Move YGLogger into YGConfig and associate YGNodeRef with log events

Summary:
Moves the `YGLogger` into `YGConfig` and pass the `YGNodeRef` into the logger to be able to associate the log messages and assertions with the specific node.

Tackles facebook/yoga#530 and facebook/yoga#446
Closes https://github.com/facebook/yoga/pull/531

Reviewed By: astreet

Differential Revision: D4970149

Pulled By: emilsjolander

fbshipit-source-id: b7fcdaa273143ea2fa35861620b2e4d79f04f0af

csharp/Facebook.Yoga/YogaConfig.cs

@@ -8,29 +8,92 @@
  */
 
 using System;
+using System.Runtime.InteropServices;
+
+#if __IOS__
+using ObjCRuntime;
+#endif
+#if ENABLE_IL2CPP
+using AOT;
+#endif
 
 namespace Facebook.Yoga
 {
     public class YogaConfig
     {
-        private Native.YGConfigHandle _ygConfig;
+        internal static readonly YogaConfig Default = new YogaConfig(YGConfigHandle.Default);
+        private static YogaLogger _managedLogger;
 
-        public YogaConfig()
+        private YGConfigHandle _ygConfig;
+        private Logger _logger;
+
+        private YogaConfig(YGConfigHandle ygConfig)
         {
-            _ygConfig = Native.YGConfigNew();
+            _ygConfig = ygConfig;
             if (_ygConfig.IsInvalid)
             {
                 throw new InvalidOperationException("Failed to allocate native memory");
             }
+
+            _ygConfig.SetContext(this);
+
+            if (_ygConfig == YGConfigHandle.Default)
+            {
+                _managedLogger = LoggerInternal;
+                Native.YGInteropSetLogger(_managedLogger);
+            }
         }
 
-        internal Native.YGConfigHandle Handle
+        public YogaConfig()
+            : this(Native.YGConfigNew())
+        {
+        }
+
+        internal YGConfigHandle Handle
         {
             get {
                 return _ygConfig;
             }
         }
 
+#if (UNITY_IOS && !UNITY_EDITOR) || ENABLE_IL2CPP || __IOS__
+        [MonoPInvokeCallback(typeof(YogaLogger))]
+#endif
+        private static void LoggerInternal(
+            IntPtr unmanagedConfigPtr,
+            IntPtr unmanagedNodePtr,
+            YogaLogLevel level,
+            string message)
+        {
+            var config = YGConfigHandle.GetManaged(unmanagedConfigPtr);
+            if (config == null || config._logger == null)
+            {
+                // Default logger
+                Console.WriteLine(message);
+            }
+            else
+            {
+                var node = YGNodeHandle.GetManaged(unmanagedNodePtr);
+                config._logger(config, node, level, message);
+            }
+
+            if (level == YogaLogLevel.Error || level == YogaLogLevel.Fatal)
+            {
+                throw new InvalidOperationException(message);
+            }
+        }
+
+        public Logger Logger
+        {
+            get {
+                return _logger;
+            }
+
+            set {
+                _logger = value;
+            }
+        }
+
         public void SetExperimentalFeatureEnabled(
             YogaExperimentalFeature feature,
             bool enabled)
@@ -68,5 +131,10 @@ namespace Facebook.Yoga
         {
             return Native.YGConfigGetInstanceCount();
         }
+
+        public static void SetDefaultLogger(Logger logger)
+        {
+            Default.Logger = logger;
+        }
     }
 }