qga: map GLib log levels to system levels

This patch translates GLib-specific log levels to system ones, so that
they may be used by both *nix syslog() (as a "priority" argument) and
Windows ReportEvent() (as a "wType" argument).

Currently the only codepath to write to "syslog" domain is slog()
function.  However, this patch allows the interface to be extended.

Note that since slog() is using G_LOG_LEVEL_INFO level, its behaviour
doesn't change.

Originally-by: Yuri Pudgorodskiy <yur@virtuozzo.com>
Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Tested-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>

qga/main.c

@@ -314,6 +314,38 @@ void ga_enable_logging(GAState *s)
     s->logging_enabled = true;
 }
 
+static int glib_log_level_to_system(int level)
+{
+    switch (level) {
+#ifndef _WIN32
+    case G_LOG_LEVEL_ERROR:
+        return LOG_ERR;
+    case G_LOG_LEVEL_CRITICAL:
+        return LOG_CRIT;
+    case G_LOG_LEVEL_WARNING:
+        return LOG_WARNING;
+    case G_LOG_LEVEL_MESSAGE:
+        return LOG_NOTICE;
+    case G_LOG_LEVEL_DEBUG:
+        return LOG_DEBUG;
+    case G_LOG_LEVEL_INFO:
+    default:
+        return LOG_INFO;
+#else
+    case G_LOG_LEVEL_ERROR:
+    case G_LOG_LEVEL_CRITICAL:
+        return EVENTLOG_ERROR_TYPE;
+    case G_LOG_LEVEL_WARNING:
+        return EVENTLOG_WARNING_TYPE;
+    case G_LOG_LEVEL_MESSAGE:
+    case G_LOG_LEVEL_INFO:
+    case G_LOG_LEVEL_DEBUG:
+    default:
+        return EVENTLOG_INFORMATION_TYPE;
+#endif
+    }
+}
+
 static void ga_log(const gchar *domain, GLogLevelFlags level,
                    const gchar *msg, gpointer opaque)
 {
@@ -327,9 +359,9 @@ static void ga_log(const gchar *domain, GLogLevelFlags level,
     level &= G_LOG_LEVEL_MASK;
     if (g_strcmp0(domain, "syslog") == 0) {
 #ifndef _WIN32
-        syslog(LOG_INFO, "%s: %s", level_str, msg);
+        syslog(glib_log_level_to_system(level), "%s: %s", level_str, msg);
 #else
-        ReportEvent(s->event_log, EVENTLOG_INFORMATION_TYPE,
+        ReportEvent(s->event_log, glib_log_level_to_system(level),
                     0, 1, NULL, 1, 0, &msg, NULL);
 #endif
     } else if (level & s->log_level) {