util: Don't expand meta_*() debug log arguments if topic not enabled

It's pointless to call into functions that produce information that will
end up nowhere, so lets not. This will generate less angst when doing
more intense data gathering and string generation in debug log calls.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1467

2 files changed, 31 insertions, 5 deletions

diff --git a/src/core/util.c b/src/core/util.c
index 681529b16..0c9a31d82 100644
--- a/src/core/util.c
+++ b/src/core/util.c
@@ -285,6 +285,18 @@ topic_name (MetaDebugTopic topic)
 
 static int sync_count = 0;
 
+gboolean
+meta_is_topic_enabled (MetaDebugTopic topic)
+{
+  if (verbose_topics == 0)
+    return FALSE;
+
+  if (topic == META_DEBUG_VERBOSE && verbose_topics != META_DEBUG_VERBOSE)
+    return FALSE;
+
+  return !!(verbose_topics & topic);
+}
+
 static void
 meta_topic_real_valist (MetaDebugTopic topic,
                         const char    *format,
@@ -295,9 +307,7 @@ meta_topic_real_valist (MetaDebugTopic topic,
 
   g_return_if_fail (format != NULL);
 
-  if (verbose_topics == 0
-      || (topic == META_DEBUG_VERBOSE && verbose_topics != META_DEBUG_VERBOSE)
-      || (!(verbose_topics & topic)))
+  if (!meta_is_topic_enabled (topic))
     return;
 
   str = g_strdup_vprintf (format, args);
diff --git a/src/meta/util.h b/src/meta/util.h
index 6d06ea572..5fddf0873 100644
--- a/src/meta/util.h
+++ b/src/meta/util.h
@@ -113,6 +113,9 @@ typedef enum
 } MetaDebugPaintFlag;
 
 META_EXPORT
+gboolean meta_is_topic_enabled (MetaDebugTopic topic);
+
+META_EXPORT
 void meta_topic_real      (MetaDebugTopic topic,
                            const char    *format,
                            ...) G_GNUC_PRINTF (2, 3);
@@ -162,8 +165,21 @@ GPid meta_show_dialog (const char *type,
 /* To disable verbose mode, we make these functions into no-ops */
 #ifdef WITH_VERBOSE_MODE
 
-#define meta_verbose    meta_verbose_real
-#define meta_topic      meta_topic_real
+#define meta_verbose(...) \
+  G_STMT_START \
+    { \
+      if (meta_is_topic_enabled (META_DEBUG_VERBOSE)) \
+        meta_verbose_real (__VA_ARGS__); \
+    } \
+  G_STMT_END
+
+#define meta_topic(debug_topic,...) \
+  G_STMT_START \
+    { \
+      if (meta_is_topic_enabled (debug_topic)) \
+        meta_topic_real (debug_topic, __VA_ARGS__); \
+    } \
+  G_STMT_END
 
 #else