics system extensions, and possible problems in the OSG backend and user applications. This is also important as a reference source for debugging OSG-based programs.

In some cases, there is no console output in an application, which prevents us from reading notifier messages and finding possible bugs. However, the osg::NotifyHandler derived class can be used to redirect the notifier to another output stream, such as files or GUI widgets.