[gnome-shell] main: Define a custom log writer to dump on structured messages

[Marge Bot <marge-bot src gnome org>]

commit 1bd9076590013e0c327f2517ac536a02ddf8e13e
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Mon Sep 2 17:05:27 2019 +0200

    main: Define a custom log writer to dump on structured messages
    
    Even though GNOME Shell is not explicitly using structured logging via
    G_LOG_USE_STRUCTURED, GLib uses it as default since 2016 [1], and so
    we're de facto using it.
    
    As per this, if backtrace on warnings is enabled, it is ignored since the
    log handler isn't used anymore, and no dump is printed.
    
    Thus, replace the default log handlers with writer functions instead, honoring
    backtrace-warnings debug string.
    
    [1] https://gitlab.gnome.org/GNOME/glib/-/commit/fce7cfaf40b6e1e50c9140aa0397f5
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/697>

 src/main.c | 56 ++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 36 insertions(+), 20 deletions(-)
---
diff --git a/src/main.c b/src/main.c
index 03708fc8fe..29275cda07 100644
--- a/src/main.c
+++ b/src/main.c
@@ -287,39 +287,55 @@ shell_init_debug (const char *debug_env)
                                        G_N_ELEMENTS (keys));
 }
 
-static void
-default_log_handler (const char     *log_domain,
-                     GLogLevelFlags  log_level,
-                     const char     *message,
-                     gpointer        data)
+static GLogWriterOutput
+default_log_writer (GLogLevelFlags   log_level,
+                    const GLogField *fields,
+                    gsize            n_fields,
+                    gpointer         user_data)
 {
-  if (!log_domain || !g_str_has_prefix (log_domain, "tp-glib"))
-    g_log_default_handler (log_domain, log_level, message, data);
+  GLogWriterOutput output;
+  int i;
 
-  /* Filter out Gjs logs, those already have the stack */
-  if (log_domain && strcmp (log_domain, "Gjs") == 0)
-    return;
+  output = g_log_writer_default (log_level, fields, n_fields, user_data);
 
   if ((_shell_debug & SHELL_DEBUG_BACKTRACE_WARNINGS) &&
       ((log_level & G_LOG_LEVEL_CRITICAL) ||
        (log_level & G_LOG_LEVEL_WARNING)))
-    gjs_dumpstack ();
+    {
+      const char *log_domain = NULL;
+
+      for (i = 0; i < n_fields; i++)
+        {
+          if (g_strcmp0 (fields[i].key, "GLIB_DOMAIN") == 0)
+            {
+              log_domain = fields[i].value;
+              break;
+            }
+        }
+
+      /* Filter out Gjs logs, those already have the stack */
+      if (g_strcmp0 (log_domain, "Gjs") != 0)
+        gjs_dumpstack ();
+    }
+
+  return output;
 }
 
-static void
-shut_up (const char     *domain,
-         GLogLevelFlags  level,
-         const char     *message,
-         gpointer        user_data)
+static GLogWriterOutput
+shut_up (GLogLevelFlags   log_level,
+         const GLogField *fields,
+         gsize            n_fields,
+         gpointer         user_data)
 {
+  return (GLogWriterOutput) {0};
 }
 
 static void
 dump_gjs_stack_alarm_sigaction (int signo)
 {
-  g_log_set_default_handler (g_log_default_handler, NULL);
+  g_log_set_writer_func (g_log_writer_default, NULL, NULL);
   g_warning ("Failed to dump Javascript stack, got stuck");
-  g_log_set_default_handler (default_log_handler, NULL);
+  g_log_set_writer_func (default_log_writer, NULL, NULL);
 
   raise (caught_signal);
 }
@@ -384,7 +400,7 @@ list_modes (const char  *option_name,
    * ShellGlobal has some GTK+ dependencies, so initialize GTK+; we
    * don't really care if it fails though (e.g. when running from a tty),
    * so we mute all warnings */
-  g_log_set_default_handler (shut_up, NULL);
+  g_log_set_writer_func (shut_up, NULL, NULL);
   gtk_init_check (NULL, NULL);
 
   _shell_global_init (NULL);
@@ -533,7 +549,7 @@ main (int argc, char **argv)
   shell_introspection_init ();
   shell_fonts_init ();
 
-  g_log_set_default_handler (default_log_handler, NULL);
+  g_log_set_writer_func (default_log_writer, NULL, NULL);
 
   /* Initialize the global object */
   if (session_mode == NULL)