GLiblog_writer_default_would_drop

Check whether g_log_writer_default() and g_log_default_handler() would ignore a message with the given domain and level.

As with g_log_default_handler(), this function drops debug and informational messages unless their log domain (or all) is listed in the space-separated G_MESSAGES_DEBUG environment variable, or DEBUG_INVOCATION=1 is set in the environment, or by g_log_writer_default_set_debug_domains().

This can be used when implementing log writers with the same filtering behaviour as the default, but a different destination or output format:

if (g_log_writer_default_would_drop (log_level, log_domain))
  return G_LOG_WRITER_HANDLED;
]|

or to skip an expensive computation if it is only needed for a debugging
message, and `G_MESSAGES_DEBUG` and `DEBUG_INVOCATION` are not set:

```c
if (!g_log_writer_default_would_drop (G_LOG_LEVEL_DEBUG, G_LOG_DOMAIN))
  {
    g_autofree gchar *result = expensive_computation (my_object);

    g_debug ("my_object result: %s", result);
  }

Available since: 2.68