[mutter] main: Parse MUTTER_DEBUG as debug string

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit b1ffd14d623c70057abf99aeff4e6a4ccfd6b90b
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Oct 1 15:05:17 2020 +0200

    main: Parse MUTTER_DEBUG as debug string
    
    This makes it possible to run e.g.
    
        env MUTTER_DEBUG=input:geometry gnome-shell
    
    which will enable the 'META_DEBUG_INPUT' and 'META_DEBUG_GEOMETRY'
    topics.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1465

 src/core/main.c | 37 +++++++++++++++++++++++++++++++++++--
 src/core/util.c |  6 +++---
 2 files changed, 38 insertions(+), 5 deletions(-)
---
diff --git a/src/core/main.c b/src/core/main.c
index 06605c5e22..5a20cd6a78 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -98,6 +98,29 @@
 #include "backends/native/meta-backend-native.h"
 #endif
 
+static const GDebugKey meta_debug_keys[] = {
+  { "focus", META_DEBUG_FOCUS },
+  { "workarea", META_DEBUG_WORKAREA },
+  { "stack", META_DEBUG_STACK },
+  { "sm", META_DEBUG_SM },
+  { "events", META_DEBUG_EVENTS },
+  { "window-state", META_DEBUG_WINDOW_STATE },
+  { "window-ops", META_DEBUG_WINDOW_OPS },
+  { "geometry", META_DEBUG_GEOMETRY },
+  { "placement", META_DEBUG_PLACEMENT },
+  { "ping", META_DEBUG_PING },
+  { "keybindings", META_DEBUG_KEYBINDINGS },
+  { "sync", META_DEBUG_SYNC },
+  { "startup", META_DEBUG_STARTUP },
+  { "prefs", META_DEBUG_PREFS },
+  { "groups", META_DEBUG_GROUPS },
+  { "resizing", META_DEBUG_RESIZING },
+  { "shapes", META_DEBUG_SHAPES },
+  { "edge-resistance", META_DEBUG_EDGE_RESISTANCE },
+  { "dbus", META_DEBUG_DBUS },
+  { "input", META_DEBUG_INPUT },
+};
+
 /*
  * The exit code we'll return to our parent process when we eventually die.
  */
@@ -535,6 +558,7 @@ meta_init (void)
 {
   struct sigaction act;
   sigset_t empty_mask;
+  const char *debug_env;
   MetaCompositorType compositor_type;
   GType backend_gtype;
 
@@ -559,8 +583,17 @@ meta_init (void)
 
   if (g_getenv ("MUTTER_VERBOSE"))
     meta_set_verbose (TRUE);
-  if (g_getenv ("MUTTER_DEBUG"))
-    meta_set_debugging (TRUE);
+
+  debug_env = g_getenv ("MUTTER_DEBUG");
+  if (debug_env)
+    {
+      MetaDebugTopic topics;
+
+      topics = g_parse_debug_string (debug_env,
+                                     meta_debug_keys,
+                                     G_N_ELEMENTS (meta_debug_keys));
+      meta_add_verbose_topic (topics);
+    }
 
   if (_compositor_configuration_overridden)
     {
diff --git a/src/core/util.c b/src/core/util.c
index 2b3dc286ca..4d9d8acb34 100644
--- a/src/core/util.c
+++ b/src/core/util.c
@@ -116,9 +116,6 @@ meta_set_verbose (gboolean setting)
 #ifndef WITH_VERBOSE_MODE
   if (setting)
     meta_fatal (_("Mutter was compiled without support for verbose mode\n"));
-#else
-  if (setting)
-    ensure_logfile ();
 #endif
 
   if (setting)
@@ -139,6 +136,9 @@ meta_add_verbose_topic (MetaDebugTopic topic)
 {
   if (verbose_topics == META_DEBUG_VERBOSE)
     return;
+
+  ensure_logfile ();
+
   if (topic == META_DEBUG_VERBOSE)
     verbose_topics = META_DEBUG_VERBOSE;
   else