[geary] Clean up engine logging API a bit.

[Michael Gratton <mjog src gnome org>]

commit c371b91340f27b85c8cad5008ca6351053b5e0c4
Author: Michael James Gratton <mike vee net>
Date:   Mon Dec 18 13:37:25 2017 +1100

    Clean up engine logging API a bit.
    
    Also fixes debug logging under the Meson build.
    
    * src/engine/api/geary-logging.vala (Logging): Use a domain for engine
      logging calls. Make Flag.NONE explicitly set to 0 so it's obvious what
      is happening in the code. Don't set up any handlers at all - this is
      something the application should be doing. Rename on_log() to
      default_handler() and make it public so that application can use the
      engine's logger if they want.
    
    * src/client/application/geary-application.vala (Application): Install
      the engine's default handler after init'ing logging — needed to fix
      logging under Meson, use stderr for logging until command-line
      arguments have been processed.
    
    * src/client/application/geary-args.vala: Stop using stderr for logging
      if --debug arg was not set.

 src/client/application/geary-application.vala |    5 +-
 src/client/application/geary-args.vala        |   11 ++-
 src/engine/api/geary-logging.vala             |  103 ++++++++++++++++---------
 3 files changed, 79 insertions(+), 40 deletions(-)
---
diff --git a/src/client/application/geary-application.vala b/src/client/application/geary-application.vala
index 27712f9..65481f3 100644
--- a/src/client/application/geary-application.vala
+++ b/src/client/application/geary-application.vala
@@ -183,8 +183,11 @@ public class GearyApplication : Gtk.Application {
         Environment.set_application_name(NAME);
         Environment.set_prgname(PRGNAME);
         International.init(GETTEXT_PACKAGE, bin);
-        
+
         Geary.Logging.init();
+        Geary.Logging.log_to(stderr);
+        GLib.Log.set_default_handler(Geary.Logging.default_handler);
+
         Date.init();
 
         // Calls Gtk.init(), amongst other things
diff --git a/src/client/application/geary-args.vala b/src/client/application/geary-args.vala
index 9c2b153..cde707e 100644
--- a/src/client/application/geary-args.vala
+++ b/src/client/application/geary-args.vala
@@ -106,10 +106,15 @@ public bool parse(string[] args) {
     
     if (log_deserializer)
         Geary.Logging.enable_flags(Geary.Logging.Flag.DESERIALIZER);
-    
-    if (log_debug)
+
+    if (log_debug) {
         Geary.Logging.log_to(stdout);
-    
+    } else {
+        // We'll be logging to stderror until this point, so stop
+        // that.
+        Geary.Logging.log_to(null);
+    }
+
     return true;
 }
 
diff --git a/src/engine/api/geary-logging.vala b/src/engine/api/geary-logging.vala
index 0ded38b..b218ccd 100644
--- a/src/engine/api/geary-logging.vala
+++ b/src/engine/api/geary-logging.vala
@@ -13,9 +13,11 @@
 
 namespace Geary.Logging {
 
+private const string DOMAIN = "Geary";
+
 [Flags]
 public enum Flag {
-    NONE,
+    NONE = 0,
     NETWORK,
     SERIALIZER,
     REPLAY,
@@ -24,11 +26,11 @@ public enum Flag {
     SQL,
     FOLDER_NORMALIZATION,
     DESERIALIZER;
-    
+
     public inline bool is_all_set(Flag flags) {
         return (flags & this) == flags;
     }
-    
+
     public inline bool is_any_set(Flag flags) {
         return (flags & this) != 0;
     }
@@ -48,10 +50,7 @@ private Timer? entry_timer = null;
 public void init() {
     if (init_count++ != 0)
         return;
-    
     entry_timer = new Timer();
-    
-    log_to(null);
 }
 
