Logging to permutations of multiple targets

It's possible to create multiple filters with multiple criteria on each filter and then route each filter to a separate target. This permits advanced logging of different types of events to different log targets.

A filter will automatically attempt to publish itself to all targets. You can change this behavior by calling UnpublishToMultiple( AllTargets() ) on that filter, followed by PublishTo() to publish that filter to an output of your choice.

    LOGOG_INITIALIZE();

    {
                GetFilterDefault().Group(_LG("Graphics"));
        Filter filter;
        filter.Group(_LG("Audio"));
        Cerr err;

        WARN(_LG("This message won't happen because it's not in the Graphics group"));

#undef LOGOG_GROUP
#undef LOGOG_CATEGORY
#define LOGOG_GROUP  "Graphics"
#define LOGOG_CATEGORY "Unrecoverable"

        EMERGENCY(_LG("The graphics card has been destroyed"));

#undef LOGOG_CATEGORY
#define LOGOG_CATEGORY  "Recoverable"

        WARN(_LG("The graphics card has been replaced"));

#undef LOGOG_GROUP
#define LOGOG_GROUP "Audio"

        WARN(_LG("The headphones are unplugged"));

#undef LOGOG_GROUP
#define LOGOG_GROUP "Inputs"

        WARN(_LG("The inputs have been yanked off but this fact won't be reported!"));

#undef LOGOG_CATEGORY
#undef LOGOG_GROUP
#define LOGOG_CATEGORY NULL
#define LOGOG_GROUP NULL
    }

    LOGOG_SHUTDOWN();