[tasque] Implement recursive update barrier

[Antonius Riha <antoniusri src gnome org>]

commit 9718bdbc4ab9aa68934e63cc04f6b426c8043aeb
Author: Antonius Riha <antoniusriha gmail com>
Date:   Mon Mar 18 11:36:30 2013 +0100

    Implement recursive update barrier

 src/libtasque/Core/Impl/Extensions.cs |   15 +++++++++++++--
 1 files changed, 13 insertions(+), 2 deletions(-)
---
diff --git a/src/libtasque/Core/Impl/Extensions.cs b/src/libtasque/Core/Impl/Extensions.cs
index fbf8dad..71f6a79 100644
--- a/src/libtasque/Core/Impl/Extensions.cs
+++ b/src/libtasque/Core/Impl/Extensions.cs
@@ -24,11 +24,16 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 using System;
+using System.Collections.Generic;
+using System.Linq;
 
 namespace Tasque.Core.Impl
 {
        public static class Extensions
        {
+               static List<Tuple<object, string>> updatingProperties
+                       = new List<Tuple<object, string>> ();
+               
                public static void SetProperty<TProperty, T> (
                        this T source, string name, TProperty val, TProperty curVal,
                        Action<TProperty> setVal, Func<T, TProperty, TProperty> update)
@@ -41,8 +46,14 @@ namespace Tasque.Core.Impl
                                return;
                        
                        if (!source.IsBackendDetached) {
-                               if (Equals (curVal, val = update (source, val)))
-                                       return;
+                               if (!updatingProperties.Any (t => Equals (t.Item1, source) &&
+                                                            t.Item2 == name)) {
+                                       var pair = new Tuple<object, string> (source, name);
+                                       updatingProperties.Add (pair);
+                                       if (Equals (curVal, val = update (source, val)))
+                                               return;
+                                       updatingProperties.Remove (pair);
+                               }
                        }
                        
                        source.OnPropertyChanging (name);