 /**
@@ -92,27 +91,28 @@ public inline bool are_all_flags_set(Flag flags) {
 
 public inline void error(Flag flags, string fmt, ...) {
     if (logging_flags.is_any_set(flags))
-        logv(null, LogLevelFlags.LEVEL_ERROR, fmt, va_list());
+        logv(DOMAIN, LogLevelFlags.LEVEL_ERROR, fmt, va_list());
 }
 
 public inline void critical(Flag flags, string fmt, ...) {
     if (logging_flags.is_any_set(flags))
-        logv(null, LogLevelFlags.LEVEL_CRITICAL, fmt, va_list());
+        logv(DOMAIN, LogLevelFlags.LEVEL_CRITICAL, fmt, va_list());
 }
 
 public inline void warning(Flag flags, string fmt, ...) {
     if (logging_flags.is_any_set(flags))
-        logv(null, LogLevelFlags.LEVEL_WARNING, fmt, va_list());
+        logv(DOMAIN, LogLevelFlags.LEVEL_WARNING, fmt, va_list());
 }
 
 public inline void message(Flag flags, string fmt, ...) {
     if (logging_flags.is_any_set(flags))
-        logv(null, LogLevelFlags.LEVEL_MESSAGE, fmt, va_list());
+        logv(DOMAIN, LogLevelFlags.LEVEL_MESSAGE, fmt, va_list());
 }
 
 public inline void debug(Flag flags, string fmt, ...) {
-    if (logging_flags.is_any_set(flags))
-        logv(null, LogLevelFlags.LEVEL_DEBUG, fmt, va_list());
+    if (logging_flags.is_any_set(flags)) {
+        logv(DOMAIN, LogLevelFlags.LEVEL_DEBUG, fmt, va_list());
+    }
 }
 
 /**
@@ -125,31 +125,62 @@ public inline void debug(Flag flags, string fmt, ...) {
  */
 public void log_to(FileStream? stream) {
     Logging.stream = stream;
-    
-    Log.set_handler(null, LogLevelFlags.LEVEL_DEBUG,
-        (domain, levels, msg) => { on_log(" [deb]", levels, msg); });
-    Log.set_handler(null, LogLevelFlags.LEVEL_INFO,
-        (domain, levels, msg) => { on_log(" [inf]", levels, msg); });
-    Log.set_handler(null, LogLevelFlags.LEVEL_MESSAGE,
-        (domain, levels, msg) => { on_log(" [msg]", levels, msg); });
-    Log.set_handler(null, LogLevelFlags.LEVEL_WARNING,
-        (domain, levels, msg) => { on_log("*[wrn]", levels, msg); });
-    Log.set_handler(null, LogLevelFlags.LEVEL_CRITICAL,
-        (domain, levels, msg) => { on_log("![crt]", levels, msg); });
-    Log.set_handler(null, LogLevelFlags.LEVEL_ERROR,
-        (domain, levels, msg) => { on_log("![err]", levels, msg); });
-}
-
-private void on_log(string prefix, LogLevelFlags log_levels, string message) {
-    if (stream == null)
-        return;
-    
-    GLib.Time tm = GLib.Time.local(time_t());
-    stream.printf("%s %02d:%02d:%02d %lf %s\n", prefix, tm.hour, tm.minute, tm.second,
-        entry_timer.elapsed(), message);
-    
-    entry_timer.start();
 }
 
+public void default_handler(string? domain,
+                            LogLevelFlags log_levels,
+                            string message) {
+    unowned FileStream? out = stream;
+    if (out != null ||
+        ((LogLevelFlags.LEVEL_WARNING & log_levels) > 0) ||
+        ((LogLevelFlags.LEVEL_CRITICAL & log_levels) > 0)  ||
+        ((LogLevelFlags.LEVEL_ERROR & log_levels) > 0)) {
+
+        if (out == null) {
+            out = GLib.stderr;
+        }
+
+        GLib.Time tm = GLib.Time.local(time_t());
+        out.printf(
+            "%s %02d:%02d:%02d %lf %s: %s\n",
+            to_prefix(log_levels),
+            tm.hour, tm.minute, tm.second,
+            entry_timer.elapsed(),
+            domain ?? "default",
+            message
+        );
+
+        entry_timer.start();
+    }
 }
 
+private inline string to_prefix(LogLevelFlags level) {
+    switch (level) {
+    case LogLevelFlags.LEVEL_ERROR:
+        return "![err]";
+
+    case LogLevelFlags.LEVEL_CRITICAL:
+        return "![crt]";
+
+    case LogLevelFlags.LEVEL_WARNING:
+        return "*[wrn]";
+
+    case LogLevelFlags.LEVEL_MESSAGE:
+        return " [msg]";
+
+    case LogLevelFlags.LEVEL_INFO:
+        return " [inf]";
+
+    case LogLevelFlags.LEVEL_DEBUG:
+        return " [deb]";
+
+    case LogLevelFlags.LEVEL_MASK:
+        return "![***]";
+
+    default:
+        return "![???]";
+
+    }
+}
+
+}