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

[verdre <jonasd src gnome org>]

commit 43c6f70605b3fb305210f4adf3ab89abd06b60ad
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Oct 2 19:30:58 2020 +0200

    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

 src/core/util.c | 16 +++++++++++++---
 src/meta/util.h | 20 ++++++++++++++++++--
 2 files changed, 31 insertions(+), 5 deletions(-)
---
diff --git a/src/core/util.c b/src/core/util.c
index 681529b167..0c9a31d824 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 6d06ea5725..5fddf08734 100644
--- a/src/meta/util.h
+++ b/src/meta/util.h
@@ -112,6 +112,9 @@ typedef enum
   META_DEBUG_PAINT_OPAQUE_REGION = 1 << 0,
 } MetaDebugPaintFlag;
 
+META_EXPORT
+gboolean meta_is_topic_enabled (MetaDebugTopic topic);
+
 META_EXPORT
 void meta_topic_real      (MetaDebugTopic topic,
                            const char    *format,
@@ -